1 00:00:01,560 --> 00:00:02,600 The Earth... 2 00:00:04,000 --> 00:00:05,640 ..third rock from the Sun. 3 00:00:07,920 --> 00:00:09,360 And it's unique... 4 00:00:12,320 --> 00:00:13,760 ..it has life. 5 00:00:16,080 --> 00:00:20,080 So how do you make a planet like ours? 6 00:00:20,080 --> 00:00:22,400 I'm going to open up the cosmic tool box 7 00:00:22,400 --> 00:00:23,920 and work it out. 8 00:00:23,920 --> 00:00:27,360 We're going to build a planet, up there... 9 00:00:29,800 --> 00:00:33,040 ..at the top of this impossibly high tower. 10 00:00:37,920 --> 00:00:40,560 It gives us the perfect platform 11 00:00:40,560 --> 00:00:44,440 to make something really big. 12 00:00:47,480 --> 00:00:50,520 Up here, we can do in seconds 13 00:00:50,520 --> 00:00:54,360 what it takes nature millions or billions of years to do. 14 00:00:59,240 --> 00:01:02,320 We are going to build our planet... 15 00:01:02,320 --> 00:01:04,720 brick by brick. 16 00:01:18,760 --> 00:01:22,000 But to do that, I'm going to need help. 17 00:01:24,440 --> 00:01:27,760 And I'll find it in the most unlikely places. 18 00:01:29,520 --> 00:01:32,360 Right now, I am effectively weightless. 19 00:01:32,360 --> 00:01:34,800 I'm on the ceiling. I am ON the ceiling. 20 00:01:36,040 --> 00:01:38,640 Of course, as with any construction work... 21 00:01:41,680 --> 00:01:43,360 ..there will be hiccups. 22 00:01:46,480 --> 00:01:49,760 But out of these mistakes will come real insights 23 00:01:49,760 --> 00:01:52,920 into what makes our planet, our solar system, 24 00:01:52,920 --> 00:01:57,080 exactly right for us - for life. 25 00:01:57,080 --> 00:01:58,960 As an engineering challenge, 26 00:01:58,960 --> 00:02:00,480 it doesn't get much bigger. 27 00:02:27,880 --> 00:02:32,680 I love it here on this hill. 28 00:02:32,680 --> 00:02:34,040 Feels like it was made 29 00:02:34,040 --> 00:02:36,880 for bracing Sunday walks with the family. 30 00:02:40,200 --> 00:02:42,640 And indeed most weekend mornings, 31 00:02:42,640 --> 00:02:45,400 the place is full of parents with their kids, 32 00:02:45,400 --> 00:02:47,760 including me with mine, sometimes. 33 00:02:47,760 --> 00:02:51,800 And when I was on those same family Sunday morning walks, 34 00:02:51,800 --> 00:02:52,960 as a kid myself, 35 00:02:52,960 --> 00:02:57,680 I spent as much of my time looking down as I did up and round. 36 00:02:57,680 --> 00:03:01,400 Rocks, stones, the very stuff of the Earth - 37 00:03:01,400 --> 00:03:02,960 they fascinated me. 38 00:03:02,960 --> 00:03:07,080 And amongst my finds was one I felt particularly important - 39 00:03:07,080 --> 00:03:09,280 a rock the size of your fist. 40 00:03:09,280 --> 00:03:13,120 A rich brown - dimpled, heavy, glinting, 41 00:03:13,120 --> 00:03:15,560 somehow special. 42 00:03:15,560 --> 00:03:18,720 It became one of my most treasured childhood possessions. 43 00:03:18,720 --> 00:03:20,840 I was convinced it was a meteorite - 44 00:03:20,840 --> 00:03:24,480 a rock that had landed here from space. 45 00:03:25,640 --> 00:03:26,720 Morning. 46 00:03:33,240 --> 00:03:36,600 Like most treasured childhood possessions, 47 00:03:36,600 --> 00:03:41,720 it got lost or swapped, probably wasn't even a real meteorite anyway. 48 00:03:41,720 --> 00:03:44,600 But it didn't matter because it had done its job - 49 00:03:44,600 --> 00:03:47,600 it sparked my interest in space, 50 00:03:47,600 --> 00:03:49,960 the idea of "out there". 51 00:03:56,800 --> 00:04:00,680 Like most kids, I suppose, I believed that "out there" 52 00:04:00,680 --> 00:04:03,440 would be full of planets like the Earth. 53 00:04:03,440 --> 00:04:05,920 Each of them full of life, 54 00:04:05,920 --> 00:04:08,560 even if it wasn't quite the same as ours. 55 00:04:10,960 --> 00:04:12,840 But as it turns out, 56 00:04:12,840 --> 00:04:16,680 the planet we live on is very, very special. 57 00:04:24,400 --> 00:04:27,400 As far as we know, our Earth 58 00:04:27,400 --> 00:04:31,120 is the only place in the solar system with life. 59 00:04:34,360 --> 00:04:36,640 To understand why, 60 00:04:36,640 --> 00:04:39,640 we are going to build our own planet... 61 00:04:42,040 --> 00:04:44,120 ..at the top of that tower. 62 00:04:59,640 --> 00:05:02,400 And to do that, 63 00:05:02,400 --> 00:05:05,360 first we have to gather up the basic raw materials... 64 00:05:07,480 --> 00:05:12,520 ..all the big ingredients we need to start making a planet. 65 00:05:12,520 --> 00:05:13,960 All right, all right! 66 00:05:15,640 --> 00:05:17,120 And here comes my delivery now... 67 00:05:19,040 --> 00:05:20,080 ..right on time. 68 00:05:32,880 --> 00:05:38,120 OK, so how much stuff do we need to build a planet like the Earth? 69 00:05:41,400 --> 00:05:45,440 I know that the entire Earth weighs around six septillion kilograms, 70 00:05:45,440 --> 00:05:48,880 that's a six followed by 24 zeros. 71 00:05:50,600 --> 00:05:52,600 But let's be sensible here, 72 00:05:52,600 --> 00:05:55,520 I've ordered the main planetary raw materials 73 00:05:55,520 --> 00:05:58,200 and in the right proportions 74 00:05:58,200 --> 00:06:00,080 but I've had to scale the delivery down... 75 00:06:01,080 --> 00:06:02,520 ..a bit. 76 00:06:28,240 --> 00:06:31,760 Now, you'd think that our living Earth 77 00:06:31,760 --> 00:06:34,400 would be made up of countless different things. 78 00:06:34,400 --> 00:06:37,680 But actually, it's constructed almost entirely 79 00:06:37,680 --> 00:06:40,720 out of just four basic ingredients. 80 00:06:40,720 --> 00:06:44,160 So that's what my convoy has delivered. 81 00:06:44,160 --> 00:06:47,640 On these trucks - girders, iron girders. 82 00:06:47,640 --> 00:06:50,280 Like most big construction projects, 83 00:06:50,280 --> 00:06:52,120 we are going to need a lot of iron. 84 00:06:54,600 --> 00:06:56,360 Ah, we need this... 85 00:06:59,000 --> 00:07:01,040 ..oxygen. 86 00:07:01,040 --> 00:07:02,840 And over here... 87 00:07:04,280 --> 00:07:05,400 ..sand... 88 00:07:09,960 --> 00:07:12,480 ..that's rich in silicon. 89 00:07:15,840 --> 00:07:18,600 Magnesium, like you find in alloy wheels. 90 00:07:21,120 --> 00:07:23,400 The convoy has brought the elements 91 00:07:23,400 --> 00:07:27,080 in exactly the same proportion as we'd find on Earth. 92 00:07:29,880 --> 00:07:33,440 So, there are 15 trucks laden with magnesium 93 00:07:33,440 --> 00:07:38,000 because 15% of our planet is made from magnesium. 94 00:07:39,000 --> 00:07:43,000 There are 16 trucks for the 16% that's silicon. 95 00:07:43,000 --> 00:07:46,120 30 trucks carrying oxygen. 96 00:07:46,120 --> 00:07:49,440 And a column of 32 trucks with iron girders 97 00:07:49,440 --> 00:07:52,800 because almost a third of our planet is made of iron. 98 00:07:54,720 --> 00:07:59,120 It is incredible to think that just these four elements 99 00:07:59,120 --> 00:08:02,240 make up 93% of our planet. 100 00:08:02,240 --> 00:08:04,800 The rest is elemental seasoning. 101 00:08:04,800 --> 00:08:07,760 HORN TOOTS 102 00:08:07,760 --> 00:08:12,520 And here's Billy Bob with some of the remaining ingredients... 103 00:08:12,520 --> 00:08:13,920 which are tiny. 104 00:08:14,960 --> 00:08:16,160 Hydrogen... 105 00:08:17,800 --> 00:08:19,240 ..aluminium, 106 00:08:19,240 --> 00:08:21,040 a pinch of salt, 107 00:08:21,040 --> 00:08:23,280 calcium. 108 00:08:23,280 --> 00:08:25,480 The question now is 109 00:08:25,480 --> 00:08:29,360 how does all of this turn into a planet? 110 00:08:36,480 --> 00:08:40,560 To find out, I need to take these basic planetary elements 111 00:08:40,560 --> 00:08:43,400 and stick them in a blender. 