How Did The Universe Expand To 46 Billion Light-Years In Just 13.8 Billion Years?

This is the way we thought about gravity for centuries, and it literally took a genius at the level of Einstein to go beyond it. It isn’t that mass at a certain distance causes a force, but that mass is a type of energy, and energy causes the fabric of the Universe to curve. The fabric of the Universe isn’t just space, but a quantity known as spacetime, where anyone and anything in it experiences space and time together, dependent on how they’re moving relative to everything else in the Universe.

In a Universe that isn’t expanding, you can fill it with matter in any configuration you like, but it will always collapse down to a black hole. Such a Universe is unstable in the context of Einstein’s gravity, and must be expanding to be stable, or we must accept its inevitable fate. (E. SIEGEL / BEYOND THE GALAXY)

One of the things we learn about a Universe governed by Einstein’s laws — General Relativity — is that it cannot be both static and stable if it has matter in it. A Universe that’s static, where the overall fabric of spacetime doesn’t change over time, would be in trouble if you put matter down into it. Over time, that matter would gravitationally attract, and would draw itself together towards a point. In a static Universe filled with matter, there’s only one possible fate: contracting down to a black hole.

Don’t worry; that’s not our fate.

The ‘raisin bread’ model of the expanding Universe, where relative distances increase as the space (dough) expands. The farther away any two raisin are from one another, the greater the observed redshift will be by time the light is received. (NASA / WMAP SCIENCE TEAM)

Because our Universe is doing the one thing it can do to prevent it: it’s expanding. The best way to imagine the Universe is as a loaf of dough in some zero-gravity oven, where the dough is filled with raisins.

Prev2 of 9Next

Leave a Reply

Your email address will not be published. Required fields are marked *