What is Time and Space

I'm having trouble with this concept. Are you saying that all gravitons attract all gravitons? If this is the correct is it true then that the gravitational field not only holds stars, planets etc in place but also hold itself in some sort of cosmic balance?

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Everybody is entitled to my opinion.

Absolutely. Most of my favourite space-times (solutions to GR) have no matter in them at all... we call them vacuum solutions. But they are highly non-trivial. The most simple black-hole solution, the Schwarzschild metric, has no matter in it. It has a measurable mass but this simply comes from the warped space-time.But it's not that strange. Of our four fources, only photons don't exhibit this behaviour. Gluons interact with gluons and the Weak bosons self-interact. As I alluded to earlier, it is the fact that photons don't self-interact (well, they do, but not straight-forwardly) that gives rise to the possibility of sight. Photons can travel from an object to our eyes without being disrupted by interactions with other photons crossing their path.

I have to do some more reading to proceed further. Man this has been great. I do have one question though. I went through several threads on this subject today. On one of them you reccommended "The Road to Reality" by Roger Penrose.I googled it and apparently it isn't an easy read. I'd like to learn some of the math but my last math high school course was back when the earth's crust was cooling and I'm wondering if you think the book would be worthwhile or not.It sounds to me like it would be more of a reference book than one that I would read right through.At any rate I'd appreciate your advice. In the meantime I'm going to re-read some more of Briam Greenes and thanks again.

I wouldn't get the road to reality if I were you.
If you aren't familiar with the maths, it is pretty hard to follow.It's basically a book for a mathematician who wants to learn physics or a physicist who has an interest in pure maths or maths methods.It certainly isn't for the lay reader.

Thanks. I'd like to try and learn some of the basic math involved. Is there a book that you know of that provides the concept, an explanation of the math and the formula?

You might want to try "Six Not So Easy Peices" by Richard Feynman. I'm in the process of reading it and it is really illuminating with regard to Special Relativity and General Relativity, along with the concept of "symmetry" in physical laws (which was new to me).It has math, most of the math is basic trigonometry and vectors, and he explains vector mathematics in the first chapter.

I read up on the Schwarzschild metric. It is amazing that with the information and the technology they had in the early 1900's that he and Einstein could come up with what they did. As the black hole singularity has infinite density does it have a mass? Is the warped space time that you referred to created solely by the gravitational field of the black hole?One of the things that I am struggling with now is this. (Hopefully I'm still on topic. It seems to me this is would be considered what is space.)Greene says that planck length is the length of a string. First off what is the length of a string? I tend to think of a string as more like an elastic band in that it's a loop. Is its length measured as it was cut and strtched out or just the length as it is? This is no doubt a dumb question but I'd like to try and at least have a workable mental image. Also I understand that in string theory a string is the basic form of a particle. Are all particles and thus all strings considered to be the same size? (Planck length)

Thanks Justin
I read up on that and it sounds as if you don't know calculus you're toast. I have no calculus whatsoever so it might be well over my head. What do you think?Right now I'm re-reading Brian Greene's, "The Fabric of the Cosmos".This message has been edited by GDR, 08-02-2005 06:43 PM

Well, I guess you're right... but Roger thinks it is which is the funniest part!We had this great head-to-head lecture series where Hawking and Penrose gave their respective views on a number of things. Atiyah was hosting, and at the end of the first one he asks

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OK, if anyone has any "relevant" questions, then fire away

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The silence was defeaning

I pretty much read the book as a physicist interested in seeing how a mathematician approached certain things.
It was also fairly good for seeing the development of certain avenues of physics, such as advanced Quantum Field Theory (I'm a relativistic astrophysicists in training, so although I'd know a good deal of QFT, I wouldn't have a detailed knowledge of QCD's finer points.) and unusual approaches to unification, outside the Loop Quantum Gravity and String Theory crowd.

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Is there a book that you know of that provides the concept, an explanation of the math and the formula?

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You said you don't know calculus, so would you like examples of good calculus books or something else.

