BenTheMan

Farsight---another thought. Why does time have to move forward in your picture? You say that time is justa measure of relative motion. Why is it that that measure always has time going FORWARD?

Yeah---strings are still the best way to understand the strong force, in my opinion. At least, when I describe hadronization to people it's always the analogy that I use. I always thought that it was ironic that it took fourty years for people to go in a huge circle, and realize that string theory really COULD describe the strong force, via AdS/CFT (which is why you should include the 1998 Maldacena paper in your 5 year index!).

Innit--- Is this ``Inuit'' with an upside down `u'? No matter. Ask your questions and I will do my best to answer. You can also trust a guy named ajb (he knows MUCH more about the mathy side of things than I do). His avatar is a penguin (presumably because he likes Linux). Anyway, perhaps we should start a general string thread? If this discussion goes long enough, perhaps we can get a moderator to do that (not Martin---I don't think he likes string theory very much). Ok, extra dimensions. The canonical example is a line strung between two poles. First some semantics---a dimension means that you can put a coordinate on it. The number of dimensions is the number of coordinates that you need to describe a surface. So, if you have a line strung between two poles, you only need one coordinate (i.e., distance from one end or the other). The top of your table needs two coordinates (`x' and `y' if you like), as does the surface of a sphere (think latitude and longitude). Suppose that you're a tightrope walker, and you wish to walk across the tightrope. Well, you can describe your position with only one coordinate, right? You can use your distance from one of the end-points to describe your location. And as long as you tell me which endpoint you're starting from, and how far from that endpoint you are, I can find you. Now suppose you're an ant living on that same string. If you're an ant, things look much bigger to you. If you are small enough, and the rope is sufficiently thick, you can see two dimensions now---you can see the distance along the rope, but you can also travel in circles laterally around the rope. In order for your ant friends to find you, you must give them two corrdinates---not only where along the rope you are, but also where around the rope you are. The thing is, unless you are an ant, or unless you look sufficiently closely, you will NEVER notice that the rope has any more than one coordinate. If this isn't clear, ask questions! Please! Now extrapolate this out. Suppose we live in four dimensions. We know very well that we live in four dimensions, but we are big. Suppose we are very very small. Are four numbers enough to describe our position? The answer that strings gives is no. Depending on HOW small you are, you either need 10 numbers or 11 numbers to describe your position. An easy way (and not completely inaccurate way) to think of this is to think of every point in space time as being described by four numbers (x,y,z,t), along with coordinates around 6 little circles. When I say little, I mean VERY little. Again, because we are so big, we never notice the little circles---just like the tightrope walker may never notice the thickness of the rope, but the ant does. I hope that this was a little clear. I haven't seen this video you have linked to, but hopefully my example was different from the video's example.

Sure, time ``stretches'', or dilates. The problem I have is that this effect is only infinite if the infalling particle is massless.

http://download.iop.org/pw/PWSep07strings.pdf This is a pretty good article, and sumarizes the attitudes of the people in the field (at least that I know) pretty well.

I don't care at all...untill he votes or raises childeren. THEN it effects me, and I DO care.

The calculation is fully valid classically, and is used to show why spin cannot be interpretted classically. Ahh, but you didn't treat the electron as a point, here: Right?

Ahh yes... I was confused about what r and r_0 meant. I believe you know, pursuant to you having derived the above equation correctly, of course So when you ignore the gravitaitonal backreaction, I will agree that it takes an infinite amount of time for a test particle to fall in to a static, unchargedm non-expanding black hole.

