1 00:00:00,246 --> 00:00:03,512 What is the Higgs? 2 00:00:03,785 --> 00:00:07,333 Since 1964 we've had this idea 3 00:00:07,579 --> 00:00:11,030 proposed by Englert, Brout and Higgs 4 00:00:11,586 --> 00:00:15,287 that empty space is like a medium 5 00:00:16,117 --> 00:00:19,575 and as particles travel through this medium 6 00:00:19,775 --> 00:00:21,752 some of them interact with it, 7 00:00:21,798 --> 00:00:23,906 some of them don't interact with it. 8 00:00:24,119 --> 00:00:26,890 The ones that do interact with this medium, 9 00:00:26,982 --> 00:00:28,667 they acquire masses, 10 00:00:28,744 --> 00:00:31,450 and the ones that pass through it without interacting, 11 00:00:31,511 --> 00:00:33,557 those are massless particles. 12 00:00:34,065 --> 00:00:36,421 Let me give you an analogy: 13 00:00:36,421 --> 00:00:39,985 imagine an infinite field of snow 14 00:00:40,139 --> 00:00:42,774 extending thoughout all of space, 15 00:00:43,113 --> 00:00:46,824 flat, featureless, going in all directions, 16 00:00:47,474 --> 00:00:49,565 maybe the middle of Siberia. 17 00:00:50,215 --> 00:00:52,264 Now imagine that you're trying to cross 18 00:00:52,279 --> 00:00:53,720 this field of snow. 19 00:00:54,028 --> 00:00:56,295 So maybe you're a skier, 20 00:00:56,356 --> 00:00:58,503 and you skim across the top, 21 00:00:58,503 --> 00:00:59,941 that's like a particle that 22 00:00:59,941 --> 00:01:02,287 does not interact with the Higgs field, 23 00:01:02,287 --> 00:01:05,869 it does not sink into the snow, it goes very fast. 24 00:01:06,053 --> 00:01:09,985 That's like a particle with no mass travelling at the speed of light. 25 00:01:10,873 --> 00:01:13,236 But maybe you've only got snow shoes, 26 00:01:13,236 --> 00:01:16,841 in that case you sink into the Higgs snow field, 27 00:01:17,444 --> 00:01:20,678 you've got less speed that the skier, 28 00:01:20,770 --> 00:01:23,010 less that the speed of light. 29 00:01:23,071 --> 00:01:25,533 That's like a particle with mass, because you are 30 00:01:25,533 --> 00:01:29,087 connecting, interacting, with that Higgs snow field. 31 00:01:29,621 --> 00:01:33,114 And then finally if you've just got boots on, 32 00:01:33,160 --> 00:01:35,769 then you you sink deeply into the snow, 33 00:01:35,769 --> 00:01:37,592 you go very very slowly, 34 00:01:37,638 --> 00:01:40,170 and that's like a particle with a big mass. 35 00:01:40,508 --> 00:01:44,586 So, think of this Higgs field as being 36 00:01:44,586 --> 00:01:47,466 like this universal field of snow. 37 00:01:48,149 --> 00:01:51,727 Now, where does the Higgs boson come in? 38 00:01:52,262 --> 00:01:55,188 We all know what snow is made out of, right. 39 00:01:55,188 --> 00:01:57,249 It's made out of snow flakes. 40 00:01:57,441 --> 00:02:01,923 In the same way this universal Higgs snow field, 41 00:02:01,923 --> 00:02:04,913 is made up out of little quanta, 42 00:02:04,913 --> 00:02:09,654 those quanta are like snowflakes, that's what we call the Higgs boson. 43 00:02:13,076 --> 00:02:16,890 The Higgs boson has this job of giving masses 44 00:02:16,890 --> 00:02:19,251 to all the other elementary particles. 45 00:02:21,835 --> 00:02:25,414 If you look at the basic equations 46 00:02:25,414 --> 00:02:29,629 of the Standard Model, as written on my T-shirt, 47 00:02:30,311 --> 00:02:33,013 they're very symmetric, that way in which 48 00:02:33,202 --> 00:02:35,681 all the different particles appear is the same. 49 00:02:36,206 --> 00:02:38,955 At least on the top two lines there is nothing 50 00:02:39,032 --> 00:02:42,887 to distinguish particles that have different masses for example. 51 00:02:43,891 --> 00:02:46,459 But this symmetry has to be broken, 52 00:02:46,998 --> 00:02:49,192 electrons are lighter than muons, 53 00:02:49,323 --> 00:02:51,318 the top quark is much much heavier 54 00:02:51,349 --> 00:02:53,657 than the quarks that make up everyday nuclei. 55 00:02:54,026 --> 00:02:57,678 So, the top two lines, the symmetric lines, 56 00:02:57,770 --> 00:02:59,350 cannot be all there is, 57 00:02:59,442 --> 00:03:02,478 there has to be something to discriminate, 58 00:03:02,540 --> 00:03:05,220 distinguish, between the different types of particle. 59 00:03:05,824 --> 00:03:07,847 And that's the job of the Higgs boson, 60 00:03:07,924 --> 00:03:11,076 that's the job of the two bottom lines. 61 00:03:11,153 --> 00:03:15,456 Depending on how those different types of quark 62 00:03:15,564 --> 00:03:17,763 or the electron and muon, 63 00:03:17,810 --> 00:03:22,839 depending on how they connect to that Higgs field, that Higgs boson, 64 00:03:22,839 --> 00:03:25,049 we believe they get different masses. 65 00:03:25,142 --> 00:03:27,967 The symmetry between these particles is broken.