Richard Feynman – Session IV (1966) | Hacker News Reader

Richard Feynman – Session IV (1966)

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65 pointslordylord25 comments

Feynman's fascination with basically everything is always so fun. Here is another, where he is talking about trying to figure out why ice is slippery...

https://newsletter.butwhatfor.com/p/takeaway-tuesday-richard...

Copy / Paste:

"But the problem, you see, when you ask why something happens, how does a person answer why something happens? For example, Aunt Minnie is in the hospital. Why? Because she went out, slipped on the ice, and broke her hip. That satisfies people. It satisfies, but it wouldn't satisfy someone who came from another planet and who knew nothing about why when you break your hip do you go to the hospital…

And you begin to get a very interesting understanding of the world and all its complications. If you try to follow anything up, you go deeper and deeper in various directions. For example, if you go, “Why did she slip on the ice?” Well, ice is slippery. Everybody knows that, no problem. But you ask why is ice slippery? That’s kinda curious. Ice is extremely slippery. It's very interesting. You say, how does it work? You could either say, “I’m satisfied that you’ve answered me. Ice is slippery; that explains it,” or you could go on and say, “Why is ice slippery?” and then you're involved with something, because there aren't many things as slippery as ice...

A solid that’s so slippery? Because it is, in the case of ice, when you stand on it (they say) momentarily the pressure melts the ice a little bit so you get a sort of instantaneous water surface on which you're slipping. Why on ice and not on other things? Because water expands when it freezes, so the pressure tries to undo the expansion and melts it. It's capable of melting, but other substances get cracked when they're freezing, and when you push them they're satisfied to be solid.

Why does water expand when it freezes and other substances don’t? I’m not answering your question, but I'm telling you how difficult the why question is. You have to know what it is that you're permitted to understand and allow to be understood and known, and what it is you're not. You'll notice, in this example, that the more I ask why, the deeper a thing is, the more interesting it gets. We could even go further and say, “Why did she fall down when she slipped?” It has to do with gravity, involves all the planets and everything else. Nevermind! It goes on and on."

And yet he totally shuts down the question of why positive and negative charges attract… which I’ve always been dying to understand.

https://www.physicsforums.com/threads/why-do-positive-and-ne...

Change your reference frame. Assume both charges are moving at constant speed != 0 in the same direction. From this view they are not charges but opposite currents. We know that opposite currents repel [1]. Therefore, one could conclude that opposite charges repel. It's this kind of question that the interviewer should ask.

[1] https://www.quora.com/Why-do-two-wires-with-current-flowing-...

The difficulty is that eventually you reach a level where there are no satisfying answers to this sort of question. There are a lot of interesting levels to explore between “why did aunt Minnie go to the hospital” and fundamental physical principles, but for things like “why do magnets repel?” (or “why do unlike charges attract?”), these questions are getting pretty close to the point where the only answer is “we don’t know, that’s just what we see happens when we watch the universe work.”

You can go farther and get stuff about the action in quantum electrodynamics, but these don’t really provide any more satisfying answers, they just lead to more questions like “why do systems follow trajectories of stationary action?” and “why is the lagrangian for electromagnetism what it is?”

But how do you know where the limit is? Isn’t it a bit like asking why the planets move in epicycles and the response being “it’s just the way it is”?

Yeah, and I don’t mean to suggest that there are no further levels to discover and understand or more fundamental properties to explain the ones we know, just that there is a limit to what we know, and that at some level things which are experimentally observed are assumed. IMO these are always excellent questions, and there are people looking to find explanations and more fundamental physics, but this is increasingly difficult as current models explain current observations very well and it is hard to go further with experiment.

Even if there are further levels to be understood, those probably won’t lead to any more satisfying answers, just a swap of one axiom to ponder with a more fundamental one.

I think it is like asking about epicycles prior to Kepler, or asking about Kepler’s laws prior to Newton (and on). There are new and better explanations, but always more questions than answers, and some things that just are (as far as we know).

You mention stationary action.

Interestingly, F=ma and Hamilton's stationary action are mutually derivable.

The usual presentation is to show that Hamilton's stationary action implies the newtonian formulation. Interestingly, it is also possible to start with F=ma, and move in all forward steps to Hamilton's stationary action. No additional assumptions are required.

