Pulsars: The Universe's gift to physics

Feb 19, 2012

Pulsars, superdense neutron stars, are perhaps the most extraordinary physics laboratories in the Universe. Research on these extreme and exotic objects already has produced two Nobel Prizes. Pulsar researchers now are poised to learn otherwise-unavailable details of nuclear physics, to test General Relativity in conditions of extremely strong gravity, and to directly detect gravitational waves with a "telescope" nearly the size of our Galaxy.

Neutron stars are the remnants of massive stars that exploded as supernovae. They pack more than the into a sphere no larger than a medium-sized city, making them the densest objects in the Universe, except for black holes, for which the concept of density is theoretically irrelevant. Pulsars are neutron stars that emit beams of outward from the poles of their magnetic fields. When their rotation spins a beam across the Earth, detect that as a "pulse" of radio waves.

By precisely measuring the timing of such pulses, astronomers can use pulsars for unique "experiments" at the frontiers of . Three scientists presented the results of such work, and the promise of future discoveries, at the meeting in Vancouver, British Columbia.

Pulsars are at the forefront of research on gravity. published his in 1916, and his description of the nature of gravity has, so far, withstood numerous experimental tests. However, there are competing theories.

"Many of these alternate theories do just as good a job as of predicting behavior within our Solar System. One area where they differ, though, is in the extremely dense environment of a neutron star," said Ingrid Stairs, of the University of British Columbia.

In some of the alternate theories, gravity's behavior should vary based on the internal structure of the neutron star.

"By carefully timing pulsar pulses, we can precisely measure the properties of the neutron stars. Several sets of observations have shown that pulsars' motions are not dependent on their structure, so General Relativity is safe so far," Stairs explained.

Recent research on pulsars in binary-star systems with other neutron stars, and, in one case, with another pulsar, offer the best tests yet of General Relativity in very strong gravity. The precision of such measurements is expected to get even better in the future, Stairs said.

Another prediction of General Relativity is that motions of masses in the Universe should cause disturbances of space-time in the form of . Such waves have yet to be directly detected, but study of pulsars in binary-star systems have given indirect evidence for their existence. That work won a Nobel Prize in 1993.

Now, astronomers are using pulsars throughout our Milky Way Galaxy as a giant scientific instrument to directly detect gravitational waves.

"Pulsars are such extremely precise timepieces that we can use them to detect gravitational waves in a frequency range to which no other experiment will be sensitive," said Benjamin Stappers, of the University of Manchester in the UK.

By carefully timing the pulses from pulsars widely scattered within our Galaxy, the astronomers hope to measure slight variations caused by the passage of the gravitational waves. The scientists hope such Pulsar Timing Arrays can detect gravitational waves caused by the motions of supermassive pairs of in the early Universe, cosmic strings, and possibly from other exotic events in the first few seconds after the Big Bang.

"At the moment, we can only place limits on the existence of the very low-frequency waves we're seeking, but planned expansion and new telescopes will, we hope, result in a direct detection within the next decade," Stappers said.

With densities as much as several times greater than that in atomic nuclei, pulsars are unique laboratories for . Details of the physics of such dense objects are unknown.

"By measuring the masses of neutron stars, we can put constraints on their internal physics," said Scott Ransom of the National Radio Astronomy Observatory. "Just in the past three to four years, we've found several massive neutron stars that, because of their large masses, rule out some exotic proposals for what's going on at the centers of ," Ransom said.

The work is ongoing, and more measurements are needed. "Theorists are clever, so when we provide new data, they tweak their exotic models to fit what we've found," Ransom said.

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Shelgeyr
2 / 5 (12) Feb 19, 2012
Neutron stars are the remnants of massive stars that exploded as supernovae.


The article starts with a wild if quite popular assumption, for which no real evidence exists (and I mean that, seriously), stated as if it was an established fact. It is not.

Thus they establish more of a "playground for the mind" than an "extraordinary physics laboratory". The rest of the article should be read in that light.

In some of the alternate theories, gravity's behavior should vary based on the internal structure of the neutron star.

"By carefully timing pulsar pulses, we can precisely measure the properties of the neutron stars.


The whole thing is an iterative structure of assumptions, with nothing "real" being involved except A) light pulses, and B) timing. To think one could determine the internal structure of an assumed object is nothing more than arrogance.

