elfmotat

Why does it take so much space for you to say so very little? Your posts are void of anything meaningful, and they're incredibly tedious to read. They're also very annoying to reply to because it's hard to figure out exactly what you're trying to say. Please distill your points into something less winded so that we can actually have a discussion. I think you'll find that very few people here are fans of wordy fluff.

Now you're just making things up. This is getting increasingly frustrating, and I'm not sure what else we can say to cure you of this strange compulsion to get rid of relativity.

There's definitely a lot of words there, but I don't think you actually said anything.

If your model correctly predicts bunch of phenomena, and it also predicts some related yet untested phenomenon, then it's reasonable to assume that your model will also accurately describe the untested phenomenon. Is it "proof" that it definitely will describe it accurately? Of course not, but it's more useful to assume the usual rules work (until they don't).

Even if that were true, what does it have to do with anything I just said?

Yeah, I kind of figured. That would be interesting though.

As I said, I'm aware that k is a constant in the FLRW metric. I'm wondering whether or not other solutions to the EFE's exist which have a parameter analogous to k, but are time-dependent.

Nothing good could possibly come from this thread.

Roughly speaking, the predictions of Newtonian gravity are equivalent to a theory with "bent time" but flat space. General Relativity includes "bent time" and "bent space." Newtonian gravity cannot and does not predict what GR predicts for this reason. They are not equivalent theories. The Newtonian calculation, no matter how you do it, will always be off by a factor of two. Any calculation that doesn't include relativistic effects is going to be wrong.

I agree that that's true in the FLRW metric, but I don't know whether it's true in general. If you have links to any related articles I'd be interested in reading them.

I was trying to visualize it like that, but the line immediately goes from being infinite to length zero with nothing intermediate. I couldn't get my brain to visualize that. I was being sloppy with my language. I don't know if it can go from being closed to open or flat. I'm not sure how that would work.

I've heard it said that notation is half the battle, and that's certainly true in my case. A lot of the time math and physics equations aren't nearly as intimidating or complicated as they seem once you're familiar with the notation.

I'm not really sure how to explain it any more simply than I already have. Like I said, I don't think it's something you can visualize. At t=0 every point is zero distance from every other point. At any time after that (even t=0.0000001), the distance between any two points isn't zero, and because there is a continuously infinite set of points the length of the space is infinite. AFAIK in all inflation models the whole universe is modeled to be infinite in size even at the big bang. When you hear talk of "the whole universe was really tiny," what they are referring to is the observable universe. Every point in the observable universe was scrunched very close together at the big bang. However the whole universe was still infinite, even at the big bang, and the observable universe was just a tiny patch. I don't know whether you can go from a bounded to an unbounded universe. That's an interesting question though.

When did you first realize how little you truly know? I was ~17, and decided to study special relativity because my high school physics class didn't go over it in any detail. I went through Taylor/Wheeler's "Spacetime Physics" pretty quickly, so I thought it would be pretty easy to learn GR. I bought a copy of Wald's book (not recommended for beginners), glanced through it a bit, and I suddenly realized that I actually knew close to nothing about physics. It's been ~4 years since then, and I'm definitely way more knowledgeable than I was, but I'm still blown away whenever I start thinking about how much is left to be learned. Anyone have any similar experiences with science-related ego-destruction?

I'm an engineering student, not a physicist, so the internet is pretty much the only place I can talk to other people about physics. I'm decently active on another site as well, but it's mostly for technical questions while this site is a lot more laid back.

Basically all it says is that the distance between any two points in space varies over time. The function f(t) is what determines that distance. I've chosen the function f(t) such that f(0)=0. So at t=0, the distance between all points in space is zero. However after t=0 there will be nonzero distance between any two points because I've chosen f(t) so that it's positive after t=0. I don't know if it's something you can really visualize.

That equation is called a metric equation. In general relativity the geometry of spacetime is defined by the metric. "s" is a measure of distance, and I've given every point in space a label for its location, "x," and time, "t." I've defined the metric so that distances between points are time-dependent. At t=0, there is zero distance between every point in space. At t>0 there is finite distance between points, and there are an infinite set of points. I.e. the space goes from length=0 to length=infinity. The metric I provided is essentially the same as the FLRW metric (see here: http://en.wikipedia.org/wiki/Friedmann%E2%80%93Lema%C3%AEtre%E2%80%93Robertson%E2%80%93Walker_metric ), which is what describes the expansion of the universe.

I guess it depends on what the OP means by "wave." I don't know whether he's talking about transverse waves (like in the video I posted) or about longitudinal waves. EDIT: I re-read the question I'm still unsure about which type of wave he's considering.

That's certainly not true. Consider, for example, the metric: [math]ds^2 = -dt^2 + f(t) dx^2[/math] where f(t=0)=0, and f(t>0)>0. At t=0 all points are condensed into a singularity, and the space has zero length. However any time after t=0 the metric describes an unbounded (infinite) line. Also notice the similarity to the FLRW metric.

You may find this helpful:

I-try, a lot of members have been very patient with you. Everyone has tried to explain that what you're saying is ill-defined, at best. (And deep down, I'm sure you already know this.) Your responses consist of pseudo-technobabble, and you're very confrontational to anyone who points out (obvious) flaws with your "theory." Why bother posting to a science forum then? If you're not interested in learning real science then why are you here? It seems like you just want praise and validation - finding out whether or not your ideas make sense and actually apply to reality appears to be a secondary concern. Just think of all the stuff you could have learned while you were busy writing all of these nonsense responses!

The formula shows no such thing, and I have no idea what you're asking.

Sure. If you're interested enough and have the discipline for it, it should be no problem. It will probably take a few years to build up all that knowledge, but I would definitely say it's worth it.

So you're proposing that each particle is a mini universe, but each universe is completely indistinguishable, and there's no way to test it even in principle. That seems pretty useless. Nobody actually believes the 1-electron universe is an accurate model, it was just an idea that Wheeler supposedly had.

Right. I'm working in Heisenberg picture. The LSZ reduction formula is what justifies our use of the interaction picture, which is technically ill-defined.