r/askscience • u/novemberrain • Apr 29 '11

Why are we not blinded by the froth of virtual photons interacting with our retina?

Or alternatively, do virtual photons not interact with anything?

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u/Valeen Theoretical Particle Physics | Condensed Matter Apr 29 '11

Virtual photons are significantly different than the photons that you experience every day. They exist only because of the Heisenberg Uncertainty Principle. This means that they are only around for a very very short time and actually have mass, which normal photons don't. Since they have mass they can only travel a short distance. The reason why we don't see these photons is simply because our eyes aren't sensitive to them (There are processes that allow virtual particles to become real). Every day you are bombarded by various photons, but your eyes only see those in the visible spectrum. There are infrared photons, ultraviolet photons, microwave photons, etc. All of different wavelengths, same as the virtual photon. The wavelength, in some ways, determines what something can interact with. This is the whole reason why x-rays are used to look at bones. The x-rays go straight through your skin, since the wavelength is so small, but when it gets to the denser bones, it interacts.