New experiments set to detect gravitational waves

May 03, 2013 by Bob Yirka report
Illustration of spacetime curvature. Credit: Wikipedia.

(Phys.org) —Over the next five years, Mansi Kasliwal writes in an astrophysics perspective in the journal Science, researchers will begin setting up experiments designed to detect gravitational waves. Kasliwal, an astronomer with the Observatories of the Carnegie Institution for Science located in Pasadena, California, says momentum is building in the physics community to find proof of the existence of gravitational waves. Thus, far, they are still considered theoretical.

Gravitational waves were predicted by Einstein's . They are distortions in the fabric of space-time and are believed to occur in measurable amounts when massive objects such as merge. They've yet to be seen, but the consensus among physicists is that they are real. Still, they can't be labeled a certainty until they are proven to exist by measuring them. That's what a team of and astronomers the world over plan to do over the next half decade.

The idea is to deploy ultra-sensitive interferometers at various points around the globe. They are very large L shaped devices and work by measuring the time it takes for a photon delivered from a laser to move from one end of the device to the other. If a gravitational wave strikes, it should cause the length of the device to change, increasing or decreasing the time it takes for a photon to traverse the distance.

Most believe that detecting gravitational waves is a matter of course, thus the purpose of deploying interferometers across the globe serves another purpose—discerning where they originated. The hope is that by collecting data at many locations at once, researchers will be able to work together to ascertain the direction from which the waves have traveled, and perhaps figure out what caused them to come about in the first place.

Kasliwal reports that the new highly sensitive interferometers will come online sometime in 2017, noting that some of them exist already, though they are not yet sensitive enough to detect . He adds that the project will be a hugely collaborative effort, especially if the interferometers begin detecting a lot of waves. Researchers will have to scramble and work together to get information from the detectors to operators of telescopes quickly enough to figure out where the waves might be coming from.

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More information: Seeing Gravitational Waves, Science 3 May 2013: Vol. 340 no. 6132 pp. 555-556 DOI: 10.1126/science.1235956

Abstract
Gravity is responsible for the long-range order of the universe. Using Einstein's general relativity, we now think of gravity as the geometrical curvature of the four-dimensional fabric of space-time (1). Extreme cosmological events such as the merging of neutron stars or black holes induce ripples in the fabric of space-time (see the figure). However, these ripples, or gravitational waves, are extremely weak, and their detection has remained elusive. To measure the small signal, an interferometric detector is required that can detect strain to one part in 1021 (that is, a billionth of a nanometer for a kilometer-length interferometer). Such extreme gravity events are also rare, occurring only once every 10,000 years per galaxy (2). An advanced version of such a detector is designed to find gravitational waves on a regular basis (roughly tens of events annually) beginning in 2017 (3). This heroic experiment alone will be somewhat unsatisfying—gravitational wave interferometers will only be able to hear the wave and detect when something happens (literally "hear" as the operational frequency of tens to thousands of Hertz overlaps with the human auditory range). The interferometers will be blind to exactly where the merger occurs. To locate the source of the gravitational waves, collaboration between the physics and the astronomy communities together with extensive simulations are under way (4).

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vacuum-mechanics
1.2 / 5 (17) May 03, 2013
Gravitational waves were predicted by Einstein's general theory of relativity. They are distortions in the fabric of space-time and are believed to occur in measurable amounts when massive objects such as neutron stars merge….

It is Einstein's genius for proposing that gravity is the manifest of space-time curvature, unfortunately the theory do not tell us how a given mass could cause empty space to curve and create the ripples as the propagating wave! Maybe this physical view could help to visualize how it works …
http://www.vacuum...18〈=en
beleg
1 / 5 (3) May 03, 2013
Speculation: the troughs and crests of gravitational waves account for OVVs appearance?
No need for interferometry for proof of existence?
Plausible? At all?
hemitite
3 / 5 (2) May 03, 2013
Since gravitational waves are supposed to be like ripples in space-time, what about measuring small changes in the rate of time? I think that there would possibly be less nose on that "channel" than on the humming world of space.
Aliensarethere
3 / 5 (1) May 03, 2013
The writer doesn't seem to know that the hunt for waves has been going on for many years. See Einstein@home
Q-Star
4.1 / 5 (9) May 03, 2013
Gravitational waves were predicted by Einstein's general theory of relativity. They are distortions in the fabric of space-time and are believed to occur in measurable amounts when massive objects such as neutron stars merge….

