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. 

 . 


 . 


 . 

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 

 . 


 . 


 . 
