Fermilab

You Wrote:
What are the virtual particles? What does it mean - "virtual"?

Sincerely,
Anthony Petrov.

Hi, you ask another very good question.

"Virtual particles" are real -- they exist in that they can be detected and can interact. But they are fleeting -- they are soon gone with no trace of their existence. This phenomenon is related to the Heisenberg uncertainty principle of quantum physics. Uncertainty in time multiplied by uncertainty in energy is equal to a constanst, Planck's constant. If you probe a particle or even the vacuum with a short time scale, there can be a large amount of energy in which virtual particles can come into existence.

An example would be everyday electromagnetic interactions. You sit on your chair without passing through it because the chair exerts a force upon you (countering gravity). On the subatomic level, one can think of virtual photons being emitted and received between electrons from your atoms and the chair's atoms. These virtual photons carry the electromagnetic force.

Another example would be a theoretical calculation of the lifetime of a B0 meson (particle composed of a bottom and down quark antiquark pair). The calculation agrees with experimental measurements only if the calculation includes virtual processes in which particles are created and absorbed in very short time scales.

Hope this helps and encourages you to keep learning.

Dr. William Wester
Fermilab

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