1 00:00:00,339 --> 00:00:03,256 (mysterious music) 2 00:00:05,719 --> 00:00:09,853 Everything in our universe has its size. 3 00:00:11,400 --> 00:00:12,803 Planets are big, 4 00:00:13,890 --> 00:00:15,423 insects are small, 5 00:00:17,540 --> 00:00:20,830 people are somewhere in between. 6 00:00:20,830 --> 00:00:23,713 Everything has its place in the grand order. 7 00:00:25,140 --> 00:00:27,203 But does it have to be this way? 8 00:00:28,585 --> 00:00:30,693 Does size really matter? 9 00:00:31,920 --> 00:00:33,478 Wouldn't it be better 10 00:00:33,478 --> 00:00:35,363 if everything were bigger? 11 00:00:36,430 --> 00:00:39,350 After all, big animals live longer than small ones 12 00:00:39,350 --> 00:00:42,243 and studies show that tall people are more successful. 13 00:00:43,695 --> 00:00:46,760 So why are things the size they are 14 00:00:46,760 --> 00:00:49,670 and what if we could change that? 15 00:00:49,670 --> 00:00:51,500 Using the latest science, 16 00:00:51,500 --> 00:00:54,950 we are going to do the ultimate thought experiment. 17 00:00:54,950 --> 00:00:57,900 We are going to increase the size of everything, 18 00:00:57,900 --> 00:00:59,810 and that includes us, 19 00:00:59,810 --> 00:01:01,920 to see whether a bigger world, 20 00:01:01,920 --> 00:01:03,873 really is a better world. 21 00:01:04,900 --> 00:01:08,560 We're going to discover just how much size matters, 22 00:01:08,560 --> 00:01:10,523 how it defines everything. 23 00:01:11,460 --> 00:01:14,990 You'll never look at yourself or your world 24 00:01:14,990 --> 00:01:15,940 the same way again. 25 00:01:18,287 --> 00:01:21,037 (dramatic music) 26 00:01:22,220 --> 00:01:25,320 (gentle music) 27 00:01:25,320 --> 00:01:27,690 You might think this looks like an ordinary house 28 00:01:27,690 --> 00:01:29,140 on an ordinary sunny morning. 29 00:01:31,395 --> 00:01:34,223 In fact, you are looking at a parallel universe. 30 00:01:36,375 --> 00:01:38,040 One just like our own 31 00:01:38,040 --> 00:01:39,740 but with one important difference. 32 00:01:41,626 --> 00:01:44,293 (alarm beeping) 33 00:01:47,860 --> 00:01:51,293 In this universe, we can change the size of things 34 00:01:51,293 --> 00:01:53,040 just to see what happens. 35 00:01:59,657 --> 00:02:01,070 We're going to follow a normal guy 36 00:02:01,070 --> 00:02:02,880 going about his normal day 37 00:02:02,880 --> 00:02:04,430 and see what happens to him 38 00:02:04,430 --> 00:02:08,060 when we increase the size of stars, planets 39 00:02:08,060 --> 00:02:09,303 and living things. 40 00:02:11,820 --> 00:02:13,820 We'll find out if the way things are 41 00:02:13,820 --> 00:02:15,810 is the only way they can be 42 00:02:15,810 --> 00:02:18,310 and explore the consequences of a world 43 00:02:18,310 --> 00:02:20,340 where things are bigger. 44 00:02:20,340 --> 00:02:23,100 Call it a thought experiment, if you like. 45 00:02:23,100 --> 00:02:25,000 Something scientists have always used 46 00:02:25,000 --> 00:02:27,053 to explore the workings of the universe. 47 00:02:28,390 --> 00:02:31,770 Thought experiments are vitally important for science 48 00:02:31,770 --> 00:02:34,110 because with thought experiments 49 00:02:34,110 --> 00:02:36,170 we have a way to quickly explore 50 00:02:36,170 --> 00:02:38,180 the realm of possibilities 51 00:02:38,180 --> 00:02:41,960 before we engage in very detailed calculations. 52 00:02:41,960 --> 00:02:44,810 So whenever we start any question in science, 53 00:02:44,810 --> 00:02:46,607 we begin with a thought experiment. 54 00:02:46,607 --> 00:02:49,140 By changing the size of things, 55 00:02:49,140 --> 00:02:51,430 we're going to explore the laws of nature 56 00:02:51,430 --> 00:02:53,120 and find out if there are limits 57 00:02:53,120 --> 00:02:55,610 to how big things can get. 58 00:02:55,610 --> 00:02:56,720 It's a thought experiment 59 00:02:56,720 --> 00:02:58,462 that will give us a deeper understanding 60 00:02:58,462 --> 00:03:01,193 of how things work in the real world. 61 00:03:03,410 --> 00:03:04,770 And we're going to begin 62 00:03:04,770 --> 00:03:08,163 by changing the size of planet Earth itself. 63 00:03:12,990 --> 00:03:16,100 With a mass of six billion trillion tons, 64 00:03:16,100 --> 00:03:18,820 that's a six followed by 21 zeroes, 65 00:03:18,820 --> 00:03:21,230 the planet Earth is only the fifth biggest 66 00:03:21,230 --> 00:03:23,280 of the eight planets of the solar system. 67 00:03:24,290 --> 00:03:28,573 Let's compare it with number one, mighty Jupiter. 68 00:03:32,270 --> 00:03:34,920 Jupiter is 11 times the width of Earth 69 00:03:34,920 --> 00:03:37,913 and has 318 times the mass. 70 00:03:38,995 --> 00:03:40,698 What would life be like 71 00:03:40,698 --> 00:03:42,890 on a Jupiter sized Earth 72 00:03:43,926 --> 00:03:45,883 and would it even be possible? 73 00:03:47,790 --> 00:03:49,460 We're going to take things slowly 74 00:03:49,460 --> 00:03:52,290 and start by gradually making Earth bigger 75 00:03:52,290 --> 00:03:54,853 until it is twice as wide as it was. 76 00:04:03,900 --> 00:04:05,360 By growing the planet, 77 00:04:05,360 --> 00:04:06,410 we are going to find out 78 00:04:06,410 --> 00:04:08,503 how much its size really matters. 79 00:04:10,373 --> 00:04:12,650 Our infrastructure, 80 00:04:12,650 --> 00:04:14,530 roads, bridges and buildings, 81 00:04:14,530 --> 00:04:17,500 are all tailor made to fit the current Earth. 82 00:04:17,500 --> 00:04:19,100 So it's no surprise 83 00:04:19,100 --> 00:04:21,830 they won't cope if the planet starts slowly growing 84 00:04:21,830 --> 00:04:23,293 towards the size of Jupiter. 85 00:04:24,892 --> 00:04:27,333 But they're more resilient than you might think. 86 00:04:28,827 --> 00:04:30,610 Bridges at least 87 00:04:30,610 --> 00:04:32,898 are designed to expand a little. 88 00:04:32,898 --> 00:04:34,841 So it'll be a few moments 89 00:04:34,841 --> 00:04:37,303 before everything falls apart. 90 00:05:05,261 --> 00:05:07,110 Roads can be rebuilt 91 00:05:07,110 --> 00:05:08,750 but the most important consequence 92 00:05:08,750 --> 00:05:10,780 of changing the size of a planet 93 00:05:10,780 --> 00:05:12,940 is far harder to work around 94 00:05:12,940 --> 00:05:14,743 and that's gravity. 95 00:05:16,597 --> 00:05:19,470 Gravity is the key force 96 00:05:19,470 --> 00:05:21,940 that governs the universe and nature 97 00:05:21,940 --> 00:05:23,730 on the largest scales. 