By measuring the masses of neutron stars...

They do violence to the definition of the word "measure" here.
bewertow
3.6 / 5 (15) Feb 19, 2012
Do you have a degree in astrophysics?

I doubt it, because you are clearly full of shit.

Pulsars have been detected in supernova remnants.
Shelgeyr
1.9 / 5 (13) Feb 20, 2012
@bewertow said:
Pulsars have been detected in supernova remnants.


You could not be more wrong.

We have detected pulsations which are ASSUMED by many to be caused by rotating neutron stars, and the "neutron stars" themselves are another ASSUMED cosmic entity established as a fudge factor for which no real actual evidence exists.

Inferring the existence of something does not mean that it actually exists, nor that your guesses about its nature are at all correct.

It may frighten you, but I actually do know what I'm talking about, and your simple statement of "Pulsars have been detected in supernova remnants" makes it clear that I am far more of an exacting adherent of the scientific method, and the rules governing what does and does not constitute "evidence", than you are.

Thank you for flying off the handle and coming across as an overly-emotional dogma-defending reactionary. Well played!
I hope that wasn't your goal.
ArnoldZiffle
3.1 / 5 (8) Feb 20, 2012
@bewertow I think you were a bit premature with you comment that @Shelgeyr is full of shit. That is clearly a presumption or an opinion.

There is however ample "evidence" that @Shelgeyr is a pompous arrogant ass!
Shelgeyr
2.3 / 5 (9) Feb 20, 2012
@ArnoldZiffle said:
There is however ample "evidence" that @Shelgeyr is a pompous arrogant ass!


Now you see, THAT's more like it! Someone evaluated actual evidence, and made an informed opinion!

Good call! 5 stars!
CardacianNeverid
3.3 / 5 (12) Feb 20, 2012
We have detected pulsations which are ASSUMED by many to be caused by rotating neutron stars, and the "neutron stars" themselves are another ASSUMED cosmic entity established as a fudge factor for which no real actual evidence exists - ShelTard.

Why do cranks always make such obvious fools of themselves? You have sum knowledge of the world at your fingertips and you still choose to remain ignorant.
Shelgeyr
2.3 / 5 (9) Feb 20, 2012
@CardacianNeverid, care to actually, you know, rebut anything in that quote you posted? Or did you simply "open your mouth and remove all doubt"?

Choose to remain ignorant of what? I'm pointing out some problems with what I can only assume you include as an item within the "sum knowledge of the world". You think I'm not fully, completely, totally aware of what the mainstream knowledge is regarding these things? And why?

Of course I am.

At the risk of further exacerbating my image as a "pompous arrogant ass", I tell you that it is not a lack of knowledge regarding these matters that leads to calling them into question.

You think I've made an obvious fool of myself? For questioning the immanently questionable? OK, I'll bite: Why do you accept such pronouncements at face value when there are bountiful reasons and mounds of evidence available at your fingertips that belie their very existence?
CardacianNeverid
2.4 / 5 (8) Feb 20, 2012
You think I'm not fully, completely, totally aware of what the mainstream knowledge is regarding these things? - ShelTard

Yes, that is what I think.

And why? - ShelTard

Your first two posts are ample evidence.

Why do you accept such pronouncements at face value - ShelTard

What you call face value, others that know what they're talking about call hard-won knowledge gained through theory and observation over time.

So instead of putting words such as "evidence" and "neutron stars" in quotes Mr MEGAMIND, why don't you stop being cute (stupid) and say what your "theory" is?
antialias_physorg
5 / 5 (5) Feb 20, 2012
Neutron stars are the remnants of massive stars that exploded as supernovae.

