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Old 02-07-2012, 04:41 PM
 
Location: Texas
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"Gravitational waves are an exciting possibility for astronomers. They are created when massive objects are accelerated, for instance when black holes coalesce or when neutron stars vibrate. Until now there has been no direct detection of gravitational waves due to their weakness. There exist telescopes for these waves, including the German-British gravitational wave detector GEO600, the American detector LIGO and the French-Italian project, VIRGO. Their sensitivity should soon be improved by utilising, amongst other methods, squeezed light. The detection of gravitational waves would allow researchers to observe black holes, probe the innermost structure of neutron stars and unveil the riddle of dark matter. Such objects cannot be detected with normal telescopes."
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Old 02-08-2012, 03:57 PM
 
Location: Texas
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Quote:
Originally Posted by Brian.Pearson View Post

An easier-to-read version of the above ...
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Old 02-08-2012, 05:18 PM
 
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I think that we can safely state that the entire universe is in a vibrational flux whether as large as galaxies or as small as string theory.

I'm still in awe that the ancient greek Pythagoras postulated this back during the 500's B.C. .
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Old 02-08-2012, 05:36 PM
 
Location: Texas
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I think once they get this new laser going, we'll learn a lot more about stars and so forth.
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Old 02-08-2012, 06:12 PM
 
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Originally Posted by Brian.Pearson View Post
I think once they get this new laser going, we'll learn a lot more about stars and so forth.
Yeah sure hope so.

I'm curious as to what NightBazaar thinks about this?
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Old 02-08-2012, 10:34 PM
 
Location: Somewhere in northern Alabama
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"The cavity where the laser light is generated is less than 100 billionths of a metre across"

Some news writer is playing with his knowledge of powers of ten to impress the proles...
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Old 02-09-2012, 08:44 PM
 
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I'm not exactly sure how the technique works, but evidently the idea is to greatly enhance observations by equipment in space as well as Earth-based equipment. Such observations might not by likely for direct visual observation, although maybe that'd be possible, but from data collected and enhanced by the equipment providing much greater detail.

Since you can't actually see gravitational waves, only the effects are observable. The bending of light by gravitational lensing is one example. The Max Planck article suggested possible uses such as with merging black holes or vibrating neutron stars. If the idea is to enhance gravitational lensing, I can understand that a couple of black holes getting close to merging is going to mix gravitational waves as they criss-cross, sort of like dropping a couple of pebbles in a still pond. The waves from each pebble are going to cross and mix. I have no idea how such mixing can be determined from a pair of black holes, unless it involves a much greater lensing effect between the two than would be generated by either black hole individually. As for neutron stars, when they vibrate, the rapid distortion of space, especially the space closer to the star, would become noticable. Using squeezed light lasers to enhance the data from the observations might capture such vibrations, sort of like using high speed cameras to allow seeing movement in slow motion that can't otherwise be seen.

As I understood the articles, the laser light is squeezed which makes the light narrower and less scattered. In terms of the data from black holes or neutron stars, it deals with wavelengths and frequencies. One thought that crossed my mind is that if this technique proves to be a huge improvement, it might be possible to detect stellar black holes that are suspected to be drifting around the galaxy that would ordinarily be undetectable apart from great luck by just happening to come across one. At least one silent loner has been spotted. Check the Hubble images in this link. The images are still very poor in resolution, so using something like the squeezed light laser might be able to bring out additional data giving greater clarity about gravitational waves.
HubbleSite - NewsCenter - Lone Black Holes Discovered Adrift in the Galaxy (01/13/2000) - Release Images


The crown jewels in the search for gravitational waves are those left over from the Big Bang, which would be extremely faint if they exist. The Planck satellite is being used for the search. I have no idea how all other more recent gravitational waves would be removed from the data to isolate only the earliest ancient waves. I would think space throughout the entire universe would be an enormous hodge-podge gravitational mess.
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Old 02-20-2012, 05:26 PM
 
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Hi everybody,

I was just browsing through some forums when I came across this one. I happen to be a Ph.D. student in the field of gravitational waves. I actually work on making the detectors more sensitive by developing new materials to use in them, but we are all trained pretty well in the basics of gravitational waves. I noticed some misconceptions, so I thought I'd speak up and see if I can help.

To begin, I don't think that first article is very well written, and the second posted article isn't related at all, as far as I can tell.

