Supernovas, such as the one which created the Crab Nebula, should send out bursts of gravity waves.NASAPosted on 08/22/2009 10:05:51 PM PDT by neverdem
Sensitive search fails to find ripples in space, but boosts hopes for future hunts.
Supernovas, such as the one which created the Crab Nebula, should send out bursts of gravity waves.NASAThe hunt for gravitational waves may not have found the elusive ripples in space-time predicted by Albert Einstein, but the latest results from the most sensitive survey to date are providing clear insight into the origins and fabric of the Universe.
General relativity predicts that gravitational waves are generated by accelerating masses. Violent yet rare events, such as a supernova explosion or the collision of two black holes, should make the biggest and most detectable waves.
A more pervasive yet weaker source of waves should be the stochastic gravitational wave background (SGWB) that was mostly created in the turmoil immediately after the Big Bang, and which has spread unhindered through the Universe ever since.
The Laser Interferometer Gravitational-wave Observatory (LIGO) detectors, based in Washington state and Louisiana, look for these cosmic gravitational waves by measuring any slight disturbance to laser beams that shuttle between heavy mirrors held kilometres apart. Whereas the gravitational wave signal from a distinct event, such as a black-hole merger, would appear as a spike in the LIGO data, the SGWB is a murmur that is more difficult to detect.
“For 40 years they've been saying that gravity waves are around the corner ... I think for the first time that's actually a true statement.”
Michael Turner
University of Chicago, Illinois
Working with the Virgo Collaboration, which runs a gravitational wave detector near Pisa, Italy, the LIGO team has now analysed what their own detector saw between November 2005 and September 2007. Although LIGO did not find any waves, the teams conclude in Nature1 that the SGWB is even smaller than LIGO can currently detect. This result rules out some theoretical models of the early Universe that would generate a relatively large background of gravitational waves.
"This is the first time that an experiment directly searching for gravitational waves is essentially going and making a statement about cosmology, about the evolution of the Universe," says Vuk Mandic, an astrophysicist at the University of Minnesota in Minneapolis, and part of the LIGO team. The data also exclude certain cosmological models involving cosmic strings — hypothetical cracks in the fabric of space that are thinner than an atom but have immense gravitational fields.
The LIGO results reduce the upper limit for the size of the SGWB, which had previously been set by indirect measurements. A relatively large SGWB in the very early Universe, for example, would have had a measurable effect on both the cosmic microwave background radiation left over from that time, and the relative amounts of light elements — such as hydrogen, helium and lithium — created within minutes of the Big Bang.
The LIGO and Virgo collaborations are in the process of merging their scientific efforts, and the teams plan to include data and collaborative work from both experiments in all of their future papers. Detector improvements should help Virgo to match LIGO's sensitivity in the next few years, and a series of upgrades to both experiments should increase their sensitivity to the SGWB by more than a thousand times by 2014 — which astrophysicists say is almost certain to be enough to pin down its quarry at last.
"For some 40 years they've been saying that gravity waves are around the corner," says Michael Turner, an astrophysicist at the University of Chicago in Illinois, who was not involved in the research. "And I think for the first time in 40 years that's actually a true statement."
In 1491 there was no scientific consensus that the world wasn’t flat....
Fascinating. Perhaps they don’t appreciate the importance search?
They contradict each other. Call that incomplete if you like. Newtonian physics gives accurate results in everyday circumstances. Go to any beginning physics class anywhere in the world, and the student begins with Newtonian physics--no mention of relativity or quantum mechanics. But does Newtonian physics describe all physical phenomena? No, that's why relativity and quantum mechanics were invented. But again those two new theories contradict each other. So the search is on for a better theory.
Science works by consensus. A theory is held until observation requires a better theory. Newtonian physics was the theory held by the majority of physicists for 200 hundred years. So should we ridicule Newton and everyone who followed his theories? No, It was a tremendous intellectual achievement. It works very well in limited situation. But we know now that it isn't true. So now there are two competing theories, relativity and quantum mechanics. And since these two theories contradiction each other, we know they are not true either. So the search is on for a better theory. And at some point a new consensus will be reached. That's the way science works.
If you are looking for absolute "truth", then I would suggest you find another subject to study--perhaps philosophy or theology.
There are two elephant in the living room kinds of problems with Einstein's description of gravity. One is that Einstein claimed information could not be passed around faster than C while gravity is known to act instantaneously to within our ability to measure it. The other is that Einstein's description of gravity as some sort of a four dimensional differential geometry thing would not allow you to think it could have changed significantly on our own planet recently, and yet it's a simple demonstration that it has and that the super animals of past ages on this planet would be crushed by their own weight in our present world. So much for Einstein; quantum mechanics to my knowledge doesn't have anything to say about gravity in the large.
I doubt that a physicist today would agree that gravity has been shown to act instantaneously. Every mass creates a gravitational field. But where is the research that says that field propagates instantaneously over millions of miles? It doesn't exist.