I give you exhibit A:
http://en.wikiped...b_pulsar

I give you exhibit B:
http://sci.esa.in...id=49784
Kinedryl
1 / 5 (6) Feb 20, 2012
The contemporary physics, including its theories is in crisis, so that the pulsars are welcomed model case for mainstream propaganda. Because the things is not, whether general relativity is correct or not, but under which conditions it gives a correct predictions and under which not. And at the case of pulsars the general relativity provides very good predictions. In dense aether theory it's such an agreement is connected with dimensional/energy density scale, at which the theory is working. We can roughly estimate this scale with deviation from sphericity of objects involved. The objects in our Universe aren't all spherical in the same way and the deviations from quantum mechanics and general relativity are the more pronounced, the more the shape of such objects differs from ideal sphere. And dense atom nuclei or pulsars (which are mostly composed of dense atom nuclei) are particularly good in it
Kinedryl
1 / 5 (7) Feb 20, 2012
From the above follows, if we would test the general relativity with pulsars, it's essentially waste of tax payers money, because this theory will be much more violated at different scales: both larger (dark matter around galaxies), both smaller (human observer scale and others). This violation is particularly connected with CP violation, which manifests macroscopically with asymmetry of objects (the Earth has a pear shape, the large black holes exhibits one jet only, so they're behaving like monopoles). One of sources of the CP violation are the neutrinos, which are floating around massive objects like the bubbles of the opposite curvature of gravitational potential, i.e. like the objects of the opposite gravitational charge. The clouds of antineutrinos are behaving like dark matter and they violate general relativity heavily by increasing of dimensionality of space-time and with violation of equivalence principle.
Noumenon
2.7 / 5 (7) Feb 20, 2012
I must agree with Vendicar_Decarian, what alternative explanation does Shelgeyr have for the evidence?
Kinedryl
1 / 5 (5) Feb 20, 2012
Such waves have yet to be directly detected, but study of pulsars in binary-star systems have given indirect evidence for their existence. That work won a Nobel Prize in 1993.
In general relativity the reference frame for motion of objects is relative, as the only reference frame can serve the curvature of space-time. The gravitational wave itself is formed with curvature of space-time, which means, it serves as a reference frame of itself. Such a reference frame is undefined. As Eddington pointed out already before many years, gravitational waves do not have a unique speed of propagation. The speed of the alleged waves is coordinate dependent. A different set of coordinates yields a different speed of propagation and such waves would propagate like the noise.

The same conclusion can be imagined easily with water surface model, where transverse waves are serving like the analogy of waves of light and the gravitational waves are behaving like longitudinal sound waves.
Kinedryl
1 / 5 (4) Feb 20, 2012
It means, when pulsars collide or interact mutually, they do really spew a waves around itself like nuclear bomb exploding in water. But these waves are spreading in underwater and at the water surface they do manifest like chaotic noise only. We even have this noise detected already: it manifest itself like the omnipresent CMBR noise, i.e. the quantum noise of the vacuum. This is the reason, why we never detected the gravitational waves directly in gravitational detectors, which are looking for harmonic waves, whereas they filtered out just the noise, which they were expected to measure. The passage of gravitational waves would manifest like less or more sudden change in CMBR noise intensity, coming from all directions at the same moment. IMO these events were observed already at many detectors - they just were ignored and excluded from results as an experimental noise. The most pronounced effect of GW's is the Allais effect, which manifest with their shielding during solar eclipse.
antialias_physorg
5 / 5 (4) Feb 20, 2012
The contemporary physics, including its theories is in crisis

What do you mean 'crisis'?

Are there things we don't know yet? Sure
Are there things that current models don't fully encompass? Absolutely.

But science is about what works. The standard model is that which gives the BEST answers at any one time. The current in-play theories fit that description (Aether theory does not). There are no others yet developed that come even close (except for those with an arbitrary number of free variables like String/Brane-theory and 'god did it').
Note that no theory ever claims to be the final one. There will certainly, someday, be better theories/models.
Kinedryl
1 / 5 (4) Feb 20, 2012
What do you mean 'crisis'?
If unsure, try to Google first...

http://aias.us/do...ay29.pdf
http://www.wbabin...oad/2126
http://wjholland....physics/
But science is about what works.
The science is what we don't know, the rest is stamp collection.
CardacianNeverid
2.1 / 5 (9) Feb 20, 2012
The contemporary physics, including its theories is in crisis - KinedrylTard

Sez who? A crank?

Because the things is not, whether general relativity is correct or not, but under which conditions it gives a correct predictions and under which not - KinedrylTard

Easy tardboy. So far, it's correct under ALL conditions of applicability (ie, non-quantum).

In dense aether theory - KinedrylTard

Is only promoted by dense crankologists like KinedrylTard.