112 00:08:51,440 --> 00:08:55,000 And I'm going to do that at the top of our tower, 113 00:08:55,000 --> 00:08:58,640 where there's a sky-full of room to break down my ingredients. 114 00:09:03,360 --> 00:09:07,160 The thing is, our planet didn't just pop into existence. 115 00:09:07,160 --> 00:09:11,160 It started out as a swirling cloud of elemental dust, 116 00:09:11,160 --> 00:09:13,880 floating in the great void of space. 117 00:09:13,880 --> 00:09:16,840 So that's how I am going to have to start, as well. 118 00:10:05,840 --> 00:10:07,480 In case you're wondering, 119 00:10:07,480 --> 00:10:09,080 yes, I am... 120 00:10:10,560 --> 00:10:12,160 ..scared of heights, that is. 121 00:10:12,160 --> 00:10:15,800 High...really high. 122 00:10:29,640 --> 00:10:34,920 4.5 billion years ago, before the Earth began to form, 123 00:10:34,920 --> 00:10:38,720 this dust and gas was all there was. 124 00:11:03,600 --> 00:11:07,400 So, how do we get from this cloud of dust 125 00:11:07,400 --> 00:11:09,640 to a planet like the Earth? 126 00:11:09,640 --> 00:11:11,920 We need something to bind it all together, 127 00:11:11,920 --> 00:11:14,080 a sort of cosmic superglue. 128 00:11:14,080 --> 00:11:17,480 Now, you might think that'd be gravity. Right? 129 00:11:17,480 --> 00:11:18,560 Wrong. 130 00:11:36,400 --> 00:11:41,400 The best way to find out what this super-strong planetary glue is 131 00:11:41,400 --> 00:11:43,560 is to discover its power 132 00:11:43,560 --> 00:11:47,120 in the weightless environment of space. 133 00:11:50,480 --> 00:11:53,120 It's why I've come to this Air Force base, 134 00:11:53,120 --> 00:11:55,120 where astronauts are trained. 135 00:11:59,040 --> 00:12:01,520 I'll be honest, I am pretty thrilled right now 136 00:12:01,520 --> 00:12:03,440 because I'm about to boldly go 137 00:12:03,440 --> 00:12:06,840 where quite few have gone before. 138 00:12:06,840 --> 00:12:08,480 I'm not actually going into space. 139 00:12:08,480 --> 00:12:10,160 There were budgetary issues with that. 140 00:12:10,160 --> 00:12:12,600 But never mind because we have come up with 141 00:12:12,600 --> 00:12:14,640 the very next best thing for our purposes. 142 00:12:14,640 --> 00:12:16,800 Where I'm headed is over there. 143 00:12:27,240 --> 00:12:30,880 This plane offers thrill-seekers something unique - 144 00:12:30,880 --> 00:12:33,360 it can cancel out the Earth's gravity. 145 00:12:36,200 --> 00:12:40,480 For me, it means I can recreate the conditions in which 146 00:12:40,480 --> 00:12:43,680 that elemental dust began to make a planet. 147 00:12:45,120 --> 00:12:48,080 Hi, how are you doing? Richard, hey. Good to see you. Welcome aboard. 148 00:12:48,080 --> 00:12:50,680 Are you ready...? I'm ready! Ready for a unique experience? 149 00:12:50,680 --> 00:12:54,160 I don't know, I've never tried it, obviously. Let's see. 150 00:12:54,160 --> 00:12:58,920 'On today's flight, my chaperone is Dan Durda...' Thank you. 151 00:12:58,920 --> 00:13:01,960 '..an expert on space dust.' 152 00:13:01,960 --> 00:13:03,400 All right, Richard. I think... 153 00:13:03,400 --> 00:13:05,720 Which seat are you here? I'm 2F. I'm just... 154 00:13:05,720 --> 00:13:08,760 In the context, having this conversation is hilarious. 155 00:13:08,760 --> 00:13:12,320 I should imagine all astronauts do this. 156 00:13:12,320 --> 00:13:14,160 The attendant service on the space flights 157 00:13:14,160 --> 00:13:16,720 is not quite up to par, though. I was wondering about that. 158 00:13:16,720 --> 00:13:19,440 Do they have, like, a trolley with all the space food on it? 159 00:13:19,440 --> 00:13:21,920 I've got a window seat but there is no window. 160 00:13:21,920 --> 00:13:24,360 That's on purpose. I don't doubt it. 161 00:13:33,640 --> 00:13:35,040 A lack of windows 162 00:13:35,040 --> 00:13:38,120 isn't the only strange thing about this plane. 163 00:13:38,120 --> 00:13:40,680 It's also got a padded interior, 164 00:13:40,680 --> 00:13:43,200 sort of like a flying asylum. 165 00:13:44,600 --> 00:13:47,680 That's because, within 15 minutes, 166 00:13:47,680 --> 00:13:50,360 we are going to experience weightlessness. 167 00:13:53,360 --> 00:13:55,600 And those zero gravity conditions 168 00:13:55,600 --> 00:13:59,640 will allow Dan to show me a fascinating experiment. 169 00:13:59,640 --> 00:14:02,000 Inside this Perspex box 170 00:14:02,000 --> 00:14:04,400 is the next step to building a planet. 171 00:14:05,880 --> 00:14:08,320 We're going to simulate the way the planets formed 172 00:14:08,320 --> 00:14:10,640 in the very earliest days of the solar system. 173 00:14:10,640 --> 00:14:13,080 Instead of microscopic dust particles, 174 00:14:13,080 --> 00:14:15,320 I've got coffee - ordinary coffee. 175 00:14:15,320 --> 00:14:18,120 So in this little box, we're going to see exhibited 176 00:14:18,120 --> 00:14:20,200 what it was that brought stuff together? 177 00:14:20,200 --> 00:14:23,720 Absolutely. So this is what kick-starts the whole process? 178 00:14:23,720 --> 00:14:25,640 Big things have small beginnings. 179 00:14:25,640 --> 00:14:27,280 So it all starts with a coffee? 180 00:14:27,280 --> 00:14:29,640 It all starts with early coffee. Just like my day. 181 00:14:29,640 --> 00:14:31,760 It does all start with a coffee. Even the solar system. 182 00:14:31,760 --> 00:14:33,480 As it turns out! We shall see. 183 00:14:33,480 --> 00:14:35,280 Right, switch the gravity off, then. 184 00:14:35,280 --> 00:14:37,000 That's right! 185 00:14:37,000 --> 00:14:38,640 It doesn't work, it's broken. 186 00:14:39,680 --> 00:14:43,320 The plane is now climbing to 34,000 feet. 187 00:14:44,560 --> 00:14:48,600 Once there, it'll throttle back down to Earth in a steep arc, 188 00:14:48,600 --> 00:14:51,080 perfectly judged so that inside, 189 00:14:51,080 --> 00:14:55,120 we're falling at the same rate as the plane drops. 190 00:14:55,120 --> 00:14:57,000 The result - 191 00:14:57,000 --> 00:15:00,880 a few moments of weightlessness. 192 00:15:00,880 --> 00:15:02,240 Oh, yeah! 193 00:15:02,240 --> 00:15:04,440 Oh, I swam, I did swim. 194 00:15:04,440 --> 00:15:05,920 Oh, that's peculiar. 195 00:15:05,920 --> 00:15:08,120 Oh, look at that! Beautiful. Oh, we got it! 196 00:15:08,120 --> 00:15:10,800 Look at! See, that's what I was trying to show you. 197 00:15:10,800 --> 00:15:12,400 Unfortunately, I'm upside down. 198 00:15:12,400 --> 00:15:15,600 I can't! I can't...it's over there. Here we go. 199 00:15:15,600 --> 00:15:16,640 Hang on, it's... 200 00:15:16,640 --> 00:15:19,000 You come here to do these experiments all the time. 201 00:15:19,000 --> 00:15:21,880 Right, I'm going to watch but I'm going to do it upside down. 202 00:15:21,880 --> 00:15:23,760 Why are you better at this than I am? 203 00:15:23,760 --> 00:15:26,520 I'm really struggling. I'm... 204 00:15:26,520 --> 00:15:28,600 Gravity, there it is. DAN LAUGHS 205 00:15:31,720 --> 00:15:33,320 What are we looking for? 206 00:15:33,320 --> 00:15:36,160 We're now weightless. That's how our planet started. 207 00:15:36,160 --> 00:15:38,480 So these clumps, what's bringing them together? 208 00:15:38,480 --> 00:15:40,400 Electrostatic forces. 209 00:15:40,400 --> 00:15:42,560 Electrostatic's clumping this coffee together. 210 00:15:42,560 --> 00:15:45,680 So this is the effect, this is what starts it all off. 211 00:15:45,680 --> 00:15:48,240 It's hard to concentrate when I'm floating. 212 00:15:48,240 --> 00:15:50,200 That's not gravity causing that clumping. 213 00:15:50,200 --> 00:15:52,000 That's electrostatics. I'm on the roof! 214 00:15:52,000 --> 00:15:54,000 How did I get on the roof? And now I'm on the floor. 