HPS 1632 Einstein for Almost Everyone
Fall term 2019

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Modules

Special Relativity, E=mc²
(3-4 weeks)

The special theory of relativity is Einstein’s best-known contribution to science. It shows that the behavior of space and time deviates from Newtonian expectations when we deal with systems moving at close to the speed of light. The theory is usually presented as deriving from simple reflections concerning the measurement of time using light signals. Its real origins, however, lay in many patient years of exploration by Einstein of the then contemporary state of electrodynamics. The equivalence of energy and mass, as expressed in the famous E=mc², follows quickly from the theory.

Primary readings:
“On the Electrodynamics of Moving Bodies” (1905)
“Does the Inertia of a Body Depend upon its Energy Content?” (1905)

Light Quantum and Wave Particle Duality
(3-4 weeks)

Einstein’s introduction of the notion of the light quantum was singled out by Einstein as “very revolutionary” in a letter written to a friend in 1905. It represents a break with physical tradition more serious than that of the special theory of relativity. For the odd behaviors of space and time of special relativity were already apparent in the electrodynamics of Einstein’s time. The light quantum hypothesis, however, threatened to overturn electrodynamics. For it posited that the energy of light is not distributed continuously in the familiar light waves of the classical theory. Rather, in certain special cases, that energy is localized in space is discrete energy quanta. The later thesis of wave-particle duality showed that, in more general cases, light behaved both as a distributed wave and as localized points of energy.

Primary readings
“On a Heuristic Point of View Concerning the Production and Transformation of Light” (1905) (Light quantum paper)
“On the Development of Our Views Concerning the Nature and Constitution of Radiation” (1909) (Paper develops wave-particle duality)

Brownian motion and dissertation.
(2-3 weeks)

A major part of Einstein’s early work was devoted to establishing the reality of atoms. That matter had an atomic structure was still a troubled claim as late as 1900. The difficulty was not so much an opposition to the atomic hypothesis itself. Rather it was a practical issue for physicist then mostly occupied with laboratory investigations: the atomic hypothesis afforded nothing that could not already be recovered by thermodynamic analysis. Einstein’s dissertation sought to estimate the true size of atoms on the basis of the viscosity and diffusion properties of dilute sugar solutions. The closely related Brownian motion paper reveals that Brownian motion is an observable effect fully explicable by the atomic hypothesis, but not by thermodynamic methods.

Primary readings
“A New Determination of Molecular Dimensions” (1905) (Doctoral dissertation)
“On the Movement of Small Particles Suspended in Stationary Liquids Required by the Molecular-Kinetic Theory of Heat” (1905) (Brownian motion paper)

General Relativity
(3-4 weeks)

This is Einstein’s theory of gravity. According to it, gravitation is a manifestation of the curvature of the geometry of spacetime, where that curvature is sourced in the matter distribution of the universe. This is Einstein’s most adventurous contribution to physics and remarkable in the sense that it is almost entirely his own work. Work on the theory spanned over seven years and was driven by his obsession with the idea that the relativity of inertial motion of the special theory of relativity must be extended to all motion.

Primary readings
“On the Influence of Gravitation on the Propagation of Light” (1911)
“The Foundation of the General Theory of Relativity” (1916)

The Einstein Universe
(1-2 weeks)

About a year after the completion of his general theory of relativity, Einstein applied his new theory to the universe as a whole. His goal was to secure the troubled program of his earlier years of extending the principle of relativity to accelerated motion. He thought a new cosmology would do this. Instead, he provided the first paper of a now flourishing area of research: cosmology.

Primary reading
“Cosmological Considerations in the General Theory of Relativity” (1917)

Einstein’s Critique of Quantum Theory
(3-4 weeks)

In his early years, Einstein was the rebel, overturning the established physics of his time. While Einstein contributed to the emerging quantum theory in many ways, he grew disaffected with it once it reached its stable, modern form in the late 1920s and early 1930s. He became the most outspoken of its critics within the community of physics experts. His debate with quantum defender Niels Bohr is likely the most celebrated scientific debate of the century. Einstein’s concern centered on whether the quantum theory was a complete theory (as Bohr urged); or whether the probabilities of the theory masked our ignorance of deeper non-probabilistic states (as Einstein believed). He co-authored the “EPR” paper with colleagues Boris Podolsky and Nathan Rosen in 1935.

Primary reading
“Can Quantum-Mechanical Description of Physical Reality Be Considered Complete?” (1935) (“EPR”)
“Discussions with Einstein on Epistemological Problems in Atomic Physics” (by Niels Bohr, 1948)

Einstein and Philosophy of Science
(2 weeks)

Einstein was a physicists, not a philosopher. However he read philosophy and found it important in his physical researches. He also developed strong views in philosophy of science. While they may not form a coherent philosophical system, they proved to be quite influential among the new community of philosophers of science that gravitated towards Einstein when the profound character of his discoveries became known. Some of the more prominent ideas are:

Primary reading (and ideas)
No logical pathway to the concepts and laws of physics ("Principles of Research," 1918, in Ideas and Opinions)
The distinction between constructive and principle theories ("What is the Theory of Relativity?" London Times, 1919, in Ideas and Opinions.)
Conventionality of Geometry ("Geometry and Experience," 1921, in Ideas and Opinions)
The role of mathematical simplicity is guiding theory choice ("On the Method of Theoretical Physics," 1933, in Ideas and Opinions.)