News article on gravitational waves
21 Aug 2009 9:14:37 UTC
Topic 194501
(moderation:
I read an article on Universetoday about the how the absence of gravitational waves in the LIGO data until now rules out some of the more exotic models of the early-universe.
This sounds like very exiting stuff! I am curious how this relates to EAH. Are they referring to EAH analysis of the data and that in that in that analysis no gravitational waves are found? If not, how was the mentioned analysis different from what we are doing? And if so, I think you guys should advertise something about these results and their consequences on your frontpage, so that people understand that they can really contribute in human's understanding of science in this project!
News article on gravitational waves
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I suggest you to visit the LIGO site. It has much more information than the Einstein@home site.
Tullio
As is par for the course with
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As is par for the course with recent LIGO research results, there is useful information that comes from non-detections. Of course a detection would be nice, but second best is to establish tighter limits on what we can expect from gravitational waves. In this case, the recent results pertain to so-called "stochastic sources" of gravitational radiation. These sources are as yet large number of unresolved sources and a variety of mechanisms in the early universe. Such mechanisms include the period of inflation, and others.
The new upper limit established by this new data analysis of S5 data is a refinement on the fractional gravitational wave contribution to the total energy budget of the Universe to a value of < 7x10^-6 at frequencies near 100Hz. This new limit is a whole order-of-magnitude better than the previous estimate.
One ramification of the new upper limit is that some string theory models of early universe evolution can now be ruled out.
Absolutely. There is nothing
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Absolutely. There is nothing wrong with a null result - as long as it's a true reflection of reality. So any absence of gravitational waves for example still tells us something very important about the universe. The idea of science is not to fit some preconception but to measure actuality. Theory always runs the risk of being falsified - meaning some measurement will require alteration so as to correct our understanding. Good science aims to bring our thinking in line with reality, not the other way around. Alas this simple strategy seems to be the cause of alot of confusion & misunderstanding about how people feel about science.
There are a couple of levels here. One is that a theory may be wrong because it is not consistent with experimental findings. So a null Michelson-Morley experiment knocked over assumptions within electromagnetic and dynamic theory. This is terrific as it triggers a rethink and is actually progress.
A deeper problem is if a theory cannot be tested to determine it's correctness or otherwise. String theory especially is currently in a lot of difficulty as it lacks a prediction for specific testing. Not for want of trying. But that's not to say it doesn't have merit, it just doesn't yet have verifiable merit. It may well be consistent, by construction usually, with a host of other existing principles but if it doesn't extend our currently validated knowledge then it is of little use. This seems harsh, but it is necessary to keep matters manageable. Interestingly Einstein didn't ( originally ) say that the 'aether' didn't exist, he said that the concept of the aether was superfluous. Having the aether in or out of one's thinking makes no odds, as it's presence isn't detectable regardless.
One instance I quite like was Copernicus's change of origin for the planets. It wasn't the epicycle business that was the advance, his theory in fact had more epicycles than Ptolemy's. But it was a simpler view to place the Sun at the centre and also extended understanding somewhat. It became easier and simpler to explain the moons of Jupiter - Jupiter is the centre of a mini-system analgous to the solar system - and led to the 'central force' concept that flowered with Kepler and Newton. Kepler got rid of the complicated epicycles by making circles a special case of ellipses. And when the full force of analysis was applied along that line it really opened a more consistent understanding of matters well beyond local space, and terrestrially too ( so the earth is a sphere because that's the compact minimum, in three dimensions, for a central attractive force ).
Galileo's troubles with the inquisition had alot of flavours running within - politics, power, personalities and whatnot - but the real valuable break was with accepting that thinking should alter with experience. Not that we should redefine our experience to suit some prejudice. So it's a good thing that string theory candidates/variants can be vetted by experimental results.
Cheers, Mike.
I have made this letter longer than usual because I lack the time to make it shorter ...
... and my other CPU is a Ryzen 5950X :-) Blaise Pascal
In the September issue of
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In the September issue of CERN Courier there are two articles about excess positrons in space. Both articles explain their presence by the standard model and exclude dark matter. Also Steven Weinberg seems to disqualify strings theory and favors the standard model plus GR. I agree with both positions.
Tullio
RE: This sounds like very
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These new S5 results, published in Nature, are upper limits on a stochastic background of gravitational waves. This is a very different type of source than E@H is searching for, so no, the E@H analysis did not contribute to this result.
(You can find links to the formal published E@H results on the E@H front page.)
Cheers,
Bruce
Director, Einstein@Home