Expanding space?

i dont think eintein was serious about gravity bending space... it was just a geometrical model to explain how gravity behaves.

so... since gravity can't bend, it can't expand ether.

 

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Nah. AE was just some joker with too much time on his hands. Right...

 

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Well, so much for your "thinking." Not only did he predict that it would, later experiments proved it to be quite true.

I urge you to say in school - you've still got a way to go to just get the basics.

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it's not possible to prove that space can bend and it's also illogical because space is not made of anything, so it can't bend. but i'm sure his theory was correct geometrically and mathematically. a theory doesn't have to be correct physically to predict things and be useful.

 

Yorda. Not too long ago, people believed that the atmosphere was nothing but then we learned to measure it's effects and it's contents, etc. I think it is just a matter of time before we do similar with space.

 

Read-Only. You seem to have no abiolity to comprehend the simplest of posts which then leads to an extremely angry and insulting retort on your part.

Time dilation is said to be relative to what? So, if it works the other way, it would be relative to what? I should not have to explain such things to you.

Do electrons have a uniform speed under all conditions or does for instance, gravity slow them down?

I was quoting AlphaNumeric on the physorg forum. A fellow text book quoter. I had to show him why such a statement was obviously wrong.

 

superluminal. The rotation rate of a super-massive black hole was shown to be almost light speed, which is not a surprise. So what would you do? Call the black hole a crackpot and refuse to be ripped to pieces by it's tidal forces?

AlphaNumeric said about entering through one of the poles where of course the tidal forces would be nothing like as bad. But that is where you get unbelievably powerful magnetic fields whip about and send out whole stars full of matertial in jets at near light speed. Even if you are Superman, you aren't going to survive that.

The use of the word "crackpot" by you is just another way of you telling us how smart you are and that you know infallibly that what I say is wrong. Real world. You're not the pope so we need evidence that you have a clue as to what you are talking about.

I think this may be another place to boast about how smart you are, so that you must be right.

 

Post your source.

Err.. no.

Now, please explain to me why you think rotation rate has anything to do with tidal forces.

Please explain why not. I'm eager to learn.

Post your source for this claim.

So far, unless you can convince me that your apparently incredible ignorance of physics, as indicated by many of your statements here, is just a joke, then I conclude that you are wrong.

Ok. What would you like to know?

You sound a bit defensive. Why? I never even attempted to tell you how smart I am. I was pointing out where you were completely wrong from a physics standpoint. That's all.

 

superluminal. The creationist tactic, I see. Question every source. My computer where I copied the article to is several thousand miles away and I won't be home again till March 2008. I gave the reference on physorg shortly after it's discovery earlier this year. Perhaps you could use your alias there to check (I upset moderator NOM who I revealed was also "fivedoughnut" and other alias who I also revealed, and he freaked and kicked me off for five months. Not a nice person).

Please explain how an acretion disk forms around the equator of a black hole rather than around it's poles?

Go read a book. Any book. The fact that jets from black holes are caused by powerful magnetic fields is OLD news. Doh!

Once again you have failed to post anything intelligible and merely wasted my time. Why don't you go troll somewhere else for a while?

 

I did not question the fact that black holes can have magnetic fields. Nor did I question whether they rotate or not (just the speed).

What I did question, and you failed to address at all was this:

So, please address your statement here.

 

Accretion disks, like any other rotating disk of material, will form about the axis of rotation as centripetal acceleration (centrifugal force) spreads the material out against the central gravity source in the plane of rotation, and gravity collapses it along the axis of rotation where there is no centripetal component.

Again, not disputing that.

Sorry.

 

Yorda's question on whether space can be bent, puzzles me too...space is nothingness...no atoms...no EM waves...or do you mean EM waves get bent in a region?

 

superluminal. Rotation drags space and so material in space around with it. The closer you get in the stronger the forces. So tidal forces.

 

dragon. Photons in a vacuum travel in a straight line. Going out of a gravity well, they cannot be slowed so are red shifted. Going past a gravity well, they cannot be slowed but close enough and they can be bent. This is not refraction as in entering a denser medium since they are often still in the vacuum of space. So, how can the path of light bend?

If photons are waves travelling through space, and you bend space (by intense gravity), then the waves travelling through space will be bent too.

Space is nothing we can measure. In the BB idea, space drags whole galaxies along with it.

 

Hmmm...

The question is, are tidal forces greater at the equator of a rotating body than at it's axis of rotation.

First, without invoking frame-dragging:

Tidal forces are due to the gravitational gradient (differential gravity) acting across an object. If the rotating body is a non-deformable sphere, then the gravitational field surrounding it is uniform, therefore the tides at the equator and the poles will be the same.

If the rotating body can deform into an oblate spheroid, the the gravity at the equator will be greater than at the poles. So yes! You are correct kaneda! Tidal forces at the poles of a deformable rotating sphere will indeed be less than about the equator! Bravo!

Now, with frame-dragging:

I have no idea if frame-dragging implies a modification of gravity at the equator vs the poles of a rotating sphere.


Note that for this analysis I am assuming that the test object is examined at an instant in time as it orbits the rotating body equatorially and in a polar fashion (it is only tested when over the poles in this case).

 

Yep.

 

superluminal. As I pointed out elsewhere, why do we have expansion. A 3D expansion would have what the BB claims, but also have a centre which everything is moving away from.

A four physical dimension expansion which seems to suit the BB better has more space forming between galaxies, etc. I know the balloon analogy is not good but if we have a balloon with lots of large black dots on it's surface, representing galaxies in the universe, then the dots do not actually move (if we ignore the increase in their size since they are held together gravitationally). We just have the areas between them growing ever larger. Essentially the universe gets a lot larger with everything becoming further from everything else without anything actually moving.

I probably haven't explained this well. Let me try again. You have a central ball. Call it the universe at a billion years old. You stick knitting needles into it. 3 billion years later, the galaxies are now a quarter of the way up the needles, 6 billion half, 12 billion (near where we are now), the galaxies are at the top of the knitting needles. The galaxies are not moving across the surface of the ever growing imaginary sphere now at 3, 6, 12 billion years as it gets ever bigger but stay in exactly the same position relative to where they have always been.

I know what I mean but am not sure I can get it across.

 

Yes, fair analogies but there are two faults. The galaxies aren't only on the surface (your dots) but also are dispersed throughout the volume. And your dots ARE moving because they are constantly being displaced from their previous positions as your balloon/ball expands.

 

Obviously you meant to say 'since space can't bend, it can't expand either.'

Actually I think Yorda is quite correct in saying 'it was just a geometrical model to explain how gravity behaves.'

It may actually be that space is a physical thing that bends, but that is thought not to be the case at present. And Einstein himself made a point out of mentioning that he does not believe space to be a physical entity. (it is in his book 'relativity' which is not in front of me right now, but I will find the quote if someone presses for it) The whole mass bending space thing is just a convenient mental picture to explain how gravity behaves, not why it behaves that way. To be perfectly honest, I was quite disappointed when I learned this. We still really have no idea of the 'mechanism' behind the force of gravity (except that it probably involves 'gravitons')

 

Hmmm... I'll check my copy of relativity for that also, but you're probably right.

I suppose I'm so used to saying "gravity is a warping of spacetime by mass" that it hides the real fact that no one knows what space is, if it has some undetected structure (not talking about quantum vacuum fluctuations, etc) and really does "warp" in the presence of matter, or if it's gravitons.