98 00:05:23,730 --> 00:05:25,100 And at very basic levels, 99 00:05:25,100 --> 00:05:27,060 every object in the universe 100 00:05:27,060 --> 00:05:28,500 is attracting every other object 101 00:05:28,500 --> 00:05:30,050 according to its mass. 102 00:05:30,050 --> 00:05:32,500 The more mass, the stronger the force of gravity. 103 00:05:34,146 --> 00:05:37,300 As the planet continues to grow, 104 00:05:37,300 --> 00:05:39,684 Earth's gravity will get stronger. 105 00:05:39,684 --> 00:05:41,450 The first casualties 106 00:05:41,450 --> 00:05:44,249 would be low Earth orbit satellites. 107 00:05:44,249 --> 00:05:45,680 Even if their orbits 108 00:05:45,680 --> 00:05:47,610 grow in proportion with the Earth, 109 00:05:47,610 --> 00:05:49,050 the planet's higher gravity 110 00:05:49,050 --> 00:05:51,200 would soon pull the closest down 111 00:05:51,200 --> 00:05:52,563 into the upper atmosphere. 112 00:05:54,163 --> 00:05:58,203 Then, atmospheric drag would do the rest. 113 00:06:05,790 --> 00:06:08,490 Falling satellites are just the beginning. 114 00:06:08,490 --> 00:06:11,860 But what does higher gravity mean for humanity? 115 00:06:11,860 --> 00:06:14,110 What would be the effect on our bodies, 116 00:06:14,110 --> 00:06:15,192 our health 117 00:06:15,192 --> 00:06:17,593 and how much more gravity can we take? 118 00:06:19,860 --> 00:06:21,210 As you will see, 119 00:06:21,210 --> 00:06:23,953 higher gravity is a big challenge. 120 00:06:39,059 --> 00:06:39,892 There are a few people 121 00:06:39,892 --> 00:06:42,910 who actually know what life on a bigger planet feels like 122 00:06:42,910 --> 00:06:44,200 because they've experienced 123 00:06:44,200 --> 00:06:47,633 something just like higher gravity, G-force. 124 00:06:49,300 --> 00:06:50,570 To do his job, 125 00:06:50,570 --> 00:06:53,580 royal air force typhoon pilot Mark Long 126 00:06:53,580 --> 00:06:56,181 has to deal with extreme G-force. 127 00:06:56,181 --> 00:06:58,540 G-force is like an increase 128 00:06:58,540 --> 00:06:59,920 in the gravitational effect. 129 00:06:59,920 --> 00:07:01,670 Your arms feel heavier. 130 00:07:01,670 --> 00:07:03,640 You find that breathing's a little bit more difficult 131 00:07:03,640 --> 00:07:06,223 because you're working harder against the force 132 00:07:06,223 --> 00:07:08,490 that you wouldn't normally be exposed to. 133 00:07:08,490 --> 00:07:11,619 So it's like gravity but just more intense. 134 00:07:11,619 --> 00:07:14,369 (dramatic music) 135 00:07:17,830 --> 00:07:19,870 Today, he's flying a display routine 136 00:07:19,870 --> 00:07:23,879 which will push him and his plane to their limits. 137 00:07:23,879 --> 00:07:26,629 (dramatic music) 138 00:07:36,710 --> 00:07:38,040 As the plane turns, 139 00:07:38,040 --> 00:07:41,320 Mark is pushed into his seat by G-force. 140 00:07:41,320 --> 00:07:43,350 Albert Einstein's equivalence principle 141 00:07:43,350 --> 00:07:45,520 tells us that the effect on his body 142 00:07:45,520 --> 00:07:47,950 is just like higher gravity. 143 00:07:47,950 --> 00:07:51,050 So that what he experiences during some maneuvers 144 00:07:51,050 --> 00:07:52,360 feels exactly the same 145 00:07:52,360 --> 00:07:54,373 as being on a higher G planet. 146 00:07:57,140 --> 00:07:59,210 So I've just bottomed down from a looping maneuver here 147 00:07:59,210 --> 00:08:02,460 and I'm turning the jet into a barrel roll maneuver. 148 00:08:02,460 --> 00:08:03,293 It's quite slow 149 00:08:03,293 --> 00:08:06,140 so the G-force is around two and a half at this point. 150 00:08:06,140 --> 00:08:07,510 And as I get towards the bottom maneuver, 151 00:08:07,510 --> 00:08:08,963 it starts to increase. 152 00:08:17,310 --> 00:08:19,061 Back in our parallel universe, 153 00:08:19,061 --> 00:08:22,260 Earth is now twice as wide as it was. 154 00:08:22,260 --> 00:08:24,200 That means the planet's circumference 155 00:08:24,200 --> 00:08:25,620 and the gravity at the surface 156 00:08:25,620 --> 00:08:26,963 have also doubled. 157 00:08:28,595 --> 00:08:31,780 So two G actually feels alright. 158 00:08:31,780 --> 00:08:33,069 You can look around fine, 159 00:08:33,069 --> 00:08:34,430 you can move your head 160 00:08:34,430 --> 00:08:37,039 but everything is just a bit more of an effort. 161 00:08:37,039 --> 00:08:40,130 Moving around under two G conditions would be tiring. 162 00:08:40,130 --> 00:08:41,820 Life would be very slow, 163 00:08:41,820 --> 00:08:42,653 you'd be lethargic, 164 00:08:42,653 --> 00:08:44,510 moving your legs would feel heavy. 165 00:08:44,510 --> 00:08:46,060 You'd just take longer to do stuff 166 00:08:46,060 --> 00:08:47,200 and you would feel tired at the end 167 00:08:47,200 --> 00:08:49,000 of every activity you tried. 168 00:08:49,000 --> 00:08:51,120 Our infrastructure destroyed, 169 00:08:51,120 --> 00:08:53,340 humanity brought to its knees, 170 00:08:53,340 --> 00:08:55,720 a mere doubling of the radius of the planet 171 00:08:55,720 --> 00:08:57,333 could be the end of days. 172 00:08:58,346 --> 00:09:00,453 But we're not finished yet. 173 00:09:01,340 --> 00:09:03,121 As this is a thought experiment, 174 00:09:03,121 --> 00:09:05,700 let's just say that everyone survives 175 00:09:05,700 --> 00:09:07,963 and rebuilds to suit two G. 176 00:09:10,330 --> 00:09:13,087 It's a world in which standing up 177 00:09:13,087 --> 00:09:15,200 is to be avoided. 178 00:09:15,200 --> 00:09:16,470 If I was lying down, 179 00:09:16,470 --> 00:09:18,280 now the heart hasn't got to work so hard 180 00:09:18,280 --> 00:09:20,352 and life would be a lot easier. 181 00:09:20,352 --> 00:09:22,260 The distance between your heart and your head 182 00:09:22,260 --> 00:09:24,430 is the most crucial thing in the vertical sense 183 00:09:24,430 --> 00:09:27,966 because your heart has to pump the blood against gravity. 184 00:09:27,966 --> 00:09:29,210 So the best physique 185 00:09:29,210 --> 00:09:32,260 is actually fairly muscular, quite short. 186 00:09:32,260 --> 00:09:34,770 It turns out the upright human design 187 00:09:34,770 --> 00:09:37,650 doesn't deal well with higher gravity. 188 00:09:37,650 --> 00:09:39,730 Had our planet been bigger, 189 00:09:39,730 --> 00:09:41,453 we might never have evolved. 