Severian

Not quite identical - the electroweak force violates CP, meaning that it behaves (slightly) differently for matter and antimatter.

10-20 eV is an absurdly small mass, and this should be proof enough for anyone. There are other good reasons for expecting the photon to be masses, e.g. it is the gauge boson of an unbroken local symmetry.

E=mc2 is only true in a the rest frame of the particle. The photon has no rest frame. The more general equation is [math] E^2 = m^2c^4+p^2c^2[/math] In the rest frame, the momentum of the particle (p) is zero, so this returns to E=mc2 But, for light, m=0, so the equation becomes E=pc and thus the momentum is E/c

Yes!!! I gave you a link in post #8 !!!!! Here it is again: http://pdg.lbl.gov/2004/listings/s000.pdf

Well, we only have to wait until 2008 to see if supersymmetry is true. If it is, the next big question will be 'How is it broken?'

Did you perhaps mean: f(x) = 3 x3 + x2 - 12 x - 4 ? If so, f(x) = (x2-4)(3x+1) = (x-2)(x+2)(3x+1) f(x) = 0 => x = -2, +2, or -1/3

I personally prefer String Theory to LQG. I am not terribly sure why to be honest, perhaps it is just more of a gut feeling (no pun intended). Perhaps the biggest attraction of string theory is supersymmetry. Supersymmetry has lots of nice features and motivations for both low and high energy. For me, only one of these is sufficient: it is the only (non-trivial) way to extend the Poincare algebra. So far every particle physics theory which has been successfully confirmed by experiment is based on symmetry groups. The question automatically arises 'why these symmetry groups?'. I feel that this will probably be answered by finding that the symmetry of the universe is the largest symmetry we can have without being inconsistent, and the low energy symmetry groups we see now are the remaining fragments left over from some symmetry breaking mechanism. If that is true, then shouldn't space-time be maximally symmetric too, which in turn would naturally lead to supersymmetry. Now while I admit that LQG can be consistent with supersymmetry, it is rather auxilliary. By contrast in string theory, gravity is local supersymmetry - supersymmetry is completely fundamantal.

No, definitely not. I did think that Americans were rather loud, pompous, arrogant and overbearing () but I did not see America as a rampaging imperial force bent on focing the world to its will. (Well, maybe a little, but only in terms of the behaviour of its corporations rather than its government.)

Again, I think you are being unfair. The language of the piece is clearly intended toward the layman - not the expert. You are objecting to him using imprecise language, and not refering to complicated theorems which would only confuse the majority of readers. Having said that, he prevents no mechanism for the collapse of a wavefunction with the interaction with complicated systems (but then again, the Copenhagen interpretation of QM has no mechanism for collapse with an observation). I still disagree with him, but your criticisms are unfair.

The problem is that the US people don't realise how Bush has managed to turn the world against the US. If I ask around (in the UK) pretty much everyone now has a negative opinion of the US. The intelligent folks realise that it is not the US people who are (entirely) to blame (although they must shoulder some responsibility) but instead their government. And the more 'western' coutries are never going to turn their backs on the US because our economies are so interlinked. But if you ask the ordinary people, they are amazingly anti-US. The US is almost universally hated. Even if Europe still supports the US on many issues, it is now done because of necessity rather than a common bond or any feeling of friendship. A desire to reverse thia is imho enough reason to vote for Kerry.

I think he meant neutralino.

Yes, as long as you removed all the air between them (otherwise you would remove photons by collision with particles in the air). In fact, if it were an infinitely good mirror and you were in a perfect vacuum, they could bounce around forever.

There are a number of things wrong with the original post. First of all, the Dirac sea doesn't exist. It is only a sort of handwavy picture used to confuse undergraduates - it isn't really there. Secondly, a 'virtual' particle is one which disobeys the equation [math]E^2=p^2c^2+m^2c^4[/math]. We call this being 'off mass-shell'. And a virtual particle feels gravity just like a normal one does. In fact, all particles are at least slightly virtual, because how off-shell they are determines how long they live. A completely on-shell particle will live forever, so it cannot interact and cannot be observed (and therefore doesn't exist). Incidentally, antiparticles (like the positron) also behave exactly like their partners the electrons under gravity. In real models (and even in the dirac model) the antiparticles have a positive mass.

Yes you are. You don't get the tax breaks, so you are paying a 'single person tax'.

Well' date=' which ED model would you prefer to discuss? The Randall-Sundrum model perhaps? Or maybe an ADD model? Which fields do you think are restricted to the brane and which fields are allowed to propagate in the bulk? Do you think the SM brane should have a finite thickness, or by infinitely thin (ie. not project into the extra dimensions)? That was why I asked. Do you feel that a UED model makes a reduction in the Plack scale reasonable, or do you feel that we would be better with a more traditional unification? Perhaps E8xE8'? What, to your mind, is the most convincing GUT scenario? What is your view of E6 breaking via E6 -> SO(10) x U(1) -> SU(5) x U(1) x U(1) -> SU(3) x SU(2) x U(1)Y x U(1) x U(1)? If you think this is OK, which representations of the extra U(1)'s would you expect at low energies? In fact, if we restrict ourselves to one extra U(1) and the SM groups at low energies, can we build an anomaly free theory? How does this mesh with the LEP2 data on Z', or indeed the WMAP data? Why do you find recent works 'unconvincing'? I await with baited breath....

OK Iridium. Let's have a serious discussion. What is your opinion on Universal Extra Dimension models? Do you think they are reasonable or just a fad? What is the true value of the Planck scale?

Arrgghhhhh..... photons are not matter, period. It is just a matter () of definition!

LOL!

Are A levels and GCSE's getting easier?? YES!!! (trust me, I am in a position to know...)

I think he is meaning that if something is travelling faster than light it cannot have interactions with normal matter (otherwise it would destablise the vacuum - I mentioned this in the tachyon thread).... ...but then if it doesn't have interactions with matter, it doesn't exist by definition.

Is the pdg limit of < 6 x 10-17 eV not good enough for you?

Remake? There has to be an original movie before there can be a remake. It has been made into a very nice radio series and a rather naff TV series, but never a movie (until now).