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Subject: Flat universe
Replies: 7 Views: 316
braveman 19.05.09 - 01:51pm
Flat universe may be the new flat Earth *
braveman 19.05.09 - 01:52pm
FOR centuries the ancients believed the Earth was flat. Evidence to the contrary was either ignored or effortlessly integrated into the dominant world view. Today we dismiss flat-Earthers as ignorant, yet we may be making an almost identical mistake not about our planet, but about the entire universe.
When it comes to the universe, flatness refers to the fate of light beams travelling large distances parallel to each other. If the universe is flat, the beams will always remain parallel. Matter, energy and dark energy all produce curvature in space-time, however. If the universe's space-time is positively curved, like the surface of a sphere, parallel beams would come together. In a negatively curved, saddle-shaped universe, parallel beams would diverge
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braveman 19.05.09 - 01:52pm
Thanks in part to the Wilkinson Microwave Anisotropy Probe (WMAP) satellite, which revealed the density of matter and dark energy in the early universe, most astronomers are confident that the universe is flat. But that view is now being questioned by Joseph Silk at the University of Oxford and colleagues, who say it's possible that the WMAP observations have been misinterpreted.
In a paper accepted for publication in Monthly Notices of the Royal Astronomical Society (www.arxiv.org/abs/0901.3354), they took data from WMAP and other cosmology experiments and an*lysed it using Bayes's theorem, which can be used to show how the certainty attached to a particular conclusion is affected by different starting assumptions.
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braveman 19.05.09 - 01:52pm
Using modern astronomers' assumptions, which presuppose a flat universe, they calculated the probability that the universe was in one of three states: flat, positively curved or negatively curved. This produced a 98 per cent probability that the universe is indeed flat. When they reran the calculation starting from a more open-minded position, however, the probability changed to 67 per cent, making a flat universe far less of a certainty than astronomers generally conclude.
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braveman 19.05.09 - 01:53pm
It's a reasonable assumption that the universe isn't entirely flat, Silk says, adding that the calculation reveals how strongly astronomers' prejudices can affect their conclusions. David Spergel of Princeton University, the spokesman for WMAP, agrees. They've developed a statistically rigorous way of examining the question, he says.
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braveman 19.05.09 - 01:53pm
Silk says astronomers need to achieve a 99.9999 per cent level of confidence on the flat universe, high enough that the case startsto look compelling no matter what the starting assumptions are. It's possible, however, that no measurements will ever be able to get to that level of accuracy *
neilmrtn 21.03.10 - 05:37pm
Great Sir Braveman ... *
samstarx 22.03.10 - 01:34am
the answer to- - h0w to find universe is flat or r0und -lies in h0w we found earth is r0und, 100percent sureness will c*m 0nly by that and s0ry but divergence ane c0nvergence are wr0nng measures cause any black h0le or planet may diverge or c0nverge lite *
