For most of human history, the prevailing wisdom was that the Earth was located at the center of the universe. Although this perspective may seem strange today, prior to the invention of the telescope, humanity had no way of knowing the Earth was just another planet orbiting a fairly normal star. From our perspective, everything does appear to move around us. We now know the reason for this is because the Earth is rotating, but for most of human history, it was assumed that everything in the universe went around our world. When scientists like Copernicus, Galileo, and Kepler finally revealed that the Earth orbits the sun, it largely dispelled any belief that the Earth was at the center of the universe. The Earth may not be at the center, yet is there a physical center to the universe?
Perspective In An Expanding Universe
When we talk about the universe, we are referring to the observable universe. The universe itself is larger than what we can physically see, a direct result of the fact that the speed of light is finite. From our perspective, we appear to exist in a vast bubble of space. No matter how powerful telescopes become, there will always be a limit to how far we can see. Thus, it is impossible to determine if the entire universe has a center. Rather, we can only determine if the observable universe has a center.
The idea that the Earth was at the center of the universe was actually revisited in the early 20th century after the discovery of other galaxies. In the 1920s, the astronomer Edwin Hubble discovered that the observable universe contained many billions of galaxies. Prior to this discovery, the consensus was that the Milky Way was all there was, and the rest of the universe was static and eternal. Hubble’s discovery shattered these views, and virtually overnight, the universe became far larger and grander than humanity could have imagined. Discovering other galaxies, however, was only part of Hubble’s discovery. Hubble also noticed that most galaxies in the universe are moving away from us at tremendous speeds. The universe, he discovered, is expanding. Space itself is pushing galaxies away from one another, with the speed of a galaxy dependent upon its distance from us. For example, if there are two galaxies, one being two million light years away and the other being four million light years away, the further one will move faster than the closer one. Astronomers noticed something strange with this discovery. When we look out into the universe, everything is moving away from us, making it look like we are at the center of the universe. However, this is merely an illusion of perspective. From here on Earth, we appear to be stationary with everything moving away from us, yet that observation will be identical regardless of where you are in the universe. If you were to stand on a planet in a galaxy 30-million light years away, you would see yourself as being at the center of the universe. Thus, an expanding universe has no center, yet any given location will see itself as being at the center of the universe.