Neutron star smashup seen for first time, 'transforms' understanding of Universe

October 16, 2017 by Marlowe Hood
This artist's impression shows two tiny but very dense neutron stars at the point at which they merge and explode as a kilonova. Such a very rare event is expected to produce both gravitational waves and a short gamma-ray burst, both of which were observed on 17 August 2017 by LIGO-Virgo and Fermi/INTEGRAL respectively. Subsequent detailed observations with many ESO telescopes confirmed that this object, seen in the galaxy NGC 4993 about 130 million light-years from the Earth, is indeed a kilonova. Such objects are the main source of very heavy chemical elements, such as gold and platinum, in the Universe. Credit: ESO/L. Calçada/M. Kornmesser

For the first time, scientists have witnessed the cataclysmic crash of two ultra-dense neutron stars in a galaxy far away, and concluded that such impacts forged at least half the gold in the Universe.

Shockwaves and light flashes from the collision travelled some 130 million light-years to be captured by Earthly detectors on August 17, excited teams revealed at press conferences held around the globe on Monday as a dozen related science papers were published in top academic journals.

"We witnessed history unfolding in front of our eyes: two neutron stars drawing closer, closer... turning faster and faster around each other, then colliding and scattering debris all over the place," co-discoverer Benoit Mours of France's CNRS research institute told AFP.

The groundbreaking observation solved a number of physics riddles and sent ripples of excitement through the scientific community.

Most jaw-dropping for many, the data finally revealed where much of the gold, platinum, uranium, mercury and other heavy elements in the Universe came from.

Telescopes saw evidence of newly-forged material in the fallout, the teams said—a source long suspected, now confirmed.

"It makes it quite clear that a significant fraction, maybe half, maybe more, of the heavy elements in the Universe are actually produced by this kind of collision," said physicist Patrick Sutton, a member of the US-based Laser Interferometer Gravitational-Wave Observatory (LIGO) which contributed to the find.

Neutron stars are the condensed, burnt-out cores that remain when massive stars run out of fuel, blow up, and die.

Typically about 20 kilometres (12 miles) in diameter, but with more mass than the Sun, they are highly radioactive and ultra-dense—a handful of material from one weighs as much as Mount Everest.

An image of Swope Supernova Survey 2017a (or SSS17a) from the night of discovery. On August 17, a team of four Carnegie astronomers provided the first-ever glimpse of two neutron stars colliding, opening the door to a new era of astronomy. Credit: Tony Piro.

'Too beautiful'

It had been theorised that mergers of two such exotic bodies would create ripples in the fabric of space-time known as gravitational waves, as well as bright flashes of high-energy radiation called gamma ray bursts.

On August 17, detectors witnessed both phenomena, 1.7 seconds apart, coming from the same spot in the constellation of Hydra.

"It was clear to us within minutes that we had a binary neutron star detection," said David Shoemaker, another member of LIGO, which has detectors in Livingston, Louisiana and Hanford, Washington.

"The signals were much too beautiful to be anything but that," he told AFP.

The observation was the fruit of years of labour by thousands of scientists at more than 70 ground- and space-based observatories on all continents.

Along with LIGO, they include teams from Europe's Virgo gravitational wave detector in Italy, and a number of ground- and space-based telescopes including NASA's Hubble.

"This event marks a turning point in observational astronomy and will lead to a treasure trove of scientific results," said Bangalore Sathyaprakash from Cardiff University's School of Physics and Astronomy, recalling "the most exciting of my scientific life."

"It is tremendously exciting to experience a rare event that transforms our understanding of the workings of the Universe," added France Cordova, director of the National Science Foundation which funds LIGO.

The detection is another feather in the cap for German physicist Albert Einstein, who first predicted gravitational waves more than 100 years ago.

The UC Santa Cruz team found SSS17a by comparing a new image of the galaxy N4993 (right) with images taken four months earlier by the Hubble Space Telescope (left). The arrows indicate where SSS17a was absent from the Hubble image and visible in the new image from the Swope Telescope. Credit: Image credits: Left, Hubble/STScI; Right, 1M2H Team/UC Santa Cruz & Carnegie Observatories/Ryan Foley

Something 'fundamental'

Three LIGO pioneers, Barry Barish, Kip Thorne and Rainer Weiss, were awarded the Nobel Physics Prize this month for the observation of gravitational waves, without which the latest discovery would not have been possible.

The ripples have been observed four times before now—the first time by LIGO in September 2015. All four were from mergers of black holes, which are even more violent than neutron star crashes, but emit no light.

The fifth and latest detection was accompanied by a gamma ray burst which scientists said came from nearer in the Universe and was less bright than expected.

"What this event is telling us is that there may be many more of these short gamma ray bursts going off nearby in the Universe than we expected," Sutton said—an exciting prospect for scientists hoping to uncover further secrets of the Universe.

Among other things, it is hoped that data from neutron star collisions will allow the definitive calculation of the rate at which the cosmos is expanding, which in turn will tell us how old it is and how much matter it contains.

"With these observations we are not just learning what happens when neutron stars collide, we're also learning something fundamental about the nature of the Universe," said Julie McEnery of the Fermi gamma ray space telescope project.

Neutron star smash-up the 'discovery of a lifetime'

"Truly a eureka moment", "Everything I ever hoped for", "A dream come true"—Normally restrained scientists reached for the stars Monday to describe the feelings that accompany a "once-in-a-lifetime" event.

The trigger for this meteor shower of superlatives was the smash-up of two unimaginably dense 130 million years ago.

Evidence of this cosmic clash hurtled through space and reached Earth on August 17 at exactly 12:41 GMT, setting in motion a secret, sleepless, weeks-long blitzkrieg of star-gazing and number-crunching involving hundreds of telescopes and thousands of astronomers and astrophysicists around the world.

It was as if a dormant network of super-spies simultaneously sprung into action.

The stellar smash-up made itself known in two ways: it created ripples called gravitational waves in Einstein's time-space continuum, and lit up the entire electromagnetic spectrum of light, from gamma rays to radio waves.

Scientists had detected gravitational waves four times before, a feat acknowledged with a Nobel Physics Prize earlier this month.

But each of those events, generated by the collision of black holes, lasted just a few seconds, and remained invisible to Earth- and space-based telescopes.

The neutron star collision was different.

It generated —picked up by two US-based observatories known as LIGO, and another one in Italy called Virgo—that lasted an astounding 100 seconds. Less than two seconds later, a NASA satellite recorded a burst of .

Artist's concept of the explosive collision of two neutron stars. Credit: Robin Dienel courtesy of the Carnegie Institution for Science.

A true 'eureka' moment

This set off a mad dash to locate what was almost certainly the single source for both.

"It is the first time that we've observed a cataclysmic astrophysical event in both gravitational and electromagnetic waves," said LIGO executive director David Reitze, a professor at the California Institute of Technology (Caltech) in Pasadena

Initial calculations had narrowed the zone to a patch of sky in the southern hemisphere spanning five or six galaxies, but frustrated astronomers had to wait for nightfall to continue the search.

Finally, at around 2200 GMT, a telescope array in the northern desert of Chile nailed it: the stellar merger had taken place in a galaxy known as NGC 4993.

Stephen Smartt, who led observations for the European Space Observatory's New Technology Telescope, was gobsmacked when the spectrum lit up his screens. "I had never seen anything like it," he recalled.

Scientists everywhere were stunned.

"This event was truly a eureka moment," said Bangalore Sathyaprakash, head of the Gravitational Physics Group at Cardiff University. "The 12 hours that followed are inarguably the most exciting of my scientific life."

"There are rare occasions when a scientist has the chance to witness a new era at its beginning—this is one such time," said Elena Pian, an astronomer at the National Institute for Astrophysics in Rome.

LIGO-affiliated astronomers at Caltech had spent decades preparing for the off chance—calculated at 80,000-to-one odds—of witnessing a neutron star merger.

Don't tell your friends

"On that morning, all of our dreams came true," said Alan Weinstein, head of astrophysical data analysis for LIGO at Caltech.

"This discovery was everything I always hoped for, packed into a single event," added Francesco Pannarale, an astrophysicist at Cardiff University in Wales.

For these and thousands of other scientists, GW170817—the neutron star burst's tag—will become a "do you remember where you were?" kind of moment.

"I was sitting in my dentist's chair when I got the text message," said Benoit Mours, an astrophysicist at France's National Centre for Research and the French coordinator for Virgo. "I jumped up and rushed to my lab."

Patrick Sutton, head of the gravitational physics group at Cardiff and a member of the LIGO team, was stuck on a long-haul bus, struggling to download hundreds of emails crowding his inbox.

A comparison of images of Swope Supernova Survey 2017a (or SSS17a) from the night of discovery, August 17, and four nights later, August 21. Credit: Tony Piro.

Rumours swirled within and beyond the astronomy community as scientists hastened to prepare initial findings for publication Monday in a dozen articles spread across several of the world's leading journals.

"There have been quite a few pints and glasses of wine or bubbly—privately, of course, because we haven't been allowed to tell anyone," Sutton told AFP.

But he couldn't resist telling his 12-year-old son, an aspiring physicist.

"He's sworn to secrecy though. He's not allowed to tell his friends."

LIGO and Virgo: The machines that unlock the universe's mysteries

The three machines that gave scientists their first-ever glimpse of gravitational waves resulting from a collision of neutron stars are the most advanced detectors ever built for sensing tiny vibrations in the universe.

The LIGO and Virgo detectors have previously picked up the "chirp" of black holes merging in the distant universe, sending out ripples in the fabric of space and time.

The detection of these gravitational waves for the first time in 2015 confirmed Albert Einstein's century old theory of general relativity.

The two US-based underground detectors are known as the Laser Interferometer Gravitational-wave Observatory, or LIGO for short.

One is located in Hanford, Washington; the other 1,800 miles (3,000 kilometers) away in Livingston, Louisiana.

Construction began in 1999, and observations were taken from 2001 to 2007.

Then they underwent a major upgrade to make them 10 times more powerful.

The advanced LIGO detectors became fully operational for the first time in September 2015.

On September 14, 2015, the detector in Louisiana first picked up the signal of a gravitational wave, originating 1.3 billion years ago in the southern sky.

Virgo

The third underground detector is near Pisa, Italy, and is known as Virgo.

Built a quarter century ago by a French-Italian partnership, the Virgo detector ended its initial round of observations in 2011 and then underwent an upgrade.

Advanced Virgo came online in April of this year, and made its first observation of gravitational waves on August 14, marking the fourth such event that scientists have observed since 2015.

Virgo is less sensitive than LIGO, but having three detectors helps scientists zero in on the area of the universe where a cosmic event is happening, and measure the distance with greater accuracy.

"A smaller search area enables follow-up observations with telescopes and satellites for cosmic events that produce gravitational waves and emissions of light, such as the collision of neutron stars," said Georgia Tech professor Laura Cadonati.

How they work

These huge laser interferometers—each about 2.5 miles (four kilometers) long—are buried beneath the ground to allow the most precise measurements.

The L-shaped instruments track gravitational waves using the physics of laser light and space.

They do not rely on light in the skies like a telescope does.

Rather, they sense the vibrations in space, an advantage which allows them to uncover the properties of black holes and neutron stars.

"As a gravitational wave propagates through space it stretches space-time," explained David Shoemaker, leader of the Advanced LIGO project at the Massachusetts Institute of Technology (MIT).

The detector, in short, "is just a big device for changing strain in space into an electrical signal."

One way to imagine the curvature of space and time is to imagine a ball falling on a trampoline.

The trampoline bows downward first, stretching the fabric vertically and shortening the sides.

Then as the ball bounces upward again, the horizontal movement of the fabric expands again.

The instrument acts like a transducer, changing that strain into changes in light—and then into an electronic signal so scientists can digitize it and analyze it.

"The light from the laser has to travel in a vacuum so that it is not disturbed by all the air fluctuations," said Shoemaker, noting that LIGO contains the "biggest high vacuum system in the world,"—measuring 1.2 meters (yards) by 2.5 miles (four kilometers) long.

The detectors contain two very long arms that contain optical instruments for bending light, and are positioned like the letter L.

If one arm shortens, and the other lengthens, scientists know they are seeing a gravitational wave.

Read more: What are neutron stars?

Read more: Gravitational waves: Why the fuss?

Explore further: LIGO and Virgo observatories detect gravitational wave signals from black hole collision

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270 comments

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TechnoCreed
5 / 5 (15) Oct 16, 2017
The press conference on the matter is still ongoing https://www.youtu...PKYl4AHs
shavera
4.7 / 5 (28) Oct 16, 2017
Gravitational and EM waves emitted from the same event. Can we now lay to rest the argument that scientists don't understand instrumental noise, and have been making real detections of gravitational waves? That GR predicts gravitational waves, something you can calculate what a detector should measure, that several independent detectors have measured these predictions within a reasonable degree of error.

*Notes: GR was not finished by Einstein alone, but a lot of other scientists have contributed over the years. You can work out, from several GR textbooks, including the seminal "Gravitation" by Meisner, Thorne and Wheeler, the maths of how, precisely GR predicts such waves yourself.

I'm not aware of any experiment that rigorously contradicts GR predictions outside of Planck-regime distances and energies; Since so many support it, much less is required to guess at when GR doesn't perfectly succeed (like we can guess that we might not know all the kinds of matter in the universe)
antialias_physorg
5 / 5 (22) Oct 16, 2017
Man, this new type of astronomy is exciting. I can't wait until they get the LISA set of satellites up and running.

The groundbreaking observation resolves several long-standing mysteries—revealing the origin of heavy metals on our planet and elsewhere in the Universe


To quote Dethklokk: "We're here to make everything metal. Blacker than the blackest black - times infinity".
Ojorf
4.3 / 5 (23) Oct 16, 2017
Wow, great news!

Na, na, na, na, naaa... at the gravity wave doubters.
Chris_Reeve
Oct 16, 2017
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jonesdave
4.6 / 5 (22) Oct 16, 2017
"It is a sobering fact that even after hundreds of satellites had circled the Earth, the generally accepted picture of our space environment was still fundamentally wrong in aspects as basic as the existence and role of electric fields and even the origin and chemical composition of the near-Earth plasma itself. In the light of this, how can we believe in detailed theoretical models of distant astrophysical objects, until we have learned -- and applied to astrophysics -- the lessons of how the real plasma behaves in the Earth's own magnetosphere."