The trouble is, I don't know what I don't know. I had algebra, and I even remember some basic Newtonian physics from high school, but I have no idea what is involved with learning some basic calculus.Also, I don't even know what learning some of the math behind the concepts will do for my overall comprehension.How is all that for a vague answer?

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I read up on that and it sounds as if you don't know calculus you're toast. I have no calculus whatsoever so it might be well over my head. What do you think?
Right now I'm re-reading Brian Greene's, "The Fabric of the Cosmos".

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I just looked through it and I realized that you do need to know calculus. I didn't really notice for some reason, probably because it is very basic calculus. You should probably read an "Idiots Guide to Calculus" or some book like that, because that is all teh calculus you need for this book.What you need to understand is that dx/dt equals the instantaneous rate of change of x with respect to time, which is velocity. The derivative of that is d'x/d't, which is the instantaneous rate of change of velocity, which is acceleration. That's about as deep as it goes.

Also, he formulates Newton's Second Law as F= d(mv)/dt, as Newton originally did.

Enjoyed reading through page 3, but figured I better back-trap some now to address or ask questions. I think the answer is that a being that could and was travelling at the speed of light would not experience time as we do and would never age, but would be present at all the points and thus places in time at the same time along that path. He would be super-positional and always in the present, from his perspective.A day with the Lord is as.....? Hmmm...Basically, imo, I think there is a superpositional, or multi-form, aspect to reality that explains the conudrum.I'd be interesting in what others more educated in physics here think about this concept. Interesting point. Is time being created non-linearly? I am not sure we can. I think your question is interesting.
If, for example, the universe is, say, 15 billion years old, but we went back in time, which time of course is the relevant question, but going back in time for rhetorical sake 8 billion years, would the universe actually be 7 billion years old?Could it be, if we plopped into space back then, that the universe would appear, say, a billion years old? QM seems to show that at least on quantum levels (and maybe higher, and definite some QM effects are now seen for larger objects such as some molecules, that physical existence is actually first superpositional, meaning several different possibilities exist in terms of form prior to that form becoming a physical reality. A photon can exist as a wave that appears to be a particle in more than one place at once, but can then collapse into a single point/pathway.What appears to cause the "collapse of the wave function" is observation, and since observation implies consciousness, you get scientists talking about the age-old concept of whether something exists if no one sees it.There was a joke told that went something like this. First they told us the earth was flat, and then the earth was round, and now that the earth doesn't exist at all!An intrigueing idea is that this suggests a universal observer present all along for matter to exist as a definite form, assuming this interpretation of quantum physics, or one alternative is that the universe evolved as a multi-verse in a superpositional state of all possible universes until one possible "universe" evolved consciousness and collapsed the multi-verse into one state, or some variant including these ideas.if such consciousness-based interpretations of QM are correct, it may be that consciousness plays a bigger role than we think.There are other interpretations, one being waves travelling back in time, and that all possible universes exist, the many-worlds interpretation.Frankly, as weird as they sound, I think there is some real merit to all of these ideas, and I am not as sure all of them are as mutually exclusive as are presented.

Ok, this small point got me excited, as I have been tried to think in those terms and apply that thinking for some time to different issues.Is it possible in your opinion, for one point "later" along that line, more on one end, to effect an "earlier" or another point along that line?I beleive we will discover (if we haven't already?) that this is possible and is occurring; that there are causal effects essentially backwards in time because things really consist not of an object floating through time but a more holistic view, a more real view in terms of science, shows that the object is line in space-time. So the whole can be affected by anything done to it.The affects from the present moment to the next are the largest causal determinative effects, but if there are smaller causal effects essentially backwards in time, from our perspective, then the longer the object in space-time, the more time elapsed from our vantage point, the larger these effects would be, and the more the past would be changed.Indeed, the universe as a whole can be imagined from an observer beyond superluminal space-time, as a thought experiment, as one streak or line, and as in the scenario above, causal effects on the whole can and do, imo, make the past non-static.This message has been edited by randman, 08-03-2005 02:32 AM