0:00:01.333,0:00:04.786 So I'm pretty sure that I'm not[br]the only one in this room 0:00:04.810,0:00:09.522 who at some point have found myself,[br]you know, looking up towards the stars, 0:00:09.546,0:00:12.180 and wondered, you know, "Are we it, 0:00:12.204,0:00:16.005 or are there other living planets[br]out there such as our own?" 0:00:17.014,0:00:20.521 I guess it is possible[br]that I'm then the only person 0:00:20.545,0:00:22.816 who has obsessed enough[br]about that question 0:00:22.840,0:00:24.458 to make it my career. 0:00:24.482,0:00:26.482 But moving on. 0:00:26.506,0:00:29.617 How do we get to this question? 0:00:29.641,0:00:32.008 Well, I would argue the first thing to do 0:00:32.032,0:00:37.450 is to turn our eyes back down from the sky[br]to our own planet, the Earth. 0:00:38.173,0:00:42.380 And think about just how lucky[br]did the Earth have to be 0:00:42.404,0:00:44.626 to be the living planet it is. 0:00:44.650,0:00:46.895 Well, it had to be[br]at least somewhat lucky. 0:00:46.919,0:00:49.427 Had we been sitting closer to the Sun 0:00:49.451,0:00:51.458 or a bit further away, 0:00:51.482,0:00:55.998 any water that we have had[br]would have boiled off or frozen over. 0:00:56.022,0:01:00.083 And I mean, it's not a given[br]that a planet has water on it. 0:01:00.107,0:01:03.725 So had we been a dry planet, 0:01:03.749,0:01:06.083 there would not have been[br]a lot of life on it. 0:01:06.107,0:01:09.664 And even if we had had all the water[br]that we have today, 0:01:09.688,0:01:11.934 if that water had not been accompanied 0:01:11.958,0:01:15.069 by the right kind of chemicals[br]to get life going, 0:01:15.093,0:01:18.012 we would have a wet planet,[br]but just as dead. 0:01:18.323,0:01:20.577 So it's so many things that can go wrong, 0:01:20.601,0:01:23.522 what are the chances that they go right? 0:01:23.546,0:01:25.983 What are the chances that the planet forms 0:01:26.007,0:01:28.657 with at least the basic ingredients needed 0:01:28.681,0:01:31.281 to have an origins of life happening? 0:01:32.515,0:01:35.166 Well, let's explore that together. 0:01:35.190,0:01:37.237 So if you're going to have[br]a living planet, 0:01:37.261,0:01:40.667 the first thing you're going to need 0:01:40.691,0:01:42.483 is a planet. 0:01:42.507,0:01:43.508 (Laughter) 0:01:43.532,0:01:45.656 But not any planet will do. 0:01:45.680,0:01:49.458 You're probably going to need[br]a rather specific and earthlike planet. 0:01:49.482,0:01:50.974 A planet that is rocky, 0:01:50.998,0:01:53.106 so you can have both oceans and land, 0:01:53.130,0:01:57.362 and it's sitting neither too close[br]nor too far away from its star, 0:01:57.386,0:01:59.838 but at the just-right temperature. 0:01:59.862,0:02:03.157 And it's just right[br]for liquid water, that is. 0:02:03.181,0:02:06.276 So how many of these planets[br]do we have in our galaxy? 0:02:06.800,0:02:10.268 Well, one of the great discoveries[br]of the past decades 0:02:10.292,0:02:12.772 is that planets are incredibly common. 0:02:13.212,0:02:16.212 Almost every star[br]has a planet around them. 0:02:16.236,0:02:17.649 Some have many. 0:02:17.673,0:02:20.562 And among these planets, 0:02:20.586,0:02:24.426 on the order of a few percent[br]are earthlike enough 0:02:24.450,0:02:28.006 that we would consider them[br]potentially living planets. 0:02:28.030,0:02:31.665 So having the right kind of planet[br]is actually not that difficult 0:02:31.689,0:02:35.927 when we consider that there's[br]about 100 billion stars in our galaxy. 0:02:35.951,0:02:40.046 So that gives you about a billion[br]potential living planets. 0:02:40.427,0:02:43.013 But it's not enough to just be[br]at the right temperature 0:02:43.037,0:02:44.847 or have the right overall composition. 