Nearly 14 billion years ago, the universe sprang into existence from a point no larger than the tip of a pen. We typically think of explosions in the real world being slowed down by air friction and gravity. Naturally, we expected the Big Bang to follow suit and gradually slow due to gravity.

In the late 1990s, two teams of scientists decided to measure this anticipated slowdown. To their surprise, they found that the universe’s expansion was not slowing down. Instead, it was speeding up.

This acceleration implies there is an enormous amount of energy in play, one that counteracts the grip of gravity across the universe. However, scientists have no clear idea what this energy truly is. Remarkably, this mysterious energy, propelling the universe’s expansion, surpasses the total visible matter by more than tenfold.

The leading theory suggests that this dark energy might be an intrinsic property of space itself. As space continues to expand, it generates more of this anti-gravity force, driving the universe to grow ever faster.