And what the hell has this got to do with GW? Falthammar, by the way, accepts magnetic reconnection. Do you agree with him? A simple yes or no will suffice.
Chris_Reeve
Oct 16, 2017
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Chris_Reeve
Oct 16, 2017
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jonesdave
4.6 / 5 (18) Oct 16, 2017
Dewey Bernard Larson (1898-1990) was the creator of Reciprocal Theory, and an otherwise irrelevant American engineer. While he was writing only a few years before the Standard Model of physics came along to more fully refute his claims, he seems to very casually ignore how successful quantum mechanics has been in, among other things, explaining the physics of the electron and in providing fundamental explanations for essentially all of chemistry, even by the 1950s and 1960s. However, Larson still maintains a strong and passionate following among a few cranks who think that they've stumbled upon some great secret body of knowledge


https://rationalw...l_Theory
Chris_Reeve
Oct 16, 2017
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Chris_Reeve
Oct 16, 2017
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jonesdave
4.3 / 5 (12) Oct 16, 2017
Prof. John Billingsley.........................who?
Chris_Reeve
Oct 16, 2017
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jonesdave
4.6 / 5 (11) Oct 16, 2017
Irving Langmuir............................died 1957.
Chris_Reeve
Oct 16, 2017
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Chris_Reeve
Oct 16, 2017
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jonesdave
4.6 / 5 (19) Oct 16, 2017
Milic Capek.......................................philosopher
Dewey Larson.....................................crank (see previous)

Irrelevant. As usual. Yawn.
Chris_Reeve
Oct 16, 2017
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jonesdave
4.4 / 5 (21) Oct 16, 2017
Ivor Catt...........................electronics engineer..............................irrelevant. Again.
jonesdave
4.4 / 5 (21) Oct 16, 2017
Miles Mathis........................................crank

Mathis is best known for his outlandish and often ridiculous theories. For instance, that π (pi) is actually equal to 4,......


https://rationalw...s_Mathis
Chris_Reeve
Oct 16, 2017
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rogerdallas
4.4 / 5 (27) Oct 16, 2017
I think we have enough evidence to conclude that Chris_Reeve is a crank. Yes?
Chris_Reeve
Oct 16, 2017
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jonesdave
4.4 / 5 (20) Oct 16, 2017
William Day.............................another 'alternative' physics loon. Keep 'em coming.
Chris_Reeve
Oct 16, 2017
This comment has been removed by a moderator.
jonesdave
4.6 / 5 (19) Oct 16, 2017
Fred Hoyle.............................was wrong.
Chris_Reeve
Oct 16, 2017
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jonesdave
4.3 / 5 (16) Oct 16, 2017
John Waller........................

Clearly intended for the "popular" market, Waller's book leaves a lot to be desired as far as the readership of this journal will be concerned. In spite of the author's repeated attempts to point to the unifying themes of his book, it comes across to the reader who knows something about the history of science and medicine, or something about the philosophy and sociology of science as a ragbag of causes célèbres of such differing kinds that it presents no sound conclusions about the nature of modern science.


https://www.ncbi....C547940/
Chris_Reeve
Oct 16, 2017
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jonesdave
4.5 / 5 (22) Oct 16, 2017
(cont'd)

"... Had the teams been measuring star beams just clipping the Sun's edge, their displacement might have been large enough to eliminate atmospheric turbulence as the sole cause. In 1919, however, with the star beams closest to the Sun obliterated by the corona, those that could be observed were some way from the Sun's rim. Consequently the displacements were so small that the entire effect could quite easily have been caused by atmospheric turbulence alone. At some level, the teams were aware of this. Thus, in discussions after the announcement of the eclipse results, Eddington and his assistants admitted that calculations of small displacements were unreliable. Yet, they refused to let this effect their presentation of the measurements. As we have seen, within a few months Einstein's ideas were being adjudged victorious from the pulpit of the Astronomer Royal."


Irrelevant. GR & SR have been repeatedly confirmed since then, Gish/ Reeve
Chris_Reeve
Oct 16, 2017
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Chris_Reeve
Oct 16, 2017
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jonesdave
4.3 / 5 (16) Oct 16, 2017
Fabulous Science Fact and Fiction in the History of Scientific Discovery
John Waller
(p53)

"Both 1918–19 eclipse expeditions comprised British physicists. The first team, which observed the eclipse from Sobral in Brazil ... The other, headed by Arthur Eddington and his assistant E. Cottingham, made its observations from the island of Principe, which lies off the coast of West Africa. Eddington, born in the English Lake District, was already an eminent Cambridge physicist and it was his interpretation of both teams' data-sets that would serve to vindicate Einstein. For this reason it is noteworthy that even before departing for Principe he was well known for his Einsteinian sympathies. As the most important expositor of general relativity within Britain, most of his colleagues knew that he was undertaking the eclipse expedition in the fervent hope of confirming his radical intuition that Einstein was right."


http://www.nature...-20.html
Chris_Reeve
Oct 16, 2017
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catsolco
4.6 / 5 (18) Oct 16, 2017
Magnificent, epic, heroic Gallileo moment for all the wonderful minds which have dug at this over the centuries.
jonesdave
4.3 / 5 (17) Oct 16, 2017
Reginald T. Cahill...................................

We reveal an underlying flaw in Reginald T. Cahill's recently promoted quantum
foam inflow theory of gravity. It appears to arise from a confusion of the idea of the
Galilean invariance of the acceleration of an individual flow with what is obtained as an
acceleration when a homogeneous flow is superposed with an inhomogeneous flow. We
also point out that the General Relativistic covering theory he creates by substituting a
generalized Painlev ́e-Gullstrand metric into Einstein's field equations leads to absurd re-
sults.


http://www.gravit...0810.pdf

Yet another crank.
Chris_Reeve
Oct 16, 2017
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Chris_Reeve
Oct 16, 2017
This comment has been removed by a moderator.
Chris_Reeve
Oct 16, 2017
This comment has been removed by a moderator.
Chris_Reeve
Oct 16, 2017
This comment has been removed by a moderator.
Chris_Reeve
Oct 16, 2017
This comment has been removed by a moderator.
jonesdave
4.4 / 5 (14) Oct 16, 2017
Tom van Flandern.....................

Tom Van Flandern strongly attacked some alternative theories, such as Velikovsky's ideas of recent planetary close approaches, turning one of Velikovsky's supporters, C. L. Ellenberger, into a strong critic.


Wonder if Gish/ Reeve would agree with him?
cantdrive85
1.4 / 5 (18) Oct 16, 2017
Gravitational and EM waves emitted from the same event. Can we now lay to rest the argument that scientists don't understand instrumental noise?

Just like the first so called GW detection, an EM event was detected. And it didn't quite happen as was predicted, but reported as a great success and vindication for their beliefs. LOL!
Chris_Reeve
Oct 16, 2017
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Da Schneib
4.4 / 5 (19) Oct 16, 2017
This is awesome: first detection of a GW event that is:
1. Associated with neutron stars, not black holes
2. Associated with EM detections, particularly GRBs
3. Shows direct evidence of heavy element production
4. Confirmed by not just a couple or a few, but scores of independent observers simultaneously

EU: 0 Standard astrophysics: 5

Get over it.
Chris_Reeve
Oct 16, 2017
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Benni
1.4 / 5 (19) Oct 16, 2017
I see the rah, rah, rah gravitaty wave gang are all here doing their cheers that these perturbations measured by these instruments are the so-called gravity waves found in General Relativity that Einstein denied existed.

If Einstein did not believe in the existence of GRAVITY WAVES, it stands to reason such GWs can't be found in GR, and they don't. Prove me wrong, put up the section of GR that defines gravity as WAVES.

The only thing they are measuring is change in ambient conditions for the few seconds or moments in time these things collide, not real gravity which does not have the transformative properties that REAL WAVES would have.
Chris_Reeve
Oct 16, 2017
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Gorgar
1.4 / 5 (21) Oct 16, 2017
Neutron stars again? What changed their mind last time when they ended up saying its was a black hole merger? Do neutron stars even exist? Proof?
Da Schneib
4.8 / 5 (16) Oct 16, 2017
Neutron stars again? What changed their mind last time when they ended up saying its was a black hole merger?
There is nothing stopping detection of both neutron star and black hole mergers by the same instrument. Why would you expect there would be?

Do neutron stars even exist? Proof?
Pulsars. Next?
cantdrive85
1 / 5 (13) Oct 16, 2017
As has been explicitly shown here, if you don't believe what jonesdumb believes you are a crank or irrelevant. This from a guy who is unaware of electrochemistry in plasmas.

cantdrive85
1 / 5 (13) Oct 16, 2017
Do neutron stars even exist? Proof?

Pulsars. Next?

By that failed reasoning one could also claim that since a pot 'o gold can be proven to exist so too leprechauns must exist...
marcush
4.8 / 5 (21) Oct 16, 2017
We need a moderator here. The spam is really annoying.
Whydening Gyre
4.7 / 5 (15) Oct 16, 2017
We need a moderator here. The spam is really annoying.

Indeed. CR is again attempting to co-op the thread with his non sequitar BS...
Benni
1.5 / 5 (17) Oct 16, 2017
The only thing they are measuring is change in ambient conditions for the few seconds or moments in time these things collide, not real gravity which does not have the transformative properties that REAL WAVES would have.


Here read more about what Einstein ACTUALLY stated about GRAVITY WAVES:

Einstein and Gravitational Waves 1936-1938. Available from:

https://www.resea...936-1938

In Einstein's paper: In 1936, Einstein wrote to his close friend Max Born telling him that, together with Nathan Rosen, he had arrived at the interesting result that gravitational waves did not exist, though they had been assumed a certainty to the first approximation. He reconfirmed it in 1938 to an even higher approximation.

So those of you neophytes continuing to insist Gravity Waves & Black Holes have a foundation in General Relativity, this is just more bad news for the Perpetual Motion Mechanics living here.

Parsec
4.5 / 5 (17) Oct 16, 2017
Even with CR on ignore he still overwhelms the site with his absurd stupid posts. Moderator needs to boot his trollness from these boards.
Benni
1.5 / 5 (16) Oct 16, 2017
We need a moderator here. The spam is really annoying.


You bet, the Perpetual Motion Mechanics living here need a good dusting. Can you imagine any rational thinking person believing that Infinite Gravity & Infinite Density can exist on the surface of a Finite Stellar Mass?
Chris_Reeve
Oct 16, 2017
This comment has been removed by a moderator.
Whydening Gyre
5 / 5 (13) Oct 16, 2017
We need a moderator here. The spam is really annoying.


You bet, the Perpetual Motion Mechanics living here need a good dusting. Can you imagine any rational thinking person believing that Infinite Gravity & Infinite Density can exist on the surface of a Finite Stellar Mass?

Since you're the only one saying it, you must be irrational...
And actually Density is a descriptor for what's beneath the surface...
Chris_Reeve
Oct 16, 2017
This comment has been removed by a moderator.
Chris_Reeve
Oct 16, 2017
This comment has been removed by a moderator.
Benni
1.3 / 5 (12) Oct 16, 2017
Density is a descriptor for what's beneath the surface..
......of the Perpetual Motion Mechanics living here who believe an isolated system of constant mass can have properties of infinite density & infinite gravity.
shadybail
1.7 / 5 (12) Oct 16, 2017
"The only thing they are measuring is change in ambient conditions for the few seconds or moments in time these things collide, not real gravity which does not have the transformative properties that REAL WAVES would have."

I was pondering this article in my backyard and I saw a coconut fall off a tree and land in the water of the canal behind my house. I was struck by the movement of the energy through the water as it rippled. I thought is this how a gravitational wave is formed? Is a gravitational wave different than an energy wave? After reading Benni's post, I realized what I saw was the energy changing the ambient conditions of the water as it passed through it. In my limited intelligence, I agree with Benni that gravitation waves do not exist or least haven't been proven. What I witnessed and the observers of the neutron star witnessed are the same energy wave? Do the other readers agree with Benni's comments on gravitational waves?

Benni
1.3 / 5 (12) Oct 16, 2017
I saw a coconut fall off a tree and land in the water of the canal behind my house. I was struck by the movement of the energy through the water as it rippled


I realized what I saw was the energy changing the ambient conditions of the water as it passed through it.


and the observers of the neutron star witnessed are the same energy wave


Everything you wrote about is exactly what the LIGO guys saw. A sudden impact releasing vast amounts of energy raising spectral density above a previously established stable background. Not a big trick to perform, I do it everyday in our lab subsequent to setting our spectroscopy to a specific Region of Interest.

shavera
4.1 / 5 (14) Oct 16, 2017
Prove me wrong, put up the section of GR that defines gravity as WAVES.

They're called 'gravitational waves.' You're constructing a strawman argument when you say that science 'defines gravity as waves'. It doesn't (disregarding for the moment quantum theories of GR). GR describes how measures of space and time change in location relative to mass and motion. As a *side effect* of these changes, a phenomenon occurs that was previously known as a 'force' of gravity.

Gravitational waves are waves (they satisfy the Helmholtz equation) of changes in measures of space and time. They aren't waves 'carrying' gravity, they're waves of changes of measures of space and time.

You are now, as always, invited to work through the standard GR textbooks that go into exhaustive detail about such things. Because Einstein is _not_ the last word in GR, just the first.
shavera
4.1 / 5 (14) Oct 16, 2017
is this how a gravitational wave is formed?

No, not really. Gravitational waves are formed by the acceleration of moving masses, much like EM waves are formed by the acceleration of moving charges.
Is a gravitational wave different than an energy wave?

"Energy wave" doesn't have meaning in physics. A wave may carry energy, like the ripples on the pond do. Gravitational waves carry energy too.
gravitation waves do not exist

Benni was misrepresenting gravitational waves. See above. Gravitational waves don't 'carry' gravity. It would have been better if people had called them "Curvature waves" to avoid this confusion.
Da Schneib
4.3 / 5 (11) Oct 16, 2017
@shavy, well explained but probably beyond the respondent.

The important part here is that just as with water waves, gravitational waves are a response of the medium. Thus they represent propagating distortions. We only directly see the surface wave in water, but there are other types of waves that can propagate in water; dolphins "see" (or if you prefer, "hear;" actually either description is unlike any human sense) those.

As a gravitational wave passes, you can measure the distortion of spacetime. A gravitational wave is a self-contained distortion that propagates in spacetime, just as sonar is a self-contained distortion that propagates in a fluid. Their reasons for self-containment are identical: conservation of energy.

One of the reasons that people don't "get" gravitational waves is they expect them to be a surface phenomenon like water waves we see, because they are often compared with water waves.
[contd]
Da Schneib
4.3 / 5 (11) Oct 16, 2017
[contd]
What's not often understood is that gravitational waves aren't like water surface waves; they're like compression waves in the body of water. That's a much more evocative interpretation, but a lot of people don't get compression waves in the body of water either, which is why sonar seems "magical" to certain individuals (not all of whom are #physicscranks posting on physorg).
Benni
1.5 / 5 (11) Oct 16, 2017
The important part here is that just as with water waves, gravitational waves are a response of the medium. Thus they represent propagating distortions


I see you're finally starting to get it, just what I've telling you. Finally you're beginning to understand that GRAVITY WAVES & GRAVITATIONAL WAVES do not refer to the same thing in the present day use of the two terms.

What most people take away from LIGO is a false interpretation that gravity has been proven to exist in the form of WAVES, in essence mimicking the Electro-magnetic Spectrum in which ENERGY varies by frequency of the wave.

LIGO did not record the FREQUENCY of a GRAVITY WAVE, a concept to which Einstein was opposed to.
Da Schneib
4.1 / 5 (13) Oct 16, 2017
@Lenni, "gravity waves" are seismic distortions of the Earth. They have nothing to do with gravitational waves other than the same dialectical analogy that is present for water body waves.

LIGO is the right way to detect gravitational waves; you use seismometers for gravity waves.

It's kinda hard to argue against gravitational waves when we got telescopes on target quickly and saw a GRB. It's kinda like arguing whether the lamp was lit in the lighthouse when you saw the beam from it and saw the rocks it warns about.

