Einstein · Special relativity
Does time flow the same for everyone?
That time, that place
He had a degree and no post, working as a third-class examiner at the patent office in Bern.
The job helped unexpectedly. Railways had made clock synchronization urgent across Europe, and patents for synchronizing devices kept arriving. How do you set two distant clocks to the same time? He looked at that problem daily.
Why this question
In Maxwell's equations the speed of light appears as a constant. But a speed relative to what? People said relative to the ether — and Michelson and Morley had not found it.
Einstein did not go looking for the ether again. He asked instead: if we simply accept that the speed of light is the same for every observer, what follows?
What was found
Then time and space must give way.
A fast-moving observer's clock runs slow. Lengths along the direction of motion shrink. And simultaneity itself becomes observer-dependent: two events simultaneous for me happen one after the other for someone moving.
Common sense collapses, and nothing in it contradicts itself.
One by-product followed: energy and mass are two faces of one thing. Mass is an enormous quantity of energy held still.
Time flowed identically everywhere in the universe
Experiments that found no ether, and a consistent system once light's speed is taken as constant
That same year he also published on the photoelectric effect and on Brownian motion. He was twenty-six