215 00:15:56,080 --> 00:15:59,760 Now gravity is coming back into play... And it's all gone. ..and it doesn't work. 216 00:15:59,760 --> 00:16:01,240 That's why we're weightless, 217 00:16:01,240 --> 00:16:03,560 to see phenomena that we can't normally see 218 00:16:03,560 --> 00:16:04,680 when gravity's turned on. 219 00:16:06,720 --> 00:16:08,440 So what's happening here? 220 00:16:09,520 --> 00:16:13,320 These coffee grains, like that first cosmic dust, 221 00:16:13,320 --> 00:16:15,560 rub together as they float. 222 00:16:18,360 --> 00:16:20,840 This means individual grains 223 00:16:20,840 --> 00:16:24,000 get either negatively or positively charged. 224 00:16:26,480 --> 00:16:30,200 And this static charge means they stick together... 225 00:16:34,000 --> 00:16:37,080 ..just like the fledgling particles of the Earth 226 00:16:37,080 --> 00:16:39,080 4.5 billion years ago. 227 00:16:44,360 --> 00:16:46,880 This is as near as we're going to get 228 00:16:46,880 --> 00:16:50,280 to being out there with those particles without gravity. 229 00:16:50,280 --> 00:16:51,760 How cool is that?! 230 00:16:52,840 --> 00:16:55,040 Oh! HE LAUGHS 231 00:17:01,520 --> 00:17:03,480 Congratulations! Thank you for that. 232 00:17:03,480 --> 00:17:05,160 I enjoyed it, thank you. 233 00:17:05,160 --> 00:17:07,200 I need you to know that I did that 234 00:17:07,200 --> 00:17:09,400 only because it was the best way of demonstrating 235 00:17:09,400 --> 00:17:11,880 an essential principle in building a planet 236 00:17:11,880 --> 00:17:13,840 and not because I had any fun at all. 237 00:17:13,840 --> 00:17:15,680 It was...yeah, it's quite boring. 238 00:17:15,680 --> 00:17:16,880 I loved that! 239 00:17:24,240 --> 00:17:26,640 So, around our planet-building tower, 240 00:17:26,640 --> 00:17:30,040 we've bound together those first clumps of dust 241 00:17:30,040 --> 00:17:31,840 without gravity present. 242 00:17:32,920 --> 00:17:34,240 But there is a problem. 243 00:17:36,800 --> 00:17:39,840 Electrostatic forces are very strong 244 00:17:39,840 --> 00:17:43,120 but are only effective over tiny distances. 245 00:17:47,840 --> 00:17:49,760 Beyond a certain point, 246 00:17:49,760 --> 00:17:51,960 about the size of gravel, 247 00:17:51,960 --> 00:17:54,080 the dust stops growing. 248 00:17:58,320 --> 00:18:02,600 So our planet-building plans have ground to a halt 249 00:18:02,600 --> 00:18:05,840 with nothing to show beyond bigger bits of dust. 250 00:18:05,840 --> 00:18:07,880 We need another force 251 00:18:07,880 --> 00:18:10,720 to somehow grow them more. 252 00:18:10,720 --> 00:18:14,400 I think it's time to introduce a little gravity to the situation. 253 00:18:25,440 --> 00:18:30,840 How, then, does gravity take those bigger bits of dust and gravel, 254 00:18:30,840 --> 00:18:33,680 and turn them into rocks 255 00:18:33,680 --> 00:18:35,800 or even an entire planet? 256 00:18:42,080 --> 00:18:44,840 At a concealed underground laboratory, 257 00:18:44,840 --> 00:18:48,480 I'm told there's a secret device 258 00:18:48,480 --> 00:18:50,520 that will help me find the answer. 259 00:18:57,840 --> 00:19:01,320 Until 2001, this was a gold mine. 260 00:19:01,320 --> 00:19:04,440 Now, it's at the cutting edge of scientific research. 261 00:19:16,600 --> 00:19:18,600 My goal lies 262 00:19:18,600 --> 00:19:21,800 nearly a kilometre and a half straight down. 263 00:19:23,240 --> 00:19:26,920 I'm going deeper underground than I've ever been before. 264 00:19:28,920 --> 00:19:30,360 You know in disaster movies... 265 00:19:31,760 --> 00:19:33,200 ..when things go wrong 266 00:19:33,200 --> 00:19:36,880 in things like giant lifts going a mile underground - 267 00:19:36,880 --> 00:19:40,000 the short guy never lasts very long, does he? 268 00:19:40,000 --> 00:19:42,240 Just thinking that out loud. 269 00:19:46,600 --> 00:19:48,600 More and more rock flashing past. 270 00:19:48,600 --> 00:19:50,040 Still plunging. 271 00:19:52,280 --> 00:19:54,720 Still, plunging is better than plummeting. 272 00:19:56,960 --> 00:19:59,800 At the bottom of this shaft is an instrument 273 00:19:59,800 --> 00:20:03,040 that's part of a global gravity research experiment. 274 00:20:03,040 --> 00:20:05,600 Apparently, it's going to help us understand 275 00:20:05,600 --> 00:20:08,120 how gravity can grow a planet from gravel. 276 00:20:21,960 --> 00:20:25,520 In the tunnels of these, the Sandford Labs, 277 00:20:25,520 --> 00:20:29,440 scientists are unravelling the workings of the universe. 278 00:20:29,440 --> 00:20:32,400 ALARM BLARES 279 00:20:34,520 --> 00:20:37,920 I might not look it but I feel a bit like James Bond - 280 00:20:37,920 --> 00:20:41,840 summoned to the underground lair of an international super-baddie. 281 00:20:45,280 --> 00:20:47,760 And here is what I've come to see. 282 00:20:47,760 --> 00:20:50,600 Meet Dr Gnome. 283 00:20:50,600 --> 00:20:54,120 Now the good doctor here is no common or garden gnome. 284 00:20:54,120 --> 00:20:57,320 He is a precision instrument of science. 285 00:20:57,320 --> 00:21:00,440 He's special because he has a super-tough coating 286 00:21:00,440 --> 00:21:03,160 that means he can't be chipped or damaged easily. 287 00:21:03,160 --> 00:21:05,240 So you would think that wherever he went, 288 00:21:05,240 --> 00:21:08,040 he remained exactly the same. 289 00:21:08,040 --> 00:21:09,720 Looks the same. 290 00:21:09,720 --> 00:21:11,080 Same expression - 291 00:21:11,080 --> 00:21:13,080 slightly puzzled. 292 00:21:15,680 --> 00:21:19,640 Well, scientists have taken Dr Gnome all over the world. 293 00:21:22,120 --> 00:21:23,680 And wherever he's been, 294 00:21:23,680 --> 00:21:27,800 he's been weighed with high precision scales. 295 00:21:27,800 --> 00:21:31,000 And it's his weight that helps explain 296 00:21:31,000 --> 00:21:35,280 how gravity can turn gravel into a planet. 297 00:21:37,280 --> 00:21:40,280 It's my job now to weigh him down here, 298 00:21:40,280 --> 00:21:42,800 a mile down beneath the surface, 299 00:21:42,800 --> 00:21:45,000 in laboratory conditions. 300 00:21:45,000 --> 00:21:48,320 So let's zero the machine, pop him on. 301 00:21:51,640 --> 00:21:54,960 And as you can see, the doctor tipping the scales 302 00:21:54,960 --> 00:21:57,960 at 330.95g. 303 00:21:57,960 --> 00:21:59,440 In the interest of thoroughness, 304 00:21:59,440 --> 00:22:02,880 he has been weighed in a number of other locations down here. 305 00:22:04,320 --> 00:22:07,600 And in all of them, we got the same reading. 306 00:22:07,600 --> 00:22:10,160 A kilometre and a half under the surface, 307 00:22:10,160 --> 00:22:13,840 he weighs 330.95g. 308 00:22:15,880 --> 00:22:18,240 And now we must travel back up to the surface 309 00:22:18,240 --> 00:22:21,080 where we shall finish this experiment. 310 00:22:21,080 --> 00:22:25,000 Right then, Doctor, you just sit there. I'll do all the walking. 311 00:22:29,280 --> 00:22:32,240 The doctor has to travel first class. 312 00:22:36,920 --> 00:22:40,880 It's vitally important that he isn't damaged on the way up, 313 00:22:40,880 --> 00:22:44,520 or picks up any dirt that might interfere with readings. 314 00:22:57,320 --> 00:22:59,560 OK, Doctor, 315 00:22:59,560 --> 00:23:03,000 time to weigh you up here, on the surface. 316 00:23:03,000 --> 00:23:05,120 Zero the machine, 317 00:23:05,120 --> 00:23:06,280 let it calm down... 318 00:23:07,680 --> 00:23:08,720 ..and here we go. 319 00:23:11,240 --> 00:23:12,720 Look at that! 320 00:23:12,720 --> 00:23:16,200 You are 0.06g heavier up here 321 00:23:16,200 --> 00:23:18,120 than you were down there. 