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Initial Tests Fail To Find Gravitational Waves
eldavojohn writes that though gravitational waves are "predicted to exist by Einstein's Theory of General Relativity, the initial tests run by the Laser Interferometer Gravitational-Wave Observatory Scientific Collaboration (LIGO) failed to find anything. It doesn't disprove their existence although it does rule out a subset of string theory. From the article, 'For example, some models predict the existence of cosmic strings, which are loops in space-time that may have formed in the early universe and gotten stretched to large scales along with the expansion of the universe. These objects are thought to produce bursts of gravitational waves as they oscillate. Since no large-amplitude gravitational waves were found, cosmic strings, if they exist at all, must be smaller than some models predict.' The scientists working in Washington and Louisiana (in tandem to rule out flukes) will now move on to Advanced LIGO which will analyze a volume of space 1,000 times larger. If they don't find any gravitational waves in that experiment, the results will be more than unsettling to many theorists."
It should be noted that the existance of gravitational waves is pretty much certain - measurements of pulsars like the Hulse-Taylor binary match up perfectly with the predictions of GR.
What LIGO is about is trying to observe them directly, rather than just observing the effects of them.
Oblig. XKCD: Lisp
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No, no...I was confused at his post too (wow this guy reads too much SF!) but then I realized that his first statement is not about the existence of advanced civilisations, but rather suggests that an advanced civilisation will have more of the tools and ability to solve these problems. He is suggesting that WE need to focus on such efforts as nanotechnology and such, because once we're one of those `high tech civilisations', doing physics will be easier. To an extent I think he's got a point; we can certainly do much better physics now than Gallileo (if only because of apparati), and nanotechnology may indeed allow us to build larger (or smaller) and more stable structures, which may be necessary to directly detect some of the more elusive universal secrets.
I think you completely missed the point. If there is a God, then studying what He/She/It created is of far lesser importance than studying God Himself. Once God is found, everything else pales in comparison. The secrets of the universe are not in what it does, or how it works; but who made it. I think that's what Jastrow was saying, anyway.
> Which always made me wonder, how do gravity waves escape a black hole?
They don't. While systems involving black holes may emit gravitational waves, the waves don't come from inside the hole.
Warning: this article may contain humor, sarcasm, parody, and perhaps even irony. Read at your own risk.
In a field of grain, you can grow wheat, barley, rye or oats.
That's very true, of course. But you can't grow wheat, barley, and Ford Pintos. I'm arguing that physics, philosophy, and automobile repair are fields of study, while ID is not. It is a platform. An agenda. It's like saying the people paid by the tobacco companies to falsify studies on the effects of tobacco smoke are conducting science. Apples to orangutans.
Disclaimer: I don't work on LIGO, but I work with people who do.
LIGO didn't expect to see a signal above the noise here. What it has done, is largely rule out a lot of 'exotic' sources - sources with equations of state that don't fit the normal matter we see, but some of the more ambitious parts of string theory thought might be possible. What they have achieved is a phenomenal reduction in their 'noise curve' - the background above which a signal must register to be considered real. So far it's only been a one-way test - just ruling out exotic sources, but nothing that we think should necessarily be there.
LIGO primer and vast oversimplification:
LIGO is an interferometer. The way it works is that a laser is split into two parts, each of which goes down an equal length tunnel, at right angles to one another. If the light went the same distance, when it is reflected back, it should still be in phase, and should interfere constructively (think back to intro physics and the way waves on a string add). If a gravitational wave which had the right polarization passed through the region in the time of detection, one tunnel will have been 'shorter' due to the contracting geometry caused by the wave, and hence the beams will no longer be in phase when they return, so will not interfere constructively in the same way.
So why is it so hard to see waves? Well, all kinds of things (drilling, trucks going by, someone sneezing!) can cause a minute wobbling of any part of the equipment and thus will cause the waves to interfere in the wrong way. What LIGO looks for is a specific 'signature' measured at three sites concurrently, the signature being the waves predicted to occur from certain galactic events (two black holes spiraling into one another, for example). They do some pretty impressive data processing to look for this, but so far have only found that they can't see anything above the noise. We've ruled out some of the less likely things that could be going on - types of matter that some string theories allow, but certainly aren't predicted to exist by established theories (like GR).
However, over time with a few additions to 'advanced' LIGO, or the amazing LISA project we should have a two-way test: Either we'll see the wave that GR predicts to exist from standard black hole collisions, or theoretical physicists have a lot of explaining to do.
Have they tried reversing the polarity of the main deflector array?
That only works if one first applies an ionized tachyon pulse to clear the emitters.
Gravity sucks.
It always lets us down
Ergo, Gravity != Rick Astley.
The visualization is sound, for a 3d representation. The problem is that space/time involves the 4th dimension, and we are 3rd demensional beings. It is impossible for us to visualize anything in the 4th dimension in a literal sense - we have no frame of reference.
We can think about it abstractly, in ways we can somewhat understand. That is what the "rubber sheet" model is. Space/time is obviously not a 2d plane in a 3d world, it's a 3d plane in a 4d world. What is actually happening is that rubbersheet exists in every direction - forward, backward, up and down. It's not many sheets, it's not a sphere surrounding everything, it is a plane that exists in all three dimensions. It's a difficult abstraction to make, and it is impossible to accurately and literally conceptualize because we have no 4d frame of reference.
For a good explanation of why that is, check out Carl Sagan's explanation, it's rather enlightening. He steps it down to a 3d object interacting with a 2d world, so that we have a frame of reference to understand what is happening.
You won't come out understanding the 4th dimension, you'll come out understanding why you can't understand the 4th dimension, and since Space/Time is a 4th dimensional concept, why the explanations don't make sense.
Security is mostly a superstition... Avoiding danger is no safer in the long run than outright exposure. - Helen Keller