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slyboy
#3
Jun22-04, 01:14 PM
P: 206
Interestingly, I was asked this exact same question in my defense of my undergrad experimental project. At the time, I said it was a point particle.

It actually depends a bit on what you mean by "how big". An excitation of the electromagnetic field can extend arbitrarily far across space. However, we only ever detect them at points.