Isaacson, Walter. Einstein: His Life and Universe. New York: Simon & Schuster, 2007.
Philosophical Moments
Early on Einstein began to question Kant’s distinction between analytic and synthetic truths (83). Kant’s famous example of an analytic truth–a triangle is 180 degrees–would be false in non-Euclidian geometry or in curved space. These contents, in Einstein’s famous words, “contain nothing of the certainty, or inherent necessity, which Kant had attributed to them.”
Key Scientific Moments
Maxwell: a changing electric field could produce a changing magnetic field. That could yield another changing electric field. This “coupling was an electromagnetic wave” (91). The important concept here is the introduction of “field.”
Light quanta: In 1905 Einstein suggested that light came in tiny packets of quanta, later to be known as photons (94). Was the universe made up of tiny particles or was it an unbroken continuum? What happens when the evidence suggests both?
Special Relativity
There are several thought experiments to explain special relativity. Galileo’s is the best. Imagine you are on a moving ship. If you are inside the ship and drop a pebble, etc., it behaves the same as on land, even if the outside is gliding past you. These are two different inertial systems. These systems also add up. If the waves are coming at you at 10 mph and you get on a jet ski at 40 mph, then the waves are coming at you at 50 mph.
Einstein’s genius was in asking if light behaves the same way. Earlier thought supposed that light behaved like sound: it was a disturbance in an unseen medium, called ether. This raised problems. If light came from a distant source, then ether must pervade the entire universe, which would seem to make it an ephemeral, gossamer substance. On the other hand, “it had to be stiff enough to allow a wave to vibrate through it at enormous speed” (111).
Einstein saw this hunt for ether as showing why Newtonian models had trouble explaining electromagnetism, leading “to a fundamental dualism which in the long run was insupportable” (113).
Imagine you are chasing after a beam of light. If you caught up with it, it would appear to be frozen, yet this seems wrong. Let’s pretend you are riding on a train. Shouldn’t you see, among other things, light beams coming at you at 186,000 mps? Newtonian models said velocities add, and Maxwell’s equations provided for the speed of light, so why don’t we see light in motion?
Einstein realized that without reference points, you couldn’t see the light in motion (if you were riding beside a light beam). Einstein had to reimagine the concepts of space and time.
General Relativity
Special relativity, however, had some shortcomings.
Equivalence-principle: there is an equivalence “between all inertial effects, such as resistance to acceleration, and gravitational effects, such as weight” (190). “Both are manifestations of the same structure, an inertio-gravitational field.
If this is true, then gravity should bend a light beam.
Central idea of general relativity: “gravity arises from the curvature of space-time…Gravity is geometry” (193).
Tensor: a vector on steroids (194).
Perihelion: the spot in a planet’s elliptical orbit when it is closest to the sun (199).
Bottom line: space and time do not have independent existences. Einstein rejected Newton’s container notion of absolute space and absolute time (223).
Cosmology and Black Holes
Main idea: “space has no borders because gravity bends it back on itself.” If we had an infinite universe, per Kant, then there “would be an infinite amount of gravity tugging at every direction” (252). Einstein’s solution was a finite universe without boundaries. It lacks boundaries because space curves.
Einstein and Religion
Einstein was very clear that his god is the same as Spinoza’s. That makes sense, since Spinoza’s hard determinism is probably the reason why Einstein never embraced quantum mechanics.
Einstein and Politics
The best way to describe Einstein is as a moderate Social Democrat. He liked the idea of socialism, but he balked at the dehumanizing practice of it. He would not have called himself a Communist and he was openly critical of Russia. Likewise, he was a pacifist. He was an intellectually honest pacifist. Like many pacifists, he could not pass the “What about Hitler?” test. Pacifism is morally bankrupt when it faces questions like, “If you could stop a genocide, would you?” To his credit, Einstein saw that and stopped his opposition to war.
Conclusion
While it is not mentioned in this review, Einstein never came to grips with quantum mechanics. Such a discussion is worth an article in its own right, so I will forgo it here. The book itself is excellent and a serious layperson can easily understand its concepts.
Logical Investigations 