Severian

Exactly! Cashio is a cat killer!

No - that isn't the point. Obviously no-one has done experiments with cats (I hope!) but one can do experiments with photons which prove that the state before one looks at the photon is a superposition of different spin states. It is not just that we do not know which state the photon is in, with different probabilities of each, but that it is not in a definites spin state. If it was in a definite spin state and we simply did not know which state that was, we would not see the interference patterns that we see.

There still is no problem' date=' because your 'logic' is in error. If the cat is not an observer, then it [b']is[/b] a superposition of dead and alive. How can 'logic' say otherwise? Since you cannot observe the cat without collapsing the wavefunction, you cannot prove my statement wrong, and therefore there is no contradiction. You are basing your logic of assumptions on the classical world around you, which is not valid quantum mechnically.

A free particle cannot have 0 energy. E2 = m2c4+p2c2, where E is energy, p is (three-)momentum and m is mass. To have E=0, you would have to have m=0. But a massless particle such as a photon have E=hf where f is the frequency of the wave, so E=0 implies a wave with zero frequency, which is unphysical (actually it can be subtracted off).

**Must resist urge to slag off Hawkings.....**

Awww, when you said 'Can we beat Wolfram?' I thought you mean you had him hostage in your cellar and were inviting people round for a go with the baseball bat! I'm disappointed....

Yes, I agree. It is a philosophical objection rather than a scientific one. It is the misuse of the word 'paradox' which makes people think it is some kind of problem. There is no paradox.

To be fair, it isn't really known yet whether neutrinos are Majorana or not. Neutrinoless double beta decay is proportional to the mass of the neutrino, so it doesn't happen in the Standard Model which assumes neutrinos to be massless. In the 'new' SM with non-zero neutrino masses, double beta decay would be very small simply because the masses are very small, and this is presumably why it has not been observed.

There is no such thing as antineutrinos. They are Majoranna particles.

I am 99.9% sure they will be combined one day.

I have never understood why this is a problem. If we hypothesise that the cat can collapse wavefunctions then the cat is always either dead or alive (ie. in an 'alive eigenstate' or a dead one). If we hypothesise that it cannot, it is in a superposition. Where is the problem? It isn't even a physically well defined issue, since we cannot experimentally distinguish the two cases (unless we are a cat).

All becomes clear.....

Yes, I agree. I wasn't advocating it, just pointing out that it is possible. There is still a finite probability of this happening, and you can argue anthropically that for us to exist it must have happened (ie. that there have been lots of other universes which just fizzled out). The antimatter for the annihilation is a separate issue, which is a problem for pretty much any big bang theory, as I pointed out in my first post. YT: I fail to see why my post was not 'sensible'. I was pointing out the cannonical point of view on the topic as seen by the scientific community.

Yes, but what is the time scale? We could just be one big vacuum fluctuation.

You don't get any energy out of the process. You have to put energy in at the start to create the matter and antimatter, and you getthis energy back again when they annihilate. However, you can of course borrow it using the HUP....

The trouble is that the 'experts' are not really experts, so there can be sutble errors in the more complex subjects which are missed by the casual reader. For example, I had to edit part of the Higgs boson entry which previously claimed the Higgs boson was the carrier of a fifth force!

That is actually not so far from the standard theory. Matter and antimatter are created out of the vacuum at the big bang in equal amounts. The obvious question then is, where has all the antimatter gone? There is a huge disparity in our observable universe between the amount of matter and antimatter... As you say, it was thought for a while that CP violation (eg. production of K mesons) could create an asymmetry between matter and anti-matter, but unfortunately when you do the maths it doesn't work . The amount of CP violation which we have measured iisn't enough to explain why there is so much matter and so little antimatter. This is actually one of the 'big problems' in fundamantal physics these days (known as the baryon asymmetry problem). I personally suspect that there may be extra CP violation lurking in the yet undiscovered Higgs bosons, and this may be enough to explain the asymmetry.

He probably means that r is the vector from the centre to a point on the circle.

These 'pseudo-photons' are more usual known as virtual photons. A 'real' particle obeys the relation E2 = m2c4+p2c2 (where for a photon m=0), but for a virtual particle this is violated. However, it is not allowed to be violated for very long, and the amount of time it is violated for is related to how much it is violated. So if it is violated a lot, the particle will have a very short lifetime. This is really the Heisenberg uncertainty principle in a different guise. (Really, all particles are virtual. A 'real' particle for which the relation is exactly obeyed will live forever, but since the act of observing a particle detroys it we can only observe particles with a finite life-time and which are therefore virtual (at least by a very small amount).)

Funny that, since I know for a fact that they are not. It seems that your definition of matter is anything that is possible to detect. This is a bad definition because then everything is matter - anything we cannot detect (in principle) by definition does not exist. The usual definition of matter is the objects apon which the fundamental forces act but not the force carriers themselves (more technically, matter is a fundamental representation of the gauge group, while force carriers are in the adjoint representation). Since the photon is the force carrier of Electromagnetism, it is not matter. Of course, this is just a definition, but it is pointless to define matter as a photon and then ask 'Is a photon matter?'.

Am I the only one who gets pissed off with people coming here and asking us to do their homework for them? This isn't supposed to be a forum for us to do their homework - they are supposed to ask questions and explain where they are stuck so that we can guide them towards better understanding.

Hey, I'm on Skype too!