We can roughly estimate this scale with deviation from sphericity of objects involved - KinedrylTard

Who is Round and to what does he object? Whoooooosh!
antialias_physorg
5 / 5 (7) Feb 20, 2012
Erm. Did you even read the links you posted?
This:
http://wjholland....physics/

has nothing to say on the crisis of physics (apart fom some very vague things and not really citing anyone or anything that could elucidate that stance)

This
http://www.wbabin...oad/2126

Implicitly posits something that is not observd (i.e. it that all galaxies rotate in the same direction.).

This:
http://aias.us/do...ay29.pdf

Just rehashes that all known forces (specifically gravity with the rest) haven't been unified yet. Duh. That's not really a new insight, now, is it. It's one of the ongoing areas of research.

So where is the crisis? Unless one can show that the theories we currently have are wrong - within the context in which they apply - then there is no crisis.

Of course when you take theories and apply them to contexts where they don't apply you will get a 'crisis'. But that's not a scientific problem. That's just disingenuous reasoning
antialias_physorg
5 / 5 (6) Feb 20, 2012
Before you go on about 7% excess rotation in one direction I'd refer you to a later paper by the same group:
http://www.mendel...alaxies/
which states that they found no indication of a dipole or quadrupole anisotropy (i.e. no indication of a primordial whirl but just tidal spinup)
Kinedryl
1 / 5 (7) Feb 20, 2012
So far, it's correct under ALL conditions of applicability (ie, non-quantum).
Dark matter and dark energy violates general relativity and the question is, where the quantum begins. http://conservape...lativity
Noumenon
3 / 5 (8) Feb 20, 2012
So far, it's correct under ALL conditions of applicability (ie, non-quantum).
Dark matter and dark energy violates general relativity and the question is, where the quantum begins. http://conservape...lativity


False.
Vendicar_Decarian
1 / 5 (7) Feb 20, 2012
It is no coincidence that a Global Warming Denialist like Shelgryr is also an enemy of science in many other areas as well.

The supremely ignorant are always unaware of the extent of their own stupidity.

"We have detected pulsations which are ASSUMED by many to be caused by rotating neutron stars, and the "neutron stars" themselves are another ASSUMED cosmic entity established as a fudge factor for which no real actual evidence exists." - Shelgeyr
antialias_physorg
5 / 5 (7) Feb 20, 2012
http://conservape...lativity

Gawd...I looked at he list and it's so patently obvious that these guys don't have a clue.

When you find stuff like this on the list:
14. The action-at-a-distance by Jesus, described in John 4:46-54, Matthew 15:28, and Matthew 27:51.

and
35. In Genesis 1:6-8, we are told that one of God's first creations was a firmament in the heavens. This likely refers to the creation of the luminiferous aether.

then the only reasonable reaction is *facepalm*

Kinedryl: Do you even READ the 'supporting links' you post? You're making a total fool of yourself at every turn.
Kinedryl
1 / 5 (6) Feb 20, 2012
So far, it's correct under ALL conditions of applicability (ie, non-quantum).
Dark matter and dark energy violates general relativity and the question is, where the quantum begins. http://conservape...lativity
So where is the crisis? Unless one can show that the theories we currently have are wrong.
We have many theories, many of them are older than forty years (i.e. two generations of physicists) and we have still no confirmation at LHC. Of course, if physicists can remain one half of century without evidence of their theories and if they can neglect the fundamental findings, like the cold fusion for thirty years during this without punishment, then indeed everything is OK with contemporary physics. It's apparently just a question of criterion chosen and the proponents of mainstream physics tend to adjust them in such a way, everything appears normally.

But in another areas of science such a situation would be considered an intellectual crisis.
bewertow
3.8 / 5 (10) Feb 20, 2012
Wow, you know nothing about general relativity. Dark energy has been part of general relativity ever since Einstein introduced the cosmological constant.

