Where is the center of the Universe?

The Universe, with its size and complexity, has continued to fascinate and puzzle curious minds for centuries. Among the most fundamental questions that captivate astronomers and cosmologists: Is there a center of the Universe? And if so, where is it?

Hubble’s discoveries

In the early 1920s, astronomer Edwin Hubble made two major discoveries that transformed our view of the cosmos. First, he observed that distant nebulae were actually separate galaxies scattered throughout the Universe. This discovery marked a major turning point in astronomy, because it showed that it was much larger and more complex than previously believed. Even more surprising, Hubble found that all of these galaxies appeared to be moving away from the Milky Way. By analyzing their light spectra, he observed a redshift proportional to their distance: the most distant galaxies seemed to be moving away more quickly than those located closer to us. This phenomenon, today known as Hubble’s law, is crucial evidence of the expansion of the universe. These revolutionary observations were explained by Einstein’s theory of general relativity, published a few years earlier. Einstein had predicted that the universe could be expanding or contracting, an idea that contrasted sharply with the static and unchanging view of the cosmos that prevailed at the time. Hubble’s discovery thus confirmed the dynamic implications of Einstein’s theory. As a result, the concept of a constantly expanding cosmos was solidified. According to this new understanding, the universe began its expansion from a state of extreme density and temperature, an initial event known as the Big BangThis theory not only changed our perception of the cosmos, but also opened the way to new explorations into the nature of space, time and our place within this immense cosmic web.
A telescope image of the Large Magellanic Cloud. Credit: Zdeněk Bardon/ESO

Where is the center of the Universe?

The question of the center of the Universe is fascinating, but puzzling. At first glance, one might think that the Big Bang, the initial moment of its expansion, is its natural center. However, our modern understanding of cosmology tells us that this notion is more complex than it seems. To understand the Universe, we must first consider its dimensions and fundamental characteristics. It itself is estimated to be about 13.77 billion yearsbut due to the limitation of the speed of light, our vision is limited to about 45 billion light years away. Beyond this distance, its expansion is so rapid that the light emitted by these regions will never reach us. Thus, most of the cosmos remains invisible to us, comparable to trying to cross a dark forest with a flashlight whose beam can only illuminate up to a certain distance.

No center

By definition, the Universe encompasses everything that exists. This means that there can be no external boundaries, because any division would imply something outside of it. Thus, it could be so vast that it would be impossible to locate a precise center in an infinite space. Another perspective is that the Universe could be finite, but curved on itself on a very large cosmic scale. This would mean that if you travel far enough in one direction, you would eventually return to your starting point, just as if you walked around the Earth and returned to your starting point after traveling through every possible direction. In this scenario, there would be nostill no privileged central point. Each point would then be equidistant from the “center” in this curved structure. Consider the analogy of the Earth: you can easily identify the center of the planet by pointing to its core, but it is impossible to designate a center on the surface of a map, because each point can appear to be at the center from its own perspective. Similarly, the Big Bang, the event that marked the beginning of our Universe, did not occur at a point in space, but at a specific moment in time. It marked the beginning of the expansion of all space and time simultaneously. So, even though from an Earthly perspective, all other galaxies appear to be moving away from the Milky Waygiving the illusion that we are at the center of the expansion of the Universe, this perception is misleading, because any galaxy could claim to be at the center of its own expansion field, each point in space having a similar perspective. The quest for the center of the Universe therefore invites us to reconsider our conception of spaceof time and our place within this vast, ever-changing cosmos. It teaches us that although we are at the centre of our own observable horizon, every point in the Universe can legitimately claim to be at the center of its own observable universeIt is a dizzying but enriching prospect that pushes us to appreciate the relativity of our position in this immense and constantly expanding space.