Quantum mystery In 1961 Eugene Wigner imagined a friend doing an experiment in a lab while he waits outside. The paradox is that Wigner and the friend predict different outcomes, yet both are right. (iStock/Floriana)
“Wigner’s friend” is a curious thought experiment that has stumped physicists and philosophers for more than 60 years. Robert P Crease, Jennifer Carter and Gino Elia advise on how to resolve this conundrum.
The quantum world provides fertile material for thought experiments that seem so strange-but-true as to defy logic. One of the most notorious is “Wigner’s friend”, which has challenged physicists and philosophers ever since it was first conceived by the Hungarian-American physicist Eugene Wigner. He published the thought experiment in a 1961 book edited by the mathematician Irving Good entitled The Scientist Speculates: an Anthology of Partly-baked Ideas.
Wigner’s thought experiment is a more humane version of Schrödinger’s less complex but more famous thought experiment a quarter century before, which involved a cat inside a box whose fate hangs on a quantum event. Inside the box Schrödinger’s cat is dead or alive, whereas for someone outside, the cat remains dead-and-alive; it’s in a “superposition”. The bizarre situation only vanishes when the box lid opens. READ MORE...
“Wigner’s friend” is a curious thought experiment that has stumped physicists and philosophers for more than 60 years. Robert P Crease, Jennifer Carter and Gino Elia advise on how to resolve this conundrum.
The quantum world provides fertile material for thought experiments that seem so strange-but-true as to defy logic. One of the most notorious is “Wigner’s friend”, which has challenged physicists and philosophers ever since it was first conceived by the Hungarian-American physicist Eugene Wigner. He published the thought experiment in a 1961 book edited by the mathematician Irving Good entitled The Scientist Speculates: an Anthology of Partly-baked Ideas.
Wigner’s thought experiment is a more humane version of Schrödinger’s less complex but more famous thought experiment a quarter century before, which involved a cat inside a box whose fate hangs on a quantum event. Inside the box Schrödinger’s cat is dead or alive, whereas for someone outside, the cat remains dead-and-alive; it’s in a “superposition”. The bizarre situation only vanishes when the box lid opens. READ MORE...