Dark energy is most likely just vacuum energy, which has all the appropriate properties.
bewertow
3.5 / 5 (8) Feb 20, 2012
So far, it's correct under ALL conditions of applicability (ie, non-quantum).
Dark matter and dark energy violates general relativity and the question is, where the quantum begins. http://conservape...lativity


Wow, I have never, ever seen someone stupid enough to cite conservapedia. It shocks me how ignorant you are.
Kinedryl
1 / 5 (5) Feb 20, 2012
I have never, ever seen someone stupid enough to cite conservapedia.
Some counterexamples are indeed naive, if not religious. But in majority they're essentially correct. Don't argue the source, argue the point - or you're using a fallacy.
Kinedryl
1 / 5 (6) Feb 20, 2012
..dark energy has been part of general relativity ever since Einstein introduced the cosmological constant...
LOL, the general relativity cannot even predict, whether the Universe will expand or collapse (Friedman models are interchangable), to expand with accelerated speed the less...:-) The finding of dark energy was solely unexpected from this perspective. In addition, the cosmological constant introduced with Einstein WAS NOT a dark energy - in particular because the Einstein introduced this constant into his theory to make the Universe Steady state in accordance to his belief in attempt for cheating, if not scientific fraud - i.e. not expanding, expanding with accelerating speed the less. It's just you, who is deeply confused with general relativity.
Kinedryl
1 / 5 (6) Feb 20, 2012
Some arguments of conservapedia can be used as an arguments for dense aether model instead. For example this one:

"Minkowski space is predicated on the idea of four-dimensional vectors of which one component is time. However, one of the properties of a vector space is that every vector have an inverse. Time cannot be a vector because it has no inverse"

In dense aether theory the time arrow has its inverse / dual version as the objects living in dimensional scale above the human observer are living in negentropic time, driven with gravity, not entropy and entropic time arrow is reversed for radiowaves (they undergo blue shift, positive violation of inverse square law, negative pressure of radiation, etc..) All these phenomena do indeed violate the general relativity in its classical sense.
Vendicar_Decarian
3 / 5 (10) Feb 20, 2012
Conservapedia has never been more useful

http://conservape...lativity

at showing the depths of American Conservative ignorance.
antialias_physorg
5 / 5 (6) Feb 20, 2012
Just picking ludicrous stuff at random here:
23. The theory predicts wormholes just as it predicts black holes, but wormholes violate causality and permit absurd time travel.

Erm. So? Just saying it feels absurd doesn't constitute a counterargument. And the theory doesn't predict wormholes. It permits wormholes. Crucial difference.

32. The Twin Paradox: Consider twins who are separated with one traveling at a very high speed such that his "clock" (age) slows down, so that when he returns he has a younger age than the twin; this violates Relativity because both twins should expect the other to be younger, if motion is relative. Einstein himself admitted that this contradicts Relativity

Patently false. Only one twin is in an accelerated frame of reference (the one accelerating on the spaceship, then decelerating and reaccelerating to get back).

19. The change in mass over time of standard kilograms preserved under ideal conditions.

Grasping at straws?
antialias_physorg
5 / 5 (5) Feb 20, 2012
28. Relativity requires that anything traveling at the speed of light must have mass zero, so it must have momentum zero. But the laws of electrodynamics require that light have nonzero momentum.
Oh boy. This is wrong on so many levels. Do I even need to start on this one?

36.It is impossible to perform an experiment to determine whether Einstein's theory of relativity is correct, or the older Lorentz aether theory is correct. Believing one over the other is a matter of faith.

No source given! This is just some statement without anything to back it up.

This is supposed to be a list of stuff that somehow puts the current theories 'in crisis'? You have to be out of your mind if you think such hogwash constitutes a crisis.
bewertow
3.3 / 5 (7) Feb 20, 2012
In addition, the cosmological constant introduced with Einstein WAS NOT a dark energy - in particular because the Einstein introduced this constant into his theory to make the Universe Steady state in accordance to his belief


You are just an ignorant troll.

Tell me, do you have a degree in astrophysics? You clearly don't know anything about cosmology or general relativity. You are just an ignorant troll.

The cosmological constant introduced by Einstein was NO DIFFERENT from dark energy. They have the EXACT same equation of state.

The only difference from the modern interpretation was that Einstein considered a matter-dominated positively curved universe, and he needed the cosmological constant to make it static.
Noumenon
3.4 / 5 (10) Feb 20, 2012
@Anti-alias_Physorg

According to the Wiki entry for "consevativepedia",
[the page criticizes] the theory of relativity as promoting moral relativism


LOL. So, obviously they are not even wrong. Don't waste your time.

