1 00:00:00,210 --> 00:00:05,160 Hello and welcome to the series on physics and philosophy from the University of Oxford. 2 00:00:06,180 --> 00:00:13,770 As children, we ask many questions like where the world comes from, what we're made of, and why the sky is blue. 3 00:00:14,830 --> 00:00:20,350 These big questions have fascinated us throughout history, and we have turned to different ways of solving them. 4 00:00:21,350 --> 00:00:24,980 Today, we may ask a physicist or a philosopher for answers. 5 00:00:25,580 --> 00:00:28,490 But once upon a time, they would have been the same person. 6 00:00:29,690 --> 00:00:37,400 What started off as just pure thought has today branched into a number of disciplines which aim to study the world around us in different ways. 7 00:00:38,220 --> 00:00:46,380 However, it seems that to gain a full understanding of the workings of the world, it is important to use these disciplines to complement each other. 8 00:00:48,160 --> 00:00:54,850 I am anchored on everyone and I am speaking to Dr. Christopher Palmer, physics lecturer at Baylor College, Oxford. 9 00:00:55,630 --> 00:01:00,160 Dr. Palmer is the head of Lab for Physics and Philosophy Undergraduates and 10 00:01:00,160 --> 00:01:04,000 also the chairman of the Joint Standing Committee for Physics and Philosophy. 11 00:01:04,840 --> 00:01:11,530 Dr. Palmer The original ideas behind modern particle physics can be traced back to ancient Greek philosophers. 12 00:01:11,920 --> 00:01:16,030 How closely would you say Greek atomism is related to modern physics? 13 00:01:17,470 --> 00:01:20,770 Well, I think that's interesting because in some ways it is. 14 00:01:20,770 --> 00:01:25,179 And in some ways it isn't. If you're thinking about the nature of matter, 15 00:01:25,180 --> 00:01:31,180 you've got a kind of choice between whether you think what's at the root of it or what's 16 00:01:31,180 --> 00:01:36,190 what's the most fundamental thing is something continuous or whether it's something discrete, 17 00:01:36,370 --> 00:01:42,450 and the discrete option is atomism. And to say that it's discrete, you have to say that. 18 00:01:43,150 --> 00:01:47,680 And also fundamental is is to suggest that it's indivisible. 19 00:01:48,040 --> 00:01:51,550 And that's what atoms fundamentally means. It's the thing that can't be cut. 20 00:01:51,790 --> 00:01:59,410 It's what is indivisible. And of course, the name Atom is now got attached to the wrong thing, because the chemical atom is, of course, 21 00:01:59,620 --> 00:02:05,620 very divisible and has been split in several different ways, both chemically and the nucleus by particle physics. 22 00:02:05,860 --> 00:02:10,540 So the indivisible is not the atom, as we now call it. 23 00:02:10,720 --> 00:02:16,760 But nonetheless, particle physics does deal with indivisible the particles, the fundamental particles of nature. 24 00:02:17,090 --> 00:02:22,030 So the idea is continuous, even though the name has got attached to the wrong thing along the way. 25 00:02:23,430 --> 00:02:30,299 So how did these ideas develop? Well, Aristotle backed the continuum idea and that was picked up by the church. 26 00:02:30,300 --> 00:02:34,740 And in the Middle Ages Atomism was associated with heretics on the whole. 27 00:02:35,190 --> 00:02:41,009 So that sort of held back the development of atomic ideas in the in the early part of the Renaissance, 28 00:02:41,010 --> 00:02:44,760 because nobody wanted to go out into the open and say that they supported Atomism. 29 00:02:45,180 --> 00:02:52,680 A lot of people thought that it offered ways of explaining things that couldn't be explained by assuming that the fundamental matter was a continuum. 30 00:02:52,920 --> 00:03:01,559 And and so from Galileo through to Newton, the fundamental atomic hypothesis got fairly well developed in physics, 31 00:03:01,560 --> 00:03:04,200 and many people began to think in those terms, 32 00:03:04,380 --> 00:03:10,080 although there were still people who didn't really believe in atoms for another couple of hundred years after that. 33 00:03:10,830 --> 00:03:14,670 Really? It was Einstein who offered quite a lot of proofs. 34 00:03:14,970 --> 00:03:15,750 Well, not proofs. 