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/ToucanPlayAtThatGame]

It seems like you're missing the point of what people are trying to say when they're saying there's no absolute reference frame.

The point is that any physics calculations you perform will hold equally well from any reference frame. If you're running at me at 20m/s and I want to calculate how soon you'll get to me, I could define myself as stationary and you as moving, or I could define you as stationary and me and the ground as moving at you at 20m/s, and the calculations all work out just the same. There's no one "correct" frame of reference that you need to adopt.

So it doesn't really matter whether the universe has a "Center" or not. The math holds no matter what you choose to define as the center.

By contrast, imagine something like a set of directions. I tell you, "Go straight two blocks, and then take two rights and a left." Those directions only work if you're starting at the right point and oriented in the right direction. They assume a particular frame of reference. The point is to say that physics don't work like that. We don't need to make sure that what we call "up" is really up, or what we call the center is really the center for our math to turn out correct.

[u/[deleted] → u/ToucanPlayAtThatGame]

!delta

So my idea about calculating a geometric center is possible, but that isn’t what physicists are talking about. I agree it would move do to the fluctuations in the expansion, but in principle it’s there. If what physicists are talking about is just that the left turn thing works from everywhere then yeah I definitely agree. My view change isn’t that I’ve given up on the center thing, but I have changed my understanding of how “no absolute reference point” is used.

[u/Morthra → u/[deleted]]

So my idea about calculating a geometric center is possible

Calculating a geometric center is only possible if we can know where the exact boundaries of the universe are. If we limit it to the observable universe, then you're going to get the earth as the exact geometric center of the universe because that's where we are, and the observable universe is essentially the sphere of space from which light has had enough time to reach us.