[codethief]

+1

In particular, dark energy is not

> "the cause of the difference between what is calculated, and what is observed"

Dark energy / the cosmological constant Λ is a completely natural parameter to the field equations, not a corrective term (even though it might feel that way if you follow the history of cosmology). It's not that we calculated Λ to be zero but observations forced us to set it to something non-zero. We had no clue what it's value should be and simply deduced from observations that it happens to be non-zero. End of story.

Now, particle physicists / field theorists have been looking for a particle physics-based explanation for Λ and preliminarily called it "dark energy". But there's no guarantee there is one. Maybe Λ is indeed just a boring parameter.