Question

What is dark energy?​

Answer 1

Answer:

More is unknown than is known. We know how much dark energy there is because we know how it affects the universe's expansion. Other than that, it is a complete mystery. But it is an important mystery. It turns out that roughly 68% of the universe is dark energy. Dark matter makes up about 27%. The rest - everything on Earth, everything ever observed with all of our instruments, all normal matter - adds up to less than 5% of the universe. Come to think of it, maybe it shouldn't be called "normal" matter at all, since it is such a small fraction of the universe.

Answer 2

Dark energy is a hypothetical form of energy that exerts a negative, repulsive pressure , behaving like the oppositie of gravity.

It is discovered by Einstein.