Naked Science Forum
Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: youdontknowme on 03/12/2008 18:16:44
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There have been articles appearing recently indicating that scientific calculations related to Dark Energy are incorrect. Specifically, the standard candle of type 1a Supernovae might have variants, and so like Cepheid variables, they would not be useful as a tick on the ruler of measurement for expansion. In addition, there have been suggestions that Einstein's model might suffice -- a scientist named Wiltshire (?) I believe -- that given the varying density of the universe, different sections would appear less or more old depending on the amount of matter present.
If it does happen that Dark Energy is in error, would this suggest that the discarded Big Crunch is more probable, given the large amount of it, 25% of the visible universe. Wouldn't it be sufficient to draw things back to a close, as it were?
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Leave aside the question of Dark Energy for a moment and consider the Friedmann-LeMaitre equation. This equation uses the average density of matter in the universe and the rate of expansion (gravitational energy and kinetic energy) to calculate whether the universe will expand forever, stay in balance, or contract to a Big Crunch.
There are various ways that the density of matter can be estimated, but all contain possible flaws. Additionally, every method so far devised comes up with a solution that is very close to showing the universe as being in balance.
Type 1a supernovae were generally regarded as being consistent as a result of the process that causes them. This process was believed to cause consistent luminosity. However, the discovery of a 1a supernova with twice the luminosity that was previously thought possible has cast doubts on this consistency (How has the distance to this 1a supernova been estimated?). Obviously, this will have implications for distance calculations across the cosmos. This, in turn, will affect estimates of the universe's average density as the volume of space in which a given density has been calculated will be smaller than previously thought. This will obviously lead to a greater estimate for the average density, and that will affect the Friedmann-LeMaitre calculations.
What the implications are for Dark Energy remains to be seen; although I think it inevitable that a certain amount of re-thinking will be required. I eagerly await further developments.
If it does happen that Dark Energy is in error, would this suggest that the discarded Big Crunch is more probable, given the large amount of it, 25% of the visible universe.
You appear to be confusing Dark Energy with Dark Matter; they are different beasties. Dark Matter is conjectured to account for the missing mass that is necessary to hold galaxies together. Dark Energy is thought to be causing the acceleration in the expansion of the universe.
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(How has the distance to this 1a supernova been estimated?)
Dunno for sure, but probably by comparing it with other type 1a supernovae in the same remote galaxy.
I've yet to see a definition of dark energy that, when you really get down to it, is any more specific than what you'd find in Lord of the Rings or Harry Potter.