A nuclear fission chain reaction —

1. An uranium-235 atom absorbs a neutron, and fissions into two (fission fragments), releasing three new neutrons and a large amount of binding energy.
2. One of those neutrons is absorbed by an atom of uranium-238, and does not continue the reaction. Another neutron leaves the system without being absorbed. However, one neutron does collide with an atom of uranium-235, which then fissions and releases two neutrons and more binding energy.

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Title page of the assembly language code that produced Altair BASIC — Developed by Allen, Gates, and Monte Davidoff, with two early Microsoft business cards showing Gates as president and Allen as vice president
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Microsoft logo/avatar — 2012–present: Fifth Microsoft logo, introduced on August 23, 2012
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Bill Gates, 2017 —
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Paul Allen (left) with Bill Gates at Lakeside School in 1970 —
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Paul G. Allen —
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An example of an induced nuclear fission event — A neutron is absorbed by the nucleus of a uranium-235 atom, which in turn splits into fast-moving lighter elements (fission products) and free neutrons. Though both reactors and nuclear weapons rely on nuclear chain reactions, the rate of reactions in a reactor is much slower than in a bomb.
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he Einstein–Szilard letter —
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FDR response to the Einstein–Szilard letter —
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Albert Einstein and Leo Szilar —
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Neutron quark structure (ring-shape) —
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