It is Einstein's genius for proposing that gravity is the manifest of space-time curvature, ,,, blah, blah, blah,,,, Maybe this physical view could help to visualize how it works …


Nope, still no help. Still as cranky and crackpotter as ever.
JIMBO
4.2 / 5 (5) May 03, 2013
Hardly considered "theoretical" at all. Only their direct detection is. This month's measurement of a pulsar-white dwarf binary system's orbital decay rate via grav waves matches GR's prediction to within a few percent; http://phys.org/n...re.html. This is even more precise than a similar measurement by Taylor/Hulse of a binary in the early 1970s, which won the Nobel prize.
Make no mistake about it: LIGO & all the world's grav wave interferometer systems are up against the wall. A decade's worth of science runs are devoid of a single direct detection event. Now they're betting everything on so-called `Adv.LIGO', not even expected to be completed until 2015.
However, evidence indicates that Pulsar Timing arrays will achieve discovery of grav waves by next yr., 2014: http://www.techno...l-waves/ .
JIMBO
5 / 5 (3) May 03, 2013
Correction: "2016 w/95% confidence" see MIT Tech.Rev.last cite.
ValeriaT
1 / 5 (7) May 03, 2013
In AWT the question isn't, whether the gravitational waves do exist or not, because they do manifest itself like the notoriously known CMBR noise, which everyone can detect with his TV set. The Tesla's scalar waves are gravitational waves too and the neutrinos are their solitons analogous to photon. After all, every photon contains subtle space-time distortion in his belly too - the gravitational waves cannot be completely separated from EM waves in similar way, like you cannot have pure transverse wave at the water surface. It's consequence of mass-energy equivalence.
ValeriaT
1.4 / 5 (8) May 03, 2013
Being superluminal, the gravitational waves in general relativity are rather the artifact of linearization of gravity field equations. Relativists use a simplified form of Enistein field equations to calculate various properties of his gravitational field, including Einstein gravitational waves, which are based on the Einstein's pseudo-tensor. This simplified form is called the linearized field equations. They do this because Einstein's field equations are highly non-linear (implicit actually) and impossible to solve analytically. So they use the linearized form, simply assuming that they can do so. However Hermann Weyl proved in 1944 already, that linearisation of the field equations implies the existence of a Einstein's pseudo-tensor that, except for the trivial case of being precisely zero, does not otherwise exist:
ValeriaT
1.3 / 5 (8) May 03, 2013
This controversy can be understood easily, if we realize that the speed of objects in general relativity is defined only with respect to some curvature of space-time, not with respect to flat space-time. But the gravitational wave is curvature of space-time by itself and nothing else. In this way we are forced to define the speed of gravitational wave with respect to itself, which is indeed singular condition, impossible to solve mathematically. But the pseudo-tensor in linearized field equations isn't exactly equivalent the curvature of space-time being a somewhat simplistic version of the actual field curvature - which enables to introduce the gravitational waves into general relativity. It's not surprising, that even Einstein has taken the concept of GWs cautiously. Now we know, his instinct was correct again.
definitude
1 / 5 (2) May 04, 2013
Been there, done LIGO and others.

I am sitting in an office staring at wellness sign that reads, "Are you insane? Definition of; Insanity: Doing the same thing over again and expecting something different to happen."