@Lenni isn't all that bright and might not understand what lighthouses are for in the real world. They indicate significant out-thrusting rocks beyond a geographical land point that might not be obvious to a passing ship. The ship is warned to get as far out past the point as possible to avoid the invisible rocks.
shavera
4.4 / 5 (13) Oct 16, 2017
While I do agree that the name isn't optimal, that's the name. That's what gravitational waves mean. Yes we could do a better job explaining to people that this isn't precisely the same thing as 'gravity' travelling in waves.
But if that ultimately is your whole argument, that people misunderstand the phrase "gravitational waves" then you could have done a better job explaining your side as well. Because GR absolutely does permit a wave solution to the field equations.
Da Schneib
4.3 / 5 (12) Oct 16, 2017
@shavy, it's the difference between a static charge and a moving one. The static charge just makes a static field; the moving charge makes a wave, which is a propagating self-contained distortion supported by energy conservation.

If gravity were stronger, we'd be able to detect gravitational waves from the electrons circling an atom; but if that were the case they'd radiate energy and death spiral into the nucleus and there wouldn't be a universe. Just sayin'.
shavera
4.6 / 5 (11) Oct 16, 2017
DS, the question is more: "should we call any effect related to GR 'gravitation'?" Let's back your hypothetical up a few orders of magnitude to small, but macroscopic spheres orbiting. Yes they're emitting very weak waves describing their motion, losing tiny amounts of energy along the way. Is that 'gravitation'? I dunno. I don't think the public at large would call it such.

This causes other confusion when you have to consider "gravitation" near to masses and "metric expansion" on the universe as a whole. They're both aspects of one continuous curvature field. as are the ripply curvature waves passing through it.
Da Schneib
4.7 / 5 (12) Oct 16, 2017
@shavy, I would say that a static body will make a static gravity field, and a moving body will make gravitational waves, and that the same is substantially true of an electrically charged body, making a static E field, and a moving charged body making a B field. Because the body has to move to make a B field, div B equals 0.

The really interesting question is, how can the gravity field be so much weaker than the EM field that it does not radiate energy?
shavera
4.7 / 5 (13) Oct 16, 2017
The reason to back up a bit to the small macroscopic spheres is because when we talk about electrons circling an atom, that's when GR gets real wonky. And when gravity, in the conventional sense, may actually be made up of waves.

Much like a small charged sphere has a "classical" electric field, but that electric field is actually the ensemble of photons carrying around the EM field energy, it may be that "classical" curvature fields may, in fact, be made of small bits of curvature excitations. Again, this is where the confusion with calling everything GR 'gravity' arises, since the 'curvature excitations' go by the name "graviton."

But otherwise, consider what GR is: "How you measure space-time"="Distribution of mass and energy and momentum". How do you solve that equation when your masses don't have specific locations in space or specific momenta?
shavera
4.6 / 5 (10) Oct 16, 2017
a static body

Let's clarify a moment, static or moving with a constant velocity, because they're the same thing. Which then modifies your next comment from "moving" to "accelerating." I don't know exactly, but linear acceleration probably wouldn't create gravitational "waves," though it would produce a change in field structure (then again, one must consider that acceleration requires force, which requires a momentum change equal and opposite, which itself has an influence in the curvature field.

But yes, a lot of the equations describing gravitational waves are formed from parallels with the maths of EM and rotating charged bodies.

Benni
1.4 / 5 (9) Oct 16, 2017
Yes we could do a better job explaining to people that this isn't precisely the same thing as 'gravity' travelling in waves.
"we"? What are you, a journalist?

But if that ultimately is your whole argument, that people misunderstand the phrase "gravitational waves" then you could have done a better job explaining your side as well.


That should have started with the LIGO guys, not me. I'm not writing the papers, they are.

Because GR absolutely does permit a wave solution to the field equations.


Oh, that it does, in fact there's even an equation for it in GR by Einstein, but NOT for a GRAVITY WAVE somehow mimicking the Electro-magnetic Spectrum whereby the strength of a gravity wave depends on its' frequency.

LIGO is the right way to detect gravitational waves; you use seismometers for gravity waves.
.....and here's Schnebo, mixing up the two issues yet again.

Benni
1.9 / 5 (9) Oct 16, 2017
LIGO is the right way to detect gravitational waves; you use seismometers for gravity waves.


Schneibo, Density Dude.........learn the difference between "gravitational waves" & "gravity waves".
shavera
4.7 / 5 (13) Oct 16, 2017
Here read more about what Einstein ACTUALLY stated about GRAVITY WAVES:

Einstein and Gravitational Waves 1936-1938.


So if you understand the difference, why this error? Is it intentional trolling? Why the constant badgering when we discuss what are very clearly noted as "Gravitational waves" and not "Gravity waves." (See my initial post, eg) Are you intentionally "misunderstanding" us to cause a ruckus? Why all this nonsense about "GRAVITY WAVE" stuff when you're the one bringing it up? People who understand the science know it's a "gravitational" wave. The article and several posters only refer to it as gravitational waves.
Da Schneib
4.6 / 5 (10) Oct 16, 2017
@shavy,
Let's clarify a moment, static or moving with a constant velocity, because they're the same thing.
Excellent point, and that's the big difference between EM and gravity: EM makes waves due to the first derivative of position, but gravity makes them as the second derivative of position. It's the difference between motion and acceleration.
shavera
4.7 / 5 (12) Oct 16, 2017
Have you ever taken a look at relativistic EM? Even just special relativity. The whole idea of relativity comes out of this conflict: If a charged particle is moving and making a magnetic field, what happens when I run along side the charged particle at the same speed? Or similarly if I move a coil of wire onto a bar magnet, the motion of the charged particles in the wire cross the magnetic field means there's a Lorentz (magnetic) force pushing charged particles, inducing a current. But if I move the magnet into the coil of wire, the changing magnetic field induces an electric field, and that electric force is what pushes the particles around. At some level they must be exactly and precisely the same thing.

So when you look at it relativistically, you'll see there's only the EM field tensor, and applying a Lorentz boost can give or take away the magnetic components.

So even in EM, it's still only accelerating charges that give you EM waves. (semi-classically speaking)
Da Schneib
4.1 / 5 (9) Oct 16, 2017
Hmmm, so how does an antenna make waves? Only at the ends? Because that's the only place the electrons are accelerating.
shavera
4.6 / 5 (11) Oct 16, 2017
it kind of depends on the shape of the antenna, considering loop antennas first: there's an alternating current passing through it. That means elections being pushed and pulled repeatedly, so accelerations changing direction.

I forget the details of like the standard straight antenna, but I think it's still an alternating voltage pushing charges toward the end, then pulling them back toward the voltage source. Even if over short time scales, net charge accumulates at the end of the antenna, on shorter scales it's being pushed and pulled along the length, so still acceleration.
Captain Stumpy
4.5 / 5 (8) Oct 16, 2017
We need a moderator here. The spam is really annoying.
@marcush
tried to get them to moderate - offered them a way to use known educated folk already here

apparently, PO thinks letting the trolls flood the site with idiocy makes them money

even if you report the gish-gallop, it, and the idiot eu poster, will remain despite the site guidelines statement that pseudoscience will be deleted

the only thing that will be deleted are the people who argue against them the most and get irritated at PO'S refusal to actually do what they say they will do in the guidelines

the pseudoscience troll rules the comments here now

proof?
see above
or here where i predicted what would happen: https://phys.org/...nic.html

even site messages are ignored anymore
Da Schneib
4.3 / 5 (6) Oct 16, 2017
I'm still thinking about it. One of the points about antennas is that they work the best if they are an even number of wavelengths. This seems to support what you say.

It seemed like such a good idea! ;)
Benni
1.4 / 5 (10) Oct 16, 2017
So if you understand the difference, why this error?


What "error"?

Are you intentionally "misunderstanding" us to cause a ruckus?


Well there's got to be an entertainment factor in here somewhere, or people will get bored. Makes them think a little bit as well.

Why all this nonsense about "GRAVITY WAVE" stuff when you're the one bringing it up?


Because it's so damned entertaining watching far less educated people, like you & Schneibo as compared to myself, get your undies all up in a knot because it is beyond your educational capacity to sort through facts versus fiction.

Whydening Gyre
4.8 / 5 (4) Oct 16, 2017
@shavy, I would say that a static body will make a static gravity field, and a moving body will make gravitational waves, and that the same is substantially true of an electrically charged body, making a static E field, and a moving charged body making a B field. Because the body has to move to make a B field, div B equals 0.

The really interesting question is, how can the gravity field be so much weaker than the EM field that it does not radiate energy?

This is gonna sound dumb, but...
it does radiate - inward...
I suspect caused by an EM or strong force "polarization" effect...
someone11235813
4.6 / 5 (10) Oct 16, 2017
This is extremely fascinating and alleviates some of the disappointment of the LHC not discovering any DM or other new physics yet.

130 million years ago, when T-rex still lorded over our planet...


T-Rex didn't evolve for another 50 million years after these neutron stars collided. Just because we're very thrilled let's not play fast and loose with evolution.
Mimath224
4.7 / 5 (12) Oct 17, 2017
Yes, I'm with the 'positives' on this one. In my opinion, this shows quite clearly that we are extending the boundary of science. The detection of gravitation waves produced by N stars really does mark a new era in Astronomy (as did the first detection). This will spur on the development of new and improved technology and we'll begin to use gravitation waves to probe mysteries. Definitely gets my vote...yes I know, that won't mean much coming from a layman.
@shavy,
Let's clarify a moment, .....
Excellent point... but gravity makes them as the second derivative of position. It's the difference between motion and acceleration.

Just a question here; I'm wondering if gravitational waves will be the next rank up, that is, a rank 3 tensor (say, cubical with positions T111...T211...T311...)?
Ojorf
4.3 / 5 (11) Oct 17, 2017
The only thing they are measuring is change in ambient conditions for the few seconds or moments in time these things collide, not real gravity which does not have the transformative properties that REAL WAVES would have.


Here read more about what Einstein ACTUALLY stated about GRAVITY WAVES:

Einstein and Gravitational Waves 1936-1938. Available from:

https://www.resea...936-1938


This is where Benni got it wrong to start off with, he even bolded his mistake.
He started with the GRAVITY WAVES nonsense.
barakn
4.2 / 5 (15) Oct 17, 2017
Judging from the amount of spittle flying out of Chris_Reeve's mouth, his side has been dealt a serious blow today.
physman
4.1 / 5 (14) Oct 17, 2017
@barakn Indeed, quite the meltdown right there.

I'm not really sure what his point is though? He seems to believe that every experiment to date is wrong and that no one bothered to check to make sure?

Or is it the thought that every scientist is united in their deceit of common people, sitting back in their luxurious chairs cackling, wiping their ass with the wads of cash from their latest grant while they adjust their monocles.

"I don't understand it therefore everyone else is lying". Sad.
Chris_Reeve
Oct 17, 2017
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Chris_Reeve
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antialias_physorg
4.6 / 5 (11) Oct 17, 2017
Even if over short time scales, net charge accumulates at the end of the antenna

All the electrons move (and the antenna radiates over the entire length). If it was just the ends then you could put up two metallic points and just connect them by a wire of any shape. While this would also radiate it would give you a different kind of field (2 point fields).

The ends of a wire antenna reflect the electric/magnetic field back (due to large complex wave resistance difference between the wire and the air...Also the reason why you add a terminator in your information transmission lines where you don't want this effect).

If it happens that this reflected field is in sync with the voltage change then you get an additive field (which is what you want because the radiation losses add up - which is the radiation the antenna gives off). You get sync at a multiple of the (half) wavelength.
Chris_Reeve
Oct 17, 2017
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Chris_Reeve
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katesisco
1 / 5 (7) Oct 17, 2017
Whenever the subject of 'gravitational wave' silliness comes up I recall this paper by NASA: A Star With Two North Poles https://www.nasa....les.html
that notes the changes in the star's current sheath --our sun Sol---from one very distinct form to another.
shavera
4.4 / 5 (13) Oct 17, 2017
I'm wondering if gravitational waves will be the next rank up, that is, a rank 3 tensor

You're not entirely off on the wrong track, even if your guess isn't correct. GR, whether gravity or metric expansion or gravitational waves, is still usually described in terms of rank-2 tensors. (look up the "Einstein Field Equations")

However, since the source of gravitation is a rank-2 tensor (the stress energy tensor) if gravitons are real fundamental particles of the curvature field, then they have to be a spin-2 "tensor" boson. The details of all of this are a little foggy in my memory now, but they're discussed to some degree in the 'graviton' wiki page. (It's been a while since I last did these maths, so I don't recall the details)
Chris_Reeve
Oct 17, 2017
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Benni
1.4 / 5 (11) Oct 17, 2017
The LIGO team really needs to explain more clearly & be more definitive about what GRAVITATATIONAL WAVES are.

The casual reader by default assumes that LIGO has proven GRAVITY exists in the form of a WAVE mimicking the Electro-magnetic Wave Spectrum, & not as a GRAVITON, seemingly laying to rest the graviton theory as the source that creates the flux field science labels as GRAVITY.

So far LIGO hasn't distinguished whether gravity is caused by GRAVITONS, or WAVES, or SOMETHING ELSE. Essentially LIGO has proven nothing more about gravity NOW than what was previously suspected, establishing only that locally merging mass creates a change in the DENSITY of an ambient flux field science calls GRAVITY, this change intensifies an existing flux field by increasing it's DENSITY, and that this change in density of a flux field can be measured within our local area of the Universe when instrumentation is sensitive enough to detect the change.

shavera
4.4 / 5 (14) Oct 17, 2017
Ah, now you're back to true form.
LIGO to date has not provided any data to help understand if gravitons exist or their details, as far as I'm aware. Nor does it 'put to rest the graviton theory' since you do not, apparently understand what is meant by a graviton. And again, it's frustrating perhaps that we label so many GR related phenomena with 'gravity' related wording.

What LIGO has supported, along with so many other experiments, is that the maths of GR are valid to explain observations about our universe. The maths of GR also show that gravity is not a "flux field"(one of your many meaningless phrases). Gravity isn't even a force within GR. If you do the maths of a *force-free* body, you'll see that the body moves around masses *as if* it was acted upon by a force. But there's no actual "force" of gravity, 'flux-field' or otherwise.
Benni
1.4 / 5 (10) Oct 17, 2017

Ah, now you're back to true form. the journalist whose first course in science was an Introductory Thermodynamics course you took in Grad School:

The maths of GR also show that gravity is not a "flux field"(one of your many meaningless phrases). Gravity isn't even a force within GR.


The intensity of Electro-magnetic & Gravity Fields are calculated by the Inverse Square Law. Your big problem is your lack of comprehension as to what is meant by the scientific terminology called FLUX. I guess your Introductory Thermodynamics course in Grad School didn't cover this? Probably didn't cover ENTHALPY or ENTROPY either from anything I've seen in your competency in discussing your advocacy for anything other than Perpetual Motion Machines.
Chris_Reeve
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shavera
4.6 / 5 (11) Oct 17, 2017
Benni, please do try to keep up with the class. Gravity "fields" involve no such thing as "flux." They are absolutely unlike EM fields*. EM is a *force*. It involves an exchange of momentum. Gravity DOES NOT OBEY AN INVERSE SQUARE LAW. It only approximately obeys an inverse square law, when the fields are sufficiently weak, but not so weak as to be overly affected by metric expansion.

