Science: Smallest Thing

When a smallest thing is discovered it must be observed more than once to be believed. In February, Cambridge University's Dr. James Chadwick proclaimed the existence of the neutron, new smallest thing (TIME, March 7). With the proton (positive electricity), electron (negative electricity) and photon (light particle), this made four smallest things. But the neutron is elusive, hard to find. It contains no detectable electric charge. It leaves no marks in the form of ionized or electrified particles when it passes through a gas. Having no charge, it is not repelled by charged atoms....

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