Severian

To answer your original question, the vacuum is defined as the lowest energy state. When constitutes the lowest energy state is still unknown, but if the Stadard Model is correct, then it is more energetically favourable to have a background higgs field than no particles at all.

It is quite different. The quarks produce normal magnetic fields too of course. The "magnetic" force arising from the strong interaction is known as "color magnetism". They are not destroyed - they pair up to form color neutral particles. For example, when the color flux tube snaps, a quark antiquark pair is created out of the vacuum (using the released energy) and the new antiquark might then bind with the old quark to form a color neutral meson. This will then decay to lighter particles. Color magnetism is more usually discussed within the context of a quark-gliuon plasma.

I examined a PhD thesis on this topic once. To answer your question, yes they do.

We know that the angular momentum must be conserved, because otherwise the universe would have physical laws which depend on the direction you are facing (this is Noether's theorem). We also know that the Dirac Hamiltonian (which describes the motion of free electrons) does not commute with the traditional angular momentum operator, so traditional angular momentum is not conserved. We also know that the solutions of the Dirac equation are eigenstates of another operator, but at this point we have no physical idea of what this operator represents. Then we notice something special. If we add the traditional angular momentum operator to this new operator, we find that the sum does commute with the Hamiltonian. The new quantity is conserved, so we interpret this new quantity as an internal angular momentum of the electron which we call spin. In hindsight, we can go back and realise that the spin eigenstates are themselves fundamental representations of the Poincarre algebra, which reinforces out idea. There are lots of reasons. Firstly, Maxwells equations require a vector potential, or in other words a spin-1 object. Then we notice that photons obey Bose Einstein statistics, so no Pauli exclusion principle (which they would have if they were spin-1/2). Also, their couplings to electrons would be entirely different if they were fermions.

Not sure what you mean by that. There are neutral fundamental particles, such as the Z boson, the photon and the neutrino.

Isn't that a bit self-defeating? Since we know that photon wavefunctions do disperse, how can they be solitons?

It is not really much of a close shave; it was still over 11 times the radius of the Earth away. Since the area goes like the square, even if you fired asteroids at the earth randomly within the radius of the 'close shave' asteroid, you would on average hit the planet one time in 130. So if a close shave like this happens even every 100 years we will still have 13,000 years to wait before one hits.

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In your opinion, which is worse? Having a wrong opinion, or having no opinion at all?

That is definitely not true. For many many purposes, peer reviewed journals are insisted upon. The Research Assessment Exercise is one example that springs to mind. They are better than all that String Theory conjecture drivel. Phenomenology papers are at least making predictions that can be tested.

I will be interviewing PhD applicants this week. The most important quality is to be enthusiastic. You should also have a clear idea of the field you want to work in and the contribution you think you can make. However, you should remember that your professor will be hiring you to help with his research, so make sure your research direction is aligned with his, and provide enough flexibility to cover whatever he wants you to do.

You can't pass information out of a black hole. But there is noting to stop you going to take a look personally, if you are really curious (other than the fact that you would be pulled apart by the gravity of course).

And why do you think that? Is popularization of an idea more important than the idea itself?

Why no Empedocles day, or Wells day, or Mathew day, or Wallace day?

The most galling thing about publishers in my field is that they don't actually add value to research. Nowadays, researchers write papers in a format which is perfectly readable and clear without the need for publishers to re-typeset anything at all. They still do of course, but no value is added. Furthermore, all the papers are available on line, and no-one reads them in the journals at all. In fact, they are often a bit out of date by the time they are published in journals. One might argue that the journals provide peer review, but the reviewers are all academics who peer-review for free (myself included). Why do we need journals at all? The only reason I still publish in journals is because journal publications are the metric by which funding bodies rank our productivity.

Haven't you answered your own question already? Your can be differentiated (at x=0) n times. Once you get to r=n, it is no longer continuous since [math]\lim_{x \to 0} \dfrac{\mathrm{d}^n}{\mathrm{d}x^n}\big(x^{2n}\sin(x^{-1})\big)=(-1)^n \lim_{x \to 0} \sin \left(x^{-1}+\frac{1}{2}n\pi \right) \neq 0[/math]

Well, the biggest issue I would have with it is that it is a sledgehammer to crack a nut. Normally one would use extra dimensions and branes to try and explain why some particles feel some interactions and not others. So, for example, some particles might feel electromagnetism, while others feel only gravity. This is indeed what you are suggesting - dark matter is on a particular brane where the SM gauge symmetry does not apply, so it feels only gravity. Fair enough, but the phenomenology (what we would see in experiment) can equally well be expressed by just saying the dark matter has no charge, no SU(2) isospin and no color. That's it! So we have a simpler (if less elegant) description of matter. Now, if your brane model can make other predictions about the universe and get them right, that would be a whole different ball game. Unfortunately it can't.

Here is my theory. The original population on Earth was human (or some variant on human). They figured out how to download their consciousness into a 'cylon' if they died, thereby making themselves immortal. They also managed to make artificial life forms (the other cylons). Some sort of interstellar war erupted, but probably human vs human, not cylons, cutting Earth off from the others (or maybe they had already been separated by some other event). The attack took them by surprise and only 5 managed to download (the final five). I suspect the series will end with the Gallactica crew figuring out how to do the rebirth as a cylon thing, and then when the Gallactica and the fleet are finally destroyed by Cavil, they (or more likely a subset) will resurrect as cylons. I also think this is what Kara has already done.

Why should a minor have a right to free speech? And if you think they do, should we also legislate that their parents aren't allowed to punish them? After all, if they haven't done anything illegal, isn't punishing them a violation of their human rights?

In my opinion, a god (small 'g') is something we cannot prove in principle (rather than just in practice) but chose to believe anyway. For example, a unified theory of all physics would be a god.

Sorry - posted in wrong thread by mistake. (I voted yes, by the way)

So would you be OK with us dropping a great big pile of nukes on the entire middle east? I am sure that would stop the fighting. A few innocents might die, but what does that matter in the scheme of things?

The motivation for gauging supersymmetry is not gravity. The motivation is that most of the other symmetries are gauged, so why not try this one too. Gravity and the graviton just falls out.

Yes, it has to be the particle's corresponding antiparticle for the annihilation to work.

You could always email him: Brian.Cox@hep.manchester.ac.uk Alternatively you could always just ask us. If it is a question like "name the fundamental particles" or "what is time" you might even get a better answer!