0:02:44.871,0:02:47.138 You also need the right chemicals. 0:02:47.553,0:02:51.768 And what the second and important[br]ingredient to make a living planet is -- 0:02:51.792,0:02:54.720 I think it's pretty intuitive -- 0:02:54.744,0:02:56.331 it's water. 0:02:56.355,0:03:01.498 After all, we did define our planet[br]as being potentially living 0:03:01.522,0:03:04.202 if it had the right temperature[br]to keep water liquid. 0:03:04.838,0:03:08.409 And I mean, here on Earth,[br]life is water-based. 0:03:08.711,0:03:10.005 But more generally, 0:03:10.029,0:03:14.283 water is just really good[br]as a meeting place for chemicals. 0:03:14.307,0:03:16.307 It is a very special liquid. 0:03:16.331,0:03:19.911 So this is our second basic ingredient. 0:03:20.276,0:03:22.208 Now the third ingredient, I think, 0:03:22.232,0:03:24.847 is probably a little bit more surprising. 0:03:24.871,0:03:27.656 I mean, we are going to need[br]some organics in there, 0:03:27.680,0:03:29.814 since we are thinking about organic life. 0:03:30.188,0:03:31.902 But the organic molecule 0:03:31.926,0:03:35.705 that seems to be at the center[br]of the chemical networks 0:03:35.729,0:03:40.155 that can produce biomolecules[br]is hydrogen cyanide. 0:03:40.481,0:03:43.814 So for those of you who know[br]what this molecule is like, 0:03:43.838,0:03:47.219 you know it's something[br]that it's a good idea to stay away from. 0:03:47.776,0:03:48.927 But it turns out 0:03:48.951,0:03:52.117 that what's really, really bad[br]for advanced life forms, 0:03:52.141,0:03:53.799 such as yourselves, 0:03:53.823,0:03:57.307 is really, really good[br]to get the chemistry started, 0:03:57.331,0:04:00.616 the right kind of chemistry[br]that can lead to origins of life. 0:04:01.180,0:04:03.983 So now we have our three[br]ingredients that we need, 0:04:04.007,0:04:06.007 you know, the temperate planet, 0:04:06.031,0:04:08.579 water and hydrogen cyanide. 0:04:08.603,0:04:11.372 So how often do these three come together? 0:04:11.396,0:04:14.045 How many temperate planets[br]are there out there 0:04:14.069,0:04:16.536 that have water and hydrogen cyanide? 0:04:17.030,0:04:18.688 Well, in an ideal world, 0:04:18.712,0:04:24.688 we would now turn one of our telescopes[br]towards one of these temperate planets 0:04:24.712,0:04:26.275 and check for ourselves. 0:04:26.299,0:04:29.933 Just, "Do these planets have water[br]and cyanides on them?" 0:04:30.529,0:04:36.663 Unfortunately, we don't yet[br]have large enough telescopes to do this. 0:04:36.687,0:04:40.569 We can detect molecules[br]in the atmospheres of some planets. 0:04:40.593,0:04:42.196 But these are large planets 0:04:42.220,0:04:44.680 sitting often pretty close to their star, 0:04:44.704,0:04:47.490 nothing like these, you know,[br]just-right planets 0:04:47.514,0:04:48.980 that we're talking about here, 0:04:49.004,0:04:51.196 which are much smaller and further away. 0:04:51.530,0:04:53.704 So we have to come up with another way. 0:04:53.728,0:04:58.662 And the other way that we have[br]conceived of and then followed 0:04:58.686,0:05:01.305 is to instead of looking[br]for these molecules 0:05:01.329,0:05:03.519 in the planets when they exist, 0:05:03.543,0:05:07.283 is to look for them in the material[br]that's forming new planets. 0:05:07.307,0:05:11.752 So planets form in discs[br]of dust and gas around young stars. 0:05:11.776,0:05:15.895 And these discs get their material[br]from the interstellar medium. 