190 00:09:46,056 --> 00:09:48,973 (mysterious music) 191 00:09:50,300 --> 00:09:52,820 Unfortunately, two G world 192 00:09:52,820 --> 00:09:55,230 has yet more pain in store. 193 00:09:55,230 --> 00:09:57,000 Changing the size of Earth 194 00:09:57,000 --> 00:09:59,193 upsets the cosmic apple cart. 195 00:10:02,450 --> 00:10:06,723 Our moon sits in perfect equilibrium with the Earth. 196 00:10:09,532 --> 00:10:11,027 If you make the Earth twice as large in radius 197 00:10:11,027 --> 00:10:12,320 and eight times more massive, 198 00:10:12,320 --> 00:10:15,029 it has a dramatic effect on the moon's orbit. 199 00:10:15,029 --> 00:10:16,430 The moon would be pulled 200 00:10:16,430 --> 00:10:18,670 into a strange new orbit 201 00:10:18,670 --> 00:10:21,613 that would pass much, much nearer to the Earth. 202 00:10:22,910 --> 00:10:24,036 Not close enough to hit 203 00:10:24,036 --> 00:10:26,680 but you'd soon see the difference. 204 00:10:34,293 --> 00:10:37,693 But this moon also has a dark side. 205 00:10:41,170 --> 00:10:42,730 In its normal orbit, 206 00:10:42,730 --> 00:10:44,820 the moon causes tides in our oceans 207 00:10:44,820 --> 00:10:47,553 that are seldom more than 10 meters high. 208 00:10:50,573 --> 00:10:52,800 If we had tides operating 209 00:10:52,800 --> 00:10:55,274 with this moon coming very, very close to the Earth 210 00:10:55,274 --> 00:10:56,990 then in fact, the heights of the tides 211 00:10:56,990 --> 00:10:58,463 would be extremely high. 212 00:11:04,929 --> 00:11:07,570 So obviously there are some cities around the world, 213 00:11:07,570 --> 00:11:08,480 many cities in fact 214 00:11:08,480 --> 00:11:11,280 which would become uninhabitable under those conditions 215 00:11:11,280 --> 00:11:13,160 because you'd have these great big tidal waves 216 00:11:13,160 --> 00:11:14,510 sweeping around the planet. 217 00:11:15,820 --> 00:11:18,390 With the moon now passing so much closer, 218 00:11:18,390 --> 00:11:21,603 tides could be up to 1,000 meters high. 219 00:11:26,986 --> 00:11:30,110 But so far, we are nowhere near the size 220 00:11:30,110 --> 00:11:32,403 of the largest planet in our solar system. 221 00:11:35,438 --> 00:11:37,400 (dramatic music) 222 00:11:37,400 --> 00:11:39,150 But just what is the limit 223 00:11:39,150 --> 00:11:40,900 for the human body? 224 00:11:40,900 --> 00:11:43,371 Doing 350 miles an hour at this point 225 00:11:43,371 --> 00:11:44,850 with the jets accelerating all the time, 226 00:11:44,850 --> 00:11:48,040 so I'm going through 4G, 5G, up to 6G 227 00:11:48,040 --> 00:11:49,623 as I turn on to a crowd line. 228 00:11:51,440 --> 00:11:53,010 At 6G I don't think the human body 229 00:11:53,010 --> 00:11:55,080 would be able to function on a bigger planet. 230 00:11:55,080 --> 00:11:57,268 It would be incapacitated. 231 00:11:57,268 --> 00:11:59,630 You would just be spending your whole time 232 00:11:59,630 --> 00:12:01,998 trying to fight against the G-force. 233 00:12:01,998 --> 00:12:03,880 You wouldn't be able to do anything. 234 00:12:03,880 --> 00:12:06,830 In fact, you'd probably spend your entire life laying down. 235 00:12:09,850 --> 00:12:11,200 But laying down 236 00:12:11,200 --> 00:12:13,403 won't help with what happens next. 237 00:12:14,548 --> 00:12:18,390 Because when the Earth reaches half the width of Jupiter, 238 00:12:18,390 --> 00:12:20,093 something very strange happens. 239 00:12:22,508 --> 00:12:25,623 The air itself becomes toxic. 240 00:12:27,020 --> 00:12:29,120 As the increasing gravity of massive Earth 241 00:12:29,120 --> 00:12:31,660 pulls the atmosphere closer to the surface, 242 00:12:31,660 --> 00:12:34,619 the oxygen is more tightly packed in. 243 00:12:34,619 --> 00:12:37,020 There are more and more oxygen molecules 244 00:12:37,020 --> 00:12:39,147 inside every lungful. 245 00:12:39,147 --> 00:12:40,907 That may sound like a good thing 246 00:12:40,907 --> 00:12:44,830 but oxygen is a highly reactive element. 247 00:12:44,830 --> 00:12:47,770 We are designed to cope with a certain amount. 248 00:12:47,770 --> 00:12:50,480 Too much of it can cause violent seizures, 249 00:12:50,480 --> 00:12:52,450 eye and breathing problems, 250 00:12:52,450 --> 00:12:54,070 loss of consciousness, 251 00:12:54,070 --> 00:12:56,360 and eventually death. 252 00:12:56,360 --> 00:12:58,120 So even the air we breathe 253 00:12:58,120 --> 00:13:00,724 depends on the size of the planet. 254 00:13:00,724 --> 00:13:03,910 (dramatic music) 255 00:13:03,910 --> 00:13:05,473 And we're not finished yet. 256 00:13:06,900 --> 00:13:08,390 I'm preparing my body right now 257 00:13:08,390 --> 00:13:09,620 for this onslaught of G's. 258 00:13:09,620 --> 00:13:12,720 So as soon as I enter that turn, I'm at 9G. 259 00:13:12,720 --> 00:13:13,960 I can barely move my head 260 00:13:13,960 --> 00:13:16,290 so I'm forcing my body against the edge of the seat 261 00:13:16,290 --> 00:13:17,493 to look 'round 262 00:13:17,493 --> 00:13:20,517 with my reference point ready for pitching up for the loop. 263 00:13:23,122 --> 00:13:24,520 When I pitch up for the loop, 264 00:13:24,520 --> 00:13:27,010 I know this could be another 9G maneuver. 265 00:13:27,010 --> 00:13:28,673 So I've pretensed my body. 266 00:13:28,673 --> 00:13:31,080 And now as I get to the top of the loop 267 00:13:31,080 --> 00:13:33,403 I'm relaxing into the G-force. 268 00:13:39,880 --> 00:13:42,460 I've had the typhoon up to 10.4G 269 00:13:42,460 --> 00:13:43,690 and it was painful 270 00:13:43,690 --> 00:13:47,320 and I would hate to be on a plant that's 11G. 271 00:13:47,320 --> 00:13:49,860 In fact, I'd look for a different planet. 272 00:13:49,860 --> 00:13:52,430 As the planet nears the size of Jupiter, 273 00:13:52,430 --> 00:13:54,150 insect and other invertebrates 274 00:13:54,150 --> 00:13:56,800 will cope better with the higher gravity than humans. 275 00:13:58,060 --> 00:14:00,963 But that won't help with that happens next. 276 00:14:03,740 --> 00:14:07,000 With gravity now 11 times what it was, 277 00:14:07,000 --> 00:14:09,223 the moon would be pulled from its orbit. 278 00:14:11,380 --> 00:14:13,430 So if you make the Earth 11 times bigger 279 00:14:13,430 --> 00:14:15,290 which is essentially the size of Jupiter, 280 00:14:15,290 --> 00:14:17,606 the moon can no longer go around the Earth anymore. 