What Creates Gravity?

Spin has nothing to do with "gravity", but it certainly affects "gravitation" - the difference being that gravity is what pulls us down, where-as gravitation is curvature of space-time causing the appearance of what we call gravity.Ang mom is a source of stress-energy, and a spinning object will also drag space-time around with it - an effect we have measured around the Earth (another great prediction+observation for GR)But in no way is "spin" the source of "gravity"

That's like asking "how does two legs, two wings, a beak, and feathers make a bird???" That's what it is!!!Mass is that which causes warping of space-time - and via some clever stuff, inertia. Our only experience of mass is in this context - it is just hidden by everyday life. It is not some unusal secondary aspect of mass.At our current level of knowledge, the universe is made of up fields (which we try to unify into one field) Excitations of these fields all contribute to affecting one particular sub-field (or master field), the metric. The level of excitation we call gravitational mass and the actual effect on the metric field we call warping of space-time.So, "how does mass make gravity?" is easy - that's what it does by definition.But, "why does mass make gravity?" is at a deeper level: "why do the fields interact in this way?" and this is where String Theory, SuperGravity and the like come in...Edited by cavediver, : inserted an 'a'... to 'make bird' sounds a little dubious

No - the principle of equivalence helped lead Einstein to the General Theory, but the EP is a *prediction* of GR as we formulate it. First check - if you think your simple hunch is going to overturn 100 years of physics and the thinking of the greatest physicists of recent times such as Einstein, Hawking, Feynman, Dirac, Pauli, Cavediver (I wish) - then you should probably doubt your hunch first. Trust me - been there, done that. Unfortuanetly, either you or Prof Giancoli is missing an exteremly important word - LOCAL. This should read: And sadly the rest of your argument now falls apart. Of course we can distinguish the acceleration if we can look sufficiently far around us to notice the tidal effects of the gravitational field. But this is irrelevant for the equivalence principle. No - you cannot detect any acceleration if you are freely falling! What you could detect with your sensitive instrument, is the difference between what is happening at the top of your frame and what is happening at the bottom of the frame. This is where the differential gravitational field will be noticed. A partcile at the top of your frame will be moving away from a particle at the bottom of your frame. Two partciles on either side of your frame will actually be moving towards each other. But again, these ar not LOCAL experiments as you are comparing partciles at different points. All you are doing is discovering that your lcoal space-time curvature is changing as you move through space-time - nothing unusual there...That all said - it is quite possible that the equivalence principle is not infallible, but it will not be because of a failure of GR, but because of corrections to GR resulting from quantum gravity.

We don't - at least those of us who know what we are talking about...But if you are ever to go beyond Einstein's Theory, you first have to understand Einstein's Theory. This is the hurdle you are falling over. Obviously not, given those of us who have carried on working on space-time physics following his death Errr, I think we are well aware of this - ever tried to model an electron with the Kerr-Newman metric? No? Remember the hurdle I mentioned? Who cares about your point of view? We are talking about mathematical physics. What do you call finite? As big as you like? No, it's not. Wasn't this clear from my previous message? If it wasn't clear, you need to brush up on your reading skills. So??? Yes, and again, so??? Given your utter ignorance of the theory of General Relativity, guess how much Your Opinion matters?The world lines of point particles trace out geodesics through space-time. The world-volumes of larger bodies will be complicated by the inter particle forces. Care to explain why this spells the downfall of GR???Edited by cavediver, : No reason given.

If the local volume is not zero, and the gravitational field is not uniform over that volume, then you do not have a frame... So? You might want to think about re-writing these statements because at the moment they make little sense. A combination of poor English and weak understanding does not make for an edifying exposition of relativity... an inertial frame follows geodesics. An accelerating frame does not... I'm not sure what you are trying to say here.Are you still claiming that GR is invalid because the tangent space is not equivalent to its base space?Edited by cavediver, : No reason given.

