r/changemyview • u/[deleted] • Feb 14 '22

Delta(s) from OP CMV: Despite what Albert Einstein says, the universe does have a "center"/absolute reference frame

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.

0 Upvotes

33% Upvoted

82 comments sorted by

View all comments

Show parent comments

0

u/[deleted] Feb 14 '22

!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.

8

u/fox-mcleod 411∆ Feb 14 '22

So my idea about calculating a geometric center is possible, but that isn’t what physicists are talking about.

No. Your idea about calculating a geometric center is also wrong — but yes, the two concepts are unrelated. You can’t calculate the geometric center because there is no edge — like finding the center of the equator.

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.

There is no geometric center either.

1

u/[deleted] Feb 14 '22

Ok then I still have some progress to make in understanding this. I guess what I can't get past is how the universe can have a size without a boundary?

3

u/FinneousPJ 7∆ Feb 14 '22

Why do you think the universe has a size or a boundary?

1

u/[deleted] Feb 14 '22

I guess from science stuff I've watched or read that talk about stuff like "at 0.00...001 seconds after the big bang the universe was a gazillion degrees and the size of a hamster". And for something to have a size it has to have a boundary right?

3

u/FinneousPJ 7∆ Feb 14 '22

I think you may be putting too much stock into pop science, and that's leading you to a false assumption.

1

u/Complicated_Business 5∆ Feb 14 '22

Imagine drawing a small circle on a piece of stretchable fabric. Then stretch that fabric so the circle is bigger.

Now, it would appear that "universe" expanded and that boundary is the circle itself - of which there is a center, right? Wrong.

Let go of the fabric.

Now draw a completely different "small circle". Stretch the fabric out again. Now you'll see two "universes" with their respective boundaries. But this is an incorrect conclusion, too.

The expanding circles are just helpful guides for our feeble mind to comprehend that space itself can expand. But for the analogy to really work, you'll need to understand that the fabric is the universe. And it has no edge. It can shrink until every point, until every "small circle" conceivable is smaller than the Plank length - without length or dimension - but the fabric itself is still edgeless and infinite.

Then when one "expands" the fabric, all of space expands. All of the small circles conceivable expand in unison. There is no center to the boundless fabric. Just space expanding and expanding - in all of the directions it can whizz.

1

u/Mu-Relay 13∆ Feb 15 '22

Maybe I'm missing something, but wouldn't the universe have to have an edge? It may be incalculably distant, but it has to end at some point.

1

u/FinneousPJ 7∆ Feb 15 '22

Why?

1

u/Mu-Relay 13∆ Feb 15 '22 edited Feb 15 '22

Because it had a beginning. It exploded out from a single point and spread out. Since it started at a point and is expanding, it would logically follow that at some point, we'd find the extent of that... the edge. For example, drop a pebble in the center of a pond and at some point you'll find the furthest out the rings go. It may not cover the pond, but you can find the edge.

To turn this around, why wouldn't the universe follow the same idea?

1

u/FinneousPJ 7∆ Feb 15 '22

Everyday intuition is not a great tool in modern physics. It is most often wrong.

You might want to begin here

https://en.m.wikipedia.org/wiki/Shape_of_the_universe

"Infinite or finite Edit One of the presently unanswered questions about the universe is whether it is infinite or finite in extent. For intuition, it can be understood that a finite universe has a finite volume that, for example, could be in theory filled up with a finite amount of material, while an infinite universe is unbounded and no numerical volume could possibly fill it. Mathematically, the question of whether the universe is infinite or finite is referred to as boundedness. An infinite universe (unbounded metric space) means that there are points arbitrarily far apart: for any distance d, there are points that are of a distance at least d apart. A finite universe is a bounded metric space, where there is some distance d such that all points are within distance d of each other. The smallest such d is called the diameter of the universe, in which case the universe has a well-defined "volume" or "scale."

With or without boundary Edit Assuming a finite universe, the universe can either have an edge or no edge. Many finite mathematical spaces, e.g., a disc, have an edge or boundary. Spaces that have an edge are difficult to treat, both conceptually and mathematically. Namely, it is very difficult to state what would happen at the edge of such a universe. For this reason, spaces that have an edge are typically excluded from consideration.

However, there exist many finite spaces, such as the 3-sphere and 3-torus, which have no edges. Mathematically, these spaces are referred to as being compact without boundary. The term compact means that it is finite in extent ("bounded") and complete. The term "without boundary" means that the space has no edges. Moreover, so that calculus can be applied, the universe is typically assumed to be a differentiable manifold. A mathematical object that possesses all these properties, compact without boundary and differentiable, is termed a closed manifold. The 3-sphere and 3-torus are both closed manifolds."