281 00:14:17,606 --> 00:14:19,007 It will crash into the Earth 282 00:14:19,007 --> 00:14:21,240 and it'll crash into the Earth in about three hours 283 00:14:21,240 --> 00:14:22,526 from the point 284 00:14:22,526 --> 00:14:24,597 where you actually increase the mass of the Earth. 285 00:14:24,597 --> 00:14:25,630 The Earth's gravity 286 00:14:25,630 --> 00:14:28,863 is now just too strong for the moon to stay in orbit. 287 00:14:34,309 --> 00:14:36,540 (moon exploding) 288 00:14:36,540 --> 00:14:38,253 The result would be catastrophic. 289 00:14:50,820 --> 00:14:53,000 Life as we know it could not survive 290 00:14:53,000 --> 00:14:54,943 an Earth the size of Jupiter. 291 00:14:58,450 --> 00:15:01,653 Size connects every part of our universe. 292 00:15:03,100 --> 00:15:05,550 Changing the size of one thing 293 00:15:05,550 --> 00:15:07,413 can affect almost everything. 294 00:15:09,330 --> 00:15:12,540 So it's time to put the planet back 295 00:15:12,540 --> 00:15:13,727 to the size it was. 296 00:15:20,150 --> 00:15:22,680 If we can't change the size of the planet, 297 00:15:22,680 --> 00:15:25,683 how about changing the size of life on the planet? 298 00:15:28,520 --> 00:15:31,693 Living things come in a huge variety of sizes. 299 00:15:33,354 --> 00:15:35,733 But can we make them bigger? 300 00:15:37,300 --> 00:15:40,023 Will giant hearts and lungs still work? 301 00:15:41,170 --> 00:15:43,493 Will giant legs still support us? 302 00:15:44,830 --> 00:15:47,380 The answer is that it depends. 303 00:15:47,380 --> 00:15:48,740 When it comes to living things, 304 00:15:48,740 --> 00:15:51,023 size works in mysterious ways. 305 00:15:52,922 --> 00:15:54,630 Take insects. 306 00:15:55,516 --> 00:15:57,300 As animals go, 307 00:15:57,300 --> 00:15:58,863 we think of them as small. 308 00:16:00,300 --> 00:16:01,787 Even the very biggest insects, 309 00:16:01,787 --> 00:16:04,755 weight no more than 115 grams 310 00:16:04,755 --> 00:16:08,373 and have wingspans no greater than 28 centimeters. 311 00:16:09,300 --> 00:16:11,300 But 300 million years ago 312 00:16:11,300 --> 00:16:15,220 insects were much, much bigger. 313 00:16:15,220 --> 00:16:16,660 Take meganeura, 314 00:16:16,660 --> 00:16:18,300 a dragonfly-like insect 315 00:16:18,300 --> 00:16:20,673 with a wing span of three quarters of a meter. 316 00:16:22,002 --> 00:16:25,120 Is there a reason history can't repeat itself 317 00:16:25,120 --> 00:16:27,250 and giant insects like Meganeura 318 00:16:27,250 --> 00:16:29,600 take to the skies once more? 319 00:16:29,600 --> 00:16:31,404 Well in fact, there is. 320 00:16:31,404 --> 00:16:34,404 Insects don't have lungs like we do. 321 00:16:35,296 --> 00:16:36,129 Insects breathe 322 00:16:36,129 --> 00:16:37,870 through tiny little openings in their body, 323 00:16:37,870 --> 00:16:39,600 so-called spiracles, 324 00:16:39,600 --> 00:16:41,700 which connect to even finer tubes called tracheals 325 00:16:41,700 --> 00:16:43,361 which permeate the entire body. 326 00:16:43,361 --> 00:16:46,030 So this network transports oxygen 327 00:16:46,030 --> 00:16:47,610 to each and every single cell 328 00:16:47,610 --> 00:16:49,233 and removes carbon dioxide. 329 00:16:50,202 --> 00:16:52,200 It's a system that works well 330 00:16:52,200 --> 00:16:53,993 but only for small bodies. 331 00:16:55,220 --> 00:16:57,250 You might think of the way that insects breathe 332 00:16:57,250 --> 00:17:00,380 as letting oxygen sink in through their tissues. 333 00:17:00,380 --> 00:17:01,430 Now that's fine for everything 334 00:17:01,430 --> 00:17:02,980 that's very close to their body surface 335 00:17:02,980 --> 00:17:04,130 but it becomes harder and harder 336 00:17:04,130 --> 00:17:07,425 to reach structures that are deep inside the body. 337 00:17:07,425 --> 00:17:09,374 And if you become larger and larger, 338 00:17:09,374 --> 00:17:12,660 you have more and more volume relative to your surface area 339 00:17:12,660 --> 00:17:14,100 and therefore it becomes harder and harder 340 00:17:14,100 --> 00:17:15,210 to actually reach the structures 341 00:17:15,210 --> 00:17:16,800 that are deep inside your body. 342 00:17:16,800 --> 00:17:18,530 If the way that insects breathe 343 00:17:18,530 --> 00:17:20,050 limits their size today, 344 00:17:20,050 --> 00:17:23,277 why were they so much bigger in the past? 345 00:17:23,277 --> 00:17:24,840 300 million years ago, 346 00:17:24,840 --> 00:17:26,580 the oxygen content in the atmosphere was a lot higher, 347 00:17:26,580 --> 00:17:28,826 around one and a half times as high as now. 348 00:17:28,826 --> 00:17:31,200 So we now have about 21% oxygen concentration 349 00:17:31,200 --> 00:17:34,764 and it used to be 32, 31 percent. 350 00:17:34,764 --> 00:17:36,670 In today's atmosphere, 351 00:17:36,670 --> 00:17:40,413 insects this big just can't get enough oxygen to function. 352 00:17:44,710 --> 00:17:48,030 Insects today have to be small to thrive. 353 00:17:48,030 --> 00:17:50,180 They have already reached their size limit. 354 00:17:55,120 --> 00:17:56,695 But for other living things, 355 00:17:56,695 --> 00:17:58,626 the rules are different. 356 00:17:58,626 --> 00:18:02,223 And some people are already making giant happen. 357 00:18:05,690 --> 00:18:07,400 My twin brother and I, 358 00:18:07,400 --> 00:18:09,610 we live and breathe pumpkins. 359 00:18:09,610 --> 00:18:11,526 We always have done. 360 00:18:11,526 --> 00:18:14,470 These two men have devoted their lives 361 00:18:14,470 --> 00:18:17,013 to making pumpkins into giants. 362 00:18:19,310 --> 00:18:22,030 When he and I were little kids, 363 00:18:22,030 --> 00:18:23,760 we took one of these seeds 364 00:18:23,760 --> 00:18:26,290 and we planted it before we went on holiday. 365 00:18:26,290 --> 00:18:27,750 And since thereabouts 366 00:18:27,750 --> 00:18:28,583 we haven't stopped 367 00:18:28,583 --> 00:18:29,980 and that's 42 years ago. 368 00:18:29,980 --> 00:18:32,263 And it's just out of total passion really. 369 00:18:35,441 --> 00:18:38,640 The seed is, they're like race horses. 370 00:18:38,640 --> 00:18:40,433 We can look year to year 371 00:18:40,433 --> 00:18:42,420 and you'll see that they get a pedigree 372 00:18:42,420 --> 00:18:44,470 and then you know that this seed in particular 373 00:18:44,470 --> 00:18:48,140 will grow lots of pumpkins to 2,000 pounds. 