0:05:15.919,0:05:18.633 Turns out that the empty space[br]you see between stars 0:05:18.657,0:05:22.391 when you are looking up towards them,[br]asking existential questions, 0:05:22.415,0:05:24.590 is not as empty as it seems, 0:05:24.614,0:05:26.574 but actually full of gas and dust, 0:05:26.598,0:05:28.844 which can, you know,[br]come together in clouds, 0:05:28.868,0:05:32.223 then collapses to form these discs,[br]stars and planets. 0:05:32.967,0:05:37.538 And one of the things we always see[br]when we do look at these clouds 0:05:37.562,0:05:38.967 is water. 0:05:38.991,0:05:41.665 You know, I think we have a tendency[br]to think about water 0:05:41.689,0:05:44.289 as something that's,[br]you know, special to us. 0:05:44.852,0:05:48.661 Water is one of the most abundant[br]molecules in the universe, 0:05:48.685,0:05:50.410 including in these clouds, 0:05:50.434,0:05:52.901 these star- and planet-forming clouds. 0:05:53.661,0:05:54.815 And not only that -- 0:05:54.839,0:05:56.815 water is also a pretty robust molecule: 0:05:56.839,0:05:59.236 it's actually not that easy to destroy. 0:05:59.260,0:06:02.339 So a lot of this water[br]that is in interstellar medium 0:06:02.363,0:06:07.950 will survive the rather dangerous,[br]collapsed journey from clouds 0:06:07.974,0:06:10.156 to disc, to planet. 0:06:10.967,0:06:13.046 So water is alright. 0:06:13.070,0:06:15.927 That second ingredient[br]is not going to be a problem. 0:06:15.951,0:06:20.173 Most planets are going to form[br]with some access to water. 0:06:21.125,0:06:23.458 So what about hydrogen cyanide? 0:06:23.482,0:06:27.990 Well, we also see cyanides[br]and other similar organic molecules 0:06:28.014,0:06:30.601 in these interstellar clouds. 0:06:30.625,0:06:35.910 But here, we're less certain[br]about the molecules surviving, 0:06:35.934,0:06:37.942 going from the cloud to the disc. 0:06:37.966,0:06:40.633 They're just a bit more delicate,[br]a bit more fragile. 0:06:40.657,0:06:43.992 So if we're going to know[br]that this hydrogen cyanide 0:06:44.016,0:06:47.222 is sitting in the vicinity[br]of new planets forming, 0:06:47.246,0:06:49.540 we'd really need to see it[br]in the disc itself, 0:06:49.564,0:06:51.794 in these planet-forming discs. 0:06:51.818,0:06:54.260 So about a decade ago, 0:06:54.284,0:06:59.522 I started a program[br]to look for this hydrogen cyanide 0:06:59.546,0:07:02.722 and other molecules[br]in these planet-forming discs. 0:07:02.746,0:07:05.983 And this is what we found. 0:07:06.007,0:07:08.928 So good news, in these six images, 0:07:08.952,0:07:15.069 those bright pixels represent emissions[br]originating from hydrogen cyanide 0:07:15.093,0:07:18.577 in planet-forming discs[br]hundreds of light-years away 0:07:18.601,0:07:20.625 that have made it to our telescope, 0:07:20.649,0:07:21.926 onto the detector, 0:07:21.950,0:07:24.684 allowing us to see it like this. 0:07:25.228,0:07:26.506 So the very good news 0:07:26.530,0:07:30.601 is that these discs do indeed have[br]hydrogen cyanide in them. 0:07:30.625,0:07:34.024 That last, more elusive ingredient. 0:07:35.159,0:07:40.215 Now the bad news is that we don't know[br]where in the disc it is. 0:07:40.810,0:07:42.207 If we look at these, 0:07:42.231,0:07:44.530 I mean, no one can say[br]they are beautiful images, 0:07:44.554,0:07:47.316 even at the time when we got them. 0:07:47.340,0:07:50.760 You see the pixel size is pretty big 0:07:50.784,0:07:53.911 and it's actually bigger[br]than these discs themselves. 0:07:53.935,0:07:55.391 So each pixel here 0:07:55.415,0:07:58.895 represents something that's much bigger[br]than our solar system. 