Within the framework of GR, gravity is not a force. Gravity is not a force. Gravity is not a force. Do you get it yet? Gravity is not a force. Please read any GR textbook. Please read Einstein. Please work out the maths of a force-free body in a Schwarzschild metric. Without any forces, bodies will move in orbits. They will behave *as if* they have a force of gravity, but that apparent force only arises as a consequence of choosing non-inertial reference frames (much like a rotating reference frame produces "centrifugal" forces.
shavera
4.6 / 5 (10) Oct 17, 2017
*: It does turn out that a lot of the maths end up being quite similar between GR and EM, but that's between _GR_ and EM, not "gravity" and EM. Gravity isn't a thing. It's not a field, flux or otherwise. You can approximate some solutions *as if* there was a gravitational field, but they're not universally true. Because again, you absolute dullard, gravity is not a force.
Robert_D
4 / 5 (12) Oct 17, 2017
Chris_Reeve - Duane Gish would be proud of you. https://en.wikipe...h_gallop
Chris_Reeve
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ShotmanMaslo
4.4 / 5 (13) Oct 17, 2017

The casual reader by default assumes that LIGO has proven GRAVITY exists in the form of a WAVE mimicking the Electro-magnetic Wave Spectrum, & not as a GRAVITON, seemingly laying to rest the graviton theory as the source that creates the flux field science labels as GRAVITY.


Causal reader by default assumes no such thing. Only an uninformed and very confused reader such as you assumes such weird things.

Gravitational waves and existence of gravitons is not in conflict at all, quite the opposite. A coherent state of many gravitons is a gravitational wave, and this wave is what LIGO observed.
Chris_Reeve
Oct 17, 2017
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ShotmanMaslo
4.7 / 5 (13) Oct 17, 2017
What does it mean that nobody seems to understand what has been observed?


Of course people do understand. Just a handful of hopeless pseudoscience conspiracy theorists that do not.
eachus
3.9 / 5 (7) Oct 17, 2017
Ouch! I read through the comments before commenting, or at least I started to. Had to use the ignore button, and it would be nice if there was a threading structure that allowed ignoring all chains started by an ignored user.

My question: Has anyone tried to use statistical methods to lift the gravitational waves out of the noise prior to the detection? In other words try to find the signal days or weeks earlier. Now that we know what a neutron star-neutron star collision looks like, it might be possible to use the statistical data to fit a profile to nearby neutron star pairs years or even centuries prior to their merger.

Also does this event kill the model of neutron star mergers as a source for type Ia supernovas? Seems to me it does, since this doesn't look anything like a typical type Ia light curve. Seems like there should be some r process nuclear synthesis with a type Ia. Now that we know what it looks like, can it be teased out of the typical Ia data?
Chris_Reeve
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Chris_Reeve
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Benni
1.3 / 5 (12) Oct 17, 2017
Please work out the maths of a force-free body in a Schwarzschild metric.


Shavo, that introductory course to Thermodynamics you took in Journalism Grad School, what was your final exam grade?

Einstein wrote about the Schwarzschild metric:

"On Stationary Systems with Spherical Symmetry consisting of many Gravitating Masses"

"The essential result of this investigation is a clear understanding as to why the "Schwarzschild singularities" do not exist in physical reality. The "Schwarzschild singularity" does not appear for the reason that matter cannot be concentrated arbitrarily. And this is due to the fact that otherwise the constituting particles would reach the velocity of light.

The problem quite naturally leads to the question, answered by this paper in the negative, as to whether physical models are capable of exhibiting such a singularity." Albert Einstein- Oct 1939

http://www.cscamm...hild.pdf

Chris_Reeve
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Chris_Reeve
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Chris_Reeve
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Chris_Reeve
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ShotmanMaslo
4.7 / 5 (13) Oct 17, 2017
Yet, anyone with a computer and orbit computation or numerical integration software can verify the consequences of introducing a delay into gravitational interactions ..."


Chris unintentionally managed to post something slightly relevant.. Simply introducing a delay into Newtonian gravity does lead to quick decay of orbits. Not so for relativity, because of aberration of field direction.

https://en.wikipe...observer

This aberration compensates for the delay and (almost perfectly) stabilizes the orbits again. But it fails when the masses are accelerating. Which leads emission of gravitational waves and orbital decay. Even Earth orbit is decaying and emitting gravity waves, just very very slowly. For colliding neutron stars or black holes, accelerations are huge and so are GW waves.
shavera
4.5 / 5 (15) Oct 17, 2017
Benni. Please do yourself a favor and work through a GR textbook.

I'm not even talking about black holes. Forget black holes for the moment. I'm talking about simple normal spherical bodies of mass. They are described by the Schwarzschild metric, and any potential "singularities" are within the massive body which would be described by a different metric altogether, so the singularities don't exist. I'm talking about normal bodies like planets producing normal orbits around them because space is curved and there's no force acting on them.

Do you believe Einstein a god? Is he infallible? Did he solve every single problem within GR? No. Even your beloved copy-paste about black holes rests on a conjecture that is unsupported by further argument: " the reason that matter cannot be concentrated arbitrarily" Why, precisely, is this true? What data supports this argument? What observation? What science backs this claim?
baudrunner
4.3 / 5 (6) Oct 17, 2017
@Chris_Reeve - stop copy/pasting content from published works. That is called plagiarism. Putting quotes around the words doesn't change anything. You are not using that content to support any personal comments or statements, just copying and pasting. It is a violation of posting rules.

And for God's sake, why is everyone avoiding saying "shock wave"? It would settle a lot of the dialogue here.

A "gravitational wave" introduces a 'shift' of sorts in the space/time context. If so, then the entire space/time context of the LIGO facility and the whole of reality it occupies must experience this same shift. How is it possible then to stand outside of that shift to detect it? I take it all with a grain of salt.

Question: ..these LIGO guys are supposed to be so smart. Can they answer the question of what do we witness from within our own inertial frame of reference when ten pounds of TNT explosive detonates while traveling in space at light speed?
antialias_physorg
4.7 / 5 (15) Oct 17, 2017
why is everyone avoiding saying "shock wave"?

Because it isn't one?
https://en.wikipe...ock_wave
There's not much point in using a word that would just be plain wrong.

How is it possible then to stand outside of that shift to detect it?

Because the shift is not uniform. You can send a laser along one path which experiences squeezing while the other path experiences elongation, then overlay the two and get an interference signal.
https://en.wikipe...peration

Can they answer the question of what do we witness from within our own inertial frame of reference when ten pounds of TNT explosive detonates while traveling in space at light speed?

Erm..whut? That sentence makes no sense. On several levels (content and grammatical)
antialias_physorg
4.6 / 5 (11) Oct 17, 2017
the reason that matter cannot be concentrated arbitrarily" Why, precisely, is this true?

It doesn't even make sense when you think about how mass remains stable (exchange of gluons and W/Z bosons respectively for the strong and weak nuclear force)...and that this doesn't work once you go within the the event horizon because the stuff just can't reach the counterpart it's supposed to interact with.

Which basically says to me that once inside a BH what you get is total conversion to energy (photons)...which can superpose quite nicely all they want.
RealityCheck
3.3 / 5 (7) Oct 17, 2017
@Chris_Reeve.

Mate, you're even pissing me off with your spam. Please control yourself, or you are just as unheeding/useless as those who you are directing your spam at. You KNOW I have always defended your right to post on-topic stuff that informs the discussion; but this latest 'spam burst' from you is too far, mate! I am now being like "The Canary in the Coal Mine" for you here, Chris; and if your spam is 'killing' even my 'tolerant air', then you can assume with great confidence that it is doing even more damage to your own 'cause', whatever it is now that you are spamming wholesale but making no contribution of your own knowledge/arguments to on-topic discussion/understanding. Can you take this 'canary's advice and COOL IT with the spam? Please? As it will allow more coherent/useful discussion on the science merits of theory claims etc involved in this very important topic (which I am observing closely). Thanks in advance for your understanding/cooperation, Chris. :)
Benni
1.7 / 5 (11) Oct 17, 2017
Do you believe Einstein a god? Is he infallible? Did he solve every single problem within GR?


Einstein certainly solved a lot more problems than he created, then someone like Schwarzschild comes along & tries to apply his black hole math to GR & is soundly rebuffed by the author, and that leaves you very unhappy.

But why should I care Shavo that you're unhappy Einstein published "On Stationary Systems with Spherical Symmetry consisting of many Gravitating Masses" ? After all, your sole standing in the realm of scientific endeavor is an introductory course in Thermodynamics you took in Journalism Grad School. Gee, did it even have any math content to it?

"the reason that matter cannot be concentrated arbitrarily" Why, precisely, is this true?
.......if you'd read the paper, you could figure it out? Oh darn, those pesky Differential Equations again & the limitations of the 2nd Law of Thermodynamics imposes on perpetual motion math.
currentevents
1.4 / 5 (11) Oct 17, 2017
This is nothing more than LIGO trying to ride the coattails of Fermi's GRB observation and shoehorn in their supposed gravitational wave detection. This supposed loudest of all GW detections started out as a low-latency signal from only one of the LIGO detectors, so low it was ignored! The LIGO team went back and massaged the data to get it to better fit the Fermi gamma-ray observation, INTEGRAL timings, and then the subsequent observations of what is obviously a supernova.
shavera
4.3 / 5 (12) Oct 17, 2017
Literally every GR class ever includes the Schwarzschild metric. Even if you are so thickheaded you won't accept the notion that black holes exist, the Schwarzschild metric is the description of space-time around a spherically symmetric mass. You don't deal with any of the singularities in such cases. Again, even if you refuse to believe in black holes, this metric provides the solution to the EFE for spherically symmetric masses. So quit avoiding the actual point, that within the framework of GR, gravity is not a force, it doesn't obey the inverse square law, and it certainly isn't a "flux field."
Benni
1.5 / 5 (8) Oct 17, 2017
Literally every GR class ever includes the Schwarzschild metric. Even if you won't accept the notion that black holes exist


It's called spinning Perpetual Motion into the mainstream of the Fundamental Laws of Physics, and just like your credentials in scientific endeavor, phony.

What was the final grade you got in that introductory course to Thermodynamics you told us you took in your journalism grad school?

shavera
4.6 / 5 (10) Oct 17, 2017
It's called spinning Perpetual Motion into the mainstream of the Fundamental Laws of Physics

See, you can't address the real question. You can't address the fact that you don't understand even basic GR. You can copy paste stuff you found on the internet that you don't understand like a high school sophomore writing a term paper.

As for the rest of my supposed "credentials" no one should believe anyone's credentials online. You don't honestly think anyone believes your "iamverysmart" nuclear engineer story, do you? You know we're mocking you and laughing about how silly you sound when you brag about differential equations as if that's the pinnacle of knowledge right? How you caps lock SCIENCE SOUNDING WORDS as if that made your argument for you? You just look like a fool. A poor delusional fool making up stories and puffing their chest to impress other people that you know better than Meisner, Thorne, Wheeler, and others.
Da Schneib
4.4 / 5 (7) Oct 17, 2017
Re antennas, I figured it out. The voltage is an approximate sine wave in the antenna, which means the electrons are constantly accelerating; as in all inductive loads, the current follows the voltage (the mnemonic for this is ELI the ICEman). Thus the electrons are always accelerating because the voltage is always changing; this generates the waves all along the antenna.

@shavy is right; it's the second derivative of position for both EM and gravity.

@antialias, yes, you can also look at it that way but it doesn't explain why the electrons radiate all along the antenna not just at the ends. My visualization does that part better.
Da Schneib
4.5 / 5 (8) Oct 17, 2017
@eachus, good questions.

Keep in mind this is the very early days of GW detection, and already they've been able to identify GWs fast enough to relate them to GRB detections, which are very short term. In addition because there are only a few GW observatories precise triangulation is not possible. They are actually doing very well in coordinating these observations in optical, X-ray, gamma, radio, and gravity considering we've only been able to do this for a few years.

As far as detecting the GWs from binaries that are not yet close enough together to merge, the noise is too strong. It's only at the very end that the signal gets strong enough to overcome the noise floor.

Regarding the neutron star merger model for Type Ia SNe, this is only one detection and can't kill any hypothesis at this point.
Mimath224
5 / 5 (4) Oct 17, 2017
@shavera
I'm wondering if gravitational...

You're not entirely off on the wrong track, even if your guess isn't correct. GR, whether gravity or metric expansion or gravitational waves, is still usually described in terms of rank-2 tensors. (look up the "Einstein Field Equations")

However, since the source of gravitation is a rank-2 tensor (the stress energy tensor) if gravitons are real fundamental particles of the curvature field, then they have to be a spin-2 "tensor" boson. The details of all of this......

Thanks for the reply. I'm obviously not experienced in actually using GR eq. but have 'acquainted' myself with them (lay mathematical, textbook on GR, the MTW giant also (Ha!)). In over simplistic terms I thought a rank 2 tensor, that is a gradient of a gradient, giving the topology in the presence of mass (not including BH here). If there were a disturbance would it be like 'ripples on a ripple' which might add to E/S tensor. Just a thought that's all.
Benni
1.4 / 5 (10) Oct 17, 2017
You don't honestly think anyone believes your "iamverysmart" nuclear engineer story, do you? You know we're mocking you and laughing about how silly you sound when you brag about differential equations as if that's the pinnacle of knowledge right?


Maybe you would like to tell us what you learned in that Introductory Thermodynamics course you took in Grad School that you imagine makes you such an expert Science Professional even though you only have a degree in journalism?

you brag about differential equations as if that's the pinnacle of knowledge right?


No, DEs are not the "pinnacle", they're where you start or you can't get hired by anyone to do my job, yeah, just a few steps above the bottom of a much higher arching pinnacle.
Whydening Gyre
5 / 5 (4) Oct 18, 2017
...
Question: ..these LIGO guys are supposed to be so smart. Can they answer the question of what do we witness from within our own inertial frame of reference when ten pounds of TNT explosive detonates while traveling in space at light speed?

Um... a really Lo-o-o-o-o-ng, skinny explosion trail...?
eachus
4 / 5 (4) Oct 18, 2017
As far as detecting the GWs from binaries that are not yet close enough together to merge, the noise is too strong. It's only at the very end that the signal gets strong enough to overcome the noise floor.


You miss my point. Generate the signal that you suspect is beneath the noise floor. Then: [H0:] all noise, [H1:] signal plus noise. By looking for a very specific signal you can increase the discrimination of your observation. You are not testing for just noise vs. noise plus any signal, you are testing for noise vs. noise plus this signal. For example if you suspect a signal at 481.3 Hz from this azimuth and elevation all noise that can't be part of that signal is irrelevant. (I suspect the real problem is that the local binary pairs are at too low a frequency for LIGO.)

If you haven't figured it out already, I'm a retired statistician. Even a few years ago I would have loved to try and dig "the music of the spheres" (all local binary pairs) out of the noise.
antialias_physorg
5 / 5 (7) Oct 18, 2017
@antialias, yes, you can also look at it that way but it doesn't explain why the electrons radiate all along the antenna not just at the ends. My visualization does that part better.

Well, that's just basic electrons being accelerated. An accelerated charge always radiates. Here's a good writeup of why:
https://thecuriou...diation/

You can also argue from a moving charge to an accelerated charge instead of from a stationary charge to an accelerated charge as in the above link. A moving charge creates a magnetic field. An accelerated charge therefore creates a changing magnetic field (proportional to the velocity at any point in time) - which in turn induces a changing electric field...when you have a time variable magnetic and electric field you have radiation.
Chris_Reeve
Oct 18, 2017
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Chris_Reeve
Oct 18, 2017
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shavera
4.4 / 5 (13) Oct 18, 2017
Maybe you would like to tell us what you learned in that Introductory Thermodynamics course you took in Grad School that you imagine makes you such an expert Science Professional even though you only have a degree in journalism?