I created a series of interactive diagrams to make Hamilton's stationary action entirely transparent.

http://www.cleonis.nl/physics/phys256/energy_position_equati...

(Of course, quantum mechanics is the overall deeper theory; we assume that classical mechanics holds good because classical mechanics is a limiting case of quantum mechanics; at scales large enough that quantum effects average out the outcome in terms of quantum mechanics converges onto the outcome in terms of classical mechanics.)

This boils down to what magnetism is. My favorite explanation is the Kaluza-Klein hypothesis that explains magnetism as an emergent effect of space geometry. If this explanation is accepted, we still need to answer what causes things to move forward and "execute" these maxwell/KK equations. And that's a great mystery.

> Feynman's fascination with basically everything is always so fun. Here is another, where he is talking about trying to figure out why ice is slippery...

He never looks bored, many people of his level of intellect only have very short moment of real hype when they actually have big wins and are proven right and recognized by peers (Nobel prize, Fields medal...)

Feynman has such a wide interests , also things which people even on here would consider mundane and not special enough to be given the time of the day such as bongos, painting as a hobby, dancing at the Rio Carnival, stripclubs, strippers and sex workers.

Also Tuva which is a territory forgotten by god himself as well as men.

Feynman could talk about the color of beer coasters and it would be a fascinating read full of great anecdotes

One of my collaborators recently wrote a paper about why beer coasters make bad frisbees.

https://arxiv.org/abs/2106.08238

Yogurt lids really rip. Not that anyone asked

"He says, 'Feynman, that's pretty interesting, but what's the importance of it? Why are you doing it?'"

"'Hah!' I say. 'There's no importance whatsoever. I'm just doing it for the fun of it.' His reaction didn't discourage me; I had made up my mind I was going to enjoy physics and do whatever I liked."

https://www.asc.ohio-state.edu/kilcup.1/262/feynman.html

It seems this article went into the second-chance pool, which is great! It didn't get much discussion last time around but might spurn a lot of interesting threads.

However, something I find a little upsetting: I commented the first time around (about 2 days ago). But currently the comments show that I commented first about 50 minutes ago. That's a little too much rewriting of history, if you ask me.

What's funny is that when I came to leave this reply, on the "Add comment" page, it correctly says that my first comment was 2 days ago. So this information IS available. So the timestamp is rewritten? @dang, seems a little too much ret-conny...

(It also makes me wonder what would happen if I visited the second-chance page before some of the other first-time comments were/are-going-to-be posted.)

Thank you, I thought I was losing my mind.

Warning, this is a book-length article. Set aside hours.

It seems like much of the source material for what became "Surely...".

Not the same interview, but a talk also covering his time at Los Alamos: https://www.youtube.com/watch?v=hTRVlUT665U

While Feynman is famous for his computational work at Project Y, perhaps his most important contribution was the Bethe-Feynman equation for the efficiency of a nuclear weapon.

That's one long read. A good one too. I wish there was an audio copy too.

Is there an audio copy?

Surely there is audio of the full interview somewhere on the Internet? I almost believe I can rationalize it into existence.

There is audio of this. Ralph Leighton has it.

So why doesn’t he release it?

yes. I have heard it. do not remember where. a series of interviews, fire side chat type r talks.

golden. his bit about the curt richter's "hope" experiment (the one with drowning rats) is very interesting:

> But then there was a talk by some guy who got up and told about experiments which were supposed to be the effect of stress on rats, on their desire to survive or something — on rats. What he had done was — I mean this is what he’d done — he described it in terms of a cylindrical glass tube, but it was a bottle. He took a jar and he put rats in the jar in water, and he screwed the lid on so that they couldn’t quite come up high enough when they were swimming to get a good breath, and they were drowning — hm? And he watched how long it took them to drown, under some kind of circumstance. Now, if that ain’t a kid fiddling around! There was nothing scientifically measured, in the sense that there was some sense to it, except that the rats got very nervous, you see, and they swam faster, or something. It was the most cruel, unnecessary, stupid thing. It was very much — except it wasn’t human beings — like the stupid kind of Nazi experiments in which they don’t exactly know what they’re doing; they’re just experimenting. Huh? It was just like a kid would experiment, God damn it, in drowning rats. It had no real scientific virtue of any kind.

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