The Origin of the Universe
The universe emerged approximately 13.77 billion years ago, but ongoing expansion has put its center beyond human reach.
A View from Earth
From our Earthly perspective, it may seem that we are at the center of everything. However, the existence and location of a cosmic center remain elusive. If the Big Bang created the universe, where did it come from and where is it heading?
Edwin Hubble's Discoveries
A century ago, astronomer Edwin Hubble made crucial observations that revolutionized our understanding of the universe. In the 1920s, he realized that galaxies reside at vast distances from Earth. Later, he discovered their general recession, meaning they were moving away from us.
Expanding Universe and the Big Bang
Einstein's theory of general relativity predicted a dynamic universe that either expands or contracts. Hubble's findings supported this notion, challenging the prevailing view of a static cosmos. Based on Einstein's equations, scientists developed the Friedmann-Lemaitre-Robertson-Walker metric, laying the foundation for modern cosmology.
Hubble Space Telescope Observations
Data from Hubble and other observations suggest that we reside in an expanding universe. Galaxies generally drift apart, originating from a minuscule singularity during the Big Bang.
The Big Bang and the Cosmic Center
Assuming the universe had a singular origin, that point would constitute the true cosmic center. However, our understanding falls short of providing a straightforward answer. The universe lacks a center or an edge; it didn't expand from a pinpoint nor expand into anything.
The Paradox of the Edge
By definition, the universe encompasses all existence. An edge implies a division, but with the universe containing everything, no such boundary exists. This implies infinite size, making finding a center in an endless expanse impossible.
A Finite but Curved Universe
Alternatively, the universe could be finite. However, this would imply that on an extremely large scale, it curves back upon itself. In this scenario, the universe still lacks a center.
Analogy with Earth
Consider Earth. Its three-dimensional core has a center, but its surface does not. Multiple points could serve as the surface center, such as the intersection of the equator and prime meridian, the poles, or even your home. Any of these points are equally valid.
The Big Bang Everywhere
Similarly, the Big Bang occurred everywhere in the universe. It happened in the room you occupy and the most distant galaxy we can detect. The Big Bang was not a location in space but a moment in time.
The Observable Universe
With light's finite speed, only a fraction of the universe is visible to us. Observations are confined to the horizon, about 45 billion light-years away. The universe expands faster than light travels, hiding vast regions from view.
Apparent Cosmic Center
For us, all other galaxies recede from the Milky Way. It appears as if we are at the center of the observable universe. However, the same is true for any galaxy; each observer perceives themselves as the center with everything else receding.
Conclusion
In an expanding universe, there is no absolute center, yet every point can be considered the center. All observers, including us, can claim central location.