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Tsung-Dao Lee, physicist who challenged a law of nature, has died

nytimes.com

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Re: Tsung-Dao Lee, physicist who challenged a law of nature, has died

#41

Post by griffzhowl »

dotancohen wrote: post #34
perihelions wrote: post #12

Feynman wrote a exceptionally clear explanation of this experiment and what it meant: - "To illustrate the whole problem still more clearly, imagine that we were talking to a Martian, or someone very far away, by telephone. We are not allowed to send him any actual samples to inspect; for instance, if we could send light, we could send him right-hand circularly polarized light and say, “That is right-hand light—just…

Why couldn't we just tell the aliens to observe the direction of the field lines of electromagnetism? We could define for them "lower potential energy direction" by describing gravity, then use that phrase for describing the motion of the electrons in a conducting wire around a magnetic coil.

How would that allow you to distinguish the coil from its mirror image?

Re: Tsung-Dao Lee, physicist who challenged a law of nature, has died

#42

Post by blipvert »

perihelions wrote: post #12

Feynman wrote a exceptionally clear explanation of this experiment and what it meant: - "To illustrate the whole problem still more clearly, imagine that we were talking to a Martian, or someone very far away, by telephone. We are not allowed to send him any actual samples to inspect; for instance, if we could send light, we could send him right-hand circularly polarized light and say, “That is right-hand light—just…

Ha, I remember this from an old Open University TV lecture. They suggested looking at the spin of a particular particle. So eventually the alien arrives and it goes to shake hands/tentacles, but it’s not holding out the right one as it has been taught is customary …

BOOM annihilation

Ah, the alien was made from antimatter, where the spin is different. Oops.

Re: Tsung-Dao Lee, physicist who challenged a law of nature, has died

#43

Post by jxy »

dotancohen wrote: post #34
perihelions wrote: post #12

Feynman wrote a exceptionally clear explanation of this experiment and what it meant: - "To illustrate the whole problem still more clearly, imagine that we were talking to a Martian, or someone very far away, by telephone. We are not allowed to send him any actual samples to inspect; for instance, if we could send light, we could send him right-hand circularly polarized light and say, “That is right-hand light—just…

Why couldn't we just tell the aliens to observe the direction of the field lines of electromagnetism? We could define for them "lower potential energy direction" by describing gravity, then use that phrase for describing the motion of the electrons in a conducting wire around a magnetic coil.

We chose a random direction as a convention, just as we chose a random charge as positive.

Re: Tsung-Dao Lee, physicist who challenged a law of nature, has died

#44

Post by nyc111 »

"for discovering that subatomic particles, [...] are always symmetrical."

"for overturning what had been considered a fundamental law of nature — that particles are always symmetrical"

The first sentence from the subhead is wrong. The second sentence is correct. "the laws of physics are not identical when observed directly or as a mirror image."

Re: Tsung-Dao Lee, physicist who challenged a law of nature, has died

#46

Post by dotancohen »

jxy wrote: post #43
dotancohen wrote: post #34

Earlier quoted context omitted.

Why couldn't we just tell the aliens to observe the direction of the field lines of electromagnetism? We could define for them "lower potential energy direction" by describing gravity, then use that phrase for describing the motion of the electrons in a conducting wire around a magnetic coil.

We chose a random direction as a convention, just as we chose a random charge as positive.

No, the electrons actually move in the same direction always, just as a free falling object always moves towards the locally dominant mass. We could call the direction of electron movement "right".

Re: Tsung-Dao Lee, physicist who challenged a law of nature, has died

#47

Post by snarkconjecture »

dotancohen wrote: post #46
jxy wrote: post #43

Earlier quoted context omitted.

We chose a random direction as a convention, just as we chose a random charge as positive.

No, the electrons actually move in the same direction always, just as a free falling object always moves towards the locally dominant mass. We could call the direction of electron movement "right".

It's the magnetic field that has the arbitrary sign convention. You can't determine the direction of a magnetic field from observations without using the right hand rule.

Re: Tsung-Dao Lee, physicist who challenged a law of nature, has died

#49

Post by noworld »

samanator wrote: post #17
Modified3019 wrote: post #13

Earlier quoted context omitted.

“Try to teach an alien on a telephone about left and right” actually sounds like a fun game to try with a class full of kids. I would solve this particular circumstance by using the andromeda galaxy (“the closest galaxy”) as a reference, but it definitely stumped me for a bit.

You can't use cancellation or heavenly bodies: "He is far away, or in some strange location, and he cannot see anything we can see. For instance, we cannot say, “Look at Ursa major; now see how those stars are arranged. What we mean by ‘right’ is …” We are only allowed to telephone him."

"imagine that we were talking to a Martian"

Re: Tsung-Dao Lee, physicist who challenged a law of nature, has died

#50

Post by indoordin0saur »

noworld wrote: post #49
samanator wrote: post #17

Earlier quoted context omitted.

You can't use cancellation or heavenly bodies: "He is far away, or in some strange location, and he cannot see anything we can see. For instance, we cannot say, “Look at Ursa major; now see how those stars are arranged. What we mean by ‘right’ is …” We are only allowed to telephone him."

"imagine that we were talking to a Martian"

I think by Martian he just meant "alien". Obviously if you're on Mars you could use all sorts of celestial bodies to demonstrate chirality.
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