Yeah, but see, I never said any of this. This is all stuff you've made up to fit some delusion about who I am. Whereas we can see you post in every thread about how you're supposedly a nuclear engineer who understands the magical mystery of differential equations.

In passing, do I mention textbooks or materials I've encountered in my life, in grad school? Sure. But I know literally no one should believe me if I was to claim some educational or employment background as if that was justification for my comments. It's the freakin' internet dude. Everyone lies about that kind of stuff. Which is why I won't bother posting my background here and now, because it's not relevant to my arguments which you have consistently avoided addressing.
shavera
4.2 / 5 (15) Oct 18, 2017
eachus: I'm sure the expert physicists working at this collaboration know a thing or two about statistical techniques to pull signal out of noise. I mean, of all the experiments in the world, Gravitational wave detection is very likely the experiment where that is absolutely the most important skill to have to do any of the work. It was thought to be impossible for so long because of the high noise floor.

So yes, I'm sure that they know what they're doing when it comes to signal detection.
antialias_physorg
4.6 / 5 (11) Oct 18, 2017
A bit of a writeup how to go about filtering gravitational wave data out of the noise (skip to section "Statistical Theory of Signal Detection" further down on the page)
https://www.ncbi....5253919/

The way I read it it's a template matching approach (i.e. they know roughly what kind of signal they're looking for) and then calculate a ratio of "likelihood that signal is present" vs "likelihood that signal is absent".

SNR is quite low, so I figure the template has to be quite constrained (but that's just my conjecture)

Chris_Reeve
Oct 18, 2017
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Benni
1.4 / 5 (11) Oct 18, 2017
In passing, do I mention textbooks or materials I've encountered in my life, in grad school?


So now you're admitting to us you didn't even take the course?

But I know literally no one should believe me if I was to claim some educational or employment background as if that was justification for my comments. It's the freakin' internet dude. Everyone lies about that kind of stuff.


So now you admit you lied about taking that Introductory Thermodynamics course in journalism grad school? All you did was look at the cover of a textbook of some kind?

Which is why I won't bother posting my background here and now, because it's not relevant to my arguments
More precisely because you don't want to embarrass yourself in light of the fact that you can't even hold a cogent discussion about anything dealing with Fundamental Laws of Physics, you're intellectually incapable of engaging in those kinds of discussions which is why you default to Perpetual Motion.

shadybail
1.3 / 5 (8) Oct 18, 2017
Aside from various grants and atta boy awards are there any practcial benefits from this research? Should I buy a gravitational wave home detector? Perhaps even a 'Mr. Neutron' gravitational wave coffee maker will be available. Seriously now, how can perpetual motion really exist?
shavera
4.6 / 5 (10) Oct 18, 2017
practcial benefits from this research?

I wouldn't say there are direct practical benefits. But realize that all of the grad students doing the analysis are learning critical data-science skills and signal analysis techniques. Many of these grad students leave physics following their degree and enter other fields, and they take these skills and knowledge with them, improving other things. Medical imaging, for instance, was improved by astronomers and particle physicists applying their techniques to other fields.

gravitational wave home detector

If you already own several square km of property, sure, why not? ;)

Seriously now, how can perpetual motion really exist

Gravitational waves have nothing to do with perpetual motion. They're just periodic changes in how you measure distances and times.
eachus
4.4 / 5 (7) Oct 18, 2017
A bit of a writeup how to go about filtering gravitational wave data out of the noise (skip to section "Statistical Theory of Signal Detection" further down on the page)
https://www.ncbi....5253919/


Excellent survey paper, I think I remember reading it at the time. (I was working on similar techniques for radars.)

The way I read it it's a template matching approach (i.e. they know roughly what kind of signal they're looking for) and then calculate a ratio of "likelihood that signal is present" vs "likelihood that signal is absent".

SNR is quite low, so I figure the template has to be quite constrained (but that's just my conjecture)


Good summary. The difference between what I am advocating and the techniques in the paper is that I am asserting that now that we know what the signals (from nearby pairs) should look like, we can assume that the signals from known pairs are present, and test for the collective effect.
eachus
4.4 / 5 (7) Oct 18, 2017
(Ran out of bytes)

Prior to the detection of an unambiguous signal of an inspiral, assuming the presence of the signal or signals would be silly. Now that we have seen a signal, and it matched expectations, rather than searching for some unknown signal, we can take information from astronomical observations and test for the presence or absence of the (now known) signals. Once past that, the individual sources can be pulled out one at a time to look for deviations from expectations. A good example would be if a particular pair had planets. That could perturb the signal enough that it did not match the expectation.

In short, now that we know that gravity waves exist, and what they look like when generated by neutron star pairs, we can improve the search by feeding the known data into our assumptions, rather than using an H0 of no signal.
antialias_physorg
5 / 5 (10) Oct 18, 2017
Aside from various grants and atta boy awards are there any practcial benefits from this research?

was there any benefit from research into how atoms work? Well, yeah, we got nuclear power out of it eventually.
Was there any benefit to researching lasers (an effect which Einstein called interesting but not of any practical use)?Well, yeah, there's hardly anything that does *not* use lasers today.
...
Practical applications don't come next day. But they always come (and mostly in totally unexpected ways).

that I am asserting that now that we know what the signals (from nearby pairs) should look like, we can assume that the signals from known pairs are present

They already (roughly) knew what the signals would look like (from simulation). That's how the template was constructed. So there's no need to assume it's present. (The detection algorithms are tested by artificially injecting the template into a pure noise signal)
Da Schneib
5 / 5 (5) Oct 18, 2017
As far as detecting the GWs from binaries that are not yet close enough together to merge, the noise is too strong. It's only at the very end that the signal gets strong enough to overcome the noise floor.


You miss my point. Generate the signal that you suspect is beneath the noise floor. Then: [H0:] all noise, [H1:] signal plus noise.
This is a common misconception. The problem is that the noise spectrum swamps the signal. You are expecting the noise to be constant and it is not; because of this signal cannot be confirmed; it might just be noise. Until the noise floor is swamped by the signal you cannot expect to reliably detect the signal. To put this another way, the noise can decrease as well as increase and if it does it will tank the signal.
Da Schneib
4.3 / 5 (6) Oct 18, 2017
@eachus, even though (and in fact because) it's a common misconception, it was still a good question. Please don't misinterpret my response as dismissive; many people ask this and a good answer is important to clear up these doubts.

The really important part here is that we've now developed templates that can allow the detection of various types of GW excursions that rise above the noise floor quite quickly due to the detections we've already characterized; this will help with coordination of observations in different regimes like visible, X-ray, gamma, radio, and GW over short timespans, and this will be considerably improved as GW localization/triangulation improves as more GW observatories come online. This is the work of the grad students @shavy referred to above.
Da Schneib
4.3 / 5 (6) Oct 18, 2017
@eachus, it's notable that the detections in optical, gamma, and GW have shown that this apparent neutron star merger made a "kilonova," not a stronger supernova, according to our measurements. You will find more information here: https://phys.org/...nal.html

So maybe neutron star mergers are indeed not powerful enough to account for Type Ia SNe, or at least one of them isn't.
Zzzzzzzz
3.7 / 5 (9) Oct 18, 2017
We need a moderator here. The spam is really annoying.


I"ve ignored the fecal regurgitators for a long time now. Believe me, its much better that way.
Whydening Gyre
5 / 5 (8) Oct 18, 2017
This again: "This is ... obviously a supernova."

Notice no interest here at all on what sounds like yet another very strong line of attack on these claims. Classic Sharpshooter Fallacy.

It's apparent that this group barrels ahead with whatever new "facts" emerge from the "experts", without ever really asking difficult questions.

The volume of critique on these topics is by now so large that nobody here even has a handle on it anymore. Always the fault of the person who posts, always dismissal, ridicule or censorship as only reaction.

And the reason for that is - this is a "science news" aggregation site designed to appeal to a broad range of people, not just insiders of a particular field...

Da Schneib
4.3 / 5 (6) Oct 18, 2017
So who supposedly said "this is... obviously a supernova?"

Not the article, and not anybody who I don't have on ignore. Is this a spurious claim? Or do we have two nutjobs having a food fight?
antialias_physorg
5 / 5 (6) Oct 19, 2017
Just a bit off topic:

What I also find noteworthy about this event: We now know with certainty that gravity moves at the speed of light (or very close to it)

With the previous observations of gravitational waves the speed could be inferred (from the lag between detectors)...and, of course, from the math on which this is based it seemed a reasonable assumption.
...but with the actual visual detection of the event we can now be sure.
Ralph
3.3 / 5 (7) Oct 19, 2017
We need a moderator here. The spam is really annoying.

Indeed. CR is again attempting to co-op the thread with his non sequitar BS...

What is the source of CR's garbage? I strongly suspect he/she/it is being paid to disrupt this board.
antialias_physorg
5 / 5 (6) Oct 19, 2017
I strongly suspect he/she/it is being paid to disrupt this board.

The question then is: Why? What could possible be the point of sabotaging a comment section?

A rival science aggregation site for the ad traffic? Unlikely, as the comment sections is only frequented by a miniscule percentage of readers - so the effect is zilch.

Convincing laymen of his insane theories? Since none of the laymen on here have any scientific 'clout', whatsoever the effect of his rants are nil in that regard.

It certainly has no impact on any of the scientists that author the originals (as they are almost certainly unaware that there is a PR blurb about their papers on some internet site...they have the original paper - and so does anyone who is actually working in the respective fields.) There's hardly a point why any of these would ever show up here.

Other than some terminally pathological Dunning Kruger and narcissism I'm out of ideas.
Chris_Reeve
Oct 19, 2017
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Chris_Reeve
Oct 19, 2017
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Chris_Reeve
Oct 19, 2017
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Chris_Reeve
Oct 19, 2017
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ShotmanMaslo
3.8 / 5 (10) Oct 19, 2017

What does scientific clout have to do with anything at all here when it is plainly obvious that this group ignores all criticisms?


Your so called "criticisms" are not scientific, they are on the level of a village idiot refusing to accept that the Earth is round. In fact there are entire internet communities believing just that, and many other demonstrably incorrect things. Ignoring or ridiculing such pseudoscience is the only correct course of action. Be open-minded, but not too open-minded or your brain falls out.
434a
4 / 5 (8) Oct 19, 2017
I'm out of ideas.


Religion, somewhere at the bottom of his delusions is creationism, not even the slightly excusable deism - hence the anti BB rhetoric - just out and out "god did it" à la old testament.
He sees modern cosmology as a direct threat to this fundamental tenant of his psyche.
He has then created a series of ever more complex delusional states designed in every way to distort what his rational brain is telling him is the truth.
Like most people suffering from this form of psychosis he then feels the need to gather support for the delusion by co-opting people into the delusion. "How can I be mad if other people believe the same thing as me?" he intones. Conspiracy theorists have a very similar pattern of behaviours. Part of the progression of this illness is the need to convert non-believers. Now in his mind there is a direct equivalence between his religious belief and his pseudoscience. Therefore conversion to EU is another soul saved.
434a
4.1 / 5 (9) Oct 19, 2017
Why here? What better place to preach to the heathens and sinners? You also have people who come here questioning their religious faith, looking for answers in science. He offers a pseudoscience that he believes will ultimately allow that lost soul to reconcile itself back to god.

An added benefit is you also get rewarded for suffering and martyrdom undergone in this life.
The attacks on his pseudoscience are one in the same thing as attacks on his religious convictions as far as he is concerned. It's all a win.
Sad really, anyone willing to put that amount of effort and energy to support such a state of mind could have probably done something really useful with it.

Chris_Reeve
Oct 19, 2017
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Mimath224
5 / 5 (1) Oct 19, 2017
@antialias_physorg
I strongly suspect he/she/it is being paid to disrupt this board.

The question then is: Why? What could possible be the point of sabotaging a comment section?....
Convincing laymen of his insane theories? Since none of the laymen on here have any scientific 'clout', whatsoever the effect of his rants are nil in that regard.
Other than some...

While I might agree that layman don't have any scientific 'clout' I don't think that's a good reason to say '..his rants are nil...' As a layman in scientific matters doesn'tmean I am a layman in other topics. Topics where I am not considered a layman, might require other disciplines, among them logical thought and common sense, guided by physics etc.Look at the volume of CR comments...that tells us something straight away. Amateurs and laypeople have helped science before and continue to do so, in that way have some 'clout' albeit very little. Maybe you are allowing CR to upset you, why not just ignore CR?
Chris_Reeve
Oct 19, 2017
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Chris_Reeve
Oct 19, 2017
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434a
4 / 5 (8) Oct 19, 2017
There's even a religious book - Thunderbolts, a prophet/martyr jebus figure in Hannes Alfvén - though, if alive he would be an unwilling participant one suspects - even a possible Peter the Denier or Judas Iscariot in the form of Carl-Gunne Fälthammar. And of course what religious delusion would be complete without beelzeinstein the great deceiver. There's three of four doctorates worth of cases on this site but this one is special.
Chris_Reeve
Oct 19, 2017
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Chris_Reeve
Oct 19, 2017
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Chris_Reeve
Oct 19, 2017
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434a
4 / 5 (8) Oct 19, 2017


Hannes Alfvén, Double Layers and Circuits in Astrophysics, IEEE Transactions on Plasma Science, Vol. PS-14, No. 6, December 1986, p.779


Could you do me a favour? Could you record your pulse before, during and after writing say 200 posts?
Should take no more than 1 hour of your time. A fitbit would do. I suspect there is a significant degree of obsessive compulsive disorder here. We should see your pulse rate falling whilst posting, the itch being scratched so to speak. I think you would also find typing gives a longer term relief rather than the quick high you get from cut and paste.
Qualitative analysis is prone to subject bias but if you could also record a score of 1 - 5 (1 low 5 high) on how you feel before and after each post that would be great. Pop them up here when you're done and we'll take a look.

Other people seem to be participating, isn't that lovely.
Captain Stumpy
4 / 5 (8) Oct 19, 2017
@chris/hannes the pseudoscience eu cult idiot
... there is no concern that the people here make erroneous statements about the electricity in space debate
1- because there is no "debate": there is science and there is your religious eu perspective

2- how is any of your perceived "debate" supposed to be comprehended after you spammed the site with 72 messages in this thread alone?

3- considering you've posted so much copy-pasta that is not only irrelevant, but completely off topic, the problem is obviously one of your fanatical beliefs, not any perceived erroneous statements from science

4- most importantly: science doesn't answer to you or any authority. if you see something wrong, then it can be easily changed by ...*gasp*... evidence!

if you had actual evidence of "erroneous" statements that can be back by hard validated science, you would be the nobel winning savior of the eu cult

that's why you need gish gallop and sock puppets - because you don't have evidence
shadybail
3 / 5 (4) Oct 19, 2017
As for the reasons THAT poster is making multiple postings, I don't know. However, as a newbie poster here I can offer my observation. Too many of the posts have been 'cut and paste' (To be honest, cutting and pasting annoys me. It's overuse makes it become like a cliche') In additon, the sheer volume of the posts coming one after another is disconcerning. The net effect on me is that I skip the majority of his posts. He still has credibility because I'm a novice in this field (if that at all) but it seems like the poster is trying to 'post over' everyone else. This can be distracting for me and many of the readers.
Chris_Reeve
Oct 19, 2017
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434a
4 / 5 (8) Oct 19, 2017

You were just shown to be misinforming the others around you, and you then cast ME as the problem. Have you considered that you guys are actually encouraging each other to lie to one another?


