Question: What are your thoughts on dark energy?

Sam Lawrence answered on 21 Nov 2019:

It seems absurd that 70% of our Universe is made up of something we can’t see! That said, there’s a large amount of evidence that suggests this is so. In general, physicists agree that dark energy exists. When we include dark energy in our equations, we can explain cosmological observations (like the cosmic microwave background and the distribution of galaxies) very well. We still don’t know exactly what it is but we know it’s there. We haven’t observed it directly, just its effect on other things. Some cosmologists are looking at ways to explain observations without dark energy. One way to do this is to modify Einstein’s theory of gravity, so that our equations explain the observations without the need to include dark energy – this is an ongoing debate.