Link here. The astrophysicist, Paul Sutter, does a very nice job of outlining the conundrum that has been causing astrophysicists to tear their hair out for the past decade-plus.
In the two decades since astronomers discovered dark energy, we’ve come upon a little hitch: Measurements of the expansion rate of the universe (and so its age) from both the CMB [cosmic microwave background] and supernovas have gotten ever more precise, but they’re starting to disagree. We’re not talking much; the two methods are separated by only 10 million or 20 million years in estimating the 13.77-billion-year history of the universe. But we’re operating at such a level of precision that it’s worth talking about.
If anything, this failure for two measurements of data spanning billions of light years — which is billions in both time and space — is a perfect illustration of the uncertainty of science. Astrophysicists are trying to come up with answers based on data that is quite thin, with many gaps in knowledge, and carries with it many assumptions. It therefore is actually surprising that these two numbers agree as well as they do.
Sutter, being in the CMB camp, puts most of the blame for this failure on the uncertainty of what we know about supernovae. He could very well be right. The assumptions about supernovae used to measure the expansion rate of the universe are many. There is also a lot of gaps in our knowledge, including a full understanding of the process that produces supernovae.
Sutter however I think puts too much faith in theoretical conclusions of the astrophysics community that have determined the age of the universe based on the CMB. The uncertainties here are as great. Good scientists should remain skeptical of this as well. Our knowledge of physics is still incomplete. Physicists really don’t know all the answers, yet.
In the end, Sutter however does pin down the biggest problem in cosmology:
The “crisis” is a good excuse to keep writing papers, because we’ve been stumped by dark energy for over two decades, with a lot of work and not much understanding. In a sense, many cosmologists want to keep the crisis going, because as long as it exists, they have something to talk about other than counting down the years to the next big mission.
In other words, the discussion now is sometimes less about science and theories and cosmology, but instead about funding and career promotion. What a shock!
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