So, squeezed light doesn't quite make the laser less scattered. The squeezing is actually in the phase or amplitude quadrature. What that means is that, if you imagine that what comes out of a laser is a bunch of photons, and each of these photons is just a little squiggle (the squiggle is in the electric and magnetic fields, but that's not really necessary to think about), then you can have either all the squiggles be the same size, or have them all line up so that they all look the same, but not both. The more you make them line up, the more their sizes change, and the more you make them the same size, the less they line up. All squeezing does is push all the uncertainty around. So a squeezed laser will have all the squiggles the same size or all lined up.

To tell you how this makes a gravitational wave detector better, I first have to clear up what kind of detector we're talking about. There are different ways to detect gravitational waves, just like there are different ways to detect light. X-rays are a really high-frequency kind of light, and if you tried to detect them with a digital camera, you wouldn't see anything, so you need a special detector to do that. In the same way, your gravitational wave detector is different based on what frequencies you want to detect. There are studies of the microwave background radiation that are trying to see very low frequency gravitational waves from the birth of the universe, and there are pulsar-timing arrays that look at objects in space to measure slightly higher-frequency gravitational waves, and then there are ground-based interferometric gravitational wave detectors like GEO600, which is discussed in the article.

So interferometric gravitational wave detectors are good for a lot of frequencies. That's good for detecting some black holes and some neutron stars, and even some supernovae, but it's limited by a bunch of different noise sources too, like earthquakes on the other side of the world, clouds floating overhead, and quantum mechanics. Believe it or not, there are ways around the earthquakes and even the clouds, but quantum mechanics is pretty serious business. Without quantum, you could make the detectors more sensitive by either increasing the power of the lasers, or by increasing the mass of the mirrors in the detector, but with quantum, you have to do both, and that gets expensive and technically challenging.

Finally, we get to squeezed light. Squeezed light lets you get around some of the quantum mechanics. You see, with quantum, you have to increase the laser power because of uncertainty in the amplitude, and you have to increase the mass of the mirrors because of uncertainty in the phase, and quantum says that there always has to be uncertainty. It's a lot cheaper to build a more powerful laser than it is to increase the mass of the mirrors (they're already pretty big, and expensive), so they use squeezed light to move all the uncertainty into the amplitude (they make all the squiggles line up, but have varying size), and then just compensate by using a more powerful laser. And that's how squeezed light helps to make interferometric gravitational wave detectors more sensitive.

So, I hope that was informative.

Just one more thing: gravitational wave need to come from things that aren't perfect spheres, and that accelerate. So you only get gravitational waves from black holes and neutron stars if they are orbiting other black holes or neutrons stars, which means you probably won't see any 'silent loners' with gravitational waves.
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Old 02-20-2012, 07:38 PM
 
Location: Texas
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Would it help to fine tune things if you could pay for the actual article in Nature Physics (http://www.nature.com/nphys/journal/v7/n12/full/nphys2083.html - broken link)?
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Old 02-20-2012, 08:02 PM
 
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Quote:
Originally Posted by Edwinhubble View Post

So, I hope that was informative.

Just one more thing: gravitational wave need to come from things that aren't perfect spheres, and that accelerate. So you only get gravitational waves from black holes and neutron stars if they are orbiting other black holes or neutrons stars, which means you probably won't see any 'silent loners' with gravitational waves.
Hi Edwin, and welcome to C-D. Interesting post. Thanks. I agree that the articles weren't all that clear. They raised more questions than answers. I made the speculation (just above your post) that using squeezed light might be used for the "slient loners", but that was pure speculation on my part.

If I'm understanding you correctly, the equipment probably wouldn't detect them because gravitational waves "need to come from things that aren't perfect spheres and that accelerate." That said, what shows in the Hubblesite.org link is that the suspected black home appears to be in motion. The reason I described it as a "silent loner" wasn't necessarily suggesting that such bh's aren't always stationary. Some could well have had a close encounter with other bh's with one being slingshoted away to drift through the galaxy, essentially as a "silent loner". There's no question that spotting these things are thought to be as rare as hens teeth, but as luck would have it, at least one was suspected to have been spotted because of the effect of gravitational lensing the bh had on a star in the background. I'm suggesting that if one has been found, then there are probably other stellar mass black holes as well.

The question then is whether the bh was in motion, or could it be more related to the apparent position the bh and star with respect to Hubble's motion and its apparent line of sight?

My question to you is that if the bh was indeed in motion, and I'm inclined to think it was, then wouldn't it be possible to detect gravitational waves from the bh as it transits across background stars? Or are you saying that it would require a close encounter between 2 black holes for gravitational waves to be detectable since such an encounter would produce a very significant and weird warping of space from the mix?
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