The universe formed about 13.77 billion years ago, but its expansion has made pinpointing the center of the universe beyond human reach .
Images taken by the James Webb Space Telescope reveal some of the oldest and most distant galaxies ever observed. (Image: NASA/ESA/CSA/STScI)
The universe is vast and from a human perspective, it seems that the Earth is in the middle of it all. But is there a center of the universe, and if so, where is it? If the Big Bang created the universe, where did it come from and where is it going? To answer these questions, let's go back about 100 years.
In the 1920s, astronomer Edwin Hubble made two startling discoveries. Early in the decade, he noticed that galaxies were very far away from Earth. By the end of the decade, he discovered that, on average, all galaxies were receding from our planet.
Fortunately, scientists had a theoretical explanation for all of this. Einstein's general theory of relativity predicted that the universe was dynamic—expanding or contracting. This contradicted the popular view at the time that the universe was completely static. Four scientists then worked to develop the Friedmann-Lemaitre-Robertson-Walker solution to Einstein's equation, laying the foundation for modern cosmology.
The Hubble Space Telescope captured this image of three spiral galaxies about to collide in the constellation Boer. (Photo: NASA/ESA)
The solution to Einstein's equation, along with the impressive observations of the Hubble Space Telescope, shows that we live in an expanding universe. On average, every galaxy is moving farther and farther away from every other galaxy, and long ago, all the matter in the universe was compressed into an infinitely tiny point called a singularity—the starting point of the Big Bang.
So where was the Big Bang? It would certainly be the real center of the universe. However, what we know about the universe is not enough to provide a simple, clear explanation. That's because the universe has no center, and no edges. It did not expand from a point, and it does not expand into anything.
First, let's address the edge problem. By definition, the universe is everything that exists. While the edge is what separates one region from another. But if the universe consisted of all regions, then there could be no edge. This means that the universe could be infinitely large, and finding the center of an infinite space would be impossible.
Another possibility is that the universe is finite. But that would mean that, on extremely large scales—far larger than what humans can observe—the universe would fold in on itself. So the universe would also have no center.
For comparison, consider the Earth. One can point to the center of the three-dimensional planet—the molten core—but not the center of the Earth's surface: It could be at the intersection of zero latitude and zero longitude, or at the poles, or even in someone's house. Any point would be equally suitable.
So the Big Bang happened simultaneously everywhere in the universe . It happened in the room you are sitting in and also in the most distant galaxy that humans can see. The Big Bang was not a point in space but a place in time.
It is possible to show the three-dimensional center of the Earth - the molten core - but not the center of the planet's surface. Photo: Salon
But here's an interesting twist: The universe is old, about 13.77 billion years old. Because the speed of light is so fast, only a small portion of the universe is illuminated by human light. There is a limit to what humans can observe, and the edge of that limit is about 45 billion light years away from Earth. This happens because the universe is expanding faster than the speed of light.
Much of the universe is hidden from humans : Like a flashlight in a distant forest, humans can only see things within the range of illumination. From a human perspective, all other galaxies are moving away from the Milky Way. Therefore, it appears that humans are at the center of the entire universe. Of course, the same can be said for any other galaxy. From the perspective of these galaxies, they are also at the center of the observable region and all other galaxies are receding.
This is the interesting thing about an expanding universe: it has no center, and yet everywhere is the center . All observers, including humans, can claim to be in the middle.
