The Size of the Universe

Space, as Douglas Adams once so aptly wrote, is big. To try imagining how big, place a penny down in front of you. If our sun were the size of that penny, the nearest star, Alpha Centauri, would be 350 miles away. Depending on where you live, that’s very likely in the next state (or possibly country) over. Attempting to imagine distances larger than this quickly becomes troublesome. At this scale, the Milky Way galaxy would be 7.5 million miles across, or more than 30 times the distance between the Earth and the moon. As you can see, these are rather inhuman dimensions that are almost impossible to really get a sense of. But that doesn’t mean it’s completely impossible. Astronomers have made observations and simulations that in some way capture the enormity of our cosmos. No one knows exactly how large the universe is. It could be infinite or it could have an edge, meaning that traveling for long enough in one direction will bring you back to where you started, like traveling on the surface of a sphere. Scientists argue over the exact shape and size of the universe but they can calculate one thing with good precision: how far away we can see. Light travels at a specific speed, and because the universe is approximately 13.7 billion years old, we can’t see anything farther away than 13.7 billion light years away, right? Wrong. The strange thing about space is that it’s expanding. And that expansion can occur at more or less any speed — including faster than light speed — so the most distant objects we can see were in fact once much closer to us. Over time, the universe has shuffled distant stars and galaxies away from us as if they were on an extremely rapid conveyor belt, and dropped them off in far away locations. Strangely, this means that our observational power is sort of “boosted” and the furthest things we can see are more than 46 billion light years away. While we are not the center of the universe, we are at the center of this observable portion of the universe, which traces out a sphere roughly 93 billion light years across.