# Tag Info

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On some level this is a philosophical question. From the physical side, to the best of our knowledge, i.e. based on all experimental data to date, nature is constrained by certain conservation laws that prohibit e.g. charge disappearing once it exists. This is related to the the totalitarian principle, one form of which says 'anything that is not forbidden ...

4

All the word vacuum means is an absence of matter. You should consider what it means to talk about a vacuum. In one sense, a perfect vacuum is never found in a large volume, as even in deep space there are particles moving about- Wikipedia states that there are a few hydrogen atoms per cubic meter. In another sense you can consider any gap between particles ...

3

There is a nice explanation from John Baez on his page where he comes up with 5 possible values for the vacuum energy density: Very close to zero. Infinite. Enormous but finite. Zero. Not determined. where 1. is based on experiment / observation and conservtive assumptions about General Relativity; 2.-4. are based on naive theoretical calculations and 5. ...

2

Retardation causes the repelled negative virtual charged particles to be further repelled from a more previous position of the conduction electron than the attracted positive virtual particles are attracted to, so there is a net virtual electric current. The positive charges in the wire have retarded and current position the same and do not affect virtual ...

1

Due to quantum (and possibly other) effects, primarily the uncertainty principle, there will always be some spread, as explained here. It is not possible, even in principle, to produce a light beam with zero divergence, unless it is infinitely large (in which case is a plane wave). In general, the greater the initial diameter of the beam, the smaller the ...

1

A new experiment was done with ions , the inside of an atom with no electrons , 2 beams of these were accelerated and a particle accelerator , the islands themselves carried virtual photons. When the beans got closer the photons themselves reacted making electron and positron pairs , like beams of real protons would do. The proton antiproton pairs acted as ...

1

I think nucleation is only relevant to first order phase transitions. This is because only a first-order phase transition has an entropy curve $S(U)$ which leads to the possibility of metastable phases (e.g. supercooled vapour or superheated liquid).

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