322 00:23:18,120 --> 00:23:20,080 I honestly didn't expect that. 323 00:23:20,080 --> 00:23:21,720 But just to be sure, 324 00:23:21,720 --> 00:23:24,560 he needs to be weighed in some other places. 325 00:23:26,360 --> 00:23:28,000 And sure enough - 326 00:23:28,000 --> 00:23:31,360 331.01g. 327 00:23:31,360 --> 00:23:34,200 The doctor is showing a consistent weight gain 328 00:23:34,200 --> 00:23:35,960 of six hundredths of a gram 329 00:23:35,960 --> 00:23:39,680 up here on the surface, compared to when he was down below. 330 00:23:43,840 --> 00:23:46,840 Have you been secretly snacking?! 331 00:23:46,840 --> 00:23:50,320 I can assure you that Dr Gnome hasn't grown on the way up. 332 00:23:50,320 --> 00:23:52,960 His weight gain can be explained 333 00:23:52,960 --> 00:23:54,600 by Earth's gravity. 334 00:23:56,440 --> 00:23:59,480 Gravity is THE universal force 335 00:23:59,480 --> 00:24:01,720 that attracts one thing to another. 336 00:24:05,720 --> 00:24:07,840 When we measure something's weight, 337 00:24:07,840 --> 00:24:11,680 we are actually measuring the Earth's gravitational pull. 338 00:24:13,720 --> 00:24:17,040 So why has the doctor's weight changed? 339 00:24:18,200 --> 00:24:20,840 Well, it's largely to do with differences 340 00:24:20,840 --> 00:24:23,240 in the amount of rock underfoot. 341 00:24:25,080 --> 00:24:28,960 Up here on the surface, there is a good mile more rock 342 00:24:28,960 --> 00:24:30,760 beneath me and Dr Gnome 343 00:24:30,760 --> 00:24:33,200 than there is in the lab down there, 344 00:24:33,200 --> 00:24:36,240 meaning more planetary bulk pulling down on us, 345 00:24:36,240 --> 00:24:38,680 making for a heavier Dr Gnome up here 346 00:24:38,680 --> 00:24:39,840 than down there. 347 00:24:39,840 --> 00:24:41,920 Nothing's changed about the gnome. 348 00:24:41,920 --> 00:24:43,560 What's changed is gravity. 349 00:24:45,760 --> 00:24:49,680 Our experiment shows that the more massive something is, 350 00:24:49,680 --> 00:24:52,280 the stronger its gravitational pull. 351 00:24:53,720 --> 00:24:57,560 So in space, around 4.5 billion years ago, 352 00:24:57,560 --> 00:25:00,920 when there were no planets, just those elemental clumps, 353 00:25:00,920 --> 00:25:03,720 any difference in the size of those clumps 354 00:25:03,720 --> 00:25:06,440 would have mattered, because of gravity. 355 00:25:15,880 --> 00:25:19,840 If we add gravity to our orbiting swarm of dust, 356 00:25:19,840 --> 00:25:24,360 we start to see the larger bits attracting the smaller bits. 357 00:25:25,800 --> 00:25:27,680 Because they are bigger, 358 00:25:27,680 --> 00:25:31,520 they have a stronger gravitational pull. 359 00:25:31,520 --> 00:25:33,720 The bigger they are, 360 00:25:33,720 --> 00:25:35,720 the bigger they get. 361 00:25:35,720 --> 00:25:37,600 They start to become rocks. 362 00:25:38,840 --> 00:25:40,440 And the larger rocks 363 00:25:40,440 --> 00:25:42,440 draw in the smaller ones. 364 00:25:43,520 --> 00:25:47,200 In space, a rock just a kilometre wide 365 00:25:47,200 --> 00:25:50,240 can grow to a near Earth-sized planet 366 00:25:50,240 --> 00:25:52,240 in just a few million years. 367 00:25:54,040 --> 00:25:55,680 Around our tower, 368 00:25:55,680 --> 00:25:57,480 we can do it in seconds. 369 00:25:59,120 --> 00:26:02,120 And we're seeing something really promising. 370 00:26:06,360 --> 00:26:09,920 The exciting thing is that even though that process 371 00:26:09,920 --> 00:26:12,320 began 4.5 billion years ago - 372 00:26:12,320 --> 00:26:14,560 on Earth, it hasn't finished. 373 00:26:14,560 --> 00:26:16,200 Because if you know where to look, 374 00:26:16,200 --> 00:26:19,840 you can see where gravity is still shaping our planet, today. 375 00:26:29,000 --> 00:26:31,520 Out in Arizona's Badlands, 376 00:26:31,520 --> 00:26:34,480 there is breathtaking evidence 377 00:26:34,480 --> 00:26:37,320 of how gravity is still building the Earth. 378 00:26:48,480 --> 00:26:51,320 This is the Barringer Crater. 379 00:26:53,240 --> 00:26:56,840 When this vast crater was first discovered, 380 00:26:56,840 --> 00:26:59,440 many believed it to be an extinct volcano. 381 00:27:01,280 --> 00:27:02,560 But in fact, 382 00:27:02,560 --> 00:27:05,480 it was created by a meteorite. 383 00:27:09,600 --> 00:27:12,720 This 1.2km wide hole 384 00:27:12,720 --> 00:27:14,480 is an impact crater. 385 00:27:16,880 --> 00:27:20,600 And it's given scientists like Matt Genge 386 00:27:20,600 --> 00:27:24,240 a unique insight into how planets are built. 387 00:27:39,480 --> 00:27:43,440 Matt, how are you? Hello, mate. Sorry about the dust. Wow! 388 00:27:43,440 --> 00:27:45,600 This crater is the scar 389 00:27:45,600 --> 00:27:49,000 left by an incredibly violent impact. 390 00:27:49,000 --> 00:27:53,440 If you look at the crater wall, you can see the strata... 391 00:27:54,840 --> 00:27:57,960 ..beds of rock, running across the crater. Yes. 392 00:27:57,960 --> 00:28:01,040 There's this nice red layer of rocks. 393 00:28:01,040 --> 00:28:04,080 Above and below, there's some lighter coloured rocks 394 00:28:04,080 --> 00:28:06,680 and they're actually the same band of rocks. 395 00:28:06,680 --> 00:28:10,560 That layer has been folded over the red layer, red layers, 396 00:28:10,560 --> 00:28:12,320 like the cheese in a sandwich. 397 00:28:12,320 --> 00:28:15,240 But they've been folded over all the way round the crater, 398 00:28:15,240 --> 00:28:19,680 like they've been thrown outwards and have collapsed back. 399 00:28:19,680 --> 00:28:22,680 How big was it? Cos it's a really big crater. 400 00:28:22,680 --> 00:28:27,040 We think the object itself was probably only about 30m in size. 401 00:28:27,040 --> 00:28:30,680 So a couple of double-decker buses back-to-back. 402 00:28:30,680 --> 00:28:33,920 And it made a hole that big? It made a hole that big. Why? 403 00:28:33,920 --> 00:28:36,760 Simply because of how fast it was moving. 404 00:28:36,760 --> 00:28:39,000 So by the time it fell towards the Earth, 405 00:28:39,000 --> 00:28:41,680 it gets faster and faster as it falls towards the Earth, 406 00:28:41,680 --> 00:28:46,920 hits the ground maybe at 26,000mph. 407 00:28:46,920 --> 00:28:48,600 And the energy... 408 00:28:50,080 --> 00:28:54,120 ..the kinetic energy associated with that speed 409 00:28:54,120 --> 00:28:57,480 is so huge, it's around two megatons, 410 00:28:57,480 --> 00:29:00,600 that it blew all that material outwards. 411 00:29:00,600 --> 00:29:05,000 The rocks actually flowed like water out of the crater. 412 00:29:05,000 --> 00:29:07,200 So this whole... all this area has been affected? 413 00:29:07,200 --> 00:29:08,840 It's not just the big hole, then, 414 00:29:08,840 --> 00:29:11,120 it's everything around that we're on. Absolutely, yeah. 415 00:29:11,120 --> 00:29:13,920 All of this. In fact, if you were here before the crater was formed, 416 00:29:13,920 --> 00:29:15,960 you'd have had all that rock on top of your head, 417 00:29:15,960 --> 00:29:18,720 so you wouldn't have been very happy. No, that would have been bad. 418 00:29:22,880 --> 00:29:26,240 The meteorite was just 30m wide 419 00:29:26,240 --> 00:29:29,680 but the shockwave of its impact would have been enough 420 00:29:29,680 --> 00:29:33,640 to obliterate a brick wall 60km away. 421 00:29:41,480 --> 00:29:43,640 The Barringer Crater is evidence 422 00:29:43,640 --> 00:29:45,760 of how gravity builds a planet. 