Introduction

Dark energy is a hypothetical form of energy that is proposed by physicists to explain why the universe is not just expanding but is doing so at an accelerating rate.

Think of dark energy as the "evil counterpart" to gravity–an "anti-gravity" force providing a negative pressure that fills the universe and stretches the very fabric of spacetime. As it does so dark energy drives cosmic objects apart at an increasingly rapid rate rather than drawing them together as gravity does.

The only real answer to the question "what is dark energy?" currently is "we don't know" as unsatisfactory as that may be. Scientists aren't completely in the dark, however. There are some leading candidates to account for dark energy.