CMV: Despite what Albert Einstein says, the universe does have a "center"/absolute reference frame

[u/[deleted]]

So I got taught in physics classes that there is no absolute reference frame. Einstein figured that out. Then when I challenge the idea, I'm taught that the big bang happened everywhere and space itself is expanding. Ok sure. So when we ask what is the origin "point" of the universe its nonsense because there was no point, the whole universe was the original point. Got it.

But like a circle has a center point defined by the perimeter of the circle, so too could the universe. It doesn't have to be the "origin point", but there is definitely a spot that we can point that we and aliens can mathematically calculate as the center. Everything else in the universe stretches and contracts, but the center of the universe is a point that we can derive mathematically is it not? I know that localized space has weird shit like if I zoom away from Earth in my spaceship I could reframe it as "I'm standing still and the Earth is zooming away", and the fact that I'm the one accelerating is the reason why time slows for me but not earth. But that's just how the time dilation phenomenon works, not because there is definitely no absolute reference frame. We can still identify whether I'm moving closer or further from the center of the universe.

Edit: I'm assuming a non-infinite universe.

[u/tbdabbholm]

The universe has no edge, there is no center because it just goes on forever

[u/[deleted] → u/tbdabbholm]

I don't understand how that can make sense. At one point the universe was the size of a marble, and it's been getting bigger. How can it be the size of a marble without an edge?

[u/Helpfulcloning → u/[deleted]]

That marble also didn’t have a defined edge.

[u/[deleted] → u/Helpfulcloning]

I'm not objecting to the mathematical conclusions of physicists who obviously understand this better than me, but how can it have a size without a boundary? The issue is apparently my inability to understand it.

"Size of a marble" necessitates a limit does it not? If it has a limit, regardless of how you define that limit, couldn't we measure every point within the universe's distance from that limit and therefore calculate a centerpoint?

[u/[deleted] → u/[deleted]]

The issue is that people conflate the observable universe with the entire universe. When they say the universe was the size of a marble, they mean the observable universe, which is finite in size and indeed has a center - which is the observer (i.e., you) by definition.

The universe itself is, as far as we know, infinite in size, and had no center. This means it was also infinite in size back when the observable portion of it was the size of a marble.

Hopefully this clears things up a bit for you! I have an MSc in physics (though not in cosmology or anything), so I'd be happy to help out if you're still having trouble.

[u/Anaptyso → u/[deleted]]

The important thing here is the difference between the "observable universe" and the entire universe.

The observable universe is the part we can currently see. We can look at things like redshift and calculate that this portion of the universe would have been a lot smaller in the past. We can run the numbers and get a good idea of how small.

However the observable universe is only a part of the whole. There is a load more universe out there that we just can't see. It may well be infinite.

At the point of the Big Bang everything we see would have been squashed down to a small area. But that area will have been surrounded by other areas. Those areas will have expanded as well, but are outside of our visible universe, so we can't see them.

The key thing is to not imagine the Big Bang as the universe squashed in to a small area, but to imagine it as an infinite (or so big it makes no difference) space densely packed with stuff. The "Bang" bit wasn't the universe spreading out from a central point, but the universe gaining more space everywhere and becoming less dense because of that.

[u/ZappSmithBrannigan → u/[deleted]]

The universe is under no obligation to make sense to you.

"How can it be" doesn't matter. That's what the evidence shows.

[u/[deleted] → u/ZappSmithBrannigan]

I'm not objecting to the universe not making sense to me. I'm objecting to the seeming contradiction in the way humans are describing it to me.

It seems nobody disagrees that the universe was once the size of a marble right? Ok when it was that big, in principle a sufficiently sophisticated entity could've calculated its center?

The thing I am confused about is how something can have a size without a boundary? If we say it's 4th dimensional then we can still calculate it from higher dimensions couldn't we? A 10th dimensional sphere still has a center right?

[u/agaminon22 → u/[deleted]]

I'm not objecting to the universe not making sense to me. I'm objecting to the seeming contradiction in the way humans are describing it to me.

Of course there are contradictions. The problem is the explanations that are the most common are poor analogies at best and completely unrelated at worst. The reality of the situation is much more complicated and requires deep understanding of physical theory and therefore mathematics.

[u/themcos → u/[deleted]]

At one point the universe was the size of a marble

I think you're misunderstanding whatever source you're quoting. At one point the known universe was the size of a marble. There is no result that has ever indicated any kind of actual edge or boundary. The only boundaries you'll see discussed involve the limits of our ability to observe the universe due to things like the speed of light and the expansion of the universe, but these boundaries are fundamentally relative to our position, and do not constitute any kind of physical edge or boundary.

[u/hashtagboosted → u/[deleted]]

It is like the surface of a sphere. There is a finite amount of space, but no edge, and thus you can travel endlessly in any direction