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In Greece, Democritus proclaims all material
things are made of tiny particles, which he calls atoms, the Greek word meaning "not
divisible". |
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The element uranium is discovered (Martin
Klaproth). |
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Dmitri Mendeleyeev develops the periodic law
of elements, which later evolves into the Table of Elements. |
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Radioactive thorium is first used in mantles
for camping lanterns because of its bright, light-producing properties when burning. |
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X-rays discovered (Wilhelm Roentgen). |
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French scientist Henri Becquerel discovers
some atoms give off energy in form of rays. Uranium gives off radiation. |
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Radium discovered (Marie and Pierre Curie).
Radioactivity is named (Marie Curie). |
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Ernest Rutherford concludes that radiation
can be divided into two types, alpha and beta rays. |
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Pierre Curie observes another type of
radiation -- the gamma ray. |
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Theory of relativity (E=mc2). Mass can be
changed into energy (Albert Einstein). |
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The first food irradiation patents are issued
in the U.S. and Europe. This is a method for processing foods by treating them with
radiation. It does not make the food radioactive. |
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Ernest Rutherford discovers that most of an
atom is empty space and identifies the atomic nucleus. |
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George de Hevesy is the first person credited
with using radioisotope tracers. As a young researcher living in the cheap boarding house,
he suspected that landlady was saving leftovers and serving them to the boarders the next
day. He added a tracer to food he left and the next day used a radiation detector to prove
he was right. She evicted him, but he later won a Nobel Prize in biology for use of
radioscopes as tracers. |
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Theory of atomic structure is developed,
dividing the atom into two parts -- a nucleus and electrons that orbit the nucleus (Niels
Bohr). |
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Hans Geiger invents the Geiger counter for
measuring radioactivity. |
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The NC-4, a Navy flyboat, crosses the
Atlantic Ocean guided by radium-powered instrument lights. |
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The proton is discovered and named (Ernest
Rutherford). |
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Herman Blumgart, a physician at Thorndike
Laboratory, Boston City Hospital, first uses radioactive tracers to diagnose heart
disease. |
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Elements are bombarded with neutrons in an
attempt to produce new isotopes or elements |
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Dental laboratories begin blending trace
amounts of uranium oxide with porcelain materials to give crowns, bridges, and dentures
the fluorescent color of natural teeth. |
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The neutron is discovered (James Chadwick). |
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When uranium-235 is bombarded with neutrons,
it does NOT produce a heavier element as expected, but instead several lighter ones
(Enrico Fermi). |
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Irene Joliot-Curie (daughter of Marie and
Pierre Curie) and her husband Frederic recieve the Nobel Prize for creating the first
artificial radioactive isotope. |
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Nuclear medicine comes into existence when
cyclotron-produced radioisotopes and nuclear radiations become available in the U.S. |
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Otto Hahn and Fritz Strassman produce lighter
elements by bombarding uranium with neutrons. Later that year this is reconized as the
splitting of the atom by Lise Meitner and Otto Frisch. The term "fission" is
first used for this event in early 1939. |
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The principle of nuclear reactors is first
recorded and sealed in an envelope where it remains secret during the war years (Irene and
Frederic Joliot-Curie). |
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U.S. Advisory Committee on Uranium recommends
a program to develop an atomic bomb. (This is later named the Manhattan Project). |
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First self-sustaining nuclear chain reaction
produced in the first reactor at the University of Chicago on December 2 (Enrico Fermi). |