If you are going to place an object (detector) in relation to two variable masses, you would be subject to garnishing only standing fluxuations with regard to a steady-state phenomena. This acception of such a paradigm shift in theory would push a new line of discovery. Don't expect results without change.
ValeriaT
1.2 / 5 (6) May 05, 2013
We can compare such a obstinacy to the speed, in which the cold fusion findings are dismissed at the moment, when few laboratories cannot confirm the results. It's evident, the scientific criterions of validity of experimental findings are very flexible.
vlaaing peerd
4 / 5 (3) May 06, 2013
would someone be able to tell me if both time and space "ripple" and bend equally?

I.e. if space contracts, let's say to half the lenght of what is observed outside that frame, does time contract just as much?

In that case I would think it must be pretty impossible to measure gravitational waves since you always have to measure it in the same frame of reference in which the ripples occur, in which there is no fluctuation.

Ot it is just a little to early in the morning and this thought didn't quite sink in yet. *gets coffee*

@vacuumcleaner repair man,
Are you just pasting the same sentence over an over again as a first post at each news article? Will you please quit it?

If you are able to grasp and spam bogus theories, you should also be able to understand you're getting annoying.
Fleetfoot
3.3 / 5 (4) May 06, 2013
would someone be able to tell me if both time and space "ripple" and bend equally?


Space stretches in a quadrupole motion, there is no component in the time direction:

http://en.wikiped...nal_wave
ant_oacute_nio354
1.3 / 5 (7) May 06, 2013
Gravitational waves are waves of acceleration or force, and must be
detected with accelerometers.
Spacetime doesn't exist.
We can produce and detect gravitational waves in a lab.
taka
1.4 / 5 (8) May 06, 2013
Being inside space it is absolutely impossible to measure distortion of that same space by any geometrical measurements. Whatever instrument will be distorted together with space and you will end with nothing. Prove? LIGO and others. Anybody with some imagination should catch that immediately, but some prefer to calculate without understanding what the calculation mean. Calculations for gravitational wave detectors are made in fifth dimension that is not distorted, unfortunately that mathematical dimension is not accessible for placing instruments in.
Try something else, probably related to vacuum energy changes. Random noise intensity changes? Radioactive decay speed changes?
definitude
1 / 5 (2) May 06, 2013
In a static state we deal with the 3rd dimension and arguably the 4th, you are on the 5th?
Fleetfoot
3.5 / 5 (4) May 07, 2013
Being inside space it is absolutely impossible to measure distortion of that same space by any geometrical measurements. Whatever instrument will be distorted together with space and you will end with nothing.


Matter is bound by EM forces so doesn't stretch with space, hence they are detectable in theory. In practice most sources like binary star systems rotate slowly but LIGO is only sensitive to frequencies around 100Hz so only very rare inspiral events are expected to be detectable.
definitude
1 / 5 (2) May 07, 2013
The problem is not the instermentation but the Theory. We spent trillians on particle accelerators only to find no particles, call a detector what you may, but don't expect the same results, just because you name it as such.
Fleetfoot
5 / 5 (3) May 07, 2013
The problem is not the instermentation but the Theory.


For gravitational waves, it is the instrument. They knew before they built it that it couldn't work at low enough frequency on Earth due to seismic noise but the technology has to be developed and it's a lot easier and cheaper to do that down here before putting it into space.

We spent trillians on particle accelerators only to find no particles, call a detector what you may, but don't expect the same results, just because you name it as such.


You mean the way the LHC didn't find the Higgs Boson?

Accelerators don't just find new particles, they are also built to measure those we already know of to greater accuracy.
taka
1 / 5 (2) May 08, 2013
EM forces do stretch with space of course. Equations that describe them use space coordinates!

It will be interesting of course to get measurements from space, but my bet is that also give nothing.

