1906Charles Barkla[?] discovers that each element has a characteristic X-ray and that the degree of penetration of these X-rays is related to the atomic weight of the element
1942 Enrico Fermi makes the first controlled nuclear chain reaction
1942Ernst Stuckelberg[?] introduces the propagator to positron theory and interprets positrons as negative energy electrons moving backwards through spacetime
1977 S.W. Herb finds the upsilon resonance implying the existence of the beauty quark
1982 A. Aspect, J. Dalibard, and G. Roger perform a polarization correlation test of Bell's inequality that rules out conspiratorial polarizer communication
... surprise attack on Port Arthur (Lushun)[?] starts Russo-Japanese War
February 23 - For $10 million the United States gains control of the Panama Canal Zone.
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