423 00:29:47,080 --> 00:29:50,600 Because every meteorite that plummets to the ground 424 00:29:50,600 --> 00:29:54,600 is drawn in by the Earth's gravitational pull. 425 00:29:56,040 --> 00:29:59,280 So when did all this happen, then? How old is that? 426 00:29:59,280 --> 00:30:04,520 So the crater itself is about 50,000 years old. 427 00:30:04,520 --> 00:30:08,160 But we actually know that meteorites like this 428 00:30:08,160 --> 00:30:10,160 have been falling on Earth 429 00:30:10,160 --> 00:30:13,240 throughout the Earth's history, for the last 4.5 billion years. 430 00:30:13,240 --> 00:30:15,280 In fact, in the past, 431 00:30:15,280 --> 00:30:17,000 they were much more frequent. 432 00:30:17,000 --> 00:30:19,520 So back when the Earth was forming, 433 00:30:19,520 --> 00:30:23,600 that bombardment was continual. 434 00:30:23,600 --> 00:30:27,720 There was probably one of them every few minutes. 435 00:30:27,720 --> 00:30:30,280 These were the objects that were making the Earth. 436 00:30:34,960 --> 00:30:36,720 Billions of years later, 437 00:30:36,720 --> 00:30:40,320 meteorite fragments that survived the initial impact 438 00:30:40,320 --> 00:30:43,280 offer a glimpse into the earliest moments 439 00:30:43,280 --> 00:30:44,920 of a planet's formation. 440 00:30:50,640 --> 00:30:52,520 This is rather a special meteorite. 441 00:30:53,680 --> 00:30:56,480 It fell in Mexico 442 00:30:56,480 --> 00:30:59,360 in 1969 443 00:30:59,360 --> 00:31:02,200 and it's called Allende. 444 00:31:02,200 --> 00:31:04,040 We give meteorites names. 445 00:31:04,040 --> 00:31:07,640 And what's special about this meteorite is 446 00:31:07,640 --> 00:31:11,520 it's perhaps the oldest material on Earth. 447 00:31:11,520 --> 00:31:14,480 So it's around 4.5 billion years old. 448 00:31:14,480 --> 00:31:17,000 So that right there 449 00:31:17,000 --> 00:31:19,640 is the oldest thing on Earth? 450 00:31:19,640 --> 00:31:21,680 Yeah. 451 00:31:21,680 --> 00:31:23,280 Wow. 452 00:31:23,280 --> 00:31:24,320 Can I hold it? 453 00:31:25,400 --> 00:31:28,000 Er...no. OK. 454 00:31:28,000 --> 00:31:29,640 But you can touch it, if you like. 455 00:31:29,640 --> 00:31:31,840 Just touch the oldest thing on Earth. Yeah. 456 00:31:31,840 --> 00:31:33,680 Oh, come on. 457 00:31:33,680 --> 00:31:34,880 Wow. 458 00:31:35,920 --> 00:31:38,960 It is kind of a goose-bump moment 459 00:31:38,960 --> 00:31:42,800 because of the significance of a little piece of rock that, 460 00:31:42,800 --> 00:31:46,040 well, frankly, I'd walk straight past. 461 00:31:46,040 --> 00:31:48,080 Well, most people probably would. 462 00:31:48,080 --> 00:31:50,240 But although they're quite rare, 463 00:31:50,240 --> 00:31:52,960 you can find them everywhere. 464 00:31:52,960 --> 00:31:55,000 They fall all over the world. 465 00:31:55,000 --> 00:31:58,240 But not always quite as spectacularly as here! 466 00:31:58,240 --> 00:32:01,160 Yeah, you'd notice that. You'd certainly notice. 467 00:32:01,160 --> 00:32:05,640 But to imagine that some of us are walking past lumps of rock 468 00:32:05,640 --> 00:32:09,000 that contain all the elements you need to build a planet... 469 00:32:09,000 --> 00:32:11,680 You know, you've got the magnesium and the silicon 470 00:32:11,680 --> 00:32:13,080 and the iron and the oxygen. 471 00:32:13,080 --> 00:32:16,160 It's just incredible that this is how we started 472 00:32:16,160 --> 00:32:18,360 and they're just scattered 473 00:32:18,360 --> 00:32:19,440 all over the world. 474 00:32:23,440 --> 00:32:26,880 If you or I were to find an actual meteorite, 475 00:32:26,880 --> 00:32:29,280 and - who knows? - we might, 476 00:32:29,280 --> 00:32:32,120 it's, I don't know, almost a haunting thought 477 00:32:32,120 --> 00:32:34,680 to consider that what you had in your hand 478 00:32:34,680 --> 00:32:37,640 might be 4.5 billion years old 479 00:32:37,640 --> 00:32:41,520 and one of the fundamental building blocks of our planet, 480 00:32:41,520 --> 00:32:42,720 our world, 481 00:32:42,720 --> 00:32:44,360 of our existence. 482 00:32:44,360 --> 00:32:46,200 But the meteorite that you found 483 00:32:46,200 --> 00:32:49,040 might not have landed billions of years ago. 484 00:32:49,040 --> 00:32:51,320 It might have landed the day before you found it. 485 00:32:51,320 --> 00:32:52,720 And that's quite exciting - 486 00:32:52,720 --> 00:32:56,160 they're still arriving. the process is still going on. 487 00:32:56,160 --> 00:32:58,760 It's just that they're late gatecrashers 488 00:32:58,760 --> 00:33:00,920 to some giant planetary party. 489 00:33:04,040 --> 00:33:09,520 Astonishingly, today, 40,000 tonnes worth of meteorites 490 00:33:09,520 --> 00:33:12,200 fall to Earth every year - 491 00:33:12,200 --> 00:33:15,640 the equivalent of 30,000 transit vans 492 00:33:15,640 --> 00:33:17,760 dropping out of the sky - 493 00:33:17,760 --> 00:33:20,160 mostly arriving as dust. 494 00:33:21,520 --> 00:33:23,280 But very occasionally, 495 00:33:23,280 --> 00:33:25,200 as something much bigger. 496 00:33:29,640 --> 00:33:31,880 Early in 2013, 497 00:33:31,880 --> 00:33:36,160 a meteorite fell near the Russian town of Chelyabinsk 498 00:33:36,160 --> 00:33:38,600 that was the largest in a century... 499 00:33:40,000 --> 00:33:43,800 ..nearly 10,000 tonnes, before breaking up. 500 00:33:45,320 --> 00:33:48,960 But such spectacular events are incredibly rare. 501 00:33:52,640 --> 00:33:56,160 In fact, you're more likely to die from falling out of bed 502 00:33:56,160 --> 00:33:58,440 than from being struck by a meteorite. 503 00:34:02,320 --> 00:34:04,600 GLASS SMASHES 504 00:34:04,600 --> 00:34:06,640 Back when the Earth was forming, though, 505 00:34:06,640 --> 00:34:09,280 huge meteorite strikes were constant, 506 00:34:09,280 --> 00:34:12,080 with tens of millions hitting a year. 507 00:34:21,440 --> 00:34:24,840 The thing is, rather than destroying it, 508 00:34:24,840 --> 00:34:27,120 the onslaught built our planet. 509 00:34:28,760 --> 00:34:31,800 Starting 4.5 billion years ago, 510 00:34:31,800 --> 00:34:36,800 it took just 100 million years to reach almost full size. 511 00:34:44,360 --> 00:34:48,160 So now we have a planet that's roughly the same size as Earth 512 00:34:48,160 --> 00:34:50,000 and the same shape. 513 00:34:50,000 --> 00:34:52,600 But at the moment, the surface of our planet 514 00:34:52,600 --> 00:34:56,080 is a molten, fiery vision of hell, 515 00:34:56,080 --> 00:34:58,000 which is going to be inconvenient. 516 00:35:10,240 --> 00:35:13,240 For starters, there's nothing to stand on - 517 00:35:13,240 --> 00:35:14,880 no solid rock. 518 00:35:16,520 --> 00:35:19,600 It's just a fiery, molten sea of magma. 519 00:35:21,720 --> 00:35:24,400 And there's no way life could start 520 00:35:24,400 --> 00:35:26,640 in this volcanic environment. 521 00:35:32,960 --> 00:35:36,600 So how are we going to get a solid surface for our planet? 522 00:35:49,200 --> 00:35:51,040 Back on the desert floor, 523 00:35:51,040 --> 00:35:53,480 Professor Jeff Karlson and his team 524 00:35:53,480 --> 00:35:56,040 are setting up a unique experiment. 525 00:35:58,760 --> 00:36:00,360 They reckon they can show me 526 00:36:00,360 --> 00:36:02,600 how to make land for our planet. 527 00:36:05,640 --> 00:36:07,840 The first step in their challenge - 528 00:36:07,840 --> 00:36:10,560 recreating that early, molten Earth. 529 00:36:12,400 --> 00:36:17,240 And that means constructing what is basically a mobile volcano. 530 00:36:22,320 --> 00:36:25,160 And now we're going to see if we can make it erupt. 