Severian

Newton's Law of gravity is non-relativistic' date=' which means that it is not compatible with special relativity. It will not hold for objects travelling at high speeds relative to each other, but is a good approximation for objects which travel slowly (so Newton's apple is fine). Part of special relativity is the introduction of space-time, unifying space and time together by saying that any event can be specified by its co-ordinates (c*t,x,y,z) where t=time, (x,y,z)=usual space co-ordinates and c is the speed of light (included to make the dimensions work). The 'distance' between two events (0,0,0,0) and (c*t,x,y,z) (I put one of them at the origin for simplicity) is simply given by a rule called the 'metric'. Euclidean space-time has the most obvious 'distance' to choose, namely c[sup']2[/sup]t2+x2+y2+z2 which is sort of analagous to a distance in 3d space: x2+y2+z2. Unfortunately(?) this rule is not compatible with special relativity, since the distance changes depending on how fast the observer moves. We really want a rule for distance which is not dependent on what the observer is up to. Minkowski space-time is a space time which has such a distance rule (metric). In Minkowski space, the space-time separation of the two events is c2t2-x2-y2-z2 Notice the minus signs. It is this metric which defines what we mean by Minkowski space. So far this has nothing to do with gravity, except to note that Newton's law isn't compatible with the Minkowski metric. However, Einstein's General Relativity was an attempt to make a law of gravity which is compatible with special relativity's principles. In GR, the presence of energy/mass actually changes the metric itself - it changes the rule by which we measure distance, and this makes it look like there is a gravitational force (even though things are really travelling in straight lines).

that is certainly not apparent from his website, or indeed the Amazon reviews. His readers seem to take hime seriously, just look at this: http://homepage.mac.com/ruske/ruske/finaltheory.html

I think I am going to cry....

This book seems to be the usual bullshit ramblings of someone who doesn't understand any science whatsoever. How can these people get published? Never ceases to amaze.... One example of extreme stupidity (I assume I don't have to explain to this audience why it is extreme stupidity): lol On a more serious note, I think it is appalling that Amazon should stock this. Maybe I should send them a letter....

I agree with Martin. These questions are designed to see if you can use your head for making order of magnitude calculations - they are not meant to be exact to the 10th decimal place. This is a really useful skill in studying science. I am amazed how many students don't realize that their answer is wrong, even though they have just 'proven' that the hydrogen atom is larger than the size of the observable universe. Frankly, if you can't do these questions without looking up info on the web, you should be flunked.

Yes, the energy isn't lost - it is just redistributed. Since it would be happenning the same everywhere you look you would still get the infinitely bright sky (I think). Also, not all photons will do this. You need to emit two photons at once to conserve momentum, which is quite unlikely, so there is a very good chance that light from a distant star came directly to your eye (otherwise spectroscopy wouldn't work). I was only pointing out that it would not live infinitely long.

If they are virtual, the energy doesn't matter.

It would still dissipate. It would split into virtual electron-positron pairs which would radiate, losing energy.

I don't believe that. You are not born with a gene dictating whether you prefer vanilla or strawberry ice-cream, so why should you be born with a gene dictating whether you prefer men or women? You may have a genetic preference for one or the other, but it is probably not one gene and I imagine that social phenotypic factors are more powerful. Ask youself this: if you were brought up in a society where it was normal to be homosexual, do you think you would be? I think if most people are being honest then they would say yes. It is only natural to be infuenced by your surroundings. Also, I get pissed off with the attitude that to be 'acceptable' homosexuality has to be a matter of 'who you are' (ie. genetic) rather than a matter what you feel like. No-one should be telling you what to feel, so why is it less acceptable if it is an expression of choice? I have had bisexual friends bullied by the gay community, claiming that they are really 'fully gay' and are just kidding themselves that they are bi. That is as bad as homophobia in my book. People should be free to have (consensual) sex with whomever they want without having to give an explanation to anyone (unless in a stable relationship with someone else of course, in which case they own an explanation to their partner). And they certainly shouldn't have to prove that their prediliction is genetic!

I am happily married. The key to dating women is not to care. I think women can sense if you don't care and then latch onto you out of a certain self-destructiveness. Either that or people who don't care are more relaxed and can be themselves more easily, making them more atrtractive. I never really cared (I was always busy with other things) and never had any problem with women. In fact, the one woman I cared about was by far the most work, even though I got there in the end and am now married to her.

The should' date=' but they won't. I don't think so. Realistically, the violence will only stop once the terrorists no longer have any motivation to continue. As long as Israel exists, there will be extremist factions out to get them. If Israel pulls out of the West Bank, pulls out of East Jerusalem, gives Palestinians (and their descendents) the right to return to 'Israel' as citizens (with full rights), and becomes a secular democracy (rather than a Jewish one), then maybe the terrorists will stop. But that will never happen. The Palestinian Authority may make a deal, but if it doesn't have the support of the people it is worthless.

