Eli5 Why is said that the universe has no center or that any point in it is the center?
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Because it’s infinite. Infinite things don’t have a center, since any point could be the center with equal arbitrariness
The idea that the universe has no center, or that any point in it could be considered the center, is based on the concept of the homogeneity and isotropy of the universe. Homogeneity means that the universe looks the same, on average, regardless of where you are in it, while isotropy means that it looks the same in all directions. These principles suggest that there is no “special” or “preferred” location in the universe that could be considered its center.
To understand why this is the case, consider what would happen if the universe did have a center. In that case, there would be a location in the universe that was, in some sense, “more important” or “more special” than any other location. This would mean that there would be a preferred direction or orientation in the universe, with the center at one end and everything else radiating out from it.
However, observations of the universe do not support this idea. Instead, they show that the universe is relatively uniform, with no obvious center or preferred direction. For example, the cosmic microwave background radiation, which is the afterglow of the Big Bang, is isotropic, meaning that it has the same temperature and properties in all directions. This supports the idea that the universe has no center and is the same, on average, regardless of where you are in it.
The idea that the universe has no center, or that any point in it can be considered the center, is based on the concept of the “cosmological principle.” This principle states that the universe is homogeneous and isotropic, meaning that it looks the same in all directions and at all points in space. In other words, there is no “special” or “privileged” point in the universe that can be considered the center. This is supported by observations of the universe, which show that the properties of distant galaxies are consistent with the idea that the universe is homogeneous and isotropic. Therefore, it is generally accepted that the universe has no center, and that any point in it can be considered the center.
You might think of the universe as a 3D ball. It’ll look like that from our point of view, because we have three space directions to look in. Were at the centre of that visible ball, by definition, because we see equal distance in all directions.
But the universe isn’t 3D. It’s 4D. SpaceTIME. So the 3D space we see is to the universe like the surface is to the earth.
Imagine a map of the earth, especially an interactive one like google maps or something. There is no center to that map, you can shift it any way you want, except for the “center” of the screen you’re looking at. But it’s only the “center” because that’s where you’re currently looking. Again, you can shift the center of the view anywhere, no point on the map is special.
It’s the same for the universe, but with one more dimension, so we can’t really visualise it. But the principle is the same.
As long as there are no margins there cannot be a determined center, or likewise, any point could be the center since we don’t know what or where the margins are.
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