Einstein 1905 and the birth of modern physics

Einstein Year Einstein 1905  Nature of Light  Atomic Theory  Special Theory of Relativity

Early Years  Born in Ulm (D) 1879  Primary and secondary school (MUC)  Family move to Milan 1894  Aarau Gymnasium (SCH) 1895  ETH (ZUR) 1896

Student Years  Not a model student  Lack of interest  Diploma in maths and physics 1900  Unable to find University assistantship  Temporary schoolteaching

Bern  Tech expert in Swiss Patent Office (Bern)  Swiss citizenship in 1901  Daughter with Mileva Maric in 1902  Adoption  Married in 1903  Son in 1904

Bern  Engineering problems (day)  Fundamental physics problems (night)  Olympia Academy of Philosophy  Arrival of Micheal Besso  Five scientific papers on thermodynamics

Contemporary Physics  Mechanics F = ma Law of Gravity  Electromagnetism Elec +Mag =EM Light = electromagnetic wave  Radiation Planck’s Law  Radioactivity Energy mystery

Einstein 1905  The Nature of Light (cornerstone of quantum theory)  Atomic Theory (reality of atoms)  Special Theory of Relativity (physics of relative motion)

I Atomic Theory  Greeks – matter composed of atoms  Dalton – atoms of the chemical elements differ  Avogadro –atoms and molecules  Mendeleev – Periodic Table  Maxwell – Kinetic theory of gases No direct evidence

Einstein and Atomic Theory  Molecular dimensions in liquids  Well received  Statistics of molecular motion in liquids  Fluctuations  Effect on immersed particle - Brownian motion  Mean free path calculation

Einstein and Atomic Theory  Perrin’s Brownian Motion experiments  1908 : Confirmation of Einstein predictions Atomic theory = reality  Role of probability and statistics in nature  Einstein established  Nobel Prize for Perrin

II Problems with Light  Radiation studies  Ultraviolet Catastrophe  Planck’s Radiation Law (1900) “Radiation emitted/absorbed in chunks (quanta)”  Mathematical artefact  Applies only to oscillators

Einstein and Light  Einstein : inconsistency in Planck’s Law  Einstein : new statistical approach (1905) “Light itself behaving like particles (quanta)”  Explained Planck’s law, Photoelectric Effect  Conflict with wave theory of light  Rejected for 17 years

III Relativity  Galileo: Principle of Relativity  Laws of mechanics independent of uniform motion  Impossible to detect motion internally  No absolute frame of reference for motion  Newton : absolute space

Relativity and Electromagnetism  Maxwell : electromagnetic theory  Radiation = electromagnetic waves (speed 3x10 8 m/s) light = em wave of speed 3x10 8 m/s  Speed relative to ether ?  Absolute frame of reference for light ?  Experiments

Einstein’s Relativity 1905  Relativity applies to all laws of physics (includes electromagnetism)  Speed of light = universal constant (general principle) Implication: time and distance not absolute

Implications of Special Relativity  Length of a body  Time interval  Mass of a body

Implications of SR  Time is relative  Time + space = spacetime  Mass is a form of energy E = mc 2

Response to relativity  Controversy ( )  Kaufmann experiments (1908)  Bucherer experiments (1909) By 1911 Special Relativity accepted

Career Progress  1905 PhD (ETH)  1908 Privatdozent (Univ Bern)  1909 Assoc Prof (Univ Zurich)  1911 Prof (Univ Prague)  1912 Prof (ETH Zurich)  1914 Prof (Univ Berlin), Director (FW Institute)  1913 Separation

Middle Years ( )  Relativity and accelerated bodies ( )  Principle of Equivalence  General Relativity (1915) “Gravity = curvature of space-time”  Bending of light by gravity  Slowing of time by gravity  Cosmological implications

After the War  1916 Photoelectric effect (Millikan)  1919 Evidence for GR (Eddington) 1921 Nobel Prize (Photoelectric effect)  1923 Compton Effect (light quanta)  1925 Electron waves (quantum duality)

Between Wars  1919 Remarried  1920s Anti-semitism in Germany Einstein’s work attacked  Rise of Nazi Party  Visiting Prof at Caltech (US)  1933 Hitler assumes power  1933 Flight to Princeton (US)

Princeton Years ( )  Hero’s Welcome  American Icon  Letter to Roosevelt (1939)  Manhattan Project  Regret at Hiroshima (1944)  Nuclear disarmament (1940s)  McCarthyism (1950s)

Princeton Years ( )  Interpretation of quantum theory  Relativity and electromagnetism Unified Field Theory  Evidence for relativity (1950s)  New York Times Iconic figure

Einstein Today Atomic Theory Reality of atoms Stat. applications Quantum Theory Wave/particle duality Applications Special Relativity Particle physics Nuclear fission and fusion

Einstein Today General Relativity Underlies cosmology Evolution of Universe Unified Field Theory Still not solved Holy grail of physics