0:07:59.345,0:08:01.276 And that means 0:08:01.300,0:08:05.410 that we don't know where in the disc[br]the hydrogen cyanide is coming from. 0:08:05.768,0:08:06.998 And that's a problem, 0:08:07.022,0:08:08.571 because these temperate planets, 0:08:08.595,0:08:11.553 they can't access[br]hydrogen cyanide just anywhere, 0:08:11.577,0:08:14.954 but it must be fairly close[br]to where they assemble 0:08:14.978,0:08:16.868 for them to have access to it. 0:08:16.892,0:08:22.034 So to bring this home,[br]let's think about an analogous example, 0:08:22.058,0:08:25.280 that is, of cypress growing[br]in the United States. 0:08:25.661,0:08:27.371 So let's say, hypothetically, 0:08:27.395,0:08:29.166 that you've returned from Europe 0:08:29.190,0:08:31.934 where you have seen[br]beautiful Italian cypresses, 0:08:31.958,0:08:34.371 and you want to understand, you know, 0:08:34.395,0:08:37.014 does it make sense to import them[br]to the United States. 0:08:37.038,0:08:38.672 Could you grow them here? 0:08:38.696,0:08:40.760 So you talk to the cypress experts, 0:08:40.784,0:08:42.448 they tell you that there is indeed 0:08:42.472,0:08:46.410 a band of not-too-hot, not-too-cold[br]across the United States 0:08:46.434,0:08:47.974 where you could grow them. 0:08:47.998,0:08:51.896 And if you have a nice,[br]high-resolution map or image like this, 0:08:51.920,0:08:54.745 it's quite easy to see[br]that this cypress strip 0:08:54.769,0:08:58.229 overlaps with a lot of green[br]fertile land pixels. 0:08:58.753,0:09:01.720 Even if I start degrading[br]this map quite a bit, 0:09:01.744,0:09:04.053 making it lower and lower resolution, 0:09:04.077,0:09:05.409 it's still possible to tell 0:09:05.433,0:09:09.027 that there's going to be some fertile land[br]overlapping with this strip. 0:09:09.466,0:09:14.497 But what about if the whole United States 0:09:14.521,0:09:17.727 is incorporated into a single pixel? 0:09:17.751,0:09:19.768 If the resolution is that low. 0:09:19.792,0:09:21.085 What do you do now, 0:09:21.109,0:09:26.231 how do you now tell whether you can grow[br]cypresses in the United States? 0:09:26.538,0:09:28.466 Well the answer is you can't. 0:09:28.490,0:09:30.878 I mean, there's definitely[br]some fertile land there, 0:09:30.902,0:09:33.656 or you wouldn't have[br]that green tint to the pixel, 0:09:33.680,0:09:35.649 but there's just no way of telling 0:09:35.673,0:09:38.871 whether any of that green[br]is in the right place. 0:09:38.895,0:09:41.663 And that is exactly the problem[br]we were facing 0:09:41.687,0:09:44.879 with our single-pixel[br]images of these discs 0:09:44.903,0:09:46.498 with hydrogen cyanide. 0:09:46.522,0:09:48.696 So what we need is something analogous, 0:09:48.720,0:09:51.791 at least those low-resolution maps[br]that I just showed you, 0:09:51.815,0:09:56.664 to be able to tell whether there's overlap[br]between where the hydrogen cyanide is 0:09:56.688,0:09:59.648 and where these planets[br]can access it as they are forming. 0:10:00.236,0:10:03.439 So coming to the rescue, a few years ago, 0:10:03.463,0:10:07.447 is this new, amazing,[br]beautiful telescope ALMA, 0:10:07.471,0:10:10.328 the Atacama Large Millimeter[br]and submillimeter Array 0:10:10.352,0:10:11.552 in northern Chile. 0:10:11.900,0:10:15.663 So, ALMA is amazing[br]in many different ways, 0:10:15.687,0:10:18.171 but the one that I'm going to focus on 0:10:18.195,0:10:22.116 is that, as you can see,[br]I call this one telescope, 0:10:22.140,0:10:25.475 but you can there are actually[br]many dishes in this image. 0:10:25.499,0:10:30.126 And this is a telescope[br]that consists of 66 individual dishes 0:10:30.150,0:10:31.750 that all work in unison. 0:10:32.483,0:10:35.046 And that means that you have a telescope 0:10:35.070,0:10:39.937 that is the size of the largest distance[br]that you can put these dishes 0:10:39.961,0:10:41.278 away from one another. 0:10:41.302,0:10:44.405 Which in ALMA's case are a few miles. 