You see this is the effect of too much Dopamine.

Dopamine is the neurotransmitter implicated in the reward response. You normally get it after doing something pleasurable or dangerous and getting away with it.

You've taught your brain to give you a hit each time you post - content doesn't matter just the act seems to be enough for you.

The problem is too much Dopamine has been implicated in ADHD, Parkinson's disease, bi-polar, depression, schizophrenia and many forms of addictive behaviour - bad as it's a self reinforcing pathway.
I'm sorry to say you're showing all the symptoms of an addict fueled by domaine.
This may be the underlying neurochemistry that has led you to your delusional state of mind.
It's treatable, abstinence from the stimulus can very effective.
Chris_Reeve
Oct 19, 2017
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antialias_physorg
4.9 / 5 (9) Oct 19, 2017
As a layman in scientific matters doesn't mean I am a layman in other topics

the point i was trying to make is this:
Researchers aren't going to stop their research or alter it one bit because of his rants - even if he managed to convince anyone of his crank ideas (which he hasn't so far and which and which he will not, ever, in the future), because such people just don't matter when it comes to who decides what to research

.Look at the volume of CR comments...that tells us something straight away.

Yep. Brevity is the soul of wit...Read: he's as dimwitted as they come.

Maybe you are allowing CR to upset you, why not just ignore CR?

I've had him on ignore since the day he registered. He doesn't upset me one bit. (I was just replying to Ralph, whom i don't have on ignore)...CR just inconveniences me as I have to scroll past all the ignored posts...but that's about all the impact he has on my life.
Captain Stumpy
4 / 5 (4) Oct 19, 2017
@shadybail
As for the reasons THAT poster is making multiple postings, I don't know
you don't need to be a scientist to see the trend with chris/hannes
one only has to wonder why the need to have sock puppets and spam with gish-gallop
https://en.wikipe...h_gallop

He still has credibility because I'm a novice in this field
some advice about topics that don't require professional training in any field:

1- examine the evidence (source material is important - if it's not in a reputable peer reviewed source it's not science. period. full stop)
claims are not equivalent to studies in science

2- repeating a debunked claim is lying (to self and others)
that is religion (or pseudoscience), not science

3- history is find to know, but it doesn't necessarily apply because things change

4- https://en.wikipe...c_method

there are sources that debunk chris/hannes claims, like this: http://pppl.gov/

experiment trumps belief

RogueParticle
4.6 / 5 (11) Oct 19, 2017
@CR
Yet, Relativity is certainly the most criticized theory ever
It certainly is criticized, mostly by those who don't understand it. Par for the course, and such concerns are like water falling from a duck's back: utterly ineffectual.

Several scientists also criticize GR, but usually from a position of having become familiar with the theory and its' math, and who would seek to either further develop it, alter it, or supplant it with something generally (pun intended) even more exotic: MOND, Brans-Dicke, loop quantum gravity, Kaluza-Klein, M-theory. Watch this space-time!
baudrunner
1.5 / 5 (8) Oct 19, 2017
Because the shift is not uniform. You can send a laser along one path which experiences squeezing while the other path experiences elongation, then overlay the two and get an interference signal.
..that is just about the most insane bit of mainstream psuedo-science indoctrination that I have ever read. I am insulted that I am expected to believe those clowns. Sure, draw a couple of lines perpendicular to one another on a page and pass an imaginary line over it perpendicular to and in the direction of one of the lines isn't the kind of low-fallootin' logic I'm prepared to buy right now. As I read it, you're telling me that space and time temporarily increase the distance between them during that "gravitational wave" detection, you know.
shadybail
4.2 / 5 (5) Oct 19, 2017
@Captain Stumpy

Thank you.
RealityCheck
1.6 / 5 (7) Oct 19, 2017
Please let's forget the 'feuds', everyone. :)

Now, can everyone address themselves to objectively and calmly considering/answering for themselves the following:

- How can a LIGO setup be 'tuned/tested for a 'template' if it is always embedded in a 'spacetime' continuously 'ringing' with gravitational waves from near and far and is hence NOT able to be 'isolated' for test signal injection/analysis procedures?

- Is the terminal merging "Ringdown" signal similar for Neutron Star Binary and Black Hole Binary mergers?

- Why, in all the YEARS since LIGO activated, did NO signal from merging NSs and/or Bhs 'detected' in our/nearby galaxy(s)? As there must have been many more relatively near source NS binary mergers than distant BHs mergers supposedly detected from OVER a BILLION lightyears away.

- How can gravitational 'shock waves' be generated? As ONLY FASTER-THAN-LIGHT MOTION in 'spacetime medium' could create such waves (as per CERENKOV Radiation physics/principle).

Ok?
shavera
4.7 / 5 (13) Oct 19, 2017
1) you're currently awash in a "ringing" electromagnetic field from all sorts of sources near and far. But the ones that are far enough are just contributing noise. That's how you still hear a radio signal from one specific station. Same deal with GW. There's some noise floor, but the signals they're finding are rising above that noise.
2) I don't know, let that to someone else to answer
3) Detectors take a long time to shake down and tune. That noise floor in 1 (though most of the noise is just physical waves (vibrations) was really hard to overcome. I think we only have like 3 or 4 detections of anything right now, so, let's just be patient now that signals are coming in. Remember the early days of exoplanet findings? every few months a single new planet? Now they come in huge batches from exoplanet surveys.
shavera
4.7 / 5 (13) Oct 19, 2017
4) It's not really a "shock wave." And it doesn't require faster-than-light motion either. GR says that all forms of energy contribute to how space-time curves. That means how bodies are moving relative to each other is a kind of energy, and that motion has its own curvature it provides. When those bodies are accelerated (as in orbiting each other), the curvature solution behaves like a wave equation. And it also causes the bodies to lose velocity and spiral in toward each other. When they collide, they go from being 2 separate orbiting bodies to 1 spinning body, and that transition is the peak of those waves.

But, as far as I'm aware, we've no reason to believe these waves travel faster or slower than c. (and some good arguments for why they travel *at* c)
RealityCheck
1 / 5 (3) Oct 19, 2017
@shavera.

Thanks for your quick and polite replies, mate; much appreciated! I will let other intending respondents have a few days to consider and answer those points, as well as consider further implications etc, before I respond to your replies. I hope that's OK with you? That way everyone has the chance to get onto the same page and hopefully thereby minimize cross-purpose exchanges, duplications and misunderstandings which have in the past only led to confusion and ill feelings etc. IN any case I think I shall be busy for a couple of days off-line, so it's probably as well not to try and rush/squeeze-in my further responses on what transpires from others. Thanks again, mate. Bye for now. :)
Kweden
4.2 / 5 (5) Oct 19, 2017
@baudrunner
Because the shift is not uniform. You can send a laser along one path which experiences squeezing while the other path experiences elongation, then overlay the two and get an interference signal.
...... As I read it, you're telling me that space and time temporarily increase the distance between them during that "gravitational wave" detection, you know.

It is not space AND time, it is spacetime. A variable principle required for Einstonian relativity mathematics. Also, whoever you quoted is correct enough that a laser or light beam etc, does get stretched and elongated by a gravitational wave. Gravity affects all electro magnetic energies. It is even possible to bring light to a complete standstill--has been done (but not with a gravitational wave, it could certainly do it though, as one explanation for a black hole).
Kweden
1 / 5 (1) Oct 19, 2017
@baudrunner
Because the shift is not uniform. You can send a laser along one path which experiences squeezing while the other path experiences elongation, then overlay the two and get an interference signal.
...... As I read it, you're telling me that space and time temporarily increase the distance between them during that "gravitational wave" detection, you know.

It is not space AND time, it is spacetime. A variable principle required for Einstonian relativity mathematics. Also, whoever you quoted is correct enough that a laser or light beam etc, does get stretched and elongated by a gravitational wave. Gravity affects all electro magnetic energies. It is even possible to bring light to a complete standstill--has been done (but not with a gravitational wave, it could certainly do it though, as one explanation for a black hole).
Da Schneib
4.3 / 5 (6) Oct 19, 2017
I'll take on the one @shavy didn't get:
Is the terminal merging "Ringdown" signal similar for Neutron Star Binary and Black Hole Binary mergers?
Yes, and it's not just the ringdown but the terminal inspiral that's similar. What's different is the magnitude and the timing. Since neutron stars aren't as massive and dense as black holes, the inspiral and ringdown signals don't get as fast, and they don't rise as far above the noise floor, thus both limiting the frequency and shortening the range at which the signal can be detected.
Da Schneib
4.5 / 5 (8) Oct 19, 2017
I also think @antalias' point about now knowing that gravity moves at c is excellent. And I'll make a similar one: another thing we now know is that at least some GRBs can emerge from neutron star mergers. Both of these are valuable pieces of information.
Mimath224
5 / 5 (5) Oct 19, 2017
@Da Schneib, shavera or other; I am not sufficiently knowledgeable to know what precisely the article says has been measured from analysis of the signals. Has /is the chirp mass been/being calculated? Perhaps some here can help me on this one. Thanks in advance.
Da Schneib
4.5 / 5 (8) Oct 19, 2017
Detection of GW170817 was accompanied within 1.7 seconds by detection of GRB 170817, and follow-up observations of NGC 4993 showed a typical "afterglow" phenomenon well known from other GRBs in the optical spectrum during the next 24 hours. The locations of the GW, the GRB, and the optical detections overlap. You can check out the various instrumental detections in the Wikipedia article on the GW detection here: https://en.wikipe...GW170817

The exact details of the chirp mass and the estimated masses of the bodies are also available in that article.

Of interest also are the spectral results which indicate that a very great deal of heavy metal was created at the same time; the best estimate is above 15 thousand times the mass of the Earth.

What's really important about this is the near-simultaneous detections by multiple different instrument types. Because neutron stars aren't contained within event horizons, this is a much more informative event.
Da Schneib
4.5 / 5 (8) Oct 19, 2017
This one is pretty much the death of any arguments about whether GW observatories "work" or not. When you see the same thing with over 70 instruments over a wide variety of detection methods, it's pretty much a fact at that point. It's impossible given the wealth of data from totally separate methods, sites, teams, and disciplines to conclude that deniers are anything but #physicscranks.
Whydening Gyre
5 / 5 (3) Oct 20, 2017
- Why, in all the YEARS since LIGO activated, did NO signal from merging NSs and/or Bhs 'detected' in our/nearby galaxy(s)? As there must have been many more relatively near source NS binary mergers than distant BHs mergers supposedly detected from OVER a BILLION lightyears away.

Ligo is not a "pointable device. It is fixed, so there is a certain amount of planetary alignment involved...
- How can gravitational 'shock waves' be generated? As ONLY FASTER-THAN-LIGHT MOTION in 'spacetime medium' could create such waves (as per CERENKOV Radiation physics/principle).

CHerenkov radiation only applies to electrons moving in some dialectric medium other than space, such that they move faster than the PHASE speed of light in that medium. It doesn't require physical motion master than light to generate a shock wave...
Da Schneib
4.5 / 5 (8) Oct 20, 2017
For once the title is not hyperbolic or overblown; this is truly the discovery of a lifetime, and this is a transformational event in both astrophysics and cosmology. We found out in a brief couple of seconds many important facts about how the universe works. The Nobel Prize for the first gravitational wave detections was well deserved and there can be no more question about it. Congratulations to the thousands of members of the astrophysics community who contributed to this pretty much unprecedented event.
ShotmanMaslo
4.4 / 5 (7) Oct 20, 2017
How can gravitational 'shock waves' be generated?


Electromagnetic waves are generated by accelerating electric charges. Analogously, gravitational waves are generated by accelerating masses. In a way, mass is the "charge" of the force of gravity. Every accelerating mass generates gravity waves. Moving your finger generates gravity waves, too. They just have very small amplitude.
Da Schneib
4.4 / 5 (7) Oct 20, 2017
It's important to differentiate between waves and shock waves. A shock wave occurs in a fluid when it is disturbed by an object moving faster than the speed of sound in that fluid. The term is appropriate when used to describe plasma phenomena among other things and has been used on this forum for such, but not when describing gravitational waves or EM waves since there is no fluid involved.
Mimath224
5 / 5 (5) Oct 20, 2017
@Da Schneib Thanks for the info, much appreciated.
Da Schneib
3.7 / 5 (3) Oct 20, 2017
If you're talking about SVT, you'd need to work out what that would mean for shockwaves in a superfluid. I'm certainly not trying it.
antialias_physorg
5 / 5 (8) Oct 20, 2017
Why, in all the YEARS since LIGO activated, did NO signal from merging NSs and/or Bhs 'detected' in our/nearby galaxy(s)?

1) Mergers are rare.
2) For the initial years LIGO wasn't sensitive enough. Only with the recent upgrade did that change

You can see an image of the sensitivity here:
https://en.wikipe...urve.png
Note how LIGO just barely scratches the field where something can be detected? Only events that are of that very specific type can be seen. There are likely a lot more events out there, but current detectors cannot see them. This will change as gravitational astronomy advances.

Ligo is not a "pointable device. It is fixed, so there is a certain amount of planetary alignment involved

Not really. LIGO is almost omnidirectional (except for gravitational waves that come from directly above the 'L'. But the closer to that direction it is the lower - read: harder to detect - the signal)
RealityCheck
1 / 5 (2) Oct 20, 2017
@Whyde.Thanks for your , as usual, polite responses.
Ligo is not a "pointable device. It is fixed, so there is a certain amount of planetary alignment involved...
That was already understood. My query was re the absence of any NS binary merger 'detection events' per se 'before now'; as there must be many occurring across 'whole sky' directions (ie, THIS latest 'detection event' means that NS mergers must be common/frequent enough to happen at THIS stage in the BB 'timeline'?).
Cherenkov radiation only applies to electrons moving in some dialectric medium other than space, such that they move faster than the PHASE speed of light in that medium.
Yes, I know that already; which is why I specifically said "Cerenkov physics/principle" as analogous 'medium-specific' 'faster-than-light-therein' phenomenon of 'shock waves' per se in 'spacetime medium'. If 'spacetime' is not an 'energy medium' then conventionally characterized gravitational waveform cannot form/propagate?
RealityCheck
1 / 5 (2) Oct 20, 2017
@shavera.

I'm back earlier than planned this morning, so I can now respond to yours (in same respective order):
1)...But the ones that are far enough are just contributing noise....
Yes, that was already understood. The point was that IF THIS 'detection event' IS a NSs merger at THIS stage in BB 'timeline', then many such must also be occurring all over in all directions near enough to have been detectable ALSO?
2) I don't know, let that to someone else to answer
DS has tackled that one, and I'll get to that in due course in later post(s). Thanks anyway, mate. :)
3) Detectors take a long time to shake down and tune. That noise floor in 1 (though most of the noise is just physical waves (vibrations) was really hard to overcome.
That's the point: if we can NEVER 'isolate' the setup from the gravitational wave signals environment, then any 'noise floor' for the looked for signals can NEVER be tenably 'determined' at all other than assuming/guessing it?

cont...
Whydening Gyre
5 / 5 (1) Oct 20, 2017
... My query was re the absence of any NS binary merger 'detection events' per se 'before now'; as there must be many occurring across 'whole sky' directions (ie, THIS latest 'detection event' means that NS mergers must be common/frequent enough to happen at THIS stage in the BB 'timeline'?).


at this point, I don't even have to qualify what type of star is involved. Just REALLY massive bodies. Additionally, you must account for the gravitational envelope which might be surrounding the event. This is contributory noise.
If 'spacetime' is not an 'energy medium' then conventionally characterized gravitational waveform cannot form/propagate.

