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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

#71

Post by altruios »

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…

... but we can determine left and right via the chirality in chemistry? sugar water in a tube has a 'right-handed' chirality (where it twists polarized light to the right)...

"left is the handedness of the rotation of the neutrino"

Steve Mold and 3b1b have videos on the subject.

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

#72

Post by perihelions »

altruios wrote: post #71
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…

... but we can determine left and right via the chirality in chemistry? sugar water in a tube has a 'right-handed' chirality (where it twists polarized light to the right)... "left is the handedness of the rotation of the neutrino" Steve Mold and 3b1b have videos on the subject.

The inverse enantiomers of sugar function exactly the same way, with the correspondingly inverted enzymes. The chirality of sugars isn't a universe-wide property inherited from fundamental physics, but just a path-dependent quirk of the evolutionary history of biochemistry on Earth. "Universal" for Earth-life only.

(The strength of the weak force is very certainly far too... weak... for it to have plausibly influenced this selection process. It was 100% chance).

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

#73

Post by Xen9 »

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…

As long as he exists within a planet instead of unknown dimension, we can simply give them a slightly modified version of Wikipedia (removing arbitrary data, arbitrary metadata; language does not matter given it is a plaintext we can encode into transmission). They will eventually figure it out.

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

#74

Post by dotancohen »

raincole wrote: post #66
dotancohen wrote: post #55

Earlier quoted context omitted.

You don't have to know the sign, you could tell which way the electrons are going. We tell the aliens: you take all sorts of organics with liquid inside (on earth we typically use a lemon, but other organics will do), and put a stake of element 29 in one side and a stake of element 30 in the other. You then connect them with a length of element 29. Keep trying different organics until you find one that works. They mi…

I'd suggest you to re-read your parent comment. They already explained it concisely but you seem to be a bit to caught up in this lemon battary idea.

I addressed that. We know which way the electrons flow from the anode to the cathode. I specifically chose this example because of the right-hand rule.

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

#75

Post by altruios »

perihelions wrote: post #72
altruios wrote: post #71

Earlier quoted context omitted.

... but we can determine left and right via the chirality in chemistry? sugar water in a tube has a 'right-handed' chirality (where it twists polarized light to the right)... "left is the handedness of the rotation of the neutrino" Steve Mold and 3b1b have videos on the subject.

The inverse enantiomers of sugar function exactly the same way, with the correspondingly inverted enzymes. The chirality of sugars isn't a universe-wide property inherited from fundamental physics, but just a path-dependent quirk of the evolutionary history of biochemistry on Earth. "Universal" for Earth-life only. (The strength of the weak force is very certainly far too... weak... for it to have plausibly influence…

Fair point about biological selection playing a part.

neutrinos (the only ones we can detect), however, are left handed.

https://physics.stackexchange.com/questions/240502/why-only-....

We simply point to the neutrino. left v right solved?

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

#76

Post by immibis »

dotancohen wrote: post #60
pgalvin wrote: post #56

Earlier quoted context omitted.

Okay, I’ve got elements 29 and 30. Which side do I put each on? See the problem? :)

No, it really doesn't matter. Have you never made a lemon or potato battery before?

The electrons are flowing towards the element 29 side. Is that left or right?

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

#77

Post by griffzhowl »

dotancohen wrote: post #55
snarkconjecture wrote: post #47

Earlier quoted context omitted.

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.

You don't have to know the sign, you could tell which way the electrons are going. We tell the aliens: you take all sorts of organics with liquid inside (on earth we typically use a lemon, but other organics will do), and put a stake of element 29 in one side and a stake of element 30 in the other. You then connect them with a length of element 29. Keep trying different organics until you find one that works. They mi…

Set up whatever apparatus you like, you can always set up its mirror image, and then the electrons are going in the opposite direction. So which is right and which is left?

Remember you haven't yet established with the alien what you mean by right and left, so you won't be able to instruct it to set up your apparatus rather than its mirror image, and of course you can't appeal to the right-hand rule.

This problem has no solution because electromagnetism is right-left symmetric. You would need to use the weak decay (and assume that your alien is made of matter rather than antimatter)

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

#79

Post by dotancohen »

immibis wrote: post #76
dotancohen wrote: post #60

Earlier quoted context omitted.

No, it really doesn't matter. Have you never made a lemon or potato battery before?

The electrons are flowing towards the element 29 side. Is that left or right?

Now arrange the apparatus such that the element 29 side is near you, and the element 30 side is far from you. Additionally, ensure that the wire is up (further from the locally dominant gravitational mass). Now place an election between the "lemon" and the wire. See which way the election moved? That was right (or left, I don't remember).

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

#80

Post by dotancohen »

griffzhowl wrote: post #41
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.

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

No coil, see my other comment here:

https://news.ycombinator.com/item?id=41195886

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