374 00:18:48,140 --> 00:18:49,750 It's a competitive business 375 00:18:49,750 --> 00:18:52,650 and the brothers put plenty of time and money 376 00:18:52,650 --> 00:18:54,420 into their passion. 377 00:18:54,420 --> 00:18:56,880 But however much work the brothers put in, 378 00:18:56,880 --> 00:19:00,313 there's one thing that limits how big a pumpkin can get. 379 00:19:01,420 --> 00:19:03,090 After around 100 days, 380 00:19:03,090 --> 00:19:05,830 pumpkins are genetically programmed to stop growing 381 00:19:05,830 --> 00:19:08,320 as their skins thicken and harden. 382 00:19:08,320 --> 00:19:11,243 So growing the biggest pumpkin is all about speed. 383 00:19:12,660 --> 00:19:14,470 It's physically got to grow that fast. 384 00:19:14,470 --> 00:19:17,310 So next year, we'll be putting the heating up at night 385 00:19:17,310 --> 00:19:18,870 to 22 degrees. 386 00:19:18,870 --> 00:19:20,407 We need to get this thing growing 387 00:19:20,407 --> 00:19:22,650 faster than 57 pounds a day. 388 00:19:22,650 --> 00:19:24,940 So we need to get it going as fast as we can. 389 00:19:24,940 --> 00:19:27,870 And it's just getting everything perfect 390 00:19:27,870 --> 00:19:29,663 and speed, speed, speedy really. 391 00:19:33,810 --> 00:19:35,980 It's a nerve wracking time for us. 392 00:19:35,980 --> 00:19:39,917 That's a year and a massive amount of work. 393 00:19:39,917 --> 00:19:41,060 It'll be the biggest one yet. 394 00:19:41,060 --> 00:19:42,291 I told you. 395 00:19:42,291 --> 00:19:44,120 That's good news. 396 00:19:44,120 --> 00:19:45,123 Bit more. 397 00:19:48,760 --> 00:19:50,170 Done. 398 00:19:50,170 --> 00:19:51,660 Good job. 399 00:19:51,660 --> 00:19:52,910 We need to get the world record 400 00:19:52,910 --> 00:19:54,560 and we're getting close to it 401 00:19:54,560 --> 00:19:56,730 and we've grown some big ones this year 402 00:19:56,730 --> 00:19:57,850 so we'll see how we do. 403 00:19:57,850 --> 00:20:00,130 Hopefully our season's gonna get rewarded 404 00:20:00,130 --> 00:20:01,163 with something good. 405 00:20:02,405 --> 00:20:05,322 (mysterious music) 406 00:20:10,850 --> 00:20:12,810 If it works for pumpkins, 407 00:20:12,810 --> 00:20:15,040 why can't people move up the scale 408 00:20:15,040 --> 00:20:17,060 to challenge the blue whale, 409 00:20:17,060 --> 00:20:18,833 the biggest animal of all time? 410 00:20:21,550 --> 00:20:23,650 Perhaps giants of legend 411 00:20:23,650 --> 00:20:25,775 could be made a reality. 412 00:20:25,775 --> 00:20:28,442 (alarm beeping) 413 00:20:29,310 --> 00:20:30,810 If two men can make a pumpkin 414 00:20:30,810 --> 00:20:33,690 200 times as big as a pumpkin should be, 415 00:20:33,690 --> 00:20:35,030 surely we can make a human 416 00:20:35,030 --> 00:20:37,380 just three times normal size, 417 00:20:37,380 --> 00:20:38,680 five meters tall. 418 00:20:46,074 --> 00:20:47,610 Not a real giant, 419 00:20:47,610 --> 00:20:50,517 but way taller than any human has ever been before. 420 00:20:58,764 --> 00:21:00,521 A human being five meters tall may look possible 421 00:21:00,521 --> 00:21:03,543 but they would be doomed to fail. 422 00:21:04,700 --> 00:21:07,053 To find out why, we need to go to Turkey. 423 00:21:18,158 --> 00:21:21,000 When I go to a hotel or to a friends, 424 00:21:21,000 --> 00:21:23,940 the biggest problem is finding a bed I fit in. 425 00:21:23,940 --> 00:21:25,927 The standard bed is just two meters. 426 00:21:25,927 --> 00:21:28,023 I usually put two beds together. 427 00:21:29,270 --> 00:21:31,258 As well as having oversized feet, 428 00:21:31,258 --> 00:21:34,620 Sultan Kosen has an oversized pituitary gland 429 00:21:34,620 --> 00:21:37,200 that has produced too much human growth hormone 430 00:21:37,200 --> 00:21:39,090 throughout his life. 431 00:21:39,090 --> 00:21:41,600 As a result, he is tall, 432 00:21:41,600 --> 00:21:43,995 2.51 meters tall, to be specific 433 00:21:43,995 --> 00:21:46,913 which makes him the world's tallest man. 434 00:21:48,220 --> 00:21:50,210 Being this tall comes with perks 435 00:21:50,210 --> 00:21:51,483 but also problems. 436 00:21:52,420 --> 00:21:53,963 He keeps breaking his legs. 437 00:22:01,630 --> 00:22:04,360 Sultan has traveled from his hometown to Ankara 438 00:22:04,360 --> 00:22:05,360 to visit his doctor. 439 00:22:16,115 --> 00:22:20,032 (speaking in foreign language) 440 00:22:21,540 --> 00:22:24,210 This is the femoral fracture 441 00:22:24,210 --> 00:22:26,380 that has occurred six years ago. 442 00:22:26,380 --> 00:22:28,260 It was a midshaft fracture 443 00:22:28,260 --> 00:22:30,503 which has replaced all the fragments 444 00:22:30,503 --> 00:22:33,660 and this long rod plaque 445 00:22:33,660 --> 00:22:35,480 has been inserted with nails 446 00:22:35,480 --> 00:22:36,840 to stabilize the fragments. 447 00:22:36,840 --> 00:22:40,540 It's a significant relationship 448 00:22:40,540 --> 00:22:41,750 with the length of the bone 449 00:22:41,750 --> 00:22:44,950 because you know that if you apply a force, 450 00:22:44,950 --> 00:22:46,890 on a very long rod, 451 00:22:46,890 --> 00:22:47,990 you can easily break it. 452 00:22:47,990 --> 00:22:50,143 If it is relatively short, 453 00:22:51,240 --> 00:22:52,940 it's not so easy to break it 454 00:22:52,940 --> 00:22:55,653 because of the physical properties of the bone. 455 00:22:58,306 --> 00:23:01,210 Sultan's other problem is more practical. 456 00:23:01,210 --> 00:23:03,150 Like our five meter human, 457 00:23:03,150 --> 00:23:04,483 he keeps falling over. 458 00:23:06,537 --> 00:23:09,117 He cannot walk as we walk. 459 00:23:09,117 --> 00:23:11,690 That's his basic problem. 460 00:23:11,690 --> 00:23:14,673 That's why he's so prone to easy falls. 461 00:23:27,158 --> 00:23:30,370 (speaking in foreign language) 462 00:23:30,370 --> 00:23:31,800 Size doesn't matter. 463 00:23:31,800 --> 00:23:33,140 What matters is health 464 00:23:33,140 --> 00:23:35,057 and overcoming obstructions. 465 00:23:35,057 --> 00:23:37,036 When obstructions are overcome, 466 00:23:37,036 --> 00:23:39,386 it doesn't matter whether you're short or tall. 467 00:23:44,870 --> 00:23:46,150 Sultan's health issues 468 00:23:46,150 --> 00:23:48,020 reveal one of the main problems 469 00:23:48,020 --> 00:23:50,023 faced by large living things. 