@Vendicar_Decarian, your generalizations are nearly as ignorant as that site. That web page has been criticized by both sides of the political spectrum.
Callippo
1 / 5 (5) Feb 20, 2012
Only one twin is in an accelerated frame of reference (the one accelerating on the spaceship, then decelerating and reaccelerating to get back).
Try to imagine, one of twins is sitting at the Earth and the second one is encircling the Earth - no one of twins is a subject of inertial forces - but the aging of twins will still differ by relativity. In addition, by relativistic formula for twin paradox only relative speed affects the time difference, so that any acceleration affects the result.
Callippo
1 / 5 (5) Feb 20, 2012
@Vendicar_Decarian, your generalizations are nearly as ignorant as that site.
Vendicar_Decarian is a liberal radical, i.e. the dual troll to ultraconservatives. It just demonstrates, the biased stance works the like quantum fluctuations of gravity field to massive bodies around black hole: the extremists are picking preferentially only these insights from pool of random opinions, which fit their own philosophy, so that their personality becomes gradually immersed and dissolved into its own scheme of thinking.
antialias_physorg
5 / 5 (4) Feb 20, 2012
Try to imagine, one of twins is sitting at the Earth and the second one is encircling the Earth - no one of twins is a subject of inertial forces

The one on Earth is experiencing a higher acceleration (gravity) than the one in orbit is gong slower. This has been verified by flying atomic clocks at high altitude. It is actually something that GPS sattelites take into account (otherwise the calculated position on the ground would be considerably off)
Callippo
1 / 5 (3) Feb 20, 2012
Try to imagine, one of twins is sitting at the Earth and the second one is encircling the Earth - no one of twins is a subject of inertial forces

The one on Earth is experiencing a higher acceleration (gravity) than the one in orbit is gong slower.
It depends on the twin's location. For example, the terrestrial twin can sit at the tunnel inside of Earth mantle, where the gravity is lower. Or it can occupy the stellar cluster, where the gravity is zero, while the second one will encircle it.
Deathclock
5 / 5 (2) Feb 20, 2012
Try to imagine, one of twins is sitting at the Earth and the second one is encircling the Earth - no one of twins is a subject of inertial forces

The one on Earth is experiencing a higher acceleration (gravity) than the one in orbit is gong slower.
It depends on the twin's location. For example, the terrestrial twin can sit at the tunnel inside of Earth mantle, where the gravity is lower. Or it can occupy the stellar cluster, where the gravity is zero, while the second one will encircle it.


What the hell? If the one is on (or in) the Earth it is in a higher gravitational field then the one orbiting Earth...
Deathclock
5 / 5 (2) Feb 20, 2012
Oh, I see what you mean... no one is going to be deep enough underground for this to matter... you're nit picking.
Deathclock
5 / 5 (1) Feb 20, 2012
ROFL @ conserva-derp-edia, never seen that site before.
ccr5Delta32
5 / 5 (3) Feb 20, 2012
Conservapedia has never been more useful

http://conservape...lativity

at showing the depths of American Conservative ignorance.

Wonderful catch Vendicar :
Relativity is a part of the liberal agenda
Crackpotism at it's finest
Shootist
1 / 5 (2) Feb 21, 2012
Compared to most of you, Oliver is a model of science; brilliance and sanity.
Callippo
1.5 / 5 (4) Feb 21, 2012
If the one is on (or in) the Earth it is in a higher gravitational field then the one orbiting Earth
Of course - and this just the point, which violates the twin paradox. Because in this case the time will pass slower just for the twin, which sits at rest - not for this one in motion.
TabulaMentis
2 / 5 (4) Feb 22, 2012
Dark energy is most likely just vacuum energy, which has all the appropriate properties.
Why don't you give it a whack at trying to explain what vacuum energy looks like since you are so smart!
wmnwmn
5 / 5 (1) Feb 24, 2012
What a pathetically shallow and uninformed comment thread compared to what was a fascinating summary article of a fascinating area of physics.
juanko
1 / 5 (2) Feb 24, 2012
my roomate's aunt makes $83/hr on the laptop. She has been without work for 8 months but last month her pay was $8682 just working on the laptop for a few hours. Read more on this site...NuttyRichdotcom

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