Dark Energy Controversy: Part 2

19Oct10

But it was not the end of the controversy.

There are three major problems with the cosmological constant that have caused the dark energy controversy to continue. The cosmological constant is controversial because:

  1. It’s often been used in the past as a fudge factor, only to be gotten rid of after more information has been gathered
  2. When calculated theoretically using quantum mechanics, scientists get a value for it that’s 10^122 times LARGER than observed! OUCH!
  3. The density of dark energy as a cosmological constant is currently in the same order of magnitude as dark matter; this is an extraordinary coincidence; it means that we are in a special period of time at which we’re actually able to detect the accelerating effects of dark energy, which is frowned upon because we are scientists of Copernicus, who said we’re not special in space or time (this is now known as the cosmological principle).

Scientists have really gone the extra mile in the search for alternative explanations…

…even to the point of risking comparison with the Queen in Alice Through the looking-glass who practiced believing “as many as six impossible things before breakfast”.

(quote from article in the New York Times on May 5, 1998, by John Noble Wilford: Cosmologists Ponder ‘Missing Energy’ of the Universe)

Broadly, there are three other possible explanations for acceleration: it could be that dark energy evolves in time; that we don’t understand gravity correctly and don’t actually need dark energy to explain acceleration; or that we must do away with the cosmological principle (which is probably the least popular option). There are many theoretical models out there based on each of these.

However, because observations fit the Lambda-CDM model so well, cosmologists stick with the cosmological constant. It’s the easiest model to ‘take aim at’ at the present time, although some appear to firmly believe it’s more than that; that the three strikes brought against the cosmological constant can be ignored based on the observations, even though scientists have not yet determined how to distinguish the cosmological constant from some other possible models in observations.

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