470 00:23:51,573 --> 00:23:53,690 Something we will need to understand 471 00:23:53,690 --> 00:23:55,573 as we begin to make bigger humans. 472 00:23:59,246 --> 00:24:02,490 A five meter human would be even more likely 473 00:24:02,490 --> 00:24:05,720 to break their legs than Sultan, but why? 474 00:24:05,720 --> 00:24:08,200 To find out, let's make this statue bigger 475 00:24:08,200 --> 00:24:09,333 and see what happens. 476 00:24:17,290 --> 00:24:19,540 You might think you just get a larger statue 477 00:24:20,600 --> 00:24:21,550 but you'd be wrong. 478 00:24:23,320 --> 00:24:24,920 There's something else going on. 479 00:24:29,520 --> 00:24:31,873 Let's try again and find out what. 480 00:24:34,260 --> 00:24:36,440 By the time it's double the size, 481 00:24:36,440 --> 00:24:39,491 the arms weigh eight times what they did 482 00:24:39,491 --> 00:24:41,993 but are only four times as strong. 483 00:24:46,914 --> 00:24:48,990 Why is that? 484 00:24:48,990 --> 00:24:52,294 The statue's weight depends on three dimensions. 485 00:24:52,294 --> 00:24:54,310 So if you double the height, 486 00:24:54,310 --> 00:24:57,000 the weight goes up eight times. 487 00:24:57,000 --> 00:24:59,897 Strength depends on cross sectional area 488 00:24:59,897 --> 00:25:02,520 which is just two dimensional. 489 00:25:02,520 --> 00:25:04,833 So it doesn't increase as fast as weight. 490 00:25:06,300 --> 00:25:07,640 The result? 491 00:25:07,640 --> 00:25:09,544 Arms that fall off. 492 00:25:09,544 --> 00:25:12,960 So if you want to double the size of a statue, 493 00:25:12,960 --> 00:25:15,193 you'll have to reengineer it to be big. 494 00:25:16,880 --> 00:25:18,360 Just ask Venus. 495 00:25:18,360 --> 00:25:19,510 She knows all about it. 496 00:25:22,734 --> 00:25:25,944 So if we're going to make bigger people 497 00:25:25,944 --> 00:25:27,700 we'd better do the same 498 00:25:27,700 --> 00:25:29,633 and reengineer the human body. 499 00:25:30,860 --> 00:25:31,693 But how? 500 00:25:33,502 --> 00:25:34,613 There are plenty of other living things 501 00:25:34,613 --> 00:25:35,860 that have managed to make it 502 00:25:35,860 --> 00:25:37,433 to the bigger end of the scale. 503 00:25:39,890 --> 00:25:42,060 What can we learn from them 504 00:25:42,060 --> 00:25:43,963 about building a giant human? 505 00:25:45,450 --> 00:25:47,390 The tallest living things on the planet 506 00:25:47,390 --> 00:25:48,760 are coast redwoods 507 00:25:48,760 --> 00:25:50,333 to be found in California. 508 00:25:51,990 --> 00:25:55,270 I love these trees because of their massive size, 509 00:25:55,270 --> 00:25:56,480 their old age 510 00:25:56,480 --> 00:26:00,333 and because of the way they build the forest that they do. 511 00:26:01,520 --> 00:26:02,810 Professor Todd Dawson 512 00:26:02,810 --> 00:26:04,550 and his team of scientists 513 00:26:04,550 --> 00:26:06,450 have studied every inch of these trees 514 00:26:11,530 --> 00:26:12,843 right to the very top. 515 00:26:16,250 --> 00:26:19,503 If anyone knows why they're so tall, it's him. 516 00:26:23,760 --> 00:26:27,860 So redwoods are a remarkably long lived tree 517 00:26:27,860 --> 00:26:31,280 and the coast redwood can live more than 2,500 years. 518 00:26:31,280 --> 00:26:33,860 Because they're plants, they're constantly growing. 519 00:26:33,860 --> 00:26:35,430 And because they're very old, 520 00:26:35,430 --> 00:26:38,520 as long as they keep growing and they have that old age, 521 00:26:38,520 --> 00:26:39,353 they're just gonna keep 522 00:26:39,353 --> 00:26:41,163 getting bigger and bigger and bigger. 523 00:26:49,133 --> 00:26:52,990 So a tree like the one we're standing next to here, 524 00:26:52,990 --> 00:26:56,420 it probably weighs thousands and thousands 525 00:26:56,420 --> 00:26:58,853 and thousands of pounds, many tons. 526 00:27:00,126 --> 00:27:02,790 One of the things that we notice about these trees 527 00:27:02,790 --> 00:27:04,120 as they grow 528 00:27:04,120 --> 00:27:07,320 is they begin to add more at the base. 529 00:27:07,320 --> 00:27:09,313 So you go from a very small tree 530 00:27:09,313 --> 00:27:11,430 that just goes right into the ground 531 00:27:11,430 --> 00:27:12,790 like a carrot in the Earth 532 00:27:12,790 --> 00:27:14,163 and as they grow larger, 533 00:27:14,163 --> 00:27:16,550 they get heavier and heavier and heavier, 534 00:27:16,550 --> 00:27:17,620 they begin to buttress, 535 00:27:17,620 --> 00:27:20,020 they begin to add mass at the base 536 00:27:20,020 --> 00:27:22,610 'cause they have to have a way to support themselves. 537 00:27:22,610 --> 00:27:25,438 Eight meters, five centimeters, 538 00:27:25,438 --> 00:27:27,003 nice sized tree. 539 00:27:28,750 --> 00:27:30,920 They sort of built some sort of a structure 540 00:27:30,920 --> 00:27:33,363 like an elephant's foot if you will at the base. 541 00:27:34,620 --> 00:27:37,410 Remarkable set of compensation mechanisms. 542 00:27:39,040 --> 00:27:40,963 So is this the limit 543 00:27:40,963 --> 00:27:43,570 or could we imagine a parallel universe 544 00:27:43,570 --> 00:27:45,797 where the biggest of living things 545 00:27:45,797 --> 00:27:47,387 may be even bigger? 546 00:27:49,340 --> 00:27:50,590 The redwood's strategy 547 00:27:50,590 --> 00:27:52,070 of shape shifting, 548 00:27:52,070 --> 00:27:54,730 getting more triangular as they grow taller, 549 00:27:54,730 --> 00:27:55,940 means that their trunks 550 00:27:55,940 --> 00:27:58,400 can support the weight of taller trees. 551 00:27:58,400 --> 00:27:59,950 But they'd hit another problem. 552 00:28:06,188 --> 00:28:07,380 So one of the factors 553 00:28:07,380 --> 00:28:09,010 that limits how tall trees get 554 00:28:09,010 --> 00:28:10,630 is their ability to get water 555 00:28:10,630 --> 00:28:13,100 to the top of the tree itself. 556 00:28:13,100 --> 00:28:16,490 And while a lot of trees may stop their growth, 557 00:28:16,490 --> 00:28:19,140 redwoods have a special way of dealing 558 00:28:19,140 --> 00:28:22,380 with that water limitation as they get taller. 