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Electron and positron spiral tracks seen in a cloud chamber at the Lawrence Berkeley Laboratory, California. The electron and positron started their lives at the bottom of the frame; they were generated by a gamma ray entering from the right. The positron, which is an electron with a positive charge, spirals (larger loops) towards the bottom left corner while the electron's smaller loops move upwards. The other tracks crossing the frame are also due to electrons and positrons created by gamma rays beyond the right hand edge of the frame; the electrons curl clockwise while the positrons curl counterclockwise.
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