A hundred years ago this year, Einstein published a series of papers that reworked what scientists thought reality was. It was such a shocking gesture that 1905 is still sometimes called Einstein's "miracle year."
In science, advances and discoveries are almost always "in the air." That is, everybody is working on the same issue and kind of knows what's going to happen next — though usually not exactly how or when.
But Einstein's papers were another matter — they were certainly not "in the air." It seems like a batch of 21st century physics shot back not just into the 20th century — into 1905. I always picture a group of scientists gathered around discussing the details of some current sticking point, when suddenly a 26-year-old patent clerk clears his throat and asks, politely, "You know ... time?"
There's been so much written on Einstein, it seems silly to go on about him here. But to give a flavor of that year, let me draw an extremely quick sketch of what Einstein said:
Light occurrs in discrete "quanta." Everybody had accepted that light is a wave, but now Einstein says it's a particle too, and each light particle has a distinct, independent energy level. Nothing in quantum mechanics would be possible without this.
Atoms exist, and kinetic energy theory works. Einstein applied the idea that heat is ceaseless agitation of atoms to a phenomenon called Brownian motion — thus more or less simultaneously proving what heat was and that atoms exist.
The velocity of light is not relative, space and time are. The velocity of light isn't just how fast light goes, it's a number somehow woven into reality itself — that is, space and time organize themselves around "c".
Mass is a form of energy. And if you transform that "stuff" into more familiar forms of energy, you know how much you'll get using this equation: E=mc², where E is energy, m is mass, and c is that same number that's woven into spacetime.
It may seem anticlimactic after all that, but to mark the year, 33 physicists are writing online diaries (apparently also known as "blogs") all year long.