The other is that Einstein's description of gravity as some sort of a four dimensional differential geometry thing would not allow you to think it could have changed significantly on our own planet recently
Gravity is a function of mass. The mass of the earth has not changed in millions of years. That has nothing to do with relativity theory.
yet it's a simple demonstration that it has and that the super animals of past ages on this planet would be crushed by their own weight in our present world.
Now I get it. You are pulling my leg. OK, very funny joke.
There is a very good reason for that. The gravitational force is the weakest in the physical universe. It only becomes significant in objects of very large mass, like a star or planet. Quantum mechanics studies subatomic particles. The masses of those particles are very small. The gravitational force that those particles exert on each other is insignificant.
As I sit here typing this post my body is exerting a gravitational force on the computer. The computer is exerting a gravitational force on me. I have a greater mass than the computer. So why doesn't the computer come crashing into me? Because the gravitational force of my body is insignificant.
Now I get it. You are pulling my leg. OK, very funny joke.
We seem to have Mr. SwordMaker as a reference on that one.
The physics of the thing are simple enough. The square/cube problem is the reason it was always the littlest kid in your gradeschool class who could do the most chin-ups and why you don't see 200-lb athletes in gymnastics.
I didn't know that dinosaurs did chinups and gymnastics. You learn something new every day.
That's not a fact. That's one theory among many. A theory is not a fact.
OK, let me generalize. Einstein's relativity and quantum mechanics contradict each other. Relativity gives wrong answers when applied to the phenomena of small particles that quantum mechanics describes. Is that better?
Sorry, that is a fact and it’s a fact which has been known for several centuries. You might want to try actually reading that link to Tom Van Flandern’s website which I posted, Tom was a director of the Naval observatory and a major authority on that sort of physics. If there were any lag at all to gravity, our solar system would fly apart in short order.
You are confusing observation with facts and theory. You give it aways with "that sort of physics". "That sort of physics" is a theory. As for our solar system showing no lag, the explanation is simple. In our solar system mass is not being created instantaneously out of nothing.
One could say they contradict each other. They are the best we’ve got though. Considering the strengths of each it might be better to assume that they agree on gravity being fundamentally misunderstood on a very basic level. The assumptions are wrong. If that means it’s ‘logical’ to invent multiple dimensions instead of rethinking the basic mechanism, then you would have to redefine the word logic.
It's not a matter of saying they could. They DO contradict each other. That's why Einstein spent the last 30 years of his life working on Unified Field Theory. He could not accept the contradiction between his relativity theory and quantum mechanics. But Einstein failed to resolve the contradiction. The search goes on for a better theory.
They are the best we’ve got though.
Yes, they are the best we've got at the moment.
Considering the strengths of each it might be better to assume that they agree on gravity being fundamentally misunderstood on a very basic level.
Well, if you are saying that relativity theory and quantum mechanics are incomplete, I would agree.
The assumptions are wrong.
OK, but assumptions are not arrived at through logical deduction. You start with assumptions and then deduce conclusions from these by the laws of logic. So today physicist are rethinking the assumptions, or perhaps re-imagining would be a better word. It will take some creative thinking to devise a better theory.
If that means it’s ‘logical’ to invent multiple dimensions instead of rethinking the basic mechanism, then you would have to redefine the word logic.
No, there is no reason to redefine the word logic. You are confusing logic with assumption. Let me give you a basic example. In plane geometry you start with a point, a line, and a plane. These are not even formally defined in geometry. It is assumed that they exist and you know what they are. These are the assumptions. From those three assumptions and a few definitions you use logic to build a great many theorems.
The assumption in Newtonian physics is that space and time are constant and that the speed of light is relative. But measurements in the late 19th century showed that the speed of light is constant. Physicists proposed many theories which preserved the assumptions that space and time are constant. But Einstein won the day with a change in assumptions. He said let space and time be relative. If you do that, then the math works out and the speed of light is constant.
With theories like string theory you do have to assume their are more dimensions than 4. It may be totally wrong. But you have to do this because string theory lets go of an assumption from plain geometry--the point that has no dimensions. In string theory there are no point particles. Instead there are strings that have dimension. Point particles do not occupy space. Strings do occupy space. And in string theory point particles are not the building blocks of matter. Instead strings are the basic units of matter.
String theory may be totally wrong. So which theory is your candidate to reconcile relativity and quantum mechanics?
Thorough answer. It’s clear that both theories are correct in their respect fields. Einstein did indeed waste many years trying to quantify the gravitational force. Some sort of legacy deal after the photoelectric effect spawned it I guess. The fact is, they are both right. Treating an inherent space-time reaction to matter’s presence with an expansion of physical theories is illogical. Virtual gravitons get grants.
You seem relatively passionate about this. This has perplexed many great minds for many years. What are your thoughts?
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