Good example of that fifth dimension is description of gravitational waves given in Wikipedia. Look to that illustration there and think from where such picture can be seen. Definitely not from inside space, light would bend and effect becomes invisible.
ValeriaT
1 / 5 (3) May 08, 2013
Inside of flat 3D space the effects like the time dilatation and gravitational lensing are manifestation of fourth dimension (in similar way, like the gravitational waves). The dark matter is merely five-dimensional effect.
cantdrive85
1 / 5 (3) May 08, 2013
Unfortunately for theoretical models, there exist but three dimensions in reality. The metaphysics of multiple dimensions is little more than philosophical nonsense.
ValeriaT
1 / 5 (3) May 08, 2013
Three-dimensional space is perfectly flat, empty void and it cannot be curved. If it does contain some lens, density blobs or even more dense composite particles, it cannot be "just 3D" anymore - despite you're willing to accept it or not. In AWT the hyperdimensional models have their limits too - they were invented with mathematicians and they're solely dependent on right-angled Euclidean geometry - so they represent schematic reductionist description of reality too. But they still can improve its understanding - and they're representing the approach, which is accessible for existing formal models. In my water surface model I'm rather explaining the concept of extra-dimensions by underwater analogy, rather than using it for actual explanations, because only few people can imagine extradimensions in illustrative way.
ValeriaT
1 / 5 (2) May 08, 2013
For example, the common material objects behaving like systems of mutually separated particles (atom, molecules) connected with various forces at distance. From AWT perspective such an objects do appear like the surface of hyperdimensional objects, penetrating the 3D space in similar way, like the jagged 3D object penetrates the 2D water surface. The quantum undulations of particles do appear like the periodic motion of hyperdimensional object across time dimension.
cantdrive85
1 / 5 (3) May 08, 2013
Three-dimensional space is perfectly flat, empty void and it cannot be curved.


I couldn't agree more that 3D space cannot be curved, the idea "spacetime" need be curved is based solely on the interpretation of observational data. I have no problem referring to Nikola Tesla on this point;
"...Supposing that the bodies act upon the surrounding space causing curving of the same, it appears to my simple mind that the curved spaces must react on the bodies, and producing the opposite effects, straightening out the curves. Since action and reaction are coexistent, it follows that the supposed curvature of space is entirely impossible - But even if it existed it would not explain the motions of the bodies, as observed."
Fleetfoot
5 / 5 (2) May 08, 2013
I have no problem referring to Nikola Tesla on this point;

"...But even if it existed it would not explain the motions of the bodies, as observed."


Unfortunately for Tesla, GR does explain the observed motions, and more simply and accurately than any other proposed alternative. Science always wins over intuition.
ValeriaT
1 / 5 (4) May 08, 2013
Science always wins over intuition
Most of scientific findings have started just with intuitive insight, their formalization later just made them more specific and qualitative. After all, even the famous heliocentric model has started with ad-hoced intuition of Copernicus, as the direct observation rationally says, that the Sun is revolving the Earth, not vice-versa. Many findings of recent era (cold fusion, magnetic motors, antigravity) are easier to explain intuitively than with equations. The solely formal approaches merely failed (string theory, SUSY). I presume, in the era of complex hyper-dimensional physics of the next century the role of intuitive thinking will complement traditional formal approach even more.
ValeriaT
1 / 5 (3) May 08, 2013
Tesla intuitions regarding scalar wave technologies advanced the science by the whole century. BTW Many intuitions of Einstein regarding the space-time concept, Big Bang theory, black holes or gravitational waves don't appear beaten at all in the light of recent era physics. Hubble didn't like the metric expansion of space as well - and now we can see more and more clearly, his intuition won over the science of the last century. So your stance merely depends on the historical perspective chosen. IMO the roles of intuitive and deterministic approaches are merely balanced. Some findings were predicted like the coincidence of equations first, but most of them has started with some intuitive insight.
beleg
1 / 5 (2) May 10, 2013
You are suppose to embed or impose any metric on a manifold. If your phenomenon is independent of space-time this doesn't make a difference. Or as Eddington said " ripples in coordinates" representing gravitational waves are meaningless. Or equivalent to Einstein's greatest blunder. Space-time, a field like no other field.