531 00:36:28,600 --> 00:36:30,240 All right, Richard? Yeah. 532 00:36:30,240 --> 00:36:31,720 Let's get the helmet on. Yeah. 533 00:36:33,480 --> 00:36:36,520 I'm guessing what we've got in here is not lunch, is it? 534 00:36:36,520 --> 00:36:38,360 It isn't. 535 00:36:38,360 --> 00:36:41,400 Whoa! That's really hot! 536 00:36:41,400 --> 00:36:45,680 So what Bob is stirring there isn't something that looks like lava... 537 00:36:45,680 --> 00:36:50,160 No, it's... ..it's actual lava. 538 00:36:50,160 --> 00:36:52,920 We just put in the ingredients, just like a recipe, 539 00:36:52,920 --> 00:36:56,640 and cook up this primordial, primitive material 540 00:36:56,640 --> 00:36:58,120 that makes up our Earth. 541 00:36:58,120 --> 00:37:00,160 It's amazing and exhilarating 542 00:37:00,160 --> 00:37:02,920 but also quite incredibly hot up here. Can I get down? 543 00:37:02,920 --> 00:37:04,920 It's very hot. Yeah. And you can see, 544 00:37:04,920 --> 00:37:08,160 we have to get it that hot so it will flow in a very viscous form. 545 00:37:10,400 --> 00:37:14,120 The recipe for lava that Jeff's team are using 546 00:37:14,120 --> 00:37:17,000 includes the essential planetary ingredients - 547 00:37:17,000 --> 00:37:19,800 iron, magnesium and silicon. 548 00:37:21,200 --> 00:37:24,080 But before this turns to solid land, 549 00:37:24,080 --> 00:37:26,280 we need to make the lava flow. 550 00:37:27,680 --> 00:37:30,080 The spout, here. I see it. Here it comes, here it comes. 551 00:37:52,600 --> 00:37:53,800 The temperatures 552 00:37:53,800 --> 00:37:56,480 reached by this lava are extraordinary. 553 00:37:59,320 --> 00:38:02,000 We know from using our infrared camera, 554 00:38:02,000 --> 00:38:06,000 where it's incandescent orange, there, it's about 1,100 degrees centigrade. 555 00:38:06,000 --> 00:38:09,160 Where it starts to get dark grey, like down at the toe here, 556 00:38:09,160 --> 00:38:12,000 it's about 850 degrees centigrade, now. 557 00:38:12,000 --> 00:38:13,240 Wow! 558 00:38:13,240 --> 00:38:15,880 And now it's coming out here at 1,100 degrees again, 559 00:38:15,880 --> 00:38:18,320 just like the temperature that we're pouring in. 560 00:38:18,320 --> 00:38:21,640 So this is much hotter than that stuff on top? It is. 561 00:38:21,640 --> 00:38:24,000 Looking at what happens here on a small scale 562 00:38:24,000 --> 00:38:26,200 but with the same materials and the same temperatures 563 00:38:26,200 --> 00:38:27,840 and the same behaviours, 564 00:38:27,840 --> 00:38:31,960 you can look back and work out what happened on the early Earth. 565 00:38:31,960 --> 00:38:36,560 Exactly. We're sort of replicating those conditions of the early Earth, 566 00:38:36,560 --> 00:38:38,120 in miniature. 567 00:38:38,120 --> 00:38:39,120 Imagine the whole planet 568 00:38:39,120 --> 00:38:41,640 covered with glowing, incandescent orange lava - 569 00:38:41,640 --> 00:38:43,080 magma oceans. 570 00:38:44,400 --> 00:38:46,120 That is intense. 571 00:38:46,120 --> 00:38:48,560 You can see the little wrinkles and folds 572 00:38:48,560 --> 00:38:50,280 starting to form on the surface 573 00:38:50,280 --> 00:38:53,000 as the surface cools and a crust starts to form. 574 00:38:53,000 --> 00:38:56,080 I can feel wrinkles and folds forming on my face, watching. 575 00:38:58,600 --> 00:39:01,680 So, in order to create land from lava, 576 00:39:01,680 --> 00:39:06,040 we need to cool it down until it turns into a crust. 577 00:39:06,040 --> 00:39:07,440 Simple. 578 00:39:07,440 --> 00:39:09,800 But there's a wrinkle in our plan. 579 00:39:13,840 --> 00:39:15,600 On the early Earth, 580 00:39:15,600 --> 00:39:18,000 the lava didn't cool in the way you'd expect. 581 00:39:19,840 --> 00:39:22,680 There was a reason the surface stayed molten. 582 00:39:26,320 --> 00:39:30,160 Jeff has a, well, slightly unusual demonstration 583 00:39:30,160 --> 00:39:32,800 of what that was. 584 00:39:32,800 --> 00:39:34,280 Site up on the target... 585 00:39:35,840 --> 00:39:37,000 Shooters, fire. 586 00:39:52,960 --> 00:39:54,680 We're going in there? Let's go have a look. 587 00:39:54,680 --> 00:39:56,720 That was quite exhilarating, I'll be honest. 588 00:39:56,720 --> 00:39:58,960 Oh, my God! I can't see the target. OK, what am I doing? 589 00:39:58,960 --> 00:40:02,080 OK, look here, Richard. Here's where all the bullets hit. 590 00:40:02,080 --> 00:40:04,200 Feel how hot it is there, still. 591 00:40:04,200 --> 00:40:06,840 It is, yes. Yes, there's definite heat in there. 592 00:40:06,840 --> 00:40:09,200 Ow, they're really... You could think of these as... 593 00:40:09,200 --> 00:40:11,840 each one of these like a tiny meteorite that struck the Earth 594 00:40:11,840 --> 00:40:15,880 and transferred its kinetic energy to heat energy, 595 00:40:15,880 --> 00:40:17,520 keeping the planet warm. 596 00:40:17,520 --> 00:40:19,560 I think I see where you're going with this 597 00:40:19,560 --> 00:40:21,000 cos I did wonder for a moment. 598 00:40:21,000 --> 00:40:22,840 So these are like meteors. 599 00:40:22,840 --> 00:40:25,880 Right. So, the planet was under bombardment at a time. Right. 600 00:40:25,880 --> 00:40:28,280 And those were going in like these and when they hit, 601 00:40:28,280 --> 00:40:30,520 this is kinetic energy converting into heat. 602 00:40:30,520 --> 00:40:32,480 And what, a meteorite hitting is enough, 603 00:40:32,480 --> 00:40:33,960 is going to make it hot? It is. 604 00:40:33,960 --> 00:40:35,840 It keeps it hot and that's one of the reasons 605 00:40:35,840 --> 00:40:37,440 your planet's not cooling down. 606 00:40:37,440 --> 00:40:39,480 And these meteorites are a lot bigger. 607 00:40:39,480 --> 00:40:42,320 The meteorites are much bigger than our little bullets, of course, 608 00:40:42,320 --> 00:40:44,440 and they're travelling about ten times as fast. 609 00:40:44,440 --> 00:40:47,200 I'd love to get a better idea, a better sense of that moment 610 00:40:47,200 --> 00:40:49,840 when that energy is converted from kinetic into heat. 611 00:40:49,840 --> 00:40:52,080 But to do that, they'd have to shoot through my hand 612 00:40:52,080 --> 00:40:53,480 and that's going to hurt, so... 613 00:40:53,480 --> 00:40:55,200 Well, we have a safer way to do that. 614 00:40:55,200 --> 00:40:58,400 A thermal infrared camera's been filming the entire experiment here 615 00:40:58,400 --> 00:41:01,000 and we can show you the images created by that. 616 00:41:07,080 --> 00:41:09,720 In here? Yeah. 617 00:41:09,720 --> 00:41:12,400 So this is a thermal camera looking at what we've just seen. 618 00:41:12,400 --> 00:41:13,600 Right. There's the plate. 619 00:41:13,600 --> 00:41:16,040 Hot areas are going to show up red 620 00:41:16,040 --> 00:41:19,120 and little cooler areas will show up in a bluer, cooler colour 621 00:41:19,120 --> 00:41:21,920 as each one of these bullets strikes the metal. 622 00:41:21,920 --> 00:41:25,280 And there they go, look! I mean, it's really pronounced. 623 00:41:25,280 --> 00:41:27,800 Look at the pieces being blasted off, there. 624 00:41:27,800 --> 00:41:30,040 Watching them go in like that, 625 00:41:30,040 --> 00:41:32,280 I can imagine they were meteorites. 626 00:41:32,280 --> 00:41:35,720 Exactly, much bigger and ten times faster. 627 00:41:35,720 --> 00:41:37,760 And this effect is one of the reasons 628 00:41:37,760 --> 00:41:39,600 why my Planet Earth won't set... 629 00:41:39,600 --> 00:41:42,160 That's right. ..remains molten. 630 00:41:58,280 --> 00:42:02,320 So, to stand a chance of creating a solid surface for our planet, 631 00:42:02,320 --> 00:42:08,040 we need to stop this constant barrage of meteors and asteroids. 632 00:42:20,640 --> 00:42:22,680 On the actual Earth, 633 00:42:22,680 --> 00:42:26,920 this bombardment petered out around four billion years ago. 634 00:42:26,920 --> 00:42:29,160 On the planet we're building, 635 00:42:29,160 --> 00:42:31,000 it can be done in a jiffy. 