Is there really a 'crisis' in cosmology?
By Paul Sutter 1 day ago
Maybe we just don't understand some cosmic phenomena as well as we think we do.
The Crab Nebula as seen by the Hubble Space Telescope and ground-based telescopes in a composite view. The nebula is the aftermath of a brilliant supernova spotted in 1054. (Image credit: NASA, ESA, NRAO/AUI/NSF and G. Dubner (University of Buenos Aires))
You may have heard about the "cosmology crisis:" Different methods of measuring the age of the universe are giving different results, and cosmologists have no idea why.
As an astrophysicist — and a cosmologist, to boot — I have my own take on this so-called crisis.
But first, let's see what the problem is.
In one corner: the cosmic microwave background
To measure the age of the universe, you have to know its expansion history. And to get the expansion history, you need to do some mathematical modeling. Mathematical modeling is pretty common in science (indeed, it basically is science), and in the case of the entire universe, the mathematical model is Einstein's theory of general relativity.
When you apply general relativity to the whole universe, you get the Friedmann equations, a set of equations that connect the contents of the universe at any one time — say, the relative amounts of dark matter, dark energy, radiation and anything else — to the expansion rate at that time.
So, measure the stuff, get the age.
More:
https://www.space.com/cosmology-crisis-age-of-the-universe?utm_source=notification
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