0:00:00.246,0:00:03.512 What is the Higgs? 0:00:03.785,0:00:07.333 Since 1964 we've had this idea 0:00:07.579,0:00:11.030 proposed by Englert, Brout and Higgs 0:00:11.586,0:00:15.287 that empty space is like a medium 0:00:16.117,0:00:19.575 and as particles travel through this medium 0:00:19.775,0:00:21.752 some of them interact with it, 0:00:21.798,0:00:23.906 some of them don't interact with it. 0:00:24.119,0:00:26.890 The ones that do interact with this medium, 0:00:26.982,0:00:28.667 they acquire masses, 0:00:28.744,0:00:31.450 and the ones that pass through it without interacting, 0:00:31.511,0:00:33.557 those are massless particles. 0:00:34.065,0:00:36.421 Let me give you an analogy: 0:00:36.421,0:00:39.985 imagine an infinite field of snow 0:00:40.139,0:00:42.774 extending thoughout all of space, 0:00:43.113,0:00:46.824 flat, featureless, going in all directions, 0:00:47.474,0:00:49.565 maybe the middle of Siberia. 0:00:50.215,0:00:52.264 Now imagine that you're trying to cross 0:00:52.279,0:00:53.720 this field of snow. 0:00:54.028,0:00:56.295 So maybe you're a skier, 0:00:56.356,0:00:58.503 and you skim across the top, 0:00:58.503,0:00:59.941 that's like a particle that 0:00:59.941,0:01:02.287 does not interact with the Higgs field, 0:01:02.287,0:01:05.869 it does not sink into the snow, it goes very fast. 0:01:06.053,0:01:09.985 That's like a particle with no mass travelling at the speed of light. 0:01:10.873,0:01:13.236 But maybe you've only got snow shoes, 0:01:13.236,0:01:16.841 in that case you sink into the Higgs snow field, 0:01:17.444,0:01:20.678 you've got less speed that the skier, 0:01:20.770,0:01:23.010 less that the speed of light. 0:01:23.071,0:01:25.533 That's like a particle with mass, because you are 0:01:25.533,0:01:29.087 connecting, interacting, with that Higgs snow field. 0:01:29.621,0:01:33.114 And then finally if you've just got boots on, 0:01:33.160,0:01:35.769 then you you sink deeply into the snow, 0:01:35.769,0:01:37.592 you go very very slowly, 0:01:37.638,0:01:40.170 and that's like a particle with a big mass. 0:01:40.508,0:01:44.586 So, think of this Higgs field as being 0:01:44.586,0:01:47.466 like this universal field of snow. 0:01:48.149,0:01:51.727 Now, where does the Higgs boson come in? 0:01:52.262,0:01:55.188 We all know what snow is made out of, right. 0:01:55.188,0:01:57.249 It's made out of snow flakes. 0:01:57.441,0:02:01.923 In the same way this universal Higgs snow field, 0:02:01.923,0:02:04.913 is made up out of little quanta, 0:02:04.913,0:02:09.654 those quanta are like snowflakes, that's what we call the Higgs boson. 0:02:13.076,0:02:16.890 The Higgs boson has this job of giving masses 0:02:16.890,0:02:19.251 to all the other elementary particles. 0:02:21.835,0:02:25.414 If you look at the basic equations 0:02:25.414,0:02:29.629 of the Standard Model, as written on my T-shirt, 0:02:30.311,0:02:33.013 they're very symmetric, that way in which 0:02:33.202,0:02:35.681 all the different particles appear is the same. 0:02:36.206,0:02:38.955 At least on the top two lines there is nothing 0:02:39.032,0:02:42.887 to distinguish particles that have different masses for example. 0:02:43.891,0:02:46.459 But this symmetry has to be broken, 0:02:46.998,0:02:49.192 electrons are lighter than muons, 0:02:49.323,0:02:51.318 the top quark is much much heavier 0:02:51.349,0:02:53.657 than the quarks that make up everyday nuclei. 0:02:54.026,0:02:57.678 So, the top two lines, the symmetric lines, 0:02:57.770,0:02:59.350 cannot be all there is, 0:02:59.442,0:03:02.478 there has to be something to discriminate, 0:03:02.540,0:03:05.220 distinguish, between the different types of particle. 0:03:05.824,0:03:07.847 And that's the job of the Higgs boson, 0:03:07.924,0:03:11.076 that's the job of the two bottom lines. 0:03:11.153,0:03:15.456 Depending on how those different types of quark 0:03:15.564,0:03:17.763 or the electron and muon, 0:03:17.810,0:03:22.839 depending on how they connect to that Higgs field, that Higgs boson, 0:03:22.839,0:03:25.049 we believe they get different masses. 0:03:25.142,0:03:27.967 The symmetry between these particles is broken.