Ask A Scientist Physics Archive

name         Daniel C. R.
status       educator
age          40s

Question -   What is the current experimental upper bound on the radius of the electron? (2003)
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Quantum mechanics correctly predicts the behavior of atomic and sub-atomic particles like the 
electron. In fact it does so with
extraordinary precision and accuracy better than 1 part per billion, at least. That is the good 
news! The bad news is that our classical "intuitive" concepts like "size" lose their meaning. 
This sacrifice is very difficult, not only for us mere mortals, but also for "experts" in 
quantum theory. The electron is as small (or as large) as you want it to be, because the 
electron exhibits properties that we associate with particles (that have a size) and waves 
(that do not have a size). This duality is not a matter of "doing a better experiment" it is 
inherent in the nature of the particles.
Author John Gribbon has written a couple of readable books on this strange world. He does not 
solve the problem, but he does help us to understand that there is a problem.

Vince Calder
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