Richard Feynman perguntando "Por quê?" (Feynman on "Why?") Legendado em português-BR

if you get hold of two magnets and you push them you can feel this pushing between them turn around the other way and then they slam together now what is it the feeling between those two magnets what do you mean what's the feeling between the two there's something there isn't there i mean that the sensation is that there's something there when you push these two magnets together listen to my question what is the meaning when you say that there's there's a feeling of course you feel it now what do you want to know what i

want to know is what's going on between these two bits these two bits of metal let's repel each other and well then what does that but what does that mean or why are they doing that or how are they doing it uh you're asking i i must say i think that's a perfectly reasonable question of course it's a reason it's an excellent question okay but the problem that you're asking 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

slipped she went out and she slipped on the ice and broke her hip that satisfies it people it satisfies but it wouldn't satisfy someone who came from another planet knew nothing about things the first should understand why when you break your hip do you go to the hospital how do you get to the hospital with the when the hip was broken well because her husband seeing that she had the hip with book and called the hospital up and sent somebody to get her all that is understood by people now when you explain a why you

have to be in some framework that you allow something to be true otherwise you're perpetually asking why why did the husband call up the hospital because husband is interested in his wife's welfare not always some husbands aren't interested in their wise wife when they're drunk and they're angry and so you begin to get a very interesting understanding of the world and all its complications in order to if you try to follow anything up you go deeper and deeper in various directions if for example you go why did she slip on the ice well lies are

slippery everybody knows that no problem but you ask why is i slippery that's kind of curious ice is extremely slippery it's very interesting you say how does it work you could you see so 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 i slippery and then you're involved with something because there aren't many things as slippery as ice it's very hard to get greasy stuff but that's sort of wet and slimy but a solid that's so slippery because it is

in the case of ice that when you stand on it they say momentarily the pressure melts the ice a little bit so you got a sort of instantaneous water surface on which you're slipping why on ice and not on other things because ice expands when it water expands when it freezes so the pressure tries to undo the expansion and melts it it's capable of melting it but other substances contract when they're freezing and when you push them they're just satisfied to be solid why does water expand when it freezes another substance don't expand when they

freeze all right i'm not answering your question but i'm telling you how difficult a 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 it gets interesting after all that's my idea that the deeper a thing is the more interesting in it and we could even go further and say why did she fall down when she slipped that has to do with gravity involves in all the planets

and everything else never mind it goes on and on now when you ask for example why two magnets repel there are many different levels it depends on whether you're a student of physics or an ordinary person that doesn't know anything or not if you're somebody who doesn't know anything at all about all i can say is that there's a magnetic force that makes them repel and that you're feeling that force you see but that's very strange because i don't feel kind of forced like that in other circumstances when you turn them the other way they

attract there's a very analogous force electrical force which is the same kind of a question and you say that's also very weird but you're not at all disturbed by the fact that when you put your hand on the chair it pushes you back but we found out by looking at it that that's the same force as a matter of fact the electrical force not magnetic exactly in that case but it's the same electrical repulsions that are involved in keeping your finger away from the chair because everything's made out of its electrical forces in minor and

microscopic details there's other forces involved but this is connected to electrical forces it turns out that the magnetic and the electric force with which i wish to explain these things this this repulsion in the first place is what ultimately is the deeper thing that we have to start that we can start with to explain many other things that looked like they were everybody would just accept them you know you can't put your hand through the chair that's taken for granted but that you can't put your hand through the chair when looked at more closely why

it involves these same repulsive forces that appear in magnets the situation you then have to explain is why it magnets it goes over a bigger distance than an ordinarily and there it has to do with the fact that in iron all the electrons are spinning in the same direction they all get lined up and they magnify the effect of the force until it's large enough at a distance that you can feel it but it's a force which is present all the time and very common and it's in a basic force of almost i mean i

can go a little further back if i were more technical but in an early level i've just got to have to tell you that's going to be one of the things you'll just have to take as an element in the world the existence of magnetic repulsion or electrical electrical attraction magnetic attraction i can't explain that attraction in terms of anything else that's familiar to you for example if we say the magnets attract like as if they were connected by rubber bands i would be cheating you because they're not connected by rubber bands i shouldn't be

in trouble you'd soon ask me about the nature of the bands and secondly if we were curious enough you'd ask me why rubber bands tend to pull back together again and i would end up explaining that in terms of electrical forces which are the very things that i'm trying to use the rubber bands to explain so i have cheated very badly you see so i'm not going to be able to give you an answer to why magnets attract each other except to tell you that they do and to tell you that that's one of the

elements in the world of different kinds of forces there are electrical forces magnetic forces gravitational forces and others and those are some of the parts if you were a student you'd go fur i could go further i could tell you that the magnetic forces are related to the electrical forces very intimately that our relationship between the gravity forces and electrical forces remains unknown and so on but i really can't do a good job any job of explaining magnetic force in terms of something else that you're more familiar with because i don't understand it in terms

of anything else that you're more familiar with