35 00:03:15,750 --> 00:03:24,360 Indications of the atomic theory by finding various different ways to calculate the number of molecules in a in a standard quantity of gas, 36 00:03:24,930 --> 00:03:29,340 all of which seem to give the same answer, which was quite indicative of the correctness of the ideas. 37 00:03:30,200 --> 00:03:39,739 But then when subatomic particles were discovered, beginning, of course, with the electron in 1897, these were seen to be constituents of atoms. 38 00:03:39,740 --> 00:03:45,620 And so the thing that can't be can't the original indivisible is not the atom itself, but some piece of the atom. 39 00:03:45,920 --> 00:03:51,800 First the electron, and the electron is still thought of as essentially indivisible and fundamental, 40 00:03:52,340 --> 00:03:55,790 although the other particles that were discovered at an early date like the proton, 41 00:03:56,420 --> 00:04:00,680 are now thought of as composite and containing more fundamental pieces within them. 42 00:04:01,040 --> 00:04:05,749 But I suppose the idea of particle physics that the name itself is suggesting some 43 00:04:05,750 --> 00:04:11,389 kind of fundamental entity which is discrete and in the original Greek sense, 44 00:04:11,390 --> 00:04:19,490 atomic. So today we have fundamental particles such as quarks and leptons, which we believe to be indivisible, 45 00:04:20,090 --> 00:04:26,210 but say that these could be divided further, which we could discover in a few years with more research. 46 00:04:26,630 --> 00:04:31,760 Do you think that by dividing atoms and quarks up infinitely, almost, 47 00:04:31,760 --> 00:04:37,370 we could reach a sort of stage where we do come to the conclusion that matters continues? 48 00:04:37,400 --> 00:04:41,330 Or do you think there is a discrete, fundamental level which we can cut it down to? 49 00:04:42,440 --> 00:04:44,809 I think maybe it's more subtle than that. 50 00:04:44,810 --> 00:04:53,090 And we're coming to see that this original Greek choice between the continuum and the particle doesn't have to be made and that they can coexist. 51 00:04:53,090 --> 00:04:59,690 Because the idea of the fundamental particle is that it's embedded in a sea of interacting 52 00:04:59,690 --> 00:05:04,550 fields which give the space between the particles something of the nature of a continuum. 53 00:05:04,820 --> 00:05:08,840 So what we now call the vacuum is now not seen just to be nothingness, 54 00:05:08,840 --> 00:05:14,310 but actually quite a fertile ground where lots of things are going on and where more things can be made to go on. 55 00:05:14,330 --> 00:05:18,739 But if you if you deposit some energy into it, that the particles themselves are not, 56 00:05:18,740 --> 00:05:22,850 in fact, separated by a nothingness, but something that's much more like a continuum. 57 00:05:23,300 --> 00:05:28,430 So it seems that the dichotomy between the Greek atomism and the Greek ideas of, for example, 58 00:05:28,430 --> 00:05:32,780 ourselves elements which are continuous, a kind of coming together now with modern physics. 59 00:05:33,350 --> 00:05:35,240 I think that's quite a fruitful way of looking at it. 60 00:05:36,600 --> 00:05:43,110 During the scientific revolution when modern physics, as we know it started, physics and philosophy were still very closely linked. 61 00:05:43,320 --> 00:05:46,800 In what ways would you say that the progress in the two disciplines influenced each other? 62 00:05:48,700 --> 00:05:57,769 That's a very big question. Originally in the early part of the Renaissance, physics was a philosophy based discipline, 63 00:05:57,770 --> 00:06:02,569 natural philosophy, and it didn't have a very strong experimental base. 64 00:06:02,570 --> 00:06:14,000 And in fact, there was a lot of debate in right up until the early 17th century as to whether experiments could refute philosophical ideas or 65 00:06:14,000 --> 00:06:21,800 whether they were necessarily too much influenced by specific and local things and didn't give you any insight into universe laws. 66 00:06:22,070 --> 00:06:29,420 And that may be the way to find universal laws was not by looking at specific experiments, but by thinking about things in a philosophical way. 67 00:06:29,660 --> 00:06:31,670 So in that sense, in the early stage, 68 00:06:31,940 --> 00:06:38,930 philosophy was a brake on physics because it prevented people from using the results of experiment to correct ideas. 