An electron's calling card

1 October 1997  

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In October 1897, The Philosphical Magazine (vol 44) published a paper by J.J.Thomson in which he describes his discovery that cathode rays consist of particles of matter far smaller than anything seen before - the particles we now know as electrons. In this image a single electron writes its spiral signature in a cloud chamber. The electron was created together with a an antielectron (positron) near the bottom of the picture. A magnetic field bends the negative electron's path clockwise, while the positive positron bends anticlockwise, out of the picture. Altogether, the electron spirals some 36 times to produce a track about 10 m long.

Credit: Ernest Orlando Lawrence Berkeley National Laboratory

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