#2 – Albert Einstein

Einstein. When a person’s name and photograph are both literal synonyms for genius, it’s a pretty good sign they’re among the greatest of the greats. But even if Einstein had not become the popular legend which lives on to this day, he’d still tower above the science of physics.

In one year – his annus mirabilis of 1905 – he wrote four papers, any of which would have cemented his reputation in the canon of the great physicists.

The first was an analysis of Brownian motion. If you drop a pollen grain into a glass of water and look very closely with a microscope, you’ll notice that it doesn’t slow to a stop. Instead, it constantly drifts and jiggles around as though being constantly impacted by tiny particles too small to see even in a microscope. Individual atoms, you might guess. And indeed that’s not too great of a leap for us, but in 1905 it wasn’t even certain that atoms existed, much less how they behaved in the statistical aggregate. Poor Boltzmann despaired of getting science to accept his statistical mechanics which wasn’t a lot of use without the reality of atoms, and Einstein was his (unfortunately posthumous) vindication. Einstein developed a formal theory of Brownian motion which more or less put the case to rest.

Now look at your pocket calculator. It might have a little strip of solar cells which power the calculator even if its batteries are dead. This effect is not properly described by Maxwell’s equations alone and remained one of the important open mysteries of physics until Einstein developed the idea that light energy was quantized into discrete pieces called photons. This was one of the precursors leading directly to the development of the dominant idea in modern physics – quantum mechanics. The photon and related concepts have been extended into the entire vast reach of quantum field theory. It’s a little ironic, because Einstein was never really comfortable with quantum mechanics and indeterminism. Interestingly, it was this and not relativity that earned Einstein his Nobel Prize.

There’s two of four. Most famous today are the other two papers, concerning special relativity and mass-energy equivalence. E = mc^{2} is the one equation everyone knows even if they don’t know what it means, and Einstein first wrote it as part of his theory. It’s hard to overstate the impact of relativity on physics. Prior to Einstein, physics was viewed as taking place on sort of an abstract invisible absolute Cartesian grid. Naively most of us today still think this way. One of the main clues that there might be a problem was in Maxwell’s equations. They seemed to work regardless of the frame of reference you chose, and experiments in locating an aether for the light to modulate found nothing. Either there was a problem with Maxwell in some very strange and subtle way, or our notions of absolute time and space were wrong. Einstein hypothesized the latter and developed the theory by which transformations between reference frames are governed. The mathematical methodology is not entirely Einstein’s; some of the ground work had already been done by other scientists and mathematicians like Lorentz. This is no way detracts from Einstein’s achievements.

And Einstein was no mathematical slouch. Once he published the special theory of relativity, the race was on to figure out how to use relativity to describe the effects of gravity. Einstein’s main competitor was none other than the absolutely brilliant mathematician David Hilbert, whose own stature might well put him on my top 10 mathematicians list (if I ever write one). Einstein succeeded (with help from Hilbert – it’s a long and somewhat controversial story), and in 1915 presented his general theory of relativity. It represents the entirely of our knowledge of gravity, with further theories remaining entirely speculative and untested.

Einstein left his mark in numerous other less well known branches of physics, from the heat capacity of solids to the statistics of bosons.

I have here just given a brief overview of his scientific work and neglected his personal biography entirely. His life outside of science is also of great interest – a probably apocryphal statement attributed to him boasts of surviving “two wives, two wars, and Hitler”. He died in 1955 and his ashes were scattered.

If I were to suggest just two books about this great man, I think I’d recommend Einstein: His Life and Universe by Walter Isaacson, and Relativity: The Special and the General Theory by Einstein himself as a very lucid and nonmathematical layman’s explanation of his most famous theory.

*The list so far (click the category name for links):
2. Einstein
3. Maxwell
4. Faraday
5. Feynman
6. Rutherford
7. Schrodinger
8. Dirac
9. Thomson
10. Pauli*

*Not-strictly-physicist honorable mentions:
Galileo
Noether
*