559 00:28:22,380 --> 00:28:25,503 For example, we've got leaves 560 00:28:25,503 --> 00:28:27,635 that come from the lower part of the ground, 561 00:28:27,635 --> 00:28:28,883 and ah, 562 00:28:31,179 --> 00:28:33,290 these much smaller leaves, 563 00:28:33,290 --> 00:28:35,287 they come from the very top of the tree. 564 00:28:35,287 --> 00:28:37,580 And as the leaf area goes down, 565 00:28:37,580 --> 00:28:41,000 the amount of water used goes down as well. 566 00:28:41,000 --> 00:28:43,200 So they become more thrifty in their water use 567 00:28:43,200 --> 00:28:44,070 at the top of the tree 568 00:28:44,070 --> 00:28:46,170 than they do at the bottom of the tree. 569 00:28:46,170 --> 00:28:49,070 Moving water upwards several hundred feet 570 00:28:49,070 --> 00:28:49,993 needs pressure. 571 00:28:50,910 --> 00:28:52,860 Fluid migrating into the roots 572 00:28:52,860 --> 00:28:54,070 pushes water up 573 00:28:54,070 --> 00:28:55,750 while at the leaves, 574 00:28:55,750 --> 00:28:58,240 sunlight causes water to evaporate 575 00:28:58,240 --> 00:28:59,690 leading to low pressure 576 00:28:59,690 --> 00:29:01,603 which pulls water upwards. 577 00:29:02,500 --> 00:29:04,570 The redwoods smaller leaves at the top 578 00:29:04,570 --> 00:29:06,680 mean only a small amount of water 579 00:29:06,680 --> 00:29:07,780 has to go all the way. 580 00:29:09,620 --> 00:29:11,830 But grow a redwood too tall 581 00:29:11,830 --> 00:29:14,400 and not even those special adaptations 582 00:29:14,400 --> 00:29:16,723 can solve the water supply problem. 583 00:29:17,957 --> 00:29:20,320 The leaves would dry out and die 584 00:29:21,730 --> 00:29:23,623 and the tree would go no further. 585 00:29:30,810 --> 00:29:33,580 Despite their problems getting water to the top, 586 00:29:33,580 --> 00:29:36,530 trees still show us just how big you can get 587 00:29:36,530 --> 00:29:38,423 if you change your shape as you grow. 588 00:29:39,783 --> 00:29:41,360 That means that bigger creatures 589 00:29:41,360 --> 00:29:44,840 can't just be scaled up version of smaller creatures. 590 00:29:44,840 --> 00:29:46,680 They need profound adaptations 591 00:29:46,680 --> 00:29:48,883 to overcome the challenges of size. 592 00:29:53,807 --> 00:29:56,080 Take a dog for example. 593 00:29:56,080 --> 00:29:58,320 This dog's skeleton makes up eight percent 594 00:29:58,320 --> 00:29:59,583 of its total body weight. 595 00:30:01,529 --> 00:30:03,670 But if we want to make it bigger 596 00:30:03,670 --> 00:30:05,220 we'll have to beef it up a bit. 597 00:30:10,690 --> 00:30:12,420 At three times the height, 598 00:30:12,420 --> 00:30:14,080 thicker bones mean a skeleton 599 00:30:14,080 --> 00:30:16,453 that weights 10% of its body weight. 600 00:30:27,220 --> 00:30:29,350 But if we want to make it bigger still, 601 00:30:29,350 --> 00:30:31,683 we've got to overcome yet another problem. 602 00:30:36,460 --> 00:30:39,960 Big animals have less surface area per kilogram of weight 603 00:30:39,960 --> 00:30:41,740 than small ones. 604 00:30:41,740 --> 00:30:45,053 So they have proportionally less skin to lose heat from. 605 00:30:46,020 --> 00:30:47,713 This means they can overheat. 606 00:30:48,870 --> 00:30:50,820 Elephants evolved to be large 607 00:30:50,820 --> 00:30:53,110 so that they could dominate their environment, 608 00:30:53,110 --> 00:30:54,620 be safe from predators 609 00:30:54,620 --> 00:30:56,193 and reach food more easily. 610 00:30:57,120 --> 00:30:58,220 But they also needed a way 611 00:30:58,220 --> 00:31:00,593 to avoid overheating in a hot environment. 612 00:31:03,039 --> 00:31:05,410 Elephants don't just have large ears 613 00:31:05,410 --> 00:31:06,780 because they look good. 614 00:31:06,780 --> 00:31:08,863 They also help them to regulate heat. 615 00:31:13,800 --> 00:31:14,900 Billy, our eight year old, 616 00:31:14,900 --> 00:31:17,150 is being very energetic right now 617 00:31:17,150 --> 00:31:19,880 but we're still seeing because of the colder temperatures 618 00:31:19,880 --> 00:31:24,760 his ears are much colder than the rest of his body. 619 00:31:24,760 --> 00:31:26,730 So it really shows how efficient they are 620 00:31:26,730 --> 00:31:29,040 at controlling their body temperature 621 00:31:29,040 --> 00:31:30,063 by using their ears. 622 00:31:31,511 --> 00:31:33,960 In the summer times, we would see the opposite. 623 00:31:33,960 --> 00:31:35,600 Their ears would be much warmer, 624 00:31:35,600 --> 00:31:37,950 the veins would be full of blood 625 00:31:37,950 --> 00:31:39,910 using it as an air conditioner 626 00:31:39,910 --> 00:31:42,903 helping cool down the rest of the body temperature. 627 00:31:48,640 --> 00:31:50,970 Maybe our giant dog could learn a lesson 628 00:31:50,970 --> 00:31:52,363 from his elephant cousins. 629 00:31:53,200 --> 00:31:54,460 Grow a pair of bigger ears 630 00:31:54,460 --> 00:31:55,930 to increase surface area 631 00:31:55,930 --> 00:31:57,110 and lose the fur, 632 00:31:57,110 --> 00:31:58,493 since hair traps heat. 633 00:31:59,710 --> 00:32:01,800 With stronger bones and a way to keep cool, 634 00:32:01,800 --> 00:32:04,203 we can safely make an even bigger dog now. 635 00:32:06,000 --> 00:32:07,283 But how big can we go? 636 00:32:09,810 --> 00:32:13,133 How about as large as a medium size dinosaur? 637 00:32:14,100 --> 00:32:15,490 Which is just big enough 638 00:32:15,490 --> 00:32:16,890 to run into another problem. 639 00:32:30,660 --> 00:32:32,073 It's just too slow. 640 00:32:42,347 --> 00:32:45,230 Herve Bocherens is a paleontologist 641 00:32:45,230 --> 00:32:48,493 who knows exactly why big animals are so slow. 642 00:32:50,582 --> 00:32:53,309 Large animals have an issue with distance 643 00:32:53,309 --> 00:32:56,307 the signal have to travel along the nerves. 644 00:32:57,920 --> 00:33:02,400 Of course, if you are already about 20 meters long, 645 00:33:02,400 --> 00:33:04,200 the signal has to be both ways 646 00:33:04,200 --> 00:33:07,280 and therefore it's already significant fraction of a second 647 00:33:07,280 --> 00:33:10,690 that takes time for the signal to travel. 648 00:33:10,690 --> 00:33:13,490 And therefore the reaction time of big animals 649 00:33:13,490 --> 00:33:17,230 will be slower than the reaction time of smaller animals 650 00:33:17,230 --> 00:33:20,433 and this will make a difference in their life. 651 00:33:22,440 --> 00:33:24,040 So today for instance, 652 00:33:24,040 --> 00:33:26,550 the largest land animals are elephants 653 00:33:26,550 --> 00:33:27,920 and it has been observed 654 00:33:27,920 --> 00:33:29,971 that elephants have to be quite careful 655 00:33:29,971 --> 00:33:31,780 when they walk 656 00:33:31,780 --> 00:33:35,460 because the signal has to travel quite a long distance. 