I always get sucked into black hole threads (HA!), even though my GR is weak. No one ever wants to talk about SO(10). I'm glad you agree

Norm--- I claim to be no GR expert, but just taking a limit [math]r_o\rightarrow\infty[/math] it is clear that the second term is constant. If r is constant, the r_o^3/2 dominates every time. What is it I'm missing? x^3/2 grows faster than log x---I know because I just graphed it... http://www.coolmath.com/graphit/index.html Maybe we are talking past each other---the idea I have is that a particle starts at rest, at some distance r_o, and crosses the horizon (at r) at a time t. As r_o tends to infinity, the particle takes infinite time to fall into the horizon. You've probably fixed your frame at r_o, so this is the time it takes an observer to watch the particle falling in. Also, you're failing to take into account gravitational backreaction---that is, because the infalling particle has a mass, then the mass of the black hole increases, which makes the radius bigger. So, for a Schwarzchild black hole, we have r = M. For a particle mass m, the black hole's new radius is r + r' = M + m. So when the particle is a distance OUTSIDE the horizon (r'-r), the horizon size INCREASES, absorbing the particle. This is a subtle point, and I don't know if it's generally addressed. My guess is that most people assume that the infalling particle is massless, or something. It's all pretty confusing to me, actually.

I think that the quote from Wikipedia that you posted is about as poor a description of me as one can find. Honestly, I've been mad twice in my life. It is easy to make a sweeping judgement of someone's personallity when you don't know them Ho hum... I would say that Farsight is only as crazy as his idea. Again, I have no problem with the guy, until he talks to someone about physics. Are you suggesting Farsight is handicapped, based on his ideas? That's a bit further than I have gone A thinly veiled threat? No matter... If you want to discuss science, then you should be prepared to be told that you are wrong. If you persist in your wrongness, in the face of MASSIVE evidence to the contrary, you should be prepared to be called a crackpot. I would be interested to see if you have the same objections to the treatment of Intelligent Design. I'm sure I can go into one of the Biology fora, find a thread on Evolution vs. Intelligent design, and find a much harsher treatment of the theists who advocate ID. Do you make it a habit to go around protecting the ``minorities'' here, or at other places on the internet? Farsight's every post is an affront to science, and this one time I have made it a point to show any interested party that this is the case. He willingly ignored data, he refuses to answer questions, he skirts issues---these are all hallmarks of a crackpot. I'm not sure Farsight is insane... I think he is probably pretty intelligent. I read this book by Michael Shermer called ``Why People Believe Weird Things'', and there is a chapter on Frank Tipler. Tipler is a formerly great physicist, a highly intelligent man, and author of a book that claims that God is a computer on a cosmological scale, and we will all be resurrected at the end of time based on quantum information. Farsight is probably no Tipler (Tipler has a PhD from Princeton, I think), but anyone who spends their time thinking about physics (I don't even spend all my time thinking about physics, and it's my job) has to be somewhat intelligent. I have no problem with people thinking about physics, or coming up with toy theories. The problem arises when people put their faith in those toy theories, so much so that they are willing to ignore experiment, expert opinion, and common sense, just because they believe that they are right. They are scientists no longer, now they are missionaries. Farsight has ventured out of the realm of science long ago, and now he is just trying to convert people by faith. While this may work for Christians, it is no way to be taken seriously by scientists. Untill Farsight admits that his theories need significant work, or scrapping altogether, his claims will not be treated as scientific, and he will be taken seriously by no one here. His work will remain ``crackpot''.

They're a feature of the classical theory---there's nothing that prevents this from happening. The gravitational forces overcome the other forces acting, to cause collapse. Conversely, it takes an infinite amount of energy to accelerate a massive particle from the speed of light---because you can't FIND an infinite amount of energy in the universe, this is impossible. You have to be careful to include GR effects here. Your argument is invalid when gravity starts becoming stronger. Also, you have no way do derive `X'. What you have said is (essentially) what happens for an observer at infinity. An observer nearby will watch the star collapse and see a black hole form in finite time. You have to SHOW this, you can't just SAY it That's being pretty cavalier... ``Modify gravity! I mean, everyone ELSE is doing it.''

Ho hum. Penrose's book is more of a general book about math and physics---I actually own this one. He is a critic of string theory, but a critique of string theory isn't the main point of his book, so no, I don't include him in my index.

