Philosophy Now Forum

Samurai Drifter wrote:Rotating relative to what?

Godfree wrote:Seems like a strange question , but I think it would answer the question of whether time began with the big bang or not . If the Universe is rotating , this would suggest that there were forces at play before the bang , forces like we see today , planets suns stars,,they all seem to be rotating,,something to do with the way objects spiral in before impact.
So I'm going to google it now but I'm sure others will already know this

chaz wyman wrote:

Godfree wrote:Seems like a strange question , but I think it would answer the question of whether time began with the big bang or not . If the Universe is rotating , this would suggest that there were forces at play before the bang , forces like we see today , planets suns stars,,they all seem to be rotating,,something to do with the way objects spiral in before impact.
So I'm going to google it now but I'm sure others will already know this

If the universe were rotating how would you ever know?
If everything there is is rotating you would need a reference point outside the universe to be able to tell, this is absurd.
We can only tell we are rotating because we see the sun move in the sky, but with the universe there is nothing like that.

converge wrote:

chaz wyman wrote:

Godfree wrote:Seems like a strange question , but I think it would answer the question of whether time began with the big bang or not . If the Universe is rotating , this would suggest that there were forces at play before the bang , forces like we see today , planets suns stars,,they all seem to be rotating,,something to do with the way objects spiral in before impact.
So I'm going to google it now but I'm sure others will already know this

If the universe were rotating how would you ever know?
If everything there is is rotating you would need a reference point outside the universe to be able to tell, this is absurd.
We can only tell we are rotating because we see the sun move in the sky, but with the universe there is nothing like that.

This is false, actually. As Godfree said, there are physicists trying to determine whether the universe is rotating and so far we are not sure.

If everything is moving at a constant linear velocity with you and you have no outside point of reference, you can't tell if you're moving. So if you're in a box in deep space, you can't tell if you're sitting still or moving thousands of mph towards the sun.

But if everything is moving at a constant rotational velocity with you, you don't need an outside point of reference. A rotational velocity is actually a constant acceleration, and you can measure and feel acceleration due to the force against you. So if you're in a box in deep space, and the box is spinning around quickly, you could tell because you'd be slammed against the wall.

Surely for each instance of rotational velocity, each objet is on a vector which is tangential to the rotation, thus, as each tangent is linear to the observer, then such universal rotation is null and void.


That's all consistent with special relativity, but once we bring general relativity in, we hit a problem, because we can't tell the difference between a constant acceleration and gravity. If you're in the box and you don't know if you're in deep space, you can't tell if you're slammed up against the wall because you're rotating, or because the box is sitting on its side on a planet and you just fell down.

When we talk about the whole universe, we know more than we do trapped in the box; we know that there is no mass outside the universe because the universe is all mass, so it doesn't make sense to say the universe is being pulled towards some other large object. There should be ways to tell if the whole thing is rotating, something to do with blue-shifts and cosmic energy and whatnot that gets a little beyond my knowledge.

What did all of that have to do with religion? I have no idea.

chaz wyman wrote:
Surely for each instance of rotational velocity, each objet is on a vector which is tangential to the rotation, thus, as each tangent is linear to the observer, then such universal rotation is null and void.

converge wrote:

chaz wyman wrote:
Surely for each instance of rotational velocity, each objet is on a vector which is tangential to the rotation, thus, as each tangent is linear to the observer, then such universal rotation is null and void.

At any given instant of time, the object is on a straight vector, and you're right that the vector would be relative to the observer. We couldn't say if the object was moving and the observer was standing still or vice versa. But in order to rotate, the vector has to keep changing direction, which requires an acceleration, and acceleration isn't symmetric. Ignoring the gravity problem for now, we can say with certainty that the object is undergoing acceleration and not the observer because the observer is not feeling the force of acceleration. Picture yourself standing still and a ball flying in a circle around your head, vs a ball standing still and you (or the room you're standing in) flying in a circle around it. You would feel yourself rotating around the ball, and be thrown to the outer wall if you were in a rotating room. Or if there was no room, you would still feel the centrifugal force pushing you outward.

chaz wyman wrote: I take your point, but `i still have reservation that i'm finding it hard on philosophical grounds to reconcile. Maybe i'll get back to you.

I assume that the imaginary centre of this rotation is the the big bang point?

converge wrote:

chaz wyman wrote: I take your point, but `i still have reservation that i'm finding it hard on philosophical grounds to reconcile. Maybe i'll get back to you.

Well it turns out you were right to doubt me! I did some more internet-searching and it seems I'm not exactly right about rotation. Like I said, we can't tell the difference between the force of acceleration and that of gravity, and after reading about Mach's Principle it makes sense that centrifugal forces only work because of the mass and gravity of the rest of the universe. So the only way the universe could rotate, it seems, is if the big bang is not correct, and there is some kind of axis that the entire thing rotates on. Apparently there is some evidence that this axis exists (called "The Axis of Evil" apparently, and I thought that only applied to terrorists ) but the observable effects are very small, so we're either rotating very slowly or there is some other weirdness going on. It turns out that if Godel's rotating universe is correct, then the big bang is incorrect, and apparently time travel would be possible as well!

I assume that the imaginary centre of this rotation is the the big bang point?

I have always understood space as only conceivable as the relationship between material objects. And in answer to the question; what happens if you kick a ball outwards at the edge of the universe? The answer has to be that you are actually creating space by that act; that an ever increasing universe is at the same time making its own space for itself as it goes along. This reduces the problematic notion of an infinite space. Infinite space is inconceivable in the sense in which such a thing is indivisible; is you cut an infinitely long piece of string what do you get? Two infinitely long pieces of string - can you keep cutting these strings? would that not mean you are creating new string by cutting? So with these problems in mind I have been happy to accept that the Universe is finite but growing.
The other big problem is that the Universe is bigger than it ought to be. If the speed of light is a limiting factor and the Universe's age is much less than a beam of light would be able to travel from its centre to the extreme edge of the universe, then how is it that there can be matter at the edge of the universe, when light could not have reached there let alone matter whose mass tends to infinity at the speed of light? Scientists applying the concept of EXPANSION seems like an appearance saving FUDGE about as useful as Ptolemy's epicycles. On wonders is anyone has ever asked whether the big bang was not so big, not the creation of all matter in a single event but just a massive event in a pre-existing Universe? Or even a series of bag bangs- why no centre? Maybe the red shift is something else?





One of the weird things about the big bang is that it doesn't really have a center. It's hard to visualize... but it's not like there was a big empty space, and a point, and all the matter exploded out of the point (even though that's a common misconception and how it's usually illustrated). It also doesn't help that there's a common confusion between "space" as in "outer space", all the stars and planets and things, and "space" as in "the space between two points", which is a geometric thing. Before the big bang, there was actually no geometric space, as in the three dimensions of space did not exist; there was no empty space for anything to be in. The big bang was the beginning of space itself (and time as well), and space, as in "the space between two points" not "outer space" expands after the big bang, and is expanding still. So there is no center of the big bang or center of the universe. There's an article about that here: link

In conclusion, physics is confusing and despite plenty of time studying it, I still find new things to confuse me even more.

Godfree wrote:Seems like a strange question , but I think it would answer the question of whether time began with the big bang or not . If the Universe is rotating , this would suggest that there were forces at play before the bang , forces like we see today , planets suns stars,,they all seem to be rotating,,something to do with the way objects spiral in before impact.
So I'm going to google it now but I'm sure others will already know this