How did the Venus Fly Trap evolve? There seem to me to be some organisms which have features that are difficult to come by through evolution, and the Venus Fly Trap seems particularly difficult to explain. To catch a fly, it needs to have 3 properties: 1. Attract the fly. This is presumably quite easy. All it needs to do is be a rotten flesh colour (and perhaps smell - do VFT's smell?) and flys will come. However this property has to be developed in conjunction with the other properties, otherwise there is no advantage to the plant in attracting flies. This is the same problem that flowers face in attracting bees (ie there has to be something for the bees to do). In that case, the pollen was possibly just being blown in the wind without the bees, and so the precence of bees helped carry it further. This can't work for the VFT since there seems to be no gain to the VFT unless it can digest the fly, so we need some other mechanism. 2. Trap the fly. To me this seems the hardest to evolve. The VFT has to sense the presence of the fly and close very quickly to trap it. The problem here is that it is all or nothing. If the fly escapes, nothing is gained. So we can't evolve a 'half-way-house' mechanism where the trap shuts more slowly. On the other hand it seems too big an evolutionary jump to move to a fast closing mechanism in one step! 3. Digest the fly. There is no point in trapping the fly if the VFT doesn't digest it. However, there is no point in trapping it if it isn't going to digest it. So it seems as if this would have to evolve simultaneously with property 2. The main problem here seems to be that it seems unlikely to evolve all of these properties at once, but all three are needed for an evolutionary advantage. So I suspect that they didn not all evolve at once, and there was some other advantage to be had for each one, perhaps by having some other complimentary mechanism already in place which was later lost. For example, there are other types of plant that eat flys, which catch the fly in some sort of liquid or sticky glue. There is a goblet like flower with sticky liquid in it, and why a fly comes to investigate, it gets stuck and is digested. There is no problem with this evolving because the plant could still photosynthesis normally, not using the dead flys it traps, until one day it's offspring mutates into something which absorbes the nutrients from the liquid. (It is not clear to me how the glue evolves, but presumably it had some other evolutionary use.) Could a similar mechanism have evolved the venus fly trap? For example, a fly might be able to crawl out of the liquid given enough time, so a flower which closes (a chance mutation) could be more efficient. Then closing faster and faster would help the plant, eventually evolving into a VFT. Does anyone know the 'official' explanation of how the VFT evolved? The few links I could dig up, aren't very helpful: http://www.strato.net/~crvny/sa03005.html http://www.talkdesign.org/faqs/icdmyst/ICDmyst.html The last one seems to support the proposal that there was a sticky substance which was lost. But why would a VFT without the sticky 'glue' be more efficient than the one with the glue? (Disclaimer: this post is not intended to disprove evolution or in any way imply that evolution is not the correct theory for the origin of species. It is simply a non-expert asking a (presumably dumb) question about something he would like to know more about. (So that I have a good answer when arguing with creationists!))

It is exactly the same thing. Our mathematical description of a particle travelling backwards in time is identical to our mathematical description of an anti-particle travelling forward in time, as you can see from my previous post. This is inherent to Quantum Field Theory, which is most certainly part of our 'current model'.

Thanks for the explanation.

My avatar is an animated self portrait, and my name is the name of a character (an executioner) from a Gene Wolfe novel.

Is it just me, or are science projects not supposed to be done by the kids rather than the parents?

So I suppose the reason you have had no work published is because you are such an innovative thinker?

Nothing in science is 100% proven since every measurement has errors and/or assumptions inherent in them. I just felt that it was a bit of an absolute statement. 99.9% proven I would have been happy with, but maybe I am being pedantic. I don't know how it is in biological science but every assertion in particle physics has a confidence associated with it so that you know exactly how supported by data it is. Of course, a lot of these confidence levels have assumptions in them too, but even I am not pedantic enough to ask for the error on the error. But while I am here (I only ever get dragged here via the admin subforum), let me ask a question. It is very clear that evolution (as in change in gene frequency) really happens and evolution by natural selection has been seen in the laboratory in organisms with short generations. But what is the real evidence of gene change by natural selection at very long time scales? Clearly it is the best mechanism we have, but is there more concrete evidence? How far back can they sample gene content? Could there be any other mechanisms at work, perhaps complementing or enhancing natural selection? (I always think 'evolution' in its modern biological usage is rather an inappropriate word. Really anything which changes 'evolves' and it would have been much better if someone had come up with a better term for gene changes.)

That sort of statement does not enhance your case.

Yes, that is what I meant. A particle state flowing backwards in time: [math] \psi = u_{(s)}(\vec{p}) e^{-i(E(-t)-\vec{p} \cdot \vec{x})}[/math] is the same as an antiparticle flowing forward in time [math]\psi = v_{(-s)}(-\vec{p}) e^{i(Et-\vec{p} \cdot \vec{x})}[/math] as long as we define [math]v_{(-s)}(-\vec{p})=u_{(s)}(\vec{p})[/math].

Some of the Star Trek technology is possible now! Like the doors which open automatically, and these two way radio things!

Since I prefaced my answer with "As far as fundamental physics which is currently being probed is concerned..." I think my answer was not at all misleading. Condensed matter is certainly not fundamental physics. And if you are such an advocate of condensed matter, why do you not explain to us what the burning issues are?

Sometimes I don't know what to do with you.... From the article you quote (in an attempt to claim CP violation is not on firm footing): So you prove my case for me. The references to 'new physics' in the article' date=' is not new physics in the way you suppose. They suggest extensions to the Standard Model, not replacements. These are things like supersymmetry. Personally I think the evidence for new physics from CP violation is rather weak (apart from maybe the baryon asymmetry problem). That is not to say that it is not a good place to look - it is, but even the circumstantial evidence is rather lacking. Dirac's anti-particles - the 'holes' in the Dirac sea - are rather different to the picture of antiparticles that we now have.