Martin---- It is possible that there is something I'm missing. It seems that Yukawa couplings of the tau neutrino to the higgs should be forbidden, especially couplings comparable to the yukawa coupling to the top. Plus, I thought that they were giving neutrinos masses with the seesaw mechanism. Don't you think so? If I'm wrong, my feelings won't be hurt if you say so. And the paper only claims to yield the structure of the standard model, not the yukawas. You seem to have claimed that this paper produced realistic phenomenology, and I found something that contradicted this claim. Perhaps you can correct me? Again, maybe there's something I'm missing. I didn't study the details of the paper (nor do I really plan to), but I assumed that perhaps you understood some of the finer points.

Perhaps I misunderstood---the AdS/CFT papers (Maldacena; Gubser, Klebanov, Polyakov; etc...) were written in 1998/1999, which is definitely eight-nine years ago. Martin---a bit smug here but perhaps I deserve it. Either way, show me how to get good low energy phenomenology out of other QG approaches and I will start reading the papers. Until then, I'll stick to heterotic strings. Martin---do you understand any of these papers? They look as if they are not written for physicists. It looks kind of iffy to me. Specifically this: Clearly this is worng. These guys are saying that the tau neutrino has to be as massive as the top quark, right? So, isn't this pretty much experimentally ruled out by astrophysical bounds, etc? So let's invent a right handed neutrino, and pretend that's what Connes is talking about. This is still no good, because the limits for a right handed neutrino which give light masses to the left-handed neutrinos is somewhere around 10^12 GeV or something. So a Yukawa to the higgs is pretty useless for giving IT mass... I said realistic phenomenology Martin

And in my index, Woit was 18,822 (up 30,000 places since I checked last!) in overall sales, giving an average of 9798.9, then the corrected index is 5098.8/90798.9 = 0.4.

I'm not bashing Aristotle at all... I am bashing the people who think it is still ok to walk around in robes and sandals, wearing laurels in their hair, and waxing poetic about the ``deeper truth'' of quantum theory, and ``explanations'' of Nature, as opposed to ``descriptions''. And to be clear, I wear sandals as often as I can, and laurels when I'm in the mood

This statement applies to many in these fora

Well, fredrik should be along shortly This all depends on what experiments they preform---let's be perfectly clear that NOTHING can be learned untill we do more experiments. Then there will be more discussion by people like you about ``deeper reality'' and so on untill we iron quantum gravity out.

No thought experiment can ever replace a real experiment. The real experiment HAD to be preforemed, otherwise Galileo was just waving his hands as Aristotle did. See the above post for links to copious handwaving.

This is about the only scentence I understood, but it can't be right. See here where I showed that if this were true, your electrons would be spinning faster than the speed of light. Is this something you want in your theory?

Are you speaking as someone who has studied science seriously?

Well, depending on what you call exotic, you are half right. If we're talking about dark matter candidates, then you attract the dark matter via gravity. But that's the only type of charge that it carries, so it will just fly through your body.

Ummmm kind of. This is how you get the compton wavelength. Set the deBroigle wavelength equal to the rest mass of the particle. The compton wavelength gives you a distance scale where you have to consider quantum effects. For example, the only dimensionful parameter in QED is the electron's mass (the coupling doesn't have any units). This sets a scale for QED effects---that is, one doesn't have to consider QED effects unless you're working at scales near the compton wavelength of the electron. This is why the Bohr model works for the hydrogen atom---the compton wavelength of the electron is much smaller than the Bohr radius. This is (I think) what Farsight has in mind when he says frequency of light and mass are tied together. This was a new idea in 1920. I made this point about ten posts back.

I think I did a pretty good job. You should hope that you're never one of my students Yes, so the time scales as [math]r_0^{3/2}[/math]. So the time to crossing the horizon goes to infinity only as [math]r_0[/math] goes to infinity. No?