This Quantum Experiment Made Reality More Uncomfortable

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If one experiment can do this to your grip on reality, the book is full of them. The strangest quantum and space discoveries, each taken apart in full.

Two people can watch the same event, record opposite results, and both be right. In 2019 a team at Heriot-Watt University in Edinburgh turned Eugene Wigner's 1961 "friend" thought experiment into a real test, using six entangled photons as stand-in observers, and broke the limit that shared, objective facts would allow by five standard deviations. In 2020 a team at Griffith University in Australia ran a stricter version built on even weaker assumptions, which they call "local friendliness", and saw those limits violated too.

This video walks through what those two experiments actually showed, why a "measurement" doesn't need a conscious mind, the trilemma they force on physics (absolute facts, locality or free choice: you can keep only two), how the main interpretations of quantum mechanics respond, and what the results do not prove.

A note on timing: the experiments covered here were published in 2019 and 2020.

SOURCES
Proietti et al., "Experimental test of local observer independence," Science Advances (2019): https://www.science.org/doi/10.1126/sciadv.aaw9832
Bong et al., "A strong no-go theorem on the Wigner's friend paradox," Nature Physics (2020): https://www.nature.com/articles/s41567-020-0990-x
Brukner, "A No-Go Theorem for Observer-Independent Facts," Entropy (2018): https://www.mdpi.com/1099-4300/20/5/350
Frauchiger & Renner, "Quantum theory cannot consistently describe the use of itself," Nature Communications (2018): https://www.nature.com/articles/s41467-018-05739-8
Further reading (MIT Technology Review): https://www.technologyreview.com/2019/03/12/136684/a-quantum-experiment-suggests-theres-no-such-thing-as-objective-reality/

0:00 Two observers, one event, two facts
1:35 Why this couldn't be tested for 60 years
1:55 Heriot-Watt: six photons as observers
2:45 Five standard deviations past the limit
4:17 Wigner's friend, the 1961 thought experiment
5:38 A measurement doesn't need a mind
7:19 Griffith University: local friendliness fails too
8:46 The trilemma: pick two
10:13 Which door physicists choose
11:11 Is a photon really an observer?
12:18 What these experiments don't prove
13:22 Why it makes scientists uncomfortable
14:21 Back to the two observers

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