450300 BC 
Leucippus, Democritos, Epicurus 

. . . Greek Atomists 
335 BC 
Aristotle 

continuous elements
(earth, air, fire, water) 
300 BC 
Zeno of Cition (founder of Stoics) 

popularizes Aristotelian view. 
60 BC 
Titus Lucretius Carus of Rome 

epitomizes ``Atomist''
philosophy. 

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1879 
Josef Stefan 
[expt] 
power emitted as blackbody radiation
varies as T^{4} 
1884 
Ludwig Boltzmann 
[theor] 
explains Stefan's empirical law 
1885 
Johann Jakob Balmer 
[expt] 
empirical description of
line spectra
emitted by H atoms 
1890 
Johannes Robert Rydberg 
[expt] 
line spectra cont'd 
1893 
Wilhelm Wien 
[expt] 
blackbody spectrum displacement law:
peak wavelength varies as 1/T 
1895 
Wilhelm Conrad Roentgen 
[expt] 
discovers Xrays 
1897 
Joseph John Thomson 
[expt] 
measures boldmath q/m
of the electron 
1900 
Max Planck 
[theor] 
derives correct blackbody radiation spectrum 
1902 
Philipp E.A. von Lenard 
[expt] 
measures
photoelectric effect 
1905 
Albert Einstein 
[theor] 
explains
photoelectric effect 
1905 
Albert Einstein 
[theor] 
publishes
Special Theory of Relativity
(STR) 
1905 
Albert Einstein 
[theor] 
explains Brownian motion
(gives mass of atoms!) 
1905 
Ernest Rutherford 
[expt] 
performs first
alphascattering
experiments at McGill Univ. (Canada) 
1907 
Robert A. Milliken 
[expt] 
measures electron charge
(now know both q_{e}
and m_{e}). 
1912 
William (H. & L.) Bragg 
[expt] 
shows that Xrays
scatter off crystal lattices 
1913 
Hans Geiger & Ernest Marsden 
[expt] 
confirm
Rutherford scattering
results at Univ. of Manchester (U.K.) 
1913 
Niels Henrik David Bohr 
[theor] 
pictures H atom
with quantized angular momentum 
1916 
Albert Einstein 
[theor] 
publishes
General Theory of Relativity (GTR) 
1916 
Robert Andrews Milliken 
[expt] 
confirms
photoelectric effect
in detail 
1922 
Arthur Holly Compton 
[expt] 
scatters Xrays
off electrons 
1924 
Louis Victor de Broglie 
[theor] 
hypothesizes
``matter waves''
with

1925 
Wolfgang Pauli 
[theor] 
formulates his
exclusion principle 
1925 
Max Born
& Werner Heisenberg 
[theor] 
introduce
quantum mechanics 
1926 
Erwin Schroedinger 
[theor] 
develops a nonrelativistic
wave equation
for quantum mechanics 
1927 
Werner Heisenberg 
[theor] 
formulates his
uncertainty principle 
1928 
Paul A.M. Dirac 
[theor] 
develops a
relativistic wave equation
for electrons and predicts
antimatter 

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