69 00:06:39,890 --> 00:06:48,410 Once the idea of an experimental program had developed more cogency and people had thought that that was a useful approach to physics, 70 00:06:48,920 --> 00:06:55,580 then there was, I think, quite a long period when physics and philosophy were in touch with each other, 71 00:06:55,880 --> 00:07:00,950 and that probably continued right up until the early part of the 20th century, 72 00:07:01,250 --> 00:07:10,220 when certainly in continental countries and to a lesser extent in Great Britain, a philosophical training was part of the training of a physicist. 73 00:07:11,030 --> 00:07:22,460 But maybe the generation of Einstein and Bull and Heisenberg was perhaps the last generation to have that real philosophical background, 74 00:07:22,970 --> 00:07:31,490 and that the later part of the 20th century saw much less explicit engagement in philosophical ideas from the physicists. 75 00:07:32,650 --> 00:07:41,740 So what would you say was a turning point when experiments started to be taken seriously and when experimental physics really took off on its own, 76 00:07:41,740 --> 00:07:45,730 away from natural philosophy, which relied more on the theoretical side of things. 77 00:07:47,000 --> 00:07:55,969 Well, you could answer that in several different ways. You could go right back to something like boil in the air pump in the 1660s and the debate with 78 00:07:55,970 --> 00:08:01,580 Hobs over whether or not they were making something that was approximating to a vacuum and so on. 79 00:08:01,580 --> 00:08:09,590 And whether or not experimental ideas were capable of being taken as reliable because of the difficulty of many 80 00:08:09,590 --> 00:08:14,239 people witnessing the experiment and what the experiment had actually shown and where the experiment had worked, 81 00:08:14,240 --> 00:08:18,590 and all questions that were much debated in the 1660s and seventies. 82 00:08:19,520 --> 00:08:26,090 Or you could take it much later and say that James Clerk Maxwell, for example, in the mid-19th century, 83 00:08:26,360 --> 00:08:30,649 used philosophical ideas to develop his theories of electricity magnetism, 84 00:08:30,650 --> 00:08:34,940 which became ultimately the Maxwell electrodynamics that we use still today. 85 00:08:35,630 --> 00:08:42,890 Richard Feynman in the 20th century was notably and perhaps famously dismissive of philosophy, although I think, 86 00:08:42,890 --> 00:08:47,900 in fact, he was probably much more sensitive to philosophical implications than he wished to admit. 87 00:08:49,720 --> 00:08:55,300 More recently, eminent physicists in the 20th century, such as Heisenberg and Seneca, 88 00:08:55,690 --> 00:09:01,060 have used philosophical ideas, as you mentioned, to explore the implications of their theories. 89 00:09:01,720 --> 00:09:04,990 What are the philosophical implications of modern scientific theories, 90 00:09:04,990 --> 00:09:10,600 and how important do you think it is for the modern physicist to have an understanding of philosophy? 91 00:09:12,110 --> 00:09:21,770 Well, I think all modern theories have got to a point where the issues that they're dealing with are quite deep and need careful, 92 00:09:22,040 --> 00:09:23,720 structured, philosophical thought. 93 00:09:24,020 --> 00:09:32,160 Quantum mechanics has been at this stage for a long time, and there's been enormous debate about the correct way to think about it. 94 00:09:32,600 --> 00:09:42,500 Which is, of course, still ongoing. But so also is field theory with this search for a unifying theory of gravitation and particle physics. 95 00:09:42,980 --> 00:09:46,730 Because our best theories of gravitation and particle physics seem to start from such 96 00:09:46,730 --> 00:09:50,930 very different starting points that it's very hard to see how to put them together. 97 00:09:51,170 --> 00:09:51,800 And therefore, 98 00:09:51,890 --> 00:09:59,180 in a sense that there is an initial philosophical question of what fundamental elements of the two theories will pass into the new theory, 99 00:09:59,180 --> 00:10:01,520 the choice of of the building blocks of the theory. 100 00:10:01,670 --> 00:10:07,040 And that's really a philosophical question, even if the physicist isn't necessarily recognising to such. 101 00:10:08,640 --> 00:10:10,110 Thank you very much, Dr. Palmer.