636 00:42:33,400 --> 00:42:37,400 And reducing the impacts from space helps the surface to cool 637 00:42:37,400 --> 00:42:39,200 so that lava... 638 00:42:40,120 --> 00:42:41,360 ..turns to rock. 639 00:42:46,400 --> 00:42:47,640 Perfect! 640 00:42:47,640 --> 00:42:52,120 We now have a planet we can stand on without being burnt. 641 00:42:52,120 --> 00:42:55,560 But there is something pretty important missing. 642 00:42:55,560 --> 00:42:58,320 If we're going to have life on this planet of ours, 643 00:42:58,320 --> 00:43:00,400 we are going to need water. 644 00:43:05,320 --> 00:43:08,360 Incredibly, some water has been with us 645 00:43:08,360 --> 00:43:11,000 from the very birth of our planet, 646 00:43:11,000 --> 00:43:15,200 trapped in dust and rock, and then locked inside of the Earth. 647 00:43:18,200 --> 00:43:22,000 Volcanic activity released this water as steam, 648 00:43:22,000 --> 00:43:25,840 forming rain clouds that then filled the first oceans. 649 00:43:33,560 --> 00:43:37,000 A lot more water arrived from space, 650 00:43:37,000 --> 00:43:40,960 because asteroids and comets actually carried ice inside them, 651 00:43:40,960 --> 00:43:43,280 adding to our already wet planet. 652 00:43:43,280 --> 00:43:45,720 So, we've got water. 653 00:43:45,720 --> 00:43:47,760 We've also got land. 654 00:43:48,800 --> 00:43:50,240 But it doesn't look right. 655 00:43:54,800 --> 00:43:58,280 All that volcanic activity hasn't just pumped steam 656 00:43:58,280 --> 00:44:03,760 into the atmosphere, it's produced a toxic cocktail of gasses. 657 00:44:05,040 --> 00:44:08,000 This isn't a planet for us yet. 658 00:44:12,360 --> 00:44:16,000 So, how do we clean up this poisonous atmosphere? 659 00:44:16,000 --> 00:44:19,720 Well, the answer lies with the oldest living thing on the planet. 660 00:44:26,760 --> 00:44:32,440 On these rocks, there's a thin film of bacteria called a stromatolite. 661 00:44:34,680 --> 00:44:37,720 These ones today are in Australia, 662 00:44:37,720 --> 00:44:41,200 but three billion years ago they were everywhere. 663 00:44:42,200 --> 00:44:46,320 They live on sunlight, and carbon dioxide in water, 664 00:44:46,320 --> 00:44:50,720 and as a waste product, they release oxygen. 665 00:44:57,680 --> 00:45:02,720 For more than a billion years, these bacteria pumped the stuff out 666 00:45:02,720 --> 00:45:06,400 until the air was right for the evolution of complex life... 667 00:45:08,080 --> 00:45:09,640 ..including us. 668 00:45:16,120 --> 00:45:20,600 To build our planet, we started with truckloads of raw materials. 669 00:45:28,920 --> 00:45:32,880 And we mixed them together... 670 00:45:35,000 --> 00:45:37,360 ..into a cosmic cloud of dust. 671 00:45:41,440 --> 00:45:44,560 We got it to stick together with static electricity. 672 00:45:48,960 --> 00:45:51,000 And then we added gravity. 673 00:46:00,000 --> 00:46:01,760 We bulked the planet up. 674 00:46:05,640 --> 00:46:10,160 Then we stopped the onslaught to cool it down, and make land. 675 00:46:14,000 --> 00:46:17,360 And then we sourced water 676 00:46:17,360 --> 00:46:19,480 and a breathable atmosphere. 677 00:46:27,240 --> 00:46:29,680 But hang on. This isn't right. 678 00:46:34,480 --> 00:46:37,480 There's something seriously amiss with our planet. 679 00:46:40,840 --> 00:46:44,280 This is definitely not how things should be looking. 680 00:46:44,280 --> 00:46:46,520 It's a bad case of the wobbles. 681 00:46:51,400 --> 00:46:55,840 A wobble this big, even slowed down over millions of years, 682 00:46:55,840 --> 00:46:57,640 would be catastrophic. 683 00:46:59,040 --> 00:47:03,160 Without stability, seasonal changes are extreme, 684 00:47:03,160 --> 00:47:05,240 ice ages are frequent, 685 00:47:05,240 --> 00:47:08,920 and the surface is scoured by hurricane-force winds. 686 00:47:13,560 --> 00:47:19,000 It's no good! Our planet has conditions completely hostile to life. 687 00:47:19,000 --> 00:47:21,440 But don't worry, because to stabilise things, 688 00:47:21,440 --> 00:47:23,600 we don't actually have to look too far. 689 00:47:26,240 --> 00:47:29,360 The solution is a moon. 690 00:47:44,040 --> 00:47:47,880 To find out how a moon can stop a planet's wobble, 691 00:47:47,880 --> 00:47:50,480 I've come to NASA in Texas... 692 00:47:56,600 --> 00:48:00,440 ..where the answer is kept in a bomb-proof vault... 693 00:48:03,680 --> 00:48:05,120 ..wrapped in foil. 694 00:48:12,200 --> 00:48:14,280 And if that isn't enough, 695 00:48:14,280 --> 00:48:18,320 this entire facility demands OCD levels of hygiene. 696 00:48:30,520 --> 00:48:34,160 One man who knows a lot about this object is Harrison Schmitt. 697 00:48:35,600 --> 00:48:39,640 And that's because he found it... on the moon. 698 00:48:42,920 --> 00:48:46,200 Four decades ago, Harrison was an astronaut. 699 00:48:46,200 --> 00:48:49,200 December 6th, 1972. 700 00:48:49,200 --> 00:48:52,320 Dr Harrison Schmitt, better known as Jack. 701 00:48:52,320 --> 00:48:56,080 He would be the first geologist to set foot on an alien world. 702 00:48:57,720 --> 00:49:00,720 We have liftoff at 2.13... 703 00:49:05,200 --> 00:49:11,160 I'm going to meet Harrison, after a final zap in the NASA microwave. 704 00:49:11,160 --> 00:49:13,120 SHRILL BEEP 705 00:49:16,360 --> 00:49:18,880 Harrison. Hey. Hello. Welcome. 706 00:49:18,880 --> 00:49:21,680 I so wanted to shake your hand but it's in there! 707 00:49:21,680 --> 00:49:23,520 A little bit later maybe. 708 00:49:23,520 --> 00:49:26,600 It's great to meet you, and what have you've got in here? 709 00:49:26,600 --> 00:49:29,560 We have one of the Apollo 17 samples. 710 00:49:29,560 --> 00:49:32,800 It's one collected near the lunar module challenger. 711 00:49:32,800 --> 00:49:36,520 And it is a... 712 00:49:36,520 --> 00:49:40,800 ..er, really quite a unique type of rock. 713 00:49:41,840 --> 00:49:46,640 That rock formed about 3.8 billion years ago. 714 00:49:46,640 --> 00:49:48,560 That's with a B! 715 00:49:48,560 --> 00:49:53,840 So it's extremely old, it's part of a mass of magma that partially 716 00:49:53,840 --> 00:49:59,160 filled the valley of Tarse Littoral where we landed on Apollo 17. 717 00:49:59,160 --> 00:50:03,080 So let's just get this into context because, for mere mortals like me 718 00:50:03,080 --> 00:50:07,000 to understand, you are standing there as the only geologist ever 719 00:50:07,000 --> 00:50:09,240 to have walked on the moon? That's correct. 720 00:50:09,240 --> 00:50:12,440 And therefore, when you saw these rocks on the moon, they would have 721 00:50:12,440 --> 00:50:15,720 meant more to you anyway because of your training and knowledge. I hope so. 722 00:50:15,720 --> 00:50:18,480 Your brain must have been just screaming! 723 00:50:18,480 --> 00:50:20,080 You were looking at that rock. 724 00:50:20,080 --> 00:50:23,040 Well, you can't believe where this geologic setting was. 725 00:50:23,040 --> 00:50:25,960 It's a valley deeper than the Grand Canyon of the Colorado 726 00:50:25,960 --> 00:50:27,760 here in the United States. 727 00:50:29,120 --> 00:50:32,800 The mountains on either side are 6,000-7,000 feet 728 00:50:32,800 --> 00:50:34,720 above the valley floor. 729 00:50:34,720 --> 00:50:36,440 This was off the valley floor. 730 00:50:39,840 --> 00:50:43,440 It's the moon that saves the real Earth from the disastrous 731 00:50:43,440 --> 00:50:45,200 climatic effects of wobbling. 732 00:50:46,600 --> 00:50:49,640 But how exactly the moon keeps us stable 733 00:50:49,640 --> 00:50:52,280 is tied into its mysterious origins. 