Feynman on Scientific Method.

situation now I'm going to discuss how we would look for a new law in general we look for a new law by the following process first we guess it then we com well don't laugh that's the really true then we compute the consequences of the guess to see what if this is right if this law that we guessed is right we see what it would imply and then we compare those computation results to Nature or we say compared to experiment or experience compare it directly with observation to see if it if it works if it

disagrees with experiment it's wrong and that simple statement is the key to science it doesn't make any difference how beautiful your guess is it doesn't make any difference how smart you are who made the GU or what his name is if it disagrees with experiment it's wrong that's all of his to it's therefore not unscientific to take a guess although many people who are not in science think it is for instance I had a conversation about frying saces some years ago with Layman cuz I'm scientifically I know all about flying sources so I said I

don't think there are flying sources so the other my antagonist said is it impossible that there were flying sources can you prove that it's impossible I no I can't prove it's impossible it's just very unlikely that they say you are very unscientific if you can't prove it impossible then why how can you say it's likely that it's unlikely well that's the way that is scientific it is scientific only to say what's more likely and less likely and not to be proving all the time possible and impossible to Define what I mean I finally said to

him listen I mean that from my knowledge of the world that I see around me I think that it is much more likely that the reports of flying sources are the result of the known irrational characteristics of terrestrial intelligence rather than the unknown rational efforts of extraterrestrial intelligence it's just more likely that's all and it's a good guess and we always try to guess the most likely explanation keeping in the back of the Mind the fact that if it doesn't work then we must discuss the other possibilities there was for instance for a while a

phenomenon called super conductivity that still is the phenomenon uh uh which is that Metals conduct electricity without resistance at low temperatures and it was not at first obvious that this was a consequence of the known laws with these particles but it turns out that it has been thought through carefully enough and it's SE in fact to be a consequence of known laws there are other phenomena such as extrasensory perception which cannot be explained by this known knowledge of physics here and uh it is interesting however that that phenomenon has not been well established and uh

that uh we cannot guarantee that it's there so if it could be demonstrated of course that would prove that the physics is incomplete and therefore it's extremely interesting to physicists whether it's right or wrong and uh many many experiments exist which show it doesn't work the same goes for astrological influences if it were true that the Stars could affect the day that it was good to go to the dentist then that as in America we have have that kind of astrology then it would be wrong the physics theory would be wrong because there's no mechanism

by understandable in principle from these things that would make it go that's the reason that there's some skepticism among scientists with regard to those ideas now you see of course that with this method we can disprove any definite theor you have a definite Theory a real guess from which you canly compute consequences which could be compared to experiment and in principle we can get rid of any Theory we can always prove any definite Theory wrong notice however we never prove it right suppose that you invent a good guess calculate the consequences discover every consequence that

you calculate agrees with experiment the theory is then right no it is simply not proved wrong because in the future there could be a wider range of experiments you could compute a wider range of consequences and you may discover then that the thing is wrong that's why a laws like Newton's laws for the motion of planets last such a long time he guessed the law of gravitation cly all the kinds of consequences for the solar system and so on compared them to experiment and it took several hundred years before the slight era of the motion

of mercury was developed during all that time the theory had been failed to be proved wrong and could be taken to be temporarily right but it can never be proved right because tomorrow's experiment May succeed in proving what you thought was right wrong so we never AR we can only be sure we're wrong however it's rather remarkable that we can last so long I mean have some idea which it last so long I must also point out to you that you cannot prove a vague Theory wrong if the guess that you make is poorly expressed

and rather vague and the method that you use for figuring out the consequences is rather a little vague you're not sure I mean you say I think everything's because it's all due to Muggles and Muggles do this and that more or less so I can sort of explain how this works then you see that that theory is good because it can't be proved wrong if the process of computing the consequences is indefinite then with a little skill any experimental result can be made to look like a an expected consequence you're probably familiar with that in

other fields for example a hates his mother the reason is of course because she didn't caress him or love him enough uh when he was a child actually if you investigate you find out that as a matter fact she he did love him very much and everything was all right well then it's because she was overindulgent when he was so by having a vague Theory it's possible to get either result all right now the cure for this one is the following it would be possible to say if it were possible to State ahead of time

how much love is not enough and how much love is overindulgent exactly then there would be a perfectly IL legitimate Theory against which you can make tests it is usually said when this is pointed out how much love is and so on oh you're dealing with psychological matters that things can't be defined so precisely yes but then you can't claim to know anything about it now I want to concentrate from now on because I'm a theoretical physicist I'm more delighted with this end of the problem as to what goes or how do you make the

guesses now it's strictly as I said before not of any importance where the guess comes from it's only important that it should agree with experiment and that it should be definite as poss as definite as possible but you say then is very simple we set up a machine a great Computing machine which has a random wheel in it that makes the succession of guesses and each time it guesses a hypothesis about how nature should work computes immediately the consequences and makes a comparison to a list of experimental results that has at the other end in

other words guessing is a dumb man's job actually it's quite the opposite and I will try to explain why the first problem is how to start you see you want start I'll start with all the known principles but the principles that are all known are inconsistent with each other so something has to be removed so we get a lot of letters from people we're always getting letters from people who are insisting that we ought to make holes in our guesses as follow you see you make a hole to make room for a new guess somebody

says to you know you all people always say space is continuous but how do you know when you get to a small enough Dimension that they really are enough points in between it isn't just a lot of dots separated by little distances or they say you know those quantum mechanical amplitudes that you told me about they're so complicated and absurd what makes you think those are right maybe they aren't right I get a lot of letters with such content but I must say that such remarks are perfectly obvious and are well are perfectly clear to

anybody who's working on this problem and it doesn't do any good to point this out the problem is not what might be wrong but what might be substituted precisely in place of it if you say anything precise for example in the case of a continuous space suppose the precise proposition is that space really consists of a series of dots only in the space between them doesn't mean anything and the dots are in a cubic array then we can prove that immediately is wrong that doesn't work you see the problem is not to make to change

or to say something might be wrong but to replace it by something and that is not so easy as soon as any real definite idea is substituted it becomes almost immediately apparent that it doesn't work work secondly there's an infinite number of possibilities on these of these simple types it's something like this you're sitting working very hard you work for a long time trying to open a safe and some Joe comes along who hasn't doesn't know anything about what you're doing or anything except that you're trying to open and sa he say you know why

don't you try to combination 10 2030 because you're busy you're trying a lot of things maybe you already tried 10 2030 maybe you know that the middle number is already 32 and not 20 maybe you know that as a matter of fact this is a five-digit combination that we have so these letters don't do any good and so please don't send me any letters trying to tell me how the thing is going to work I don't I read them to make sure that I haven't already thought of that but it takes too long to answer

them because they usually in the class try 10 2030 [Music]