At the center of a black hole is it the same time as the moment of its formation?

[Lancer]

If the universe is infinite HOW THE HECK can it be expanding?!??

[MattBowron]

sorry if my post didn't make much sense, i thought that the Coriolas Force or Effect or something like that was the energy a rotating body gave off, or it was to do with the energy created via rotation, used mostly in the idea of a rotating centrifuge's Coriolas force being used to create artificial gravity on space stations such as in 2001: a space odyssey, i was wondering if the big bang had a coriolas force or something like that which was causing the rotation and spinning of galaxies, stars and other bodies alike

anyhow just my two cents

[Lancer]

It's ok not to know stuff.

[KrazyHorse]

Originally posted by Kuciwalker

a) The Universe is infinite.

Um, are you claiming that it can't possibly have finite volume?

Not unless it has some compactification, and there is no evidence of that currently.

[KrazyHorse]

Originally posted by Lancer
If the universe is infinite HOW THE HECK can it be expanding?!??

Quite easily.

[KrazyHorse]

Specifically as far as compactification goes, the characteristic volume has to be significantly greater than the Hubble volume or else we would have seen it. At the very least, the Universe is much larger than the visible Universe.

[Lul Thyme]

Originally posted by KrazyHorse
Specifically as far as compactification goes, the characteristic volume has to be significantly greater than the Hubble volume or else we would have seen it. At the very least, the Universe is much larger than the visible Universe.

Yes but infinite is much MUCH larger than finite

[Lul Thyme]

Originally posted by KrazyHorse


Not unless it has some compactification, and there is no evidence of that currently.

If compact is used in a similar sense as in mathematics, it is a global property. It may turn out that we may never be able to decide this question. Is this correct?

[KrazyHorse]

Originally posted by MattBowron
sorry if my post didn't make much sense, i thought that the Coriolas Force or Effect or something like that was the energy a rotating body gave off, or it was to do with the energy created via rotation, used mostly in the idea of a rotating centrifuge's Coriolas force being used to create artificial gravity on space stations such as in 2001: a space odyssey, i was wondering if the big bang had a coriolas force or something like that which was causing the rotation and spinning of galaxies, stars and other bodies alike

anyhow just my two cents

a) "Coriolis force" is not the important concept in centrifuges. Coriolis force is a "fictitious force" that shows up in a rotating frame of reference. Specifically, it is the tangential force which appears when an object has some radial velocity. The force you're thinking about in terms of "artificial gravity" is "centrifugal force", which is a radial force which does not depend on radial velocity.

b) I have no idea where you heard that "during the big bang scientists say that space and time uncurled", nor do I really understand what is meant by that.

c) There's no need for the universe as a whole to be rotating in order to explain the rotation of many astronomical structures. These structures coalesced from more dispersed elements under gravitational force. These more dispersed elements were moving around with some sort of random velocities. This leads to some residual angular momentum about their center of mass. As teh structures collapsed into smaller, denser objects the angular momentum was (roughly speaking) conserved. This led to increasing velocity. The standard demonstration of this principle is to sit in a chair spinning with your arms out, then draw them in. As you might know from experience, you start spinning faster. Or you can look at figure skaters in spins

Here's a good video on conservation of angular momentum. As the dudes on the outside of the merry-go-round move toward the center the thing spins faster.

http://youtube.com/watch?v=us6CCWJPp3c

Here's the best demo of coriolis force I've ever seen:

http://video.google.com/videoplay?docid=-6469142924514101084

Much respect to these guys for actually putting a pool table on a merry go round.

[KrazyHorse]

Originally posted by Lul Thyme


But there is no evidence to the opposite either is there?

If compact is used in a similar sense as in mathematics, it is a global property and we may never be able to decide this question?

There is evidence against compactifications with small dimensions (small being many multiples of the "radius of the observable Universe")

If the Universe was compactified on the same scale as the Hubble volume then you would see patterns in the CMB which were repeated (because light could have traveled around the Universe and back again). Even if the Universe was compactified on a scale of say 10X the Hubble volume then there would still be an effect (just not as dramatic).

[KrazyHorse]

Originally posted by Lul Thyme


Yes but infinite is much MUCH larger than finite

The Universe is infinite to the limits of present detection.



And yes, that is how I think of it as a physicist.

[KrazyHorse]

By the way, the study of how CMB measurements constrain compactification is an area of active research. I'm not an expert in it, but I do know more than the average bear.

[KrazyHorse]

Note that this is not the same as the study of how compactified extra dimensions would affect the CMB (which is also an area of active research).

[Lul Thyme]

Yes, I had read a little about these measurement that give lower bounds of the size of the universe.

I agree with you that, from a scientific point of view, it's unclear that there is a difference between infinite and large enough.

[KrazyHorse]

The problem is that the compactification does not have to be simple. The simple cases are obviously the best studied (spherical, for instance) but more complicated ones can be designed to evade current detection.