Question

We see that the Universe is also called (sky) when Aristotle talks about it.

But I thought about it and I came to the conclusion when someone asked the question about my belief in what Aristotle said that I understood what they were saying and it was this: If the sky was the universe then the earth is inside of the sky. I asked this question because I did not believe his claim.

What is the boundary of the universe? Since the universe is always getting bigger because matter is expanding. This means that the universe would need to be inside of something for it to expand. My question is: What is the universe inside of if it is always able to get bigger because matter expands?

If the universe is not inside of anything then that means that it has a boundary and matter would not be able to expand because there is not enough room to expand.

Do you think that the Universe has a boundary?

Answer 1

The question of the universe having a boundary ties into cosmology and general relativity. Modern science sees the universe as expanding, not into something else, but as the spacetime fabric stretching. Current theories suggest our universe might be flat and possibly infinite without an edge or boundary.

Step-by-step explanation:

The question of whether the universe has a boundary or what it could be expanding into is deeply connected to the field of cosmology and our understanding of general relativity and the cosmological principle. Aristotle's ancient view saw the cosmos as a finite, structured whole, but modern science has shown that the universe is expanding, with galaxies moving away from each other. This expansion, discovered by looking at distant galaxies and observing the redshift of their light, is explained by the Big Bang theory where the universe started out as a singularity. According to the theory of general relativity, space itself is expanding, and it doesn't require a space 'outside' it to expand into; in essence, it's not expanding 'into' anything we can comprehend.

To further complicate matters, spacetime according to general relativity can be curved or flat, and our universe appears to be fundamentally flat on large scales. The nature of this 'flatness' suggests a universe that's at least 100 times larger than our observable horizon, and possibly infinite. As such, the universe may not have an edge or a boundary in the conventional sense. Instead of seeing the universe as something expanding into another space, it is more accurate to see it as a spacetime fabric that is stretching.

Furthermore, puzzling over the edge of the universe can be analogous to ancient thinkers' struggles with celestial movements. Just as the model of an Earth-centered universe was eventually overturned by a heliocentric one better suiting observations, our current understanding of the universe may evolve as more evidence and better theories emerge.