The Ladder Paradox
A ladder too long to fit inside a barn fits inside it — and also does not — depending entirely on who is watching.
1905 (the physics), 1961 (first prominent published version)19 min read
German-Swiss-American theoretical physics
Albert Einstein
1879 – 1955
Author of special relativity (1905), general relativity (1915) and the light quantum hypothesis for which he received the 1921 Nobel Prize. He was one of the founders of quantum theory and its most formidable lifelong critic, arguing through the 1927 and 1930 Solvay conferences and the 1935 EPR paper that the quantum description of reality is incomplete rather than wrong. Bell's theorem later showed that the kind of completion Einstein wanted is not available.
4 entries
The Twin Paradox
One twin flies away and comes home younger than the other. Yet each of them saw the other's clock running slow.
1905 (implicit in Einstein), 1911 (Langevin's traveller)20 min read
Schrödinger's Cat
A cat sealed in a box, neither alive nor dead until somebody looks. The story was invented to show the idea was absurd.
193514 min read
The EPR Paradox
Measure one particle here and you instantly know something about its partner light-years away. Einstein thought this proved physics was unfinished.
1935 (argument), 1964 (Bell's theorem), 2015 (loophole-free tests)21 min read