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Physics Questions People Ask Fermilab

You wrote:
The exchange of virtual photons in the elastic scattering of particles of charged particles explains the phenomenon of electrostatic repulsion of particles of the same charge. How does the exchange of virtual photons as per QED explain the electrostatic attraction of particles of opposite charge?

- Colin Cumming

Dear Colin,

I know that it's hard to visualize, but it works the same way. When it comes to repulsion, you can think of two people facing each other, throwing a basketball back and force. Throwing the ball and catching the ball pushes the people further apart. (This becomes very clear when you place these two people in separate boats on a lake. The boats will move away from each other.) Well, in Einstein's four-dimensional quantum world of space and time, you can have the same process with negative energy. In the macroworld, this would lead to the two people/boats moving closer together. I've seen a graphic explaining it in this way: Think of two people facing AWAY from each other. Now one of them skillfully launches a Frisbee in a nice curve that lands directly in the hands of the second person. In this case, both people experience a "kick" that pushes them (and their boats) toward each other.

Best wishes,

Kurt Riesselmann
Fermilab

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