WEBVTT 00:00:00.246 --> 00:00:03.512 What is the Higgs? 00:00:03.785 --> 00:00:07.333 Since 1964 we've had this idea 00:00:07.579 --> 00:00:11.030 proposed by Englert, Brout and Higgs 00:00:11.586 --> 00:00:15.287 that empty space is like a medium 00:00:16.117 --> 00:00:19.575 and as particles travel through this medium 00:00:19.775 --> 00:00:21.752 some of them interact with it, 00:00:21.798 --> 00:00:23.906 some of them don't interact with it. 00:00:24.119 --> 00:00:26.890 The ones that do interact with this medium, 00:00:26.982 --> 00:00:28.667 they acquire masses, 00:00:28.744 --> 00:00:31.450 and the ones that pass through it without interacting, 00:00:31.511 --> 00:00:33.557 those are massless particles. 00:00:34.065 --> 00:00:36.421 Let me give you an analogy: 00:00:36.421 --> 00:00:39.985 imagine an infinite field of snow 00:00:40.139 --> 00:00:42.774 extending thoughout all of space, 00:00:43.113 --> 00:00:46.824 flat, featureless, going in all directions, 00:00:47.474 --> 00:00:49.565 maybe the middle of Siberia. 00:00:50.215 --> 00:00:52.264 Now imagine that you're trying to cross 00:00:52.279 --> 00:00:53.720 this field of snow. 00:00:54.028 --> 00:00:56.295 So maybe you're a skier, 00:00:56.356 --> 00:00:58.503 and you skim across the top, 00:00:58.503 --> 00:00:59.941 that's like a particle that 00:00:59.941 --> 00:01:02.287 does not interact with the Higgs field, 00:01:02.287 --> 00:01:05.869 it does not sink into the snow, it goes very fast. 00:01:06.053 --> 00:01:09.985 That's like a particle with no mass travelling at the speed of light. 00:01:10.873 --> 00:01:13.236 But maybe you've only got snow shoes, 00:01:13.236 --> 00:01:16.841 in that case you sink into the Higgs snow field, 00:01:17.444 --> 00:01:20.678 you've got less speed that the skier, 00:01:20.770 --> 00:01:23.010 less that the speed of light. 00:01:23.071 --> 00:01:25.533 That's like a particle with mass, because you are 00:01:25.533 --> 00:01:29.087 connecting, interacting, with that Higgs snow field. 00:01:29.621 --> 00:01:33.114 And then finally if you've just got boots on, 00:01:33.160 --> 00:01:35.769 then you you sink deeply into the snow, 00:01:35.769 --> 00:01:37.592 you go very very slowly, 00:01:37.638 --> 00:01:40.170 and that's like a particle with a big mass. 00:01:40.508 --> 00:01:44.586 So, think of this Higgs field as being 00:01:44.586 --> 00:01:47.466 like this universal field of snow. 00:01:48.149 --> 00:01:51.727 Now, where does the Higgs boson come in? 00:01:52.262 --> 00:01:55.188 We all know what snow is made out of, right. 00:01:55.188 --> 00:01:57.249 It's made out of snow flakes. 00:01:57.441 --> 00:02:01.923 In the same way this universal Higgs snow field, 00:02:01.923 --> 00:02:04.913 is made up out of little quanta, 00:02:04.913 --> 00:02:09.654 those quanta are like snowflakes, that's what we call the Higgs boson. 00:02:13.076 --> 00:02:16.890 The Higgs boson has this job of giving masses 00:02:16.890 --> 00:02:19.251 to all the other elementary particles. 00:02:21.835 --> 00:02:25.414 If you look at the basic equations 00:02:25.414 --> 00:02:29.629 of the Standard Model, as written on my T-shirt, 00:02:30.311 --> 00:02:33.013 they're very symmetric, that way in which 00:02:33.202 --> 00:02:35.681 all the different particles appear is the same. 00:02:36.206 --> 00:02:38.955 At least on the top two lines there is nothing 00:02:39.032 --> 00:02:42.887 to distinguish particles that have different masses for example. 00:02:43.891 --> 00:02:46.459 But this symmetry has to be broken, 00:02:46.998 --> 00:02:49.192 electrons are lighter than muons, 00:02:49.323 --> 00:02:51.318 the top quark is much much heavier 00:02:51.349 --> 00:02:53.657 than the quarks that make up everyday nuclei. 00:02:54.026 --> 00:02:57.678 So, the top two lines, the symmetric lines, 00:02:57.770 --> 00:02:59.350 cannot be all there is, 00:02:59.442 --> 00:03:02.478 there has to be something to discriminate, 00:03:02.540 --> 00:03:05.220 distinguish, between the different types of particle. 00:03:05.824 --> 00:03:07.847 And that's the job of the Higgs boson, 00:03:07.924 --> 00:03:11.076 that's the job of the two bottom lines. 00:03:11.153 --> 00:03:15.456 Depending on how those different types of quark 00:03:15.564 --> 00:03:17.763 or the electron and muon, 00:03:17.810 --> 00:03:22.839 depending on how they connect to that Higgs field, that Higgs boson, 00:03:22.839 --> 00:03:25.049 we believe they get different masses. 00:03:25.142 --> 00:03:27.967 The symmetry between these particles is broken.