GRAVITY PROBLEMS -- off topic from {Falsifying a young Universe}

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GR does have a real problem, in that it doesn't quantise consistently. The bulk of the papers in theoretical physics are related to trying to sort out this problem...

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So you too admit, really, you don't really understand it!

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I was referring to vanFlandern, not you. I was urging you not to listen to his rubbish, which is totally contrary to GR, despite whatever he says on the matter.

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Oh. Ha. Hate to admit it was just the first thing I searched on the topic. What I liked about it was it seemed to admit we don't know everything about gravity. But you say as much, as did the thread originator, so I guess it's pretty unnamimous. What I feel has been missed is the GCR. With this, no quantum mysteries remain. (General combined relativity-combined with the spiritual!) But thats a long story.

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". If you are interested in this area of science, search out a good book such as Brian Greene's, or of course there is always A Brief History of Time and The Universe in a Nutshell. Perahps others here can suggest some more titles. I tend not to be too aquainted with the popular texts.

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OK, thanks. Of course, I have some reservations about someone trying to tell me where time came from and what it is, when really, they haven't much of a clue! About all they could manage is how it works in this physical only universe. or how they think it theoreically works only in the physical universe. I think time is a temporary force that is set in place in a temporary physical only universe, that will be forever replaced by a merged (Physical and spiritual together), eternal universe, where time shall be no more. Just part of our present, 'prison'.

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Objects curve their surrounding space-time. An object follows the straightest path it can find through space-time. ..

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Isn't this saying, basically that we know things attract each other, or move toward each other, etc? But why exactly does it do this? Why does it, and how does it follow the straightest path? How and why does it curve time and space? What is the heart of the force?

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..or around the larger object in what we call an orbit; which one depends upon the initial conditions of the objects.

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This describes how it works, not what it really is.

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Your straight path through space-time is towards the centre of the Earth. However, the solid ground is preventing you from following your path by exerting an upwards force upon you. That force is what you call gravity. There is no pulling

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My path through space time? I know what you mean, in other words, where I would go, if there were no material stopping gravity from pulling us into the center of the earth.
I realize my path through time and space is temporary, and while I will continue to exist, time itself will not. Therefore, in one sense, time's path through me may be a more apt phrase.

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Don't know as I've ever seen a good explanation of what makes a surface seem to be a surface.

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Do you mean what makes it look solid or what makes it solid?For the former things look solid or continous when there is enough individual particles in a certain area to give the illusion of a continous surface.What makes them solid is Coulomb repulsion between the outer electron shells.

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But why exactly does it do this? Why does it, and how does it follow the straightest path? How and why does it curve time and space?

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For the first question the answer comes straight from the geometry.
It follows the straightest path because unless there is a force being exerted on it, it does nothing.
And doing nothing is following the straightest possible path in spacetime.
I could explain in more detail but it would require Geodesics and (pseudo)Riemannian geometry.To the second question, General Relativity doesn't do why and how in the human sense.
It is background independant, which means that spacetime is an active participant in the physics.
Matter doesn't create gravity, any more than gravity creates matter.
In a human manner of thinking it is easier to look at it that way, but it isn't the case.It is simply "This is the Matter distribution" and "This is the geometry that goes with it".
One doesn't create the other.

what makes some things "solid" and some not. there is nothing stationary in either rock or water.Coulomb repulsion? That explains the repulsion between molecules but not the solidness.the rest is a reply to simple\cosmo

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we are limited in our ability to understand
by our ability to understand

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RebelAAmerican.Zen[Deist
... to learn ... to think ... to live ... to laugh ...
to share.

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To the second question, General Relativity doesn't do why and how in the human sense.
It is background independant, which means that spacetime is an active participant in the physics.
Matter doesn't create gravity, any more than gravity creates matter.
In a human manner of thinking it is easier to look at it that way, but it isn't the case.

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It is simply "This is the Matter distribution" and "This is the geometry that goes with it".
One doesn't create the other.

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So, what, in other words, this is the way it is, thats it we can't know more than this? Now, regardless of how much matter there is in this physical universe, or how it is distributed, how does that tell us how gravity works. All that says is there is matter, it reacts this or this way, but not the why. If I throw a ball at you, you know why the ball got it's power or energy, or momentum, etc. If there is a toy car with a battery, we know it moves, because of so and so. But if a sun moves, or planet, we say it is gravity, but this doesn't explain what is really doing the moving. It's all well and good to say, well, it's going to go straight, unless something makes it go crooked, but why is it going in the first place? Where does that force come from, that makes it move?This message has been edited by simple, 10-10-2005 07:48 PM

Actually, its not, but now we are entering real quantum stuff. The fermions in each atom are effectively points, so fermionically, atoms are 100% empty! But when you take into account the gluons, the nucleons gain an actual size and thus so does the nucleus. In the same way, the photons bulk out the atom, giving it its size. So bosonically, the atom is 100% full We are too keen to say that fermion = matter and boson = force but it's not as simple as that. And your/my solidity is generated by the coupling of the two in what we call QED. SG called it Coulomb repulsion becasue that is what we call the bulk "emergent" behaviour of all of those QED interactions.The "force" of solidity is directly related to the strength of E/M. This is unfathomly greater than the strength of gravity, which is why we stand or sit rather than sink As to what makes a surface... I'm not sure to which level you're referring. The difference between solid and liquid is simply chemical bonding. And liquids can be rather solid. If you hit water faster than it can get out of the way, it hurts!