657 00:33:35,460 --> 00:33:38,166 And when they hit something with their foot, for instance, 658 00:33:38,166 --> 00:33:41,840 it takes a couple of milliseconds 659 00:33:41,840 --> 00:33:42,970 to reach the brain. 660 00:33:42,970 --> 00:33:46,390 And therefore, they hae to wait until the signal comes back 661 00:33:46,390 --> 00:33:48,890 to know if they have hit something with their foot 662 00:33:49,795 --> 00:33:50,628 before they make the next step. 663 00:33:54,170 --> 00:33:56,810 Being slow is not good news for a dog 664 00:33:56,810 --> 00:33:58,720 which needs to catch prey. 665 00:33:58,720 --> 00:34:00,820 A giant dog might starve to death 666 00:34:02,141 --> 00:34:04,233 unless it has someone to feed it. 667 00:34:10,010 --> 00:34:11,440 We've managed a dog, 668 00:34:11,440 --> 00:34:14,090 so it should be straight forward to scale up a human. 669 00:34:16,520 --> 00:34:17,600 First thing to remember 670 00:34:17,600 --> 00:34:20,480 is that a human just five times normal height 671 00:34:20,480 --> 00:34:24,370 would weigh 125 times normal weight. 672 00:34:24,370 --> 00:34:26,343 So he would need much thicker bones. 673 00:34:29,690 --> 00:34:32,070 Then of course he'll need big ears like an elephant 674 00:34:32,070 --> 00:34:33,470 to get rid of all that heat. 675 00:34:36,570 --> 00:34:38,800 But before our giant gets any bigger, 676 00:34:38,800 --> 00:34:41,963 we have to face one challenge that most big animals don't. 677 00:34:43,080 --> 00:34:44,783 Humans walk on two legs. 678 00:34:51,037 --> 00:34:54,470 Herve Bocherens is studying another primate 679 00:34:54,470 --> 00:34:57,420 that tried to get giant in the past. 680 00:34:57,420 --> 00:34:59,913 It's a story that begins in an unusual place. 681 00:35:01,220 --> 00:35:04,434 It started in a Chinese pharmacy in Hong Kong 682 00:35:04,434 --> 00:35:06,320 where a paleontologist 683 00:35:06,320 --> 00:35:09,183 was looking at what is called dragon teeth. 684 00:35:11,620 --> 00:35:13,480 And among these fossil material, 685 00:35:13,480 --> 00:35:15,130 there were some fossil human teeth 686 00:35:15,130 --> 00:35:17,300 but also teeth that were much bigger, 687 00:35:17,300 --> 00:35:18,950 looked like humans. 688 00:35:18,950 --> 00:35:21,150 And these were the first discoveries 689 00:35:21,150 --> 00:35:23,190 of Gigantopithecus. 690 00:35:23,190 --> 00:35:24,970 They weren't dragon's teeth. 691 00:35:24,970 --> 00:35:28,580 They were teeth from the biggest ape to ever live, 692 00:35:28,580 --> 00:35:30,530 Gigantopithecus. 693 00:35:30,530 --> 00:35:33,140 Estimating the size of an animal 694 00:35:33,140 --> 00:35:35,410 based on just teeth and lower jaw 695 00:35:35,410 --> 00:35:37,440 is a difficult thing 696 00:35:37,440 --> 00:35:41,060 but we can say that at least it was twice as heavy 697 00:35:41,060 --> 00:35:42,380 as a gorilla. 698 00:35:42,380 --> 00:35:44,920 So the weight could be up to 500 kilogram 699 00:35:44,920 --> 00:35:47,193 which is a maximum estimate. 700 00:35:48,735 --> 00:35:51,130 That makes it the largest primate 701 00:35:51,130 --> 00:35:53,280 that has ever existed. 702 00:35:53,280 --> 00:35:55,563 But estimating its height is even harder. 703 00:36:00,590 --> 00:36:01,600 Most probably, 704 00:36:01,600 --> 00:36:03,370 it was not standing so much 705 00:36:03,370 --> 00:36:05,230 because with such a heavy weight, 706 00:36:05,230 --> 00:36:07,243 it was probably essentially quadrupedal. 707 00:36:08,416 --> 00:36:12,050 And therefore, it's more a comparison with a gorilla 708 00:36:12,050 --> 00:36:15,140 who is mostly walking on four legs 709 00:36:15,140 --> 00:36:17,023 rather than walking erect. 710 00:36:19,421 --> 00:36:21,900 Gigantopithecus was just too big 711 00:36:21,900 --> 00:36:23,543 to stand tall like a human. 712 00:36:24,943 --> 00:36:27,540 We have many examples of in the past 713 00:36:27,540 --> 00:36:29,610 of animals that started bipedal 714 00:36:29,610 --> 00:36:31,980 and had to go back to their four legs. 715 00:36:31,980 --> 00:36:33,780 And when they grew bigger, 716 00:36:33,780 --> 00:36:35,720 it means that they had to carry their weight 717 00:36:35,720 --> 00:36:36,553 on four legs 718 00:36:36,553 --> 00:36:38,083 and not anymore on two legs. 719 00:36:41,200 --> 00:36:44,900 So as we continue to grow our giant human, 720 00:36:44,900 --> 00:36:48,377 should he walk on all fours like a Gigantopithecus? 721 00:36:57,530 --> 00:36:58,363 Perhaps not. 722 00:37:04,490 --> 00:37:07,030 If it's going to be a giant human, 723 00:37:07,030 --> 00:37:08,940 it has to be bipedal 724 00:37:08,940 --> 00:37:13,560 because bipedalism is the thing, the one major thing, 725 00:37:13,560 --> 00:37:18,500 that sets our genus or our group, the hominids, 726 00:37:18,500 --> 00:37:21,050 off from al of the other primates. 727 00:37:21,050 --> 00:37:22,993 We are habitually bipedal. 728 00:37:24,290 --> 00:37:26,890 Being bipedal has upsides. 729 00:37:26,890 --> 00:37:28,130 Your head is raised 730 00:37:28,130 --> 00:37:30,270 so you can see danger further away. 731 00:37:32,225 --> 00:37:34,383 And you can reach higher to get food. 732 00:37:35,370 --> 00:37:36,350 But for humans, 733 00:37:36,350 --> 00:37:38,980 perhaps the biggest evolutionary advantage 734 00:37:38,980 --> 00:37:41,773 is that it keeps your hands free for other things. 735 00:37:44,992 --> 00:37:45,825 But the bottom line 736 00:37:45,825 --> 00:37:47,610 is if it's not on two legs 737 00:37:47,610 --> 00:37:48,983 it's just not a human. 738 00:37:50,350 --> 00:37:53,430 So if we're going to make a giant bipedal human, 739 00:37:53,430 --> 00:37:55,670 that means we hae to support all that weight 740 00:37:55,670 --> 00:37:56,903 on just two legs. 741 00:37:58,823 --> 00:38:00,290 If you're a giant 742 00:38:00,290 --> 00:38:01,830 and you're really, really tall, 743 00:38:01,830 --> 00:38:05,170 well you've got to get that blood pumped away from the heart 744 00:38:05,170 --> 00:38:07,850 and up to the brain, very important. 745 00:38:07,850 --> 00:38:09,430 So you need a big pump, 746 00:38:09,430 --> 00:38:10,620 a big heart, 747 00:38:10,620 --> 00:38:12,070 and that means a big chest 748 00:38