The only point you make clear is that you have no clue. Yes, a measurably large frame will be able to detect differences in curvature across that frame. Great. Wonderful. So what??? Perhaps you could follow through the mathematics to show me how this is a problem for GR. Forget about the equivalence principle. Show me the algebra... and then explain where GR would fail and what experimental observations would be affected.

I'm sorry, but under my doctor's recommendation, I'm only allowed to repsond to a certain quota of stupid each day, and I'm way over limits now.

The metric is the entirety of space-time. I would not call that arbitrarily small. No, it most certainly is not. It is symmetric tensor field spanning all of existence. Well, geodesics described by the metric give rise to the equivalence principle. This is simply nonsense. And this makes even less sense if that is possible. You have some very misguided ideas about GR. It is blatently obvious that having a curved manifold means that the equivalence principle will only be exact at a point, and any extended laboratory will reveal the local curvature. This is not a problem for GR, it is a f'ing prediction. If it is predicted by GR, how can it possibly be a problem for GR? How could the EP possibly suggest that an extended frame would not be able to reflect the local curvature? Your thinking is simply bizarre.

No, the EP holds for all gravitational fields if you consider it at a point. Sheesh...Repeating the same obvious point over and over again does not make the case for General Relativity any weaker. Perhaps it is time for you to move on to another topic?

The metric IS the gravitational field... No - in a freely-falling frame, the LOCAL metric can be regarded as flat. This is a consequence of the Pseudo-Riemannian geometry of space-time. Yes, by those that do not understand General Relativity, this is very ill-understood. But those of us who have spent a good portion of our lives working in this area, it is very well understood.

Not at this latitude

Really? I am surprised... Of course GR incorporates the local variation in Gravity - why would suggest otherwise? Of course GR explains why space time should curve - you just don't understand the explanation Of course GR explains the effects of measurement on point particles - you're really out of your depth by now... What temperature or randomness in initial conditions? Amd which initial conditions are you talking about? And what has this to do with GR? You really have no clue as to what you are talking about. Oh FFS, where do you get this garbage? GR may be thought of as a meta-theory but it's not a sodding meta-meta-theory, with the ability to explain why other specific theories are not correct Good job too, as curvature is not mass, nor is it "gravity". But it certainly explains the relationship between curavture, mass and "gravity" - you just don't understand the explanation. Actually it gives some of the deepest insights into the nature of mass that we have - unsurprisingly, you have no clue as to these insights... Of course it accounts for it - how the fuck do you think we KNOW that there is zero acceleration inside a massive shell For your little mind? I quite agree... Edited by cavediver, : No reason given.Edited by cavediver, : No reason given.

Oh, so you completely agree with Special Relativity? Which derivation? Can you show me? For real particles, it doesn't. So? Next? Ah, if you define "useless" to mean "one of the two most successful theories that science has ever discovered" then I'm in complete agreement. Just for laughs, if GR is completely incorrect, how do you explain the evidence? Just coincidence?

Then you are an idiot and there is no sense talking to you at all. I saw a glimmer of a slight chance you were going to come up with something interesting in your last post, and maybe talk about whether we have true tests of GR or just linearised spin 2 gravity. But no, that was just wishful thinking on my part. You are sadly just an idiot. Oh well.

Define "force" A "change" in curavture??? What "change" in the Schwazschild Solution produces what we think of as the force of gravity? You have completely lost it, haven't you? Oh, you seem to have mentioned Whitehead at least a couple of times now. I smell a wannabee "philosopher" with ideas far above his mental capacity. Whitehead's work was indeed interesting, though it is clear you have no understanding of it. And sadly, it is completely ruled out on several grounds. Check out On the Multiple Deaths of Whitehead's Theory of Gravity coauthored by none-other than one of my original teachers and mentors (and general all round genius) Actually, the one time I was stupid enough to think that I knew something that no-one else did (and no-one seemd to be able to correct me), I took it to Gary and with one quick sketch on his board, he demolished my argument and taught me more black hole math-physics than you would normally learn in a year