Speed of Light Barrier

Sorry, I was being a little unfair there. Understand that there are two very different things: the time dimension, and elasped time. The latter we call "proper time" and is essentially how much time you experience. But this has little to do with the time dimension unless you always move such that v<

Obviously

Some cool stuff there, especially in that first topic. Personally, I think Ned's comment is great Unfortunately this is true. To think sensibly about these topics requires a certain level of background to keep you on the straight and narrow and away from "crackpot" land! There was definitely a deal of that in those threads BUT, the questions posed (in the main by you) were excellent, and very relevant.To answer your first thread - take the earth (spherically symmetric ball) in an otherwise empty universe. Translational motion is trivial, in that you can always jump to a moving frame and view the earth as "moving". It has no consequences. Acceleration is always detectable, and would have a definite effect on the space-time. There is the "C-metric" which essentially describes two objects in an otherwise empty universe accelerating away from each other. Rotation in an empty universe is rather un-Machian in Relativity - it has definite consequences despite no "distant stars": there is the frame-dragging. Now, the two planets orbiting each other is interesting... I'm tempted to say that at distance it would appear to be a rotating point source and so there will be evident frame-dragging, and hence a frame in which the planets were not-rotating and supposedly in-falling would be invalid.One other point... objects in orbit (if "small" enough) are precisely those that are NOT accelerating!

Ok, fine... let's use geometric units: c=1, G=1, h_bar=1.Now, instead of why 3x10^8, let's have...why is alpha 1/137?
why is Mp/Me 1836?
why is Me:Mm:Mt = 1:207:3477etc, etc...(Mp: mas of proton, and electron , muon, tauon)

To me, a change in c is a change in alpha. Otherwise it is just an unobservable scale-change. Which I guess is what you were arguing...

This is a convenience... it is not real. What is "45 degrees" in the t-x plane of Minkowski space? You think "45 degrees" as a result of embedding the t-x plane in a positive definite space... i.e. a sheet of paper/diagram. You can compare scales among the spatial dimensions because you can rotate a space-like vector from say pure-x to pure-y. You cannot rotate a time-like vector into a null-vector or a space-like vector to compare scales. Remember, orthogonality and "angles" do not retain their usual sense in pseudo-Riemannian geometry. True, but the original question was asked in respect of our universe, where you certainly need to consider the quantum aspects.

I'm not sure I follow... and I could be wrong, but I don't think it's down to Bernard that we draw null rays at 45 degrees.

No, I appreciate what you were saying... I just hadn't heard it called the "Schutz description".Is his book still that popular? It was good, but D'Inverno's was a huge improvement and there must have been several in the last decade of which I am unaware...But I must say that his "Geometrical Methods of Mathematical Physics" is what helped turn me from an astrophysicist into a mathematical physcist.

Hi person7! Yes, that's about right. What was the book?

The problem with this statement is the "passing the speed of light". That contains the naivity. Both "passing" and "speed" have no meaning...Given that at the speed of light, you are going zero distance in zero time, it is difficult to understand a concept of "faster".But space-like travel is possible. This is not a "speed" beyond light, but really a different concept all together. Two events are space-like seperated if light cannot travel from one event to the other... e.g. here on earth "now", and on a planet around Alpha Centauri "now" (or "now" plus any amount of time <4.3 yrs as it is 4.3 lyrs away) If I can teleport somehow from earth now to Alpha C now, that is synonymous with time travel. One way to do this is with a convenient wormhole. Unfortunately, we have the Chronology Protection Conjecture (CPC) that dictates that this will not be possible... sadly the physics seems to suggest that this is the case. Actually, in most things relativistic, there is That is because most things we are looking at are actually 3d projections of 4d quantities. The projection can shoot off to infinity, but the 4d variable remains perfectly well defined. Just because tan(x)-> +infinity as x->pi/2-, doesn't mean that I can't look at tan(x) for x>pi/2.

Yes It doesn't have a width so all is ok - each particle making up your body has its own world-line. And all particles making up your body interact causally. Likewise with the particles making up the pole in the 'famous' pole and barn paradox of Special Relativity. Hmmm, yes and no - this is much more complex that your other issues. Light cones can become fuzzy (or smeared) but also coordinates can be specified without being subject to the Uncertainty Principle. However, these two points also depend upon your particular view of quantum gravity, so there is no definitive answer (yet)

Where do you get this shit? I assume this is a joke? An ERB by definition is non-traversable. Lorentzian wormholes are not ERBs. Maybe we'll build one by 3008... maybe. Well, he's a bit slow. I was working on them in 1991, after they were first developed by Morris and Thorne in the mid-80s - in response to Sagan asking Thorne for a plausible FTL mechanism for the book he was working on, 'Contact'.

I said Percy noted that it's actually a lift from hereand checking the date of the entry, you'll find the answers to my questions

Why do we need an alternative view when Special Relativity is the most successfully tested theory of all time? No, it would not. 'spooky action at a distance' has nothing to do with FTL interactions - instead, it is simply a feature of non-classical variables. What is difficult to explain regarding the two slit phenomena?

By train, presumably?Have fun, SG. I had quite enough of V-bird over at IIDB...