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  • Most physical objects in everyday life maintain the same identity whether were interacting

  • with them, or not.

  • Like, a baseball is a baseball whether you're holding it in your hand or it's flying through

  • the air.

  • Even electrons are electrons whether they're part of an atom or flying freely through interstellar

  • space; they have the same mass, same charge: they are electrons.

  • But neutrinos, those weird, super light, super fast, electrically neutral, hard-to-interact-with

  • particles - they are identity-agnostic.

  • Neutrinos have different identities depending on whether theyre interacting with other

  • particles, or traveling freely, and on top of that their identities can change over time!

  • Here’s what I mean: when they interact with other particles, like when they're produced

  • in fusion in the sun or in radioactive decay, there are three different kinds of neutrinos,

  • characterized by the particles involved in their creation or annihilation.

  • And when they're traveling through space, there are three different kinds of neutrinos,

  • characterized by their masses.

  • But these two sets of identities don't match up in a one-to-one correspondence; instead,

  • each of the "interaction" identities is actually a mix of the three "traveling" identities.

  • And this weirdness allows neutrinos to change their identities.

  • That's because the traveling identities have different masses, so they travel differently

  • from each othertechnically what happens is they each pick up a complex-numbered phase

  • depending on their mass and how far theyve traveled, but I’ll just show that using

  • arrows that rotate at different speeds, which is essentially the same thing.

  • Anyway, because the arrows rotate at different speeds, over time a combination that initially

  • looked like an electron-interacting neutrino might become the muon-interacting combination.

  • And then, if you wait longer, the combination will look like an electron-interacting neutrino

  • again, then muon-interacting, and so on, back and forthall happening as the neutrino

  • flies super fast through space.

  • It’s kind of like if I took my violin and played an A , and somehow by the time the

  • sound waves reached your ear, the relative strengths of the frequencies had shifted so

  • you heard the sound as an E, or a D, or an A, depending on how far away you were.

  • In fact, the oscillation of neutrinos back and forth between different identities was

  • discovered in part because we didn’t see as many neutrinos coming from the sun as our

  • understanding of fusion suggested.

  • It turned out that about 2/3 of the electron-interacting neutrinos had turned into muon and tau-interacting

  • neutrinos en route to the earth, in a very real, very long-range example of quantum superposition!

  • Oh, and one other little technicality: even though the threeinteraction”-neutrinos

  • are named after the specific electron-family particles that are involved in their creation

  • and annihilation, they can still interact with (that’s physics-speak forbounce

  • off of”) other members of the electron family as well as quarks .

  • Ok, I’d like to thank the Heising Simons foundation for their support of this video

  • and of neutrino research!

  • They put me in touch with some of the neutrino researchers they help fund, who were awesome

  • to talk to and learn from.

  • And Heising Simons also funds a variety of research in other fields, like exoplanets,

  • microscale gravity, climate change, and so on.

  • To learn more about Heising Simons, check out

Most physical objects in everyday life maintain the same identity whether were interacting


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B2 中上級

量子シェイプシフト:ニュートリノ振動 (Quantum SHAPE-SHIFTING: Neutrino Oscillations)

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    林宜悉 に公開 2021 年 01 月 14 日