As I've said before, we have theories of a second, third, fourth and even fifth "gravity" particle! Trying to find one consistent with observations is the problem. Turning it the other way round, we can postulate a particle that will "fix" the galactic rotation curves but not affect local observations, but we find that it is totally inconsistent with all that we know of particle and gravitational physics.I completely understand your objections but what you have to realise is that just about every decent scientist out there in this field feels exactly as you do. It would be nice to have a tweak to GR or even a new theory of gravity that perfectly explains grav phenom on all scales. But it just isn't that easy. The conclusion to which the vast majority have arrived is that adding dark matter is by far the most simple solution.From bitter personal experience I offer the following advice: if you think something fundemental has been overlooked by every one of the professionals working in a field, you are mistaken. Simple as that I'm open to counterexamples...

Just a couple of after-thoughts...1) Don't think I'm defending CDM to the death. I am simply defending its rightful place in the Standard Model. I haven't worked within the SM since leaving astrophysics and moving into theoretical physics. I wouldn't be at all surprised if something like ekpyrosis wasn't behind the phenomenon. In fact, I would be delighted, because I share your dislike of CDM for the same reasons, and string/M-theory is one of my areas. Howvever, at present, CDM is the best solution we have.2) Don't get too hung up on differentiating gravity from matter... they are one and the same, whether by geometradynamics, string theory, supergravity, etc.

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It's all well and good to say, well, it's going to go straight, unless something makes it go crooked, but why is it going in the first place? Where does that force come from, that makes it move?

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You're looking at General Relativity from a Newtonian viewpoint of abstract forces making things move.In General Relativity, Earth doesn't orbit the sun because of some force.From the point of view of somebody far away from the Solar System, the Earth goes around the sun.
This is because this observer is comparing his standard (Minkowski) time against the Earth and sees the earth move through what he calls space around the Sun from his vantage point.From Earth's vantage point it is simply existing and there is no force on it.This comes from the Earth's time being warped around the Sun by the Sun's mass, from the point of view of an external observer.
To this external observer, this warped timeline looks like a worldline around the sun.

I like this point. I'm too keen to talk about "moving" along straightest paths (with a nod towards Newton I), but "moving" has too many layman ideas of "what's making it move?" (i.e. unaware of Newton I).

Simple, we know as much about gravity as we do power, energy and momentum. All of these are intimately connected. However, the level of understanding required to appreciate this is immense... far far beyond any layman's guide or popular book, or indeed any undergrad course. No you don't. You've been sold a plausible analogy of what actually happens, and you have accepted it and decided to not ask another "why". The why of the car moving is in fact far more complex than the planet orbiting the star.If you push the "why"s far enough you get down to mathematics. We don't have anything else.

No, I do not admit that. That is misleading. From the point of view of the layman or indeed anyone outside of the field of gravitational research, I understand gravity exceptionally well. Where I fail to grasp at what is going on is at such a fundemental level that it is not worth talking about outside of the professionals working in that area, other than to say we have trouble quantising gravity, it is an active area of research at this time, and we have several very promising ideas.This message has been edited by cavediver, 10-11-2005 09:51 AM

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Simple, we know as much about gravity as we do power, energy and momentum. All of these are intimately connected. However, the level of understanding required to appreciate this is immense... far far beyond any layman's guide or popular book, or indeed any undergrad course.

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Know about as much about how it works, or also what really causes it, and it's actual nature? I can know how to turn on a light by flipping the awitch, and that it will shine so brightly, unless we stick an umbrella right by the bulb, where it would throw less light, etc. It seems we can predict how gravity will operate, but I have heard some say we have our limits to understanding it. You seem to indicate we have some elite knowledge of this, not available to the average man, and, apparently, not able to be explained simply, even to those with years of education. In other areas of life, I found that those who can't explain something, usually really don't really understand it. Guess we'll have to take your word here.

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If you push the "why"s far enough you get down to mathematics. We don't have anything else.

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So it's a number game here. In this forum, God has no number, I wonder if He has one in the math that 'explains' what gravity really actually is, and comes from?

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Where I fail to grasp at what is going on is at such a fundemental level that it is not worth talking about outside of the professionals working in that area, other than to say we have trouble quantising gravity, it is an active area of research at this time, and we have several very promising ideas.

