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 ...
I would assume that, with light from more distant areas in space reaching the earth, we should be able to see more distant (and older) objects. However there's lot of weird stuff regarding the space ...