734 00:50:57,240 --> 00:50:59,160 Until the Apollo programme, 735 00:50:59,160 --> 00:51:02,960 we had no real idea of how the Earth got its moon. 736 00:51:04,680 --> 00:51:08,760 Finding out was an important goal for Harrison Schmitt 737 00:51:08,760 --> 00:51:15,040 when his Apollo 17 module touched down on December 11th, 1972. 738 00:51:15,040 --> 00:51:17,760 Feels good, stand by for touchdown. 739 00:51:17,760 --> 00:51:20,120 Stand by, down at two. 740 00:51:20,120 --> 00:51:23,040 Feels good. Ten feet. 741 00:51:23,040 --> 00:51:25,000 That's contact! 742 00:51:27,040 --> 00:51:29,120 Harrison had just three days 743 00:51:29,120 --> 00:51:31,960 to collect as many lunar samples as possible. 744 00:51:33,520 --> 00:51:36,800 Late in the mission, things got a little tense. 745 00:51:36,800 --> 00:51:39,840 Harrison had just half an hour of oxygen left 746 00:51:39,840 --> 00:51:43,080 and he was getting a bit carried away with his work. 747 00:51:44,400 --> 00:51:46,320 I've got to dig a trench, Houston. 748 00:51:48,680 --> 00:51:51,480 Fantastic, sports fans! 749 00:51:51,480 --> 00:51:53,800 It's trench time! 750 00:51:53,800 --> 00:51:55,280 They got to leave at a certain time, 751 00:51:55,280 --> 00:51:56,720 regardless of what they got. 752 00:51:56,720 --> 00:52:00,440 There isn't enough time to do it, no matter which way we want to do it. 753 00:52:00,440 --> 00:52:02,520 We need more time. 754 00:52:02,520 --> 00:52:06,200 We need to make it clear, we've got to pull out. 755 00:52:06,200 --> 00:52:09,080 We'd like you to leave immediately. 756 00:52:09,080 --> 00:52:10,920 OK. 757 00:52:10,920 --> 00:52:13,200 By golly, this time goes fast! 758 00:52:13,200 --> 00:52:15,200 We're on our way, Houston. 759 00:52:20,680 --> 00:52:24,320 Once Harrison and NASA were able to examine the rocks, 760 00:52:24,320 --> 00:52:29,000 they began to understand fully just how the moon had formed, 761 00:52:29,000 --> 00:52:32,240 and the massive stabilising effect it brought. 762 00:52:36,600 --> 00:52:40,360 What the scientists discovered was an extraordinary connection. 763 00:52:41,920 --> 00:52:46,040 It seems this moon rock was made of pretty much the same stuff 764 00:52:46,040 --> 00:52:47,280 as Earth rock. 765 00:52:49,320 --> 00:52:53,200 The oxygen isotope ratios in the rocks are identical 766 00:52:53,200 --> 00:52:55,600 to those ratios that we have here on Earth 767 00:52:55,600 --> 00:52:59,880 and it tells you that the Earth and the moon formed in, basically, 768 00:52:59,880 --> 00:53:02,720 almost identically the same part of the solar system. 769 00:53:02,720 --> 00:53:05,360 And this information that you brought back has helped 770 00:53:05,360 --> 00:53:09,600 people narrow down the theories as to how the moon came to be 771 00:53:09,600 --> 00:53:12,800 where it is and like it is. No question about that. 772 00:53:12,800 --> 00:53:15,960 The primary hypothesis right now is giant impact. 773 00:53:21,800 --> 00:53:24,040 Soon after the Earth formed, 774 00:53:24,040 --> 00:53:26,880 another planet-sized rock crashed into it. 775 00:53:28,680 --> 00:53:31,720 The impact threw huge chunks into orbit. 776 00:53:32,880 --> 00:53:36,440 And these clumped together to make the moon. 777 00:53:38,840 --> 00:53:43,600 When first formed, it was much, much closer than it is now. 778 00:53:50,040 --> 00:53:54,320 One of the primary reasons that we still are here on this planet 779 00:53:54,320 --> 00:53:59,360 is that the Earth is a stable planet and it's been stabilised by the moon. 780 00:53:59,360 --> 00:54:03,280 With the moon there, there's a gravitational stabilisation 781 00:54:03,280 --> 00:54:08,560 that occurs that keeps the Earth wobble down to an absolute minimum 782 00:54:08,560 --> 00:54:11,280 and that makes a big difference for us, because 783 00:54:11,280 --> 00:54:15,920 if you wanted to have major climate change on Earth, introduce a wobble. 784 00:54:15,920 --> 00:54:18,280 It doesn't mean that life wouldn't be here 785 00:54:18,280 --> 00:54:22,720 but it would be a very difficult and different kind of life that we 786 00:54:22,720 --> 00:54:23,960 would have to deal with 787 00:54:23,960 --> 00:54:26,800 with this wobble over fairly long periods of time. 788 00:54:31,360 --> 00:54:35,480 So, let's see what happens to our planet when we add a moon. 789 00:54:39,360 --> 00:54:43,240 Our planet and its new moon are two dancers 790 00:54:43,240 --> 00:54:47,040 locked in a gravitational embrace, 791 00:54:47,040 --> 00:54:51,400 steadying themselves as they swirl round and round. 792 00:54:54,160 --> 00:54:57,360 Having a moon has one other vital effect. 793 00:54:57,360 --> 00:55:02,120 Tiny variations in its gravitational pull on our planet's oceans 794 00:55:02,120 --> 00:55:04,560 have given it tides, 795 00:55:04,560 --> 00:55:07,360 and that's more important than you might think. 796 00:55:10,080 --> 00:55:15,560 Without the tides, early life on Earth may never have left the sea, 797 00:55:15,560 --> 00:55:19,400 because the tides created damp strips along the coast 798 00:55:19,400 --> 00:55:21,960 that tempted life onto land. 799 00:55:24,000 --> 00:55:27,120 And the actual positioning of the moon is crucial. 800 00:55:27,120 --> 00:55:31,400 Ever since its formation, it's been drifting away from the Earth. 801 00:55:31,400 --> 00:55:35,520 But when it was closer, it generated immense tides. 802 00:55:39,120 --> 00:55:43,800 If we had them today, every few hours, New York and London 803 00:55:43,800 --> 00:55:47,080 would disappear under tens of metres of water. 804 00:55:49,680 --> 00:55:53,680 And if the moon was further away, the planet's spin would slow 805 00:55:53,680 --> 00:55:55,760 and the days would be longer. 806 00:55:55,760 --> 00:55:58,280 But put it at just the right distance, which in reality 807 00:55:58,280 --> 00:56:03,880 is about 239,000 miles, and we have the stability we need. 808 00:56:03,880 --> 00:56:07,560 So, there it is - the perfect planetary relationship. 809 00:56:12,600 --> 00:56:17,480 After trial and error, I have built my planet and its moon... 810 00:56:19,120 --> 00:56:21,600 ..and got them working just right. 811 00:56:27,440 --> 00:56:32,520 In reality, this whole process took four and a half billion years. 812 00:56:34,880 --> 00:56:39,240 The sheer scale of it all is understandably mind-blowing, 813 00:56:39,240 --> 00:56:43,080 especially when you realise that with just one element 814 00:56:43,080 --> 00:56:44,400 out of place... 815 00:56:46,560 --> 00:56:50,000 ..nothing works, and life stops. 816 00:56:56,080 --> 00:56:59,560 So what holds the Earth and moon in place? 817 00:57:02,200 --> 00:57:05,440 They need a sun to orbit around, 818 00:57:05,440 --> 00:57:08,440 and other planets to make our solar system... 819 00:57:10,480 --> 00:57:14,400 ..all of which is just a tiny part of a Milky Way galaxy 820 00:57:14,400 --> 00:57:17,240 with 300 billion stars. 821 00:57:24,160 --> 00:57:29,400 And that galaxy is just one amongst half a trillion other galaxies. 822 00:57:36,520 --> 00:57:41,600 So, to keep it all working, we're going to have to build a universe. 823 00:57:51,920 --> 00:57:53,880 And to build a universe, 824 00:57:53,880 --> 00:57:55,200 I'm going to need 825 00:57:55,200 --> 00:57:56,400 a lot of help. 826 00:57:57,440 --> 00:57:59,880 Oh, this is really difficult! 827 00:58:03,920 --> 00:58:05,360 Oh, my God, it's beautiful! 828 00:58:11,440 --> 00:58:14,000 Do I look faintly ridiculous? Yes! 829 00:58:24,360 --> 00:58:26,400 I'll be honest. I'm faintly nervous. 830 00:58:56,040 --> 00:58:58,840 Subtitles by Red Bee Media Ltd