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It is the fundamental level that relates to the creation/evolution debate. Glad you have some ideas that you think are 'promising', you're not the only one.

oh that helps ... photons? or is this a typo for protons? and the {temperature\pressure\density} environment. everything is really {plastic} just to different degrees in different {temperature\pressure\density} regimens.it's more a question of the perceived discretizing of experience and why is there so little interchange beteen {objects} in contact. kind of a one hand clapping thought. Well see now, the {honest?} thing (for physics) to say is that we don't know, this is our best guess, but we have no corroborating evidence yet, and we're checking into it. Reading all the books, articles, etc it seems more to be accepted as gospel without question. That's dangerous. time will tell, eh?read an article last weekend titled "wheres the other half?" or some such, about the 'missing' anti-matter. not well written, didn't give me much of any new ideas except for one item: it mentioned a geiser of antimatter that seemed to be eminating from a black hole. this leads to two thoughts:1 an easy place to have antimatter is inside a black hole: perhaps the anti-holes formed first leaving 'normal' stuff out in the cold2 an easy way to obliterate a black hole is to pour in anti-stuff, letting it anhilate the stuff at the core until it no longer has the {gravity\density} to be dark. would it outplode (not explode but the reverse of implode)?this doesn't solve the dark-stuffs issue because it's not enough stuff One of my paridigms (see signature) is that "we are limited in our ability to understand by our ability to understand"new ideas depend on the foundation of old ideas but also on a new understanding, new ways of looking at old informations.cultural diversity is a good way to generate different views of the same information, and I've heard that physics is 'easier' from a buddhist view than a christian (generalizing on purpose). fundies talk about dogmatic scientists, and there is an observable tendency in that direction. we could also be seeing science becoming more 'globalized' due to rapid {communication\internet} sharing so that there actually be less diversity of {ideas\approaches} in all sciences. you get to quantum mechanics and why are some things "solid" and what is friction ... {I think I came in here ...}thanks.This message has been edited by RAZD, 10*11*2005 09:51 PM

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we are limited in our ability to understand
by our ability to understand

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RebelAAmerican.Zen[Deist
... to learn ... to think ... to live ... to laugh ...
to share.

Welcome to quantum mechanics Photons. Remember the energy levels that the electrons occupy? How do these arise? Action at a distance It's all the photon-fermion interactions involving the electrons, the quarks, and the photons. The atom is much much more complicated than the simple atomic picture usually presented. Well surface physics is a whole area. [abe 'cos I forgot] Surfaces become surfaces precisely because they are not that reactive. I guess most solid surfaces are either "crystaline" (rock, metal) or biological, where the latter have evolved to be non-reactive. As two surfaces approach, electrostatic repulsion overcomes anything else. Bring two iron blocks together and they will stay as two blocks unless you heat them sufficiently to where the surface atoms are sufficiently energetic to overcome the repulsion and form new metal bonds. Friction arises from irregularities in the surfaces "catching" on each other. This is not my area, but it's not that deep and doesn't require any real quantum knowledge. I think we are approaching a consensus. I agree and it is not how I would present the situation. But I think this is the fault of the popular science press, and not of the scientists. Black holes do not differentiate matter and anti-matter... it's all energy. Anti-matter does not have anti-mass (although demonstrating this is exceptionally difficult given our lack of anti-matter to hand)... Anti-matter is always portrayed as this nemesis of matter, but it's not an accurate picture. Ant-matter is all around and in us all of the time. It's just not there in bulk. Mesons are what bind the protons and neutrons together in the nucleus, and a meson is a quark, anti-quark pair.So pouring anti-matter into a black hole just makes the balck hole fatter. There's only one way black holes lose mass and that is via Hawking radiation.BTW, you do know that anti-matter is just matter travelling backwards in time, don't you? Yes, I agree with all of this. If I sound dogmatic at times, it is my defending of the Standard Model as our publicity brochure. I admit that I have doubts about a good proportion of the physics I explain. But these doubts are concerned with far deeper issues that I do not have the time to explain. Without a similar background in my subject, no-one else would understand my doubts. There are only so many analogies you can pile on top of another without completely losing the plot! This was essentially my message to Simple.I guess my point is that very few ideas have ever occurred in isolation. The concepts that gave rise to Relativity were spread across many different physicists and mathematicians, not confined to Einstein, as was the case with qunatum theory. And today we have orders of magnitude more scientists working on this stuff.Pick any plausible idea and I can guarentee it has been beaten to death. The real discoveries are made at the coal face. 100 years ago, the coal face was SR/GR/QM. We are a lot deeper than that now.But you are right, the real insights do seem to come from taking a step back and reconsidering. It's just that one step back (or one hundred) from the coal face is still several miles deeper in the mine than anyone outside the field has ever ventured. India has produced some astounding mathematicians but I think the majority of the really weird stuff has come from the western world. I think this eastern/western view comes again from popular science. I know what it is implied, but the depth of the concepts in theoretical physics transcends any preconceptions of eastern/western philosophy! Remember And it's interesting that the majority of theoretical physicists that I know have strong Platonistic/pseudo-Platonistic leanings based upon their experience in the field. I have yet to meet anyone with serious exposure to theoretical physics who takes a strong counter-position.cheersThis message has been edited by cavediver, 10-12-2005 09:36 AM