Quantum Entanglement & Spooky Action at a Distance
Why Hacker News recommends it
HN recommends it as one of the clearest layman explanations of Bell's theorem.
What it is
Veritasium explains quantum entanglement and spooky action at a distance, walking through Bell's inequality and the experiments that rule out hidden variables, in under ten minutes.
Recommended by 9 HN commenters across 9 different months, 2015 to 2022.
What Hacker News said
Strong rec slaxman · 2015-09 · on “Informative YouTube channels”
I can't recommend Veritasium and CGP Grey enough. They are amazing YouTube Channels! Check out this video where Veritasium explains Quantum Entanglement. [this video] It amazes me how he explains something so difficult in less than 10 minutes!
Strong rec gibybo · 2015-11 · on “The quantum source of space-time”
Check out [this video] It's my favorite video for explaining how we know that the state is not determined until it has been measured. It's not just a decision we thought up on paper. It is real and well proven.
Recommends gbelote · 2015-02 · on “Quantum Physics and the Abuse of Reason”
If quantum-entangled particles exist (they do) you can use them to coordinate in a way that's impossible within a "hidden variable" model of the universe. You can dig into this by searching for "bell's inequality" or "bell test experiments", there are a few different experiments that have been done many, many times. There's a pretty good Veritasium video that explains one such experiment in non-physicist terms: [this video]
Recommends blueplanet200 · 2016-08 · on “Interactive explanation of the quantum Bell test”
[this video] is a good overview that I really like for Bell's inequality. Worth a watch if you have the time.
Recommends strmpnk · 2017-01 · on “Bell's Theorem: No EPR “Reality””
I don't think that explanation is clear. It takes a bit more work to get something which proves the experimental difference. One of the better explanations I've seen is regarding measuring spin with three state detectors: [this video] This would give specific probabilities to certain outcomes (not just 50/50) IF there were a local hidden variable. (Note: the word local is important there. It means information encoded and carried by or with the particles themselves.)
Recommends CookieMon · 2018-02 · on “You thought quantum mechanics was weird: check out entangled time”
If you watch for more than 4 minutes, this 9 minute video explains how Bell proved that the particles can't have been given opposite "ball colors" at the time they became entangled. [this video] It's quite clever how he proved it, and that it's actually possible to rule out "information that we're just not aware of".
Recommends chii · 2019-03 · on “Experimental rejection of observer-independence in the quantum world”
> it's both simply because it hasn't been measured ... Meaning it's either one or the other A common misconception about quantum superposition is that the particle "has" some state, and we only use superposition to model that we "dont know". This is called the hidden-variable theory ( [LINK] ). It's been proven that this hidden variable theory can't be true because of [LINK] . This is completely non-intuitive. See this video for a laymen's explanation: [LINK] (you may also need to watch the prev. video about the EPR paradox [LINK] ). Edit: actually, this is a much better video [this video] - less technical and more visual.
Recommends rhinokungfoo · 2022-07 · on “Record-setting quantum entanglement connects two atoms across 20 miles”
Your example is akin to the Hidden variable theory (in the example the hidden variable will be the fact the two letters are copies). Bell's inequality tests have ruled out the hidden variable theory. Veritasium has a good video explaining Bell's inequality - [this video]