How much space does the universe occupy when expanding?

Philosophically speaking, the universe is everything.

That means that it cannot be expanded towards anything because there is nothing that is not the universe.

To understand this, the analogy that the Big Bang, the so-called explosion that gave rise to the universe, is not like a nuclear bomb that starts from a central point and has a radial expansion is usually raised.

The Big Bang, and not only that beginning of the universe but also the expansion of the cosmos since then, is more like the surface of a swelling balloon: everything separating from everything else.

A first approximation is that, imagine the galaxies on the surface of a balloon or a ball that inflates.

Everything distances itself from everything, there is no point that has a particular geometric significance.

They are all equivalent.

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What are the limits of our universe?

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cosmic void

What happens is that the surface of the globe has two dimensions and the universe has three and a fourth, which is time.

There is another model with which we can make an approximation adjusted to these characteristics.

It is the model of the

, the galaxies are the raisins and when you make a cake and the dough grows, the raisins separate from each other but do not change in size.

This is a very good approximation because, locally, the universe does not expand.

But the plumcake expands into an outer dimension that may be the space in the oven it occupies.

There is a person who measures that expansion that is you checking that the baking is going well.

The problem with the plumcake model is that there's really no way to test if there's an extra dimension that your universe expands into, so you'd have to imagine yourself inside a plumcake that has no observable edge.

The galaxy is similar to baking a cake: the dough rises and the raisins separate from each other, but do not change in size

Here you have to keep in mind that in the universe there is the curvature that you can measure and the one that you cannot measure or that you cannot erase in some way.

Imagine that you are an ant and that you live in a cylinder, if you draw a triangle in your cylinder, the sum of the three angles measures 180 degrees.

But if you are an ant that lives in a sphere, the space that defines the surface of your sphere is curved, the same sum as before gives more than 180º.

That means that it is an intrinsic curvature, on the other hand, to see the curvature of the cylinder that seems flat to you, you would have to look at it from the outside, using one more dimension.

But who defines that extra dimension?

How do you measure it?

You are that ant that lives there and you cannot launch yourself into that new dimension.

The person outside is the only one who can appreciate it.

Outside the universe there is nothing.

And we're not talking about a vacuum, because the theory of relativity with its oddities can also describe the parts of the universe where there is a vacuum, as long as space and time can be defined.

What we are talking about is authentic nothing, where those geometric notions do not make sense.

So the answer to your question is that, since everything that exists is a universe, it does not expand to any place other than the universe itself.

The space-time that the cosmos occupies is created as the universe expands.

Ruth Lazkoz

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