The Traveler said:
/me shouts out.
Kind regards,
The Traveler
Allright, here goes
These virtual particles pop in and out of existence through something called Quantum Fluctuations. It is indeed very strange and incredible. I mean, how can "something" pop out of "nothing"? What makes this remarkable phenomenon possible? It is something that lies in the very heart of Quantum Mechanics, namely Heisenbergs Uncertainty Principle. It asserts that you simply can't measure both position and momentum (momentum being the product of mass and velocity) for a given particle precisely. In words the equation can be written as:
Uncertainty in position x uncertainty in momentum is bigger than or equal to a fundamental constant.
This means that the more you know about for example the position of say, an electron, the less you will know about its momentum and vice versa. One might wonder why this is the case, and I'll try to give an idea: To make it simple, one cannot detect anything with better precision than the wavelength of the radiation used to detect it. To localize something that is incredibly small means we need to use incredibly small wavelengths as well, and the smaller the wavelength the greater the frequency of radiation, and the greater the frequency the greater the energy of the individual photons the radiation is composed of will be. When the photon hits the object of interest, say again an electron, we can find its position pretty accurately because the wavelength is so small, but the energetic photon will upon hitting the electron disturb its momentum. If its the other way around, using longer wavelengths, the radation will have smaller frequency and thus the individual photons less energy, and we do not disturb the electron so much. However, with longer wavelengths we must sacrifice precision in position (because the wavelength is longer).
Heisenbergs Uncertainty Principle also asserts a similar situation when it comes to the precision in measuring the energy of a particle and how long the particle has this definite energy. It is a little bit more of a delicate matter, but the general idea is that you can't say that a particle has a definite energy in a definitive time. The bigger the precision in an energy measurement, the greater the time the particle has this energy must be. Equivalently a particle can't have a definite energy in a very short timespan, so it can fluctuate wildly between different extremes as long as the interval of time is short enough. Here lies the key to Quantum Fluctuations. Just the way that you can borrow big money form your bank as long as you pay it back quick enough, Quantum Mechanics lets a particle "borrow" large chunks of energy as long as it is "paid back" fast enough. In this way the law of energy conservation is satisfied at macroscopic scales.
As we can see, the microcosmos is extremely chaotic and nuts. So nuts that even in an empty box these uncertainties in energy and momentum exists, and they will fluctuate more wildly the more we shrink the box and the lesser the time is. If the energies of these fluctuations gets big enough, we can have matter production from E = mc^2. For example we can out of nothing suddenly have that an electron and its anti-particle, the positron, pops into existence even though we had total empty space to begin with. This is what we call virtual particles, and they will annihilate eachother almost instantly to "pay back" the energy that was borrowed. This happens all the time, but since these fluctuations in average cancel eachother out, empty space seems rather calm and boring.
This all sounds very incredible, but this is not something crazy physicists just make up for fun. These fluctuations have effects that we can observe, whereas a famous example is known as the Casimir Effect. Here we have two neutral metal plates placed parallel to eachother with a very very small distance between them, in complete vacuum. What we actually can observe here is an attractive force between the plates that is caused by the virtual particles popping into existence between them. If each plate for example has the area 1m^2 and the distance between them is 10^-6 m, the attractive force between them will be 0.0013 N.
And don't be bothered if you don't understand this crazy shit, because no one understands quantum mechanics =)