0:10:44.429,0:10:47.897 So you have a more[br]than mile-sized telescope. 0:10:48.267,0:10:50.140 And when you have such a big telescope, 0:10:50.164,0:10:52.665 you can zoom in on really small things, 0:10:52.689,0:10:57.561 including making maps of hydrogen cyanide[br]in these planet-forming discs. 0:10:57.585,0:11:00.410 So when ALMA came online a few years ago, 0:11:00.434,0:11:04.507 that was one of the first things[br]that I proposed that we use it for. 0:11:05.086,0:11:09.022 And what does a map of hydrogen cyanide[br]look like in a disc? 0:11:09.046,0:11:11.560 Is the hydrogen cyanide[br]at the right place? 0:11:11.584,0:11:13.695 And the answer is that it is. 0:11:13.719,0:11:15.726 So this is the map. 0:11:15.750,0:11:19.694 You see the hydrogen cyanide emission[br]being spread out across the disc. 0:11:19.718,0:11:21.568 First of all, it's almost everywhere, 0:11:21.592,0:11:23.155 which is very good news. 0:11:23.179,0:11:26.364 But you have a lot[br]of extra bright emission 0:11:26.388,0:11:29.591 coming from close to the star[br]towards the center of the disc. 0:11:29.965,0:11:33.125 And this is exactly[br]where we want to see it. 0:11:33.149,0:11:35.791 This is close to where[br]these planets are forming. 0:11:35.815,0:11:39.601 And this is not what we see[br]just towards one disc -- 0:11:39.625,0:11:41.982 here are three more examples. 0:11:42.006,0:11:44.089 You can see they all show[br]the same thing -- 0:11:44.113,0:11:46.577 lots of bright hydrogen cyanide emission 0:11:46.601,0:11:48.926 coming from close[br]to the center of the star. 0:11:49.228,0:11:51.910 For full disclosure,[br]we don't always see this. 0:11:51.934,0:11:54.466 There are discs where we see the opposite, 0:11:54.490,0:11:57.712 where there's actually a hole[br]in the emission towards the center. 0:11:57.736,0:12:00.276 So this is the opposite[br]of what we want to see, right? 0:12:00.300,0:12:02.458 This is not places where we could research 0:12:02.482,0:12:06.490 if there is any hydrogen cyanide around[br]where these planets are forming. 0:12:06.514,0:12:08.093 But in most cases, 0:12:08.117,0:12:10.125 we just don't detect hydrogen cyanide, 0:12:10.149,0:12:12.549 but we detect it in the right place. 0:12:13.038,0:12:15.077 So what does all this mean? 0:12:15.101,0:12:17.547 Well, I told you in the beginning 0:12:17.571,0:12:20.958 that we have lots[br]of these temperate planets, 0:12:20.982,0:12:22.887 maybe a billion or so of them, 0:12:22.911,0:12:25.433 that could have life develop on them 0:12:25.457,0:12:27.981 if they have the right ingredients. 0:12:28.005,0:12:29.179 And I've also shown 0:12:29.203,0:12:33.078 that we think a lot of the time,[br]the right ingredients are there -- 0:12:33.102,0:12:35.281 we have water, we have hydrogen cyanide, 0:12:35.305,0:12:37.506 there will be other[br]organic molecules as well 0:12:37.530,0:12:39.197 coming with the cyanides. 0:12:39.879,0:12:44.101 This means that planets[br]with the most basic ingredients for life 0:12:44.125,0:12:47.148 are likely to be incredibly[br]common in our galaxy. 0:12:48.133,0:12:50.688 And if all it takes for life to develop 0:12:50.712,0:12:54.014 is to have these basic[br]ingredients available, 0:12:54.038,0:12:56.901 there should be a lot[br]of living planets out there. 0:12:57.400,0:12:59.337 But that is of course a big if. 0:12:59.361,0:13:02.313 And I would say the challenge[br]of the next decades, 0:13:02.337,0:13:04.821 for both astronomy and chemistry, 0:13:04.845,0:13:07.585 is to figure out just how often 0:13:07.609,0:13:10.363 we go from having[br]a potentially living planet 0:13:10.387,0:13:12.791 to having an actually living one. 0:13:12.815,0:13:13.966 Thank you. 0:13:13.990,0:13:18.825 (Applause)