Breakthrough Junior Challenge 2020 | EPR Paradox and Bell's Inequality | Arpan Dey

#breakthroughjuniorchallenge
*Sorry for the bad audio quality, I'm not a professional at video-editing!
Hi! This is my first video for the Breakthrough Junior Challenge! It's a great opportunity, and winning is not an issue; the experience gained is invaluable. My topic, this time, is Bell's Inequality & EPR Paradox. I have tried my best to provide a good explanation. Though Einstein termed this as "spooky-action-at-a-distance"; it is not a spooky phenomena, contrary to common misconception. It is just a new science that we aren't yet comfortable with. While it is generally accepted that EPR Paradox has been reasonably settled, there remain questions to answer. However, much of modern physics stands on quantum mechanics, which is not just a theory, but has been, arguably, the greatest scientific revolution of 20th century (with the possible exception of relativistic mechanics and the study of nonlinear dynamics or chaos theory). Thus, EPR Paradox does not entirely disprove quantum mechanics. Rather, it holds the key for a deeper and better understanding of the subject. Quantum mechanical description of nature, like any other theory, is not complete. Neither is it incomplete. It is the best theory so far, and so, we need to keep working on it.
Start with two coherent particles with similar (in magnitude) spins (electrons/photons) whose combined spin is zero. If such an entangled pair is released in opposite directions at near-light velocities, over time they will reach opposite ends of the universe. But as per quantum mechanics, the spins of the particles are undefined before observed. If a particle is observed when it is already light-years away from the other, its spin will collapse from a superposition of all possible states to a distinct state. At that instant, the other particle's spin also, without direct observation, collapses to the opposite spin. Information passes between the particles faster than light, violating causality.
This was too much for Einstein. It was assumed that there are some “hidden variables” yet to be discovered; and they, even before observation, carry the information about the spin of the particles. But John Bell has mathematically proved that there can be no hidden theory compatible with quantum theory. The violation of Bell’s theorem has been repeatedly verified experimentally. Things separated through spacetime can, in fact, remain entangled.
To derive his inequality, Bell used certain facts with which all could agree, except for Einstein’s condition of locality, which he assumed to be true. If experiments show that the inequality was violated, this would mean that one of the premises in his derivation was false. Bell chose to interpret this to mean that nature is non-local.
According to Einstein, “A sufficient condition for the reality of a physical quantity is the possibility of predicting it with certainty, without, in any manner, disturbing the system.” Niels Bohr, who has already refuted Einstein’s previous arguments against quantum mechanics, pointed out that “without, in any manner, disturbing the system”, is, in itself impossible due to the inevitable interaction between the objects and the measuring instruments. The act of measurement is fundamentally crucial.
John Bell was to physics what Kurt Godel was to mathematics. Indeed, something as simple as Bell's inequality can address a question as fundamental and important as the one put forward by Einstein and his colleagues - Podolsky and Rosen!
To quote Daniel Greenberger, "Einstein said that if quantum mechanics was correct, the world would be crazy. Einstein was right, the world is crazy." Finally, it would be a great injustice to not acknowledge the people who inspired me in the amazing field of science. It is for them that I have developed a liking in explaining things, and if it was not for them, I would not even have heard of the Breakthrough Junior Challenge. Apart form my parents, teachers, relatives and scientists whom I really admire, I would particularly like to thank the following persons for their encouragement and support:
1. Respected Pooja Mazumdar, my Physics teacher
2. Respected Anupa Bhattacharya, my Chemistry teacher
If you would like to know more about EPR Paradox and Bell's Inequality, do check out these links:
Finally, I encourage ANYONE watching these video, to pursue a career in research. Under present circumstances, we need scientists more than ever before..., and in all probability, you may be the scientist to propose a better interpretation of quantum mechanics, and change forever, once more, the way we look at the universe.
Thanks a lot. Hope you enjoyed the video, and it was of help. Feel free to comment below.
Music: "Starlight Glow"
App: "Photos" (Windows 10)
So long, then! ---- Arpan Dey

[eshanbajaj]

Wow Arpan. This was such an interesting video. I can't believe you explained such a complex topic in such simple words.
That being said, I only wish my Physics was as strong as yours.
All the very best.

[suchismitadalal]

Congratulations and best wishes for your next adventure!

[deabrahimaj]

Great job! I really like the way how you explained the concept in a really entertaining way and made the parts of the parts together. Every element in this video is in harmony with each other. Amazing work! Participant here✌ Good luck!

[anjolasworld]

Your video is nice !!!!I learnt a lot .Great Video, from a fellow competitor !!!

[suchismitadalal]

You’ve worked so hard for this. Congrats!