Who says it isn't? It's just at a MUCH lower energy level than the generating event...
RealityCheck
1 / 5 (3) Oct 20, 2017
cont... @shavera:
4)It's not really a "shock wave." And it doesn't require faster-than-light motion either.
A 'shock wave' form/phenomena is the only way that a gravity well energy content CAN SEPARATE from 'parent' gravity-generating 'body(ies); otherwise it remains part of the normal ATTACHED 'gravity well field pattern'. The ambiguity arises if we examine actual nature of an 'abstract spacetime' construct as opposed to an actual 'physically coupling' motion of/in 'energy-space' field, which are real, not abstract (since forces/effects etc consequences are observable/measurable). Hence, unless one claims 'spacetime' is a 'real physical coupling medium', then what 'waves' and 'curves' etc? And what 'energy' is being emitted/transmitted across space other than EM-energy-matter forms (photons, Neutrinos, quarks/gluons etc)? What 'real physically coupling form' does a COMPONENT part of 'abstract spacetime gravitational energy wave' take?

Thanks again, mate. :)
RealityCheck
1 / 5 (2) Oct 20, 2017
@Da Schneib.

Thanks for your trouble and your polite reply on this item, mate; much appreciated (sincerely). :)
Is the terminal merging "Ringdown" signal similar for Neutron Star Binary and Black Hole Binary mergers?
Yes, and it's not just the ringdown but the terminal inspiral that's similar. What's different is the magnitude and the timing. Since neutron stars aren't as massive and dense as black holes, the inspiral and ringdown signals don't get as fast,...
I observe it might not be as simple as that, mate. Consider the Event Horizon 'diameters' of Black Holes involved in the recent detections for a moment: their EH-encapsulated-volume may be larger than the volumes of NSs? If so, then the NSs may be able to approach each other more closely before merging than the BHs can (ie, when latters' EHs make contact, no 'signal' can ESCAPE from EH, so we would not detect any 'faster inspiraling signal' of their INTERIOR concentration/density volumes)? Your thoughts?
shavera
4.4 / 5 (7) Oct 20, 2017
then many such must also be occurring

I dunno, do you have statistics on how many neutron stars are in binary pairs in the last seconds of their existence right now? It feels like it's probably not a ton, but not nothing.

As for your signals analysis objections, I dunno, I mean the maths of GR have worked to predict an awful lot of experiments. Once again they've worked to predict another experimental outcome. They predicted a deviation of distance of some magnitude, found they were able to get their noise below that distance threshold, and can detect signals when it rises above the noise floor. To exaggerate some in scale, imagine theory predicts 1 mm of deviation for a collision. And when your detector bounces around from +/- 1 micron, that's your noise floor.
RealityCheck
1 / 5 (2) Oct 20, 2017
@antialias_physorg.

Also thanks to you for your polite and timely response, mate. Much appreciated as well. :)

Re your response per se, it may be more efficient to refer you to my above posts responding to @Whyde, @shavera and #Da Schneib, as these further clarify the thrust and issues of my queries/considerations re the relevant points/items in question, so your responses are answered and your further thoughts/responses are invited having regard to those further clarifications of my original queries/observation. Thanks again, mate. :)
shavera
4.5 / 5 (8) Oct 20, 2017
Space-time isn't a real physical medium. Space is what you measure with rulers, and time is what you measure with clocks. It sounds silly, I know. But it's not a stuff or a medium. So what waves? Well different observers with different relative motions, distance to energy sources, and so on, fundamentally disagree with each other on how long their rulers are and fast their clocks tick. What waves is that as time passes, your rulers stretch in one direction, and then stretch in another, back and forth. It's not a wave like a water wave, it's a variation in how long rulers are over a period of time. The maths are a 'wave equation' solution to the equation, so they're still a 'wave.'
RealityCheck
1 / 5 (2) Oct 20, 2017
I have to go out again and may not be back until late. So I'll 'see' you all again tomorrow morning, I hope, to continue the conversation with respondents. Cheers all. :)
shavera
4.3 / 5 (6) Oct 20, 2017
I'm entirely speculating in the following about the exact details of the energy transfer mechanism solely because I haven't actually done the maths. But: In order to calculate energy, there's a dependency on how long your rulers are and how fast your clocks run. Since a gravitational wave is a variation of ruler length and clock rate, I would guess that in these variations, there is an associated degree of energy that is being carried along with the wave. I would have to actually do the maths, or god forbid, look up a research paper where they've already been done. But that's what I'd suspect accounts for energy being carried.
Da Schneib
4.2 / 5 (5) Oct 20, 2017
I'll take on some of your questions, @RC, but first I want to cover some background; I've been desultorily doing some research today, in off moments, and have some information to share.

First, these are not particularly common events. A paper I dug up from 1991 estimates rates of around 3 neutron star mergers within 600 million light years (200Mpc) per year. http://adsabs.har...80L..17P
[contd]
Da Schneib
4.2 / 5 (5) Oct 20, 2017
[contd]
Now, this particular event was about 160 mly (40 Mpc) away. The waveform lasted about 2 minutes, as opposed to earlier BH detections which lasted only a few seconds. The amplitude suggests that we might expect to detect events like this one only up to about twice as far away as this one; they're not nearly as "loud" as a BH merger.

Since volume of a sphere increases as the cube of radius, then, we can expect to detect about 3*(80³/200³) = 0.192 of these every year, or one every five years or so, on average; I'd say one every 2 to 10 years, since this is a pretty rough computation. This of course assumes constant sensitivity, whereas aLIGO has only been online about 3 years. It's therefore unsurprising that this is the first one we've seen, and in fact it's right about on schedule and maybe a bit early.
[contd]
Da Schneib
4.2 / 5 (5) Oct 20, 2017
[contd]
The 1991 paper guesstimates BH mergers at something like the same rate, but I have some questions about this since SN candidate stars at masses likely to make NS are much more common than those likely to make BH. I might go look up some better estimates of this, but my sense is that we can probably expect to see circa 5x the number of BH mergers as NS mergers mostly because we can't hear NS mergers nearly as far. (By "hear" I mean "detect with LIGO and other GOs.") That's pretty much on track too; we've seen four or five GWs, and this one is the first NS merger.

So that's what I found out today while poking around.
Da Schneib
4.3 / 5 (6) Oct 20, 2017
Please let's forget the 'feuds', everyone. :)
I'm willing if you are.

How can a LIGO setup be 'tuned/tested for a 'template' if it is always embedded in a 'spacetime' continuously 'ringing' with gravitational waves from near and far
It requires many GW detections in order to have a pretty good set of parameters experimentally; from the theoretical POV this is a matter of predictions by GRT and in fact we saw just about what we expected five times now. The main concept here is that of a "noise floor;" aLIGO was enhanced to eliminate all the terrestrial sources possible, and gets some immunity because the Hanford and Livingston sites are thousands of km apart, and VIRGO is even farther. Thus much or even most of the remaining noise is from various celestial sources.

and is hence NOT able to be 'isolated' for test signal injection/analysis procedures?
Test signals are regularly used; this is discussed on LIGO's site.
[contd]
Da Schneib
4.3 / 5 (6) Oct 21, 2017
[contd]
Why, in all the YEARS since LIGO activated, did NO signal from merging NSs and/or Bhs 'detected' in our/nearby galaxy(s)?
I think I have addressed this adequately above.

As there must have been many more relatively near source NS binary mergers than distant BHs mergers supposedly detected from OVER a BILLION lightyears away.
It's important here to understand that BH mergers are at significantly higher masses (50-80M☉ as opposed to 2-3M☉) and are therefore much "louder." This is to be expected.

How can gravitational 'shock waves' be generated?
These are not shock waves. Just plain old ordinary waves.
Da Schneib
4.3 / 5 (6) Oct 21, 2017
That's the point: if we can NEVER 'isolate' the setup from the gravitational wave signals environment, then any 'noise floor' for the looked for signals can NEVER be tenably 'determined' at all other than assuming/guessing it?
Actually the noise floor is pretty easily detected; we can't necessarily completely deconvolve all terrestrial noise from it, but we can get very high isolation by various methods, some quite ingenious, which are documented on LIGO's site. Combine that with two (and now three) instruments isolated by thousands of km distance, and you've got a pretty good direct measure of the noise floor.

As a good example of the isolation methods, an ingenious "compound pendulum" design- a pendulum hanging from a pendulum, multiple times- has been proven both theoretically and in practice outside LIGO to provide excellent isolation from vibrations and is in use at LIGO.
Mimath224
5 / 5 (4) Oct 21, 2017
@shavera, Da Schneib Because the technology is cutting edge stuff and detectors able to read at subatomic scales do you think that gravitational waves might, and I emphasize might, be route to a unified theory of quantum physics and gravity?. Again this is just a thought on how important these discoveries might be in other topics.
Da Schneib
4.3 / 5 (6) Oct 21, 2017
A 'shock wave' form/phenomena is the only way that a gravity well energy content CAN SEPARATE from 'parent' gravity-generating 'body(ies); otherwise it remains part of the normal ATTACHED 'gravity well field pattern'.
This is incorrect. The energy comes from the gravitational field itself, not necessarily from the bodies; as energy is removed from the gravitational potential between the orbiting bodies they move closer together converting potential to real energy. If the potential remained the same they would not move closer together. Remember that gravitational potential energy is dependent upon the distance. The GWs are generated by the conversion of potential to real energy; the situation is much more complex when BHs are involved, but quite straightforward with NSs since there are no event horizons.

That's one of the reasons this is such a significant event: this is the first GW detection that did not involve BHs.

[contd]
Da Schneib
4.4 / 5 (7) Oct 21, 2017
[contd]
Hence, unless one claims 'spacetime' is a 'real physical coupling medium', then what 'waves' and 'curves' etc? And what 'energy' is being emitted/transmitted across space other than EM-energy-matter forms (photons, Neutrinos, quarks/gluons etc)? What 'real physically coupling form' does a COMPONENT part of 'abstract spacetime gravitational energy wave' take?
The actual intervals (this is the equivalent of spatial "distance," in spacetime one must include time) are altered as a GW passes. Our conception of spacetime being somehow immutable is incorrect, according to GRT; it is fungible. A GW can affect the (otherwise constant) interval, and it is thus we can detect them. Spacetime itself bends and flexes according to GRT. If we had lasers probing it, we could detect this just as Eddington detected it in the positions of stars near the Sun during an eclipse nearly a hundred years ago; and in fact we do. That's LIGO, and that's why it uses lasers.
Da Schneib
4.4 / 5 (7) Oct 21, 2017
Thanks for your trouble and your polite reply on this item, mate; much appreciated (sincerely). :)
I accept your sincerity at face value and so far you are presenting that way. I in turn sincerely hope this continues as it is much more pleasant than what has come before, and I do have respect for your ability to think. You are asking probing questions that demonstrate it and will illuminate these matters for others. These questions need to be asked and need to be answered. And thank you in turn for that.

Consider the Event Horizon 'diameters' of Black Holes involved in the recent detections for a moment: their EH-encapsulated-volume may be larger than the volumes of NSs?
It's quite important that we differentiate BH mergers from NS mergers because of the EH that a BH has. We do not know anything about what happens inside an EH; but there is no such barrier to knowledge with NSs because there is no EH.
[contd]
Da Schneib
4.4 / 5 (7) Oct 21, 2017
[contd]
If so, then the NSs may be able to approach each other more closely before merging than the BHs can (ie, when latters' EHs make contact, no 'signal' can ESCAPE from EH, so we would not detect any 'faster inspiraling signal' of their INTERIOR concentration/density volumes)?
Don't forget the potential energy. Because we do not know what physics looks like inside an EH we cannot calculate potential energy inside an EH. Using LIGO we can only state that it appears mass-energy from inside the EH which is beyond the gravitational potential energy is radiated; we don't know how this happens, but it is unquestionable that we observe it.

[contd]
Whydening Gyre
5 / 5 (6) Oct 21, 2017
DS,
Thanks for that GREAT explanation.
Clear, concise and bang on!
Understandable by even me!
Da Schneib
4.2 / 5 (5) Oct 21, 2017
[contd]
Nevertheless, it is clear that some energy is being extracted from beyond the EH; this is apparent from the GW profile. It does not match the power spectrum we would expect merely from potential to real energy conversion during the inspiral and ringdown. It has to come from somewhere unless someone is suggesting violation of energy conservation.

Remember that even the potential to real energy conversion of the inspiral must obey energy conservation; you can't get blood from a stone. If there is additional energy, it must come from somewhere, and the only place is inside the EH. How that works we do not know and will not until we have a quantum gravity theory.
Da Schneib
4.2 / 5 (5) Oct 21, 2017
@shavera, Da Schneib Because the technology is cutting edge stuff and detectors able to read at subatomic scales do you think that gravitational waves might, and I emphasize might, be route to a unified theory of quantum physics and gravity?. Again this is just a thought on how important these discoveries might be in other topics.
@Mimath, first of all you should understand that when you say "cutting edge" this is not cutting edge physics; it's a hundred years old. It may be cutting edge lab technique. But I wouldn't even stipulate to that.

I doubt this is a strong lead to quantum gravity; it is however a definite experimental constraint on it.
Da Schneib
4 / 5 (4) Oct 21, 2017
An important item to note is that Wikipedia has guesstimated parsecs as equal to 4x light years; in actuality a parsec is only about 3.26 ly, so my use of 3x instead of 4x is more correct than theirs. The numbers come out close enough to the experimental results within the error bars that I am not concerned.
Da Schneib
4.4 / 5 (7) Oct 21, 2017
One last important fact: In this case, because this is a NS merger and not a BH merger, we have pretty good EM records in addition to the GW records, and thus we can connect the two. This is expected because NS don't have EHs. This has confirmed that GW are real because we see EM as well as GW signals, within 1700 ms of one another. We can confidently expect to see another of these within the next ten years. By then we should have additional GW assets online and be able to precisely triangulate the GW and GRB detections, and direct optical, UV, IR, and X-ray assets onto them. This is very much a strong confirmation of many different astrophysical theories, a very strong confirmation of GRT, and a very strong confirmation of GW detection and GRB source theories, with strong confirmation of cosmological theories. As I said above. A truly groundbreaking and once in a lifetime event.
Mimath224
5 / 5 (3) Oct 21, 2017
@Da Schneib, Yes, of course you're right and I was lame brain in neglecting the essential historical point. Many thanks for taking the time to reply.
Da Schneib
4 / 5 (4) Oct 21, 2017
@Mimath I wouldn't call it lame-brained. You were looking at the direct evidence not the history. Short-range glasses. It's an easy mistake to make. I've made similar mistakes myself and certainly wouldn't support making pejorative accusations against you or anyone else based on that.
Mimath224
5 / 5 (3) Oct 21, 2017
@Da Schneib Ha, in my case age might be a good excuse. Quoting an earlier comment from you 'A truly groundbreaking and once in a lifetime event.' is certainly true in my case but of course maybe not for you. I hope you (and others here) have a chance to see this new 'tool' grow.
But getting back to the topic at hand. The production of heavy elements (nucleosynthesis). I know that Fred Hoyle theorized about this way back but today we have synthesized (artificial) elements too, although some are short lived and decay quickly (Og for example). Since the r process creates a neutron rich environment I wonder whether or not at least some of the latter might be produced in N stars collision (say El. 110-118). Is our technology advanced enough to detect these if they were produced?
Da Schneib
4 / 5 (4) Oct 21, 2017
@Mimath, we'd have to detect spectral fingerprints which I'm not entirely sure we have really good samples of, for sure detection. As for detecting radioactive decay products like beta particles keep in mind these don't come out at the speed of light so it could be a while. Like a few hundred million years a while. ;)
shavera
4.4 / 5 (7) Oct 21, 2017
route to a unified theory of quantum physics and gravity?


