52-6 Which hand is right? So the fact of the matter is that in studying any phenomenon there are always two right-hand rules, or an even number of them and the net result is that the phenomena always look symmetrical. In short, therefore, we cannot tell right from left if we also are not able to tell north from south. However it can tell the north pole of a magnet. The north pole of a compass needle, for ex- ample, is one that points to the north. But of course that is again a local property that has to do with geography of the earth; that is just like talking about in which direction is Chicago, so it does not count. If we have seen compass needles, we may have noticed that the north-seeking pole is a sort of bluish color. But that is just due to the man who painted the magnet. These are all local, conventional cre to have the property that if enough we would see small hairs growing on its north pole but not on its south pole, if that were the general rule, or if there were any unique way to distinguish ne north from the south pole of a magnet, then we could tell which of the two 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 watch the way it is going. But we cannot give him anything, we can only talk to him. 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 rightis.. "We are only allowed hone him Now we want to tell him all about us. Of course, first we start defining num- bers, and say, "Tick, tick, two, tick, tick, tick, three.. so that gradually he can understand a couple of words, and so on. After a while we may become very famil- iar with this fellow, and he says, " What do you guys look like? We start to de scribe ourselves, and say, " "Well, we are six feet tall. "He says, "Wait a minute what is six feet? "Is it possible to tell him what six feet is? Certainly! We say, You know about the diameter of hydrogen atoms-we are 17,000, 000,000 hydrogen atoms high!" That is possible because physical laws are not variant under change of scale, and therefore we can define an absolute length. and so we define the size of the body, and tell him what the general shape is-it has prongs with five bumps sticking out on the ends, and so on, and he follows us along, and we finish describing how we look on the outside, presumably without encountering any particular difficulties. He is even making a model of us as we go along. He says y, you are certainly very handsome fellows; now what is on the inside?" So we start to describe the various organs on the inside and we come to the heart, and we carefully describe the shape of it, and say, "Now put the heart on the left side He says, " Duhhh-the left side? Now our problem is to describe to him which side the heart goes on without his ever seeing anything that we see, and without our ever sending any sample to him of what we mean by"right"no standard right-handed object. Can we do it? 52-7 Parity is not conserved! It turns out that the laws of gravitation, the laws of electricity and magnetism nuclear forces, all satisfy the principle of reflection symmetry, so these laws, or anything derived from them, cannot be used. But associated with the many par ticles that are found in nature there is a phenomenon called beta decay, or weak decay. One of the examples of weak decay, in connection with a particle discovered in about 1954, posed a strange puzzle. There was a certain charged particle which disintegrated into three Mesons, as shown schematically in Fig.52 particle was called, for a while, a T-meson. Now in Fig. 52-5 we also see another particle which disintegrates into two mesons; one must be neutral, from the con