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Two new and independent studies have put Einstein's General Theory of Relativity to the test like never before. These results, made using NASA's Chandra X-ray Observatory, show Einstein's theory is still the best game in town.
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The first finding significantly weakens a competitor to General Relativity known as "f(R) gravity."
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Schmidt and colleagues used mass estimates of 49 galaxy clusters in the local universe from Chandra observations, and compared them with theoretical model predictions and studies of supernovas, the cosmic microwave background, and the large-scale distribution of galaxies.
They found no evidence that gravity is different from General Relativity on scales larger than 130 million light years. This limit corresponds to a hundred-fold improvement on the bounds of the modified gravitational force's range that can be set without using the cluster data.
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A second, independent study also bolsters General Relativity by directly testing it across cosmological distances and times. Up until now, General Relativity had been verified only using experiments from laboratory to Solar System scales, leaving the door open to the possibility that General Relativity breaks down on much larger scales.
To probe this question, a group at Stanford University compared Chandra observations of how rapidly galaxy clusters have grown over time to the predictions of General Relativity. The result is nearly complete agreement between observation and theory.
"Einstein's theory succeeds again, this time in calculating how many massive clusters have formed under gravity's pull over the last five billion years," said David Rapetti of the Kavli Institute for Particle Astrophysics and Cosmology (KIPAC) at Stanford University and SLAC National Accelerator Laboratory, who led the new study. "Excitingly and reassuringly, our results are the most robust consistency test of General Relativity yet carried out on cosmological scales."
Originally posted by mnemeth1
reply to post by OnceReturned
Well well well where to begin with this one.
First off, the measurements of galaxies showing gravity is constant by looking at galaxies is based on the assumption that gravity is indeed a cosmological constant and that galaxies themselves are held together by gravity alone.
Given that scientists must add dark matter, which has never been proven to exist, to their galaxy models in order to make them work, the assumption that gravity alone is the force that's holding galaxies together is a hypothesis, not a fact.
Further, measurements of gravity here on earth have all shown that gravity changes over time. No measurement of gravity here on earth has proven gravity to be a constant force.
Measurements using beam balances showed a variation by as much as 1% over time. Measurements using atom interferometry also showed variation outside standard deviation. Further, atom interferometry is a ridiculous tool to use to measure gravity considering atomic scale structures are governed by special relativity.
So we have actual verifiable proof that gravity is NOT constant as it is measured here on earth. We also have no proof of dark matter, which is required for the galaxy models hypothesized to be correct.
This pretty much blows Einstein's theories out of the water.
By saying "Einstein's theories fights off challengers" - they are referring to other gravity-centric models, which are just as ridiculous as Einstein's.
[edit on 20-4-2010 by mnemeth1]
Originally posted by mnemeth1
reply to post by OnceReturned
Well well well where to begin with this one.
First off, the measurements of galaxies showing gravity is constant by looking at galaxies is based on the assumption that gravity is indeed a cosmological constant and that galaxies themselves are held together by gravity alone.
Given that scientists must add dark matter, which has never been proven to exist, to their galaxy models in order to make them work, the assumption that gravity alone is the force that's holding galaxies together is a hypothesis, not a fact.
Further, measurements of gravity here on earth have all shown that gravity changes over time. No measurement of gravity here on earth has proven gravity to be a constant force.
Measurements using beam balances showed a variation by as much as 1% over time. Measurements using atom interferometry also showed variation outside standard deviation. Further, atom interferometry is a ridiculous tool to use to measure gravity considering atomic scale structures are governed by special relativity.
So we have actual verifiable proof that gravity is NOT constant as it is measured here on earth. We also have no proof of dark matter, which is required for the galaxy models hypothesized to be correct.
This pretty much blows Einstein's theories out of the water.
By saying "Einstein's theories fights off challengers" - they are referring to other gravity-centric models, which are just as ridiculous as Einstein's.
[edit on 20-4-2010 by mnemeth1]
Originally posted by Grifter.be
Are you serious?
Originally posted by mnemeth1
reply to post by OnceReturned
Further, measurements of gravity here on earth have all shown that gravity changes over time. No measurement of gravity here on earth has proven gravity to be a constant force.
The fact that this famous fundamental constant is still so uncertain testifies to the difficulty of gravitational measurements. The recent flurry of new ideas for measuring G would surely have pleased Isaac Newton (quite a clever experimenter himself) who started this whole enterprise over 300 years ago.
First off, the measurements of galaxies showing gravity is constant by looking at galaxies is based on the assumption that gravity is indeed a cosmological constant and that galaxies themselves are held together by gravity alone.