Is the universe infinite or finite?

If the universe is expanding, then into and from what is it expanding? Does the universe have a limit? Let's find out!

After a century of observations spanning the universe and theoretical insights pushing humanity's vision of the cosmos to its ultimate limits, we can finally confidently assert that the universe is infinite.

Let's start with something we can say for sure: We live in an expanding universe. But if the universe is expanding, what is it expanding into? And where is it expanding from? Where are the edges of the universe, and where is its center?

It's easy to imagine an expanding universe, and there are plenty of analogies to guide our thinking. Imagine drawing tiny galaxies on the surface of a balloon and blowing it up to see the galaxies moving further and further apart. We can imagine baking a loaf of bread with raisins inside and seeing that, as the bread inflates, the raisins move further and further apart.

But a balloon has both a center and an edge. And bread has both a center and a crust. So where is the center of the universe, and where are its edges?

Here's the harsh answer: The Big Bang had no center, and it had no edges. How can this be reasonable?

Let's start with the mind. Where did the Big Bang begin? Right here. And right there. And in the next galaxy over. The Big Bang happened everywhere, at the same time. It had to happen everywhere, because by definition, everywhere is part of the universe. It wasn't an explosion somewhere in space. It was a spatial explosion—when the expansion of the universe began. It wasn't a place, it was a moment.

So if the universe is expanding, what is it expanding into? Where is our expanding 'bread crust,' and what is the 'oven' we are sitting in?

It's so tempting to imagine a wall or boundary, with galaxies and matter on one side and nothingness on the other, with the universe expanding to fill that nothingness.

But that's wrong. Even the vacuum of space is something. There are still points, places, and existence. There is no " outside " of the universe because " outside " implies existence, even if it is empty space. But the universe, by definition, is all that exists. Nothing belongs to physical reality except the universe. Walls separate these regions from each other, but the universe includes all regions at the same time.

If there were a boundary, you might imagine yourself having to make a conscious effort to go beyond it. But that is impossible. There are no boundaries; there are no edges. There is only the universe.

Samuel Daniel

Update 14 October 2025