Does the "amount" of dark energy in the universe change over time, or is it constant? The dark energy I am asking about is the rate of acceleration of the universe's expansion.
The new Cosmos extra features mentions that at about 6,771,500,000 years ago the universe began an accelerated expansion. How do we know this? What evidence do we have for this renewed and accelerated ...
In this article which nicely explains why it is really the quantity $\rho + 3p$ which is relevant to determine if the expansion of the universe is accelerating or decelerating by making use of the for ...