I'd say it's probably our best chance to date. We're dealing with space-time in motion, with waves. We may see something in those waves that indicates some kind of non-classical behaviour. At worst, it will probably be used to rule out some of the possibilities currently proposed that unite the two. Theory X will have to not only explain gravitation and many other GR experiments, but will also have to produce these kinds of wavelike observations in these kinds of detectors.
Captain Stumpy
4.2 / 5 (5) Oct 21, 2017
@Captain Stumpy

Thank you.
@shadybail
you're welcome

just remember that the only time you really need to be well versed in the topic is when the topic devolves into specific arguments (like above)

if you need some easily accessible and free resources to explain it factually, or learn science, try this one: https://ocw.mit.e...y-topic/

here is another link you may want to peruse as it pertains to evidence and how to view comments on a news aggregate like this site: http://www.auburn...ion.html

it is a good way to classify comments for reply and/or establish a method for refute

there are also posters with great knowledge here... i would consider those with ratings above 3.8 or so more qualified or knowledgeable, typically

but always validate the claim before accepting it, regardless

again, as a reminder, i wholeheartedly reiterate that source is vital

PEACE
Da Schneib
3.7 / 5 (3) Oct 21, 2017
@shavy, what do you think of the various QG conjectures floating around, like LQG, strings, and SVT? Also do you know of any alternatives out there I didn't just mention? And how does AdS-CFT correspondence look to you?
Whydening Gyre
5 / 5 (4) Oct 21, 2017
@shavy, what do you think of the various QG conjectures floating around, like LQG, strings, and SVT? Also do you know of any alternatives out there I didn't just mention? And how does AdS-CFT correspondence look to you?

All the acronyms (that I don't know or can't figure out) are gonna make my head esplode...!
shavera
4.4 / 5 (7) Oct 21, 2017
I used to be a fan of Loop Quantum Gravity, but I've just become entirely agnostic on the question. I think strings got a lot more press than they really deserved, so my bias on them is not particularly rational. Maybe we'll just find a way to resolve the maths of gravitons and there will just be a straightforward quantum field theory of GR.

AdS-CFT is a really neat maths trick in strong force calculations. I don't particularly see if it really goes beyond that. Similarly, holographic universe stuff. It's neat that black hole entropy maths simplify 3 dimensions down to 2 in a certain way, but I'm not persuaded that our entire universe is a 2-dimensional system behaving as if it's 3 dimensional. But it's all outside my personal wheelhouse. I loved GR in undergrad, but didn't really have an opportunity to dig into it in grad school. (interestingly, went into strong force stuff, so I guess i'm a little AdS-CFT myself)

Mimath224
5 / 5 (4) Oct 21, 2017
@Whydening Gyre yes, what physicists don't realize sometimes is that some other branch of knowledge already has the acronym they've chosen. SVT was and is the acronym for Supraventricular Tachycardia, Supralaryngeal vocal tract but there is also an SVT in Silicon technology. Here I think SVT= Superfluid vacuum theory but I might be wrong,Ha! Although I don't know the actual determined relationships, AdS refers to Anit-de Sitter space(s) and CFT to Conformal Field theory. basically as I understand it, it has something to do with possible relationships between theories such as QFT, sorry, Quantum Field Theories, (Super)String theories...but again I might be wrong. Da or Shav will correct me if I'm wrong.
RealityCheck
1 / 5 (2) Oct 23, 2017
@shavera.

Finally, enough time to reply to all!
Space-time isn't a real physical medium. Space is what you measure with rulers, and time is what you measure with clocks. It sounds silly, I know. But it's not a stuff or a medium. So what waves? Well different observers with different relative motions, distance to energy sources, and so on, fundamentally disagree with each other on how long their rulers are and fast their clocks tick. What waves is that as time passes, your rulers stretch in one direction, and then stretch in another, back and forth. It's not a wave like a water wave, it's a variation in how long rulers are over a period of time. The maths are a 'wave equation' solution to the equation, so they're still a 'wave.'
The problem has always been, and remains: how are remote clocks/rulers affected by 'spacetime' waves/curvatures if 'spacetime' is not a 'medium' that waves/propagates an 'energetic field' perturbation from source to remote clocks/rulers? :)
RealityCheck
1 / 5 (2) Oct 23, 2017
@Whyde.
If 'spacetime' is not an 'energy medium' then conventionally characterized gravitational waveform cannot form/propagate.
Who says it isn't? It's just at a MUCH lower energy level than the generating event...
Careful, mate! You just effectively opened the door to the "Luminiferous aether" medium/interpretations of photonic motion in 'spacetime'. :)

Seriousy, though, this has been the 'Jekyl and Hyde' problem of GR and modern cosmology in general. On the one hand denying a 'medium' but on the other hand requiring someting that can wave/affect remote clocks/rulers.

You will note that @shavera just reminded us all that it is the 'measurements' that vary as per clocks (motion/time) and as per rulers (distance/space), and NOT the actual spacetime per se (which as shavera agrees, is not a real energy-medium).

Hence the problem remains: what waves/propagates to affect REMOTE clocks/rulers if it isn't some FUNDAMENTAL form of energy field/perturbation at root? :)
RealityCheck
1 / 5 (2) Oct 23, 2017
@Da Schneib.
Please let's forget the 'feuds', everyone. :)
I'm willing if you are.
I've no problem with that, since I do not start/perpetuate personal feuds; only defended against same whenever such were foisted upon me. I have lost count of how many 'olive branches' I've offered, ony to be rebuffed by said 'foisters'. I am ever ready to forgive and forget, if allowed to. :)
and is hence NOT able to be 'isolated' for test signal injection/analysis procedures?
Test signals are regularly used; this is discussed on LIGO's site.
Yes, I am familiar with the whole setup and operations involved, as demonstrated in past discussions re aLIGO testing, instabilities, operator inputs etc. The point was: how to 'isolate/identify' Gravitational-Waves ALWAYS going through aLIGOS from a range of directions/distances/sources? If this grav-waves background cannot be 'turned off', then 'signal cleaning/modeling' procedures may confound what is 'desired/test' signal.
RealityCheck
1 / 5 (2) Oct 23, 2017
Damn it! Called away again. I'll 'see' you all again tomorrow sometime, I hope. Cheers all. :)
Mimath224
5 / 5 (2) Oct 23, 2017
@RealityCheck I am sympathetic with the problems where appellations are involved. One often reads, hears the term 'fabric of space-time' and of course it's the choice of name which is the problem (rather like Fred Hoyle who coined the phrase 'big bang' on the radio simply because it was radio). We are all used to the idea of what a fabric is in everyday life and it's a bit difficult to use such a term for something else without some overlap of meaning. Seeing the many videos on gravity/gravitational waves, ripples in the space-time 'rubber' sheet analogy always follow. As we all know here they are only useful up to a point. If we were to say 'fabric' as being near the truth then mainstream science might have to concede to the Aether and similarly with the rubber sheet (which also gives the 2D impression). These analogies might be fine for the general public but even here it is,imho, wrong. Computer graphics today are quite capable of showing ideas in 3D format so why don't we do it?
antialias_physorg
5 / 5 (4) Oct 23, 2017
I used to be a fan of Loop Quantum Gravity

Same here. It just tickles my "this sounds so neat"-bone. Whatever it turns out to be though, I'm OK with it.

As for the holographic principle. The way I understand it is that a poissible 2D mapping does not imply that the universe is therefore 2D.
shavera
4.2 / 5 (5) Oct 23, 2017
how are remote clocks/rulers affected by 'spacetime' waves/curvatures if 'spacetime' is not a 'medium' that waves/propagates an 'energetic field' perturbation from source to remote clocks/rulers?


At the root of this question is ultimately: why is it that mass or energy cause rulers to stretch or time to speed up? If we had a quantum theory of GR, we maybe might have some particle that has some coupling to mass and energy and these particles (in the QFT sense of a particle being a discrete energetic state of a field) go between all the other stuff with energy and communicate how to measure distances.
Whatever the answer ends up being, it has to address the fact that thinking in terms of 'medium' tends to lead one to think in terms of a fixed 'stage' upon which things move about. And GR explicitly removes that stage.
Jabberwockey
not rated yet Oct 23, 2017
So EM Waves and Gravitational waves propagate at the same speed? Why?
Jabberwockey
not rated yet Oct 23, 2017
Everyone is saying this event proves GW detectors work. I don't get it. In fact it seems the opposite to me. Why would EM and G waves move at the same speed? If G does move a the same speed as C does that mean that when we make cosmological models, that we have to model everything based on where they "were" instead of where they "are". If a star blows up. Other stars still feel it's gravity for years?
Da Schneib
4 / 5 (4) Oct 23, 2017
The point was: how to 'isolate/identify' Gravitational-Waves ALWAYS going through aLIGOS from a range of directions/distances/sources?
I'm not sure what you're asking about here. GWs strong enough to be detected by this apparatus happen, based on what we've seen so far, a few times a year. This accords well with estimates of how often events that make strong enough GWs to be detected happen in the visible universe. These seem to be interactions involving black holes and neutron stars coalescing.

If this grav-waves background cannot be 'turned off', then 'signal cleaning/modeling' procedures may confound what is 'desired/test' signal.
Since we only see these major events, and only a few times a year, it's easy to establish a background level and therefore easy to recognize when something unusual happens a few times a year.

Can you rephrase your question so I can give a clearer answer?
Da Schneib
4 / 5 (4) Oct 23, 2017
The problem has always been, and remains: how are remote clocks/rulers affected by 'spacetime' waves/curvatures if 'spacetime' is not a 'medium' that waves/propagates an 'energetic field' perturbation from source to remote clocks/rulers? :)
I don't know if @shavy will show up and answer this, so I'll take a hack at it. @shavy can correct me later if I make any mistakes.

According to Maxwell, spacetime is a medium that can propagate EM waves. We know this because we can see stars and galaxies through it, and we can easily demonstrate the wave-like properties of EM waves; spectroscopy is an excellent example of this since it relies on diffraction (a specifically wave-like effect) to distinguish among different wavelengths (or if you prefer, frequencies). This does not imply that there is any material in the spacetime traversed.
[contd]
Da Schneib
4 / 5 (4) Oct 23, 2017
[contd]
Spacetime is filled with fields, though in empty spacetime (AKA vacuum) these fields are all at or near zero in value. That doesn't mean they don't exist there, any more than a temperature with a value of 0 degrees means there is "no temperature."

In the same way, spacetime can also propagate gravitational waves.

Note that both EM (a static field) and gravity (another static field) impose fields on spacetime; these fields have their origin in, respectively, electric charges and masses.

It seems therefore reasonable, since spacetime can propagate these fields, and these waves (which are just variations of the field strength at a particular event, i.e. spacetime location), that one would not call it a transmission medium for both. But it's important to distinguish between a material medium and spacetime.
[contd]
Da Schneib
4 / 5 (4) Oct 23, 2017
[contd]
Meanwhile, @shavy appears to have answered while I wasn't looking! Or perhaps I didn't look carefully enough. And I see nothing to disagree with in that answer.

Moving right along, we can actually measure the variations in spacetime for EM; these break down to a pair of constants called the permittivity and permeability of the vacuum. They are not zero. These calculate out to a value for Coulomb's Constant in the basic field equation for the EM force, another well-known and well-measured constant which also is not zero.

It is thus an experimentally verified fact that empty spacetime with no material in it can propagate EM and gravity, and can propagate waves in both.

Since spacetime itself is affected by gravity, all objects in spacetime are affected by gravity; this is even true of EM forces and waves.

So knowing this, please restate the "problem" because I don't see one.
Da Schneib
3.7 / 5 (3) Oct 23, 2017
In short, @RC, you appear to be claiming that because spacetime serves as a transmission medium it must contain some material substance, and this appears to be incorrect (i.e. you are claiming "aether" must be correct). Can you tell us why that is not so? Two different and distinct forces both appear to propagate in spacetime without any material in it. And science has described these forces and the waves they propagate with such exquisite accuracy and precision that we have extraordinarily accurate and precise theories that describe them in detail. Can you explain what your objection is to these two theories, Maxwell's Equations and GRT?
Whydening Gyre
5 / 5 (2) Oct 24, 2017
[contd]
Meanwhile, ...
It is thus an experimentally verified fact that empty spacetime with no material in it can propagate EM and gravity, and can propagate waves in both.

Since spacetime itself is affected by gravity, all objects in spacetime are affected by gravity; this is even true of EM forces and waves.
...
DS,
A point of curiousity...
might this suggest... that the fields, themselves, are the propagating entity?
ShotmanMaslo
4 / 5 (4) Oct 24, 2017
So EM Waves and Gravitational waves propagate at the same speed? Why?


Because both photons and gravitons are massless particles.

If a star blows up. Other stars still feel it's gravity for years?


If a star blows up, then the resulting explosion is where the mass of the star is to be found. It is not like the mass of the exploded star disappears from the universe. So other stars still feel the gravity of the remnant of the star.

But essentially yes, all the changes in the gravity field move at the speed of light. If Sun magically disappeared, Earth would continue to orbit the empty place for next 8 minutes, just like it would continue to receive light for next 8 minutes.
Da Schneib
3.7 / 5 (3) Oct 24, 2017
@Whyde, as best we can tell, yes. But we don't see these fields without charge, in the case of EM, and without mass-energy, in the case of gravity, we can only make the mass-energy or charge move and make waves in the fields. Charge and mass-energy are conserved, and wherever they go, they always have a field. We can shield EM; but we can't shield gravity. These are all empirical facts we have discovered by observation and analysis.

Ultimately, reality is made from spacetime and fields. That's how it seems to be in our universe.
Whydening Gyre
5 / 5 (2) Oct 24, 2017
@Whyde, as best we can tell, yes. But we don't see these fields without charge, in the case of EM, and without mass-energy, in the case of gravity, we can only make the mass-energy or charge move and make waves in the fields. Charge and mass-energy are conserved, and wherever they go, they always have a field. We can shield EM; but we can't shield gravity. These are all empirical facts we have discovered by observation and analysis.

Ultimately, reality is made from spacetime and fields. That's how it seems to be in our universe.

Uh-oh... This is gonna take me down a rabbit-hole, I believe....:-)
Could we then conjecture a possibility of "something" moving faster than C as a possible cause of gravity fields...?
Da Schneib
1 / 5 (1) Oct 24, 2017
@Whyde, no. Nothing classical can move faster than the speed of causality. That is the speed of light and the speed of gravity. Quantum things can move faster than causality but only over very short distances and during very short times, and not consistently.

This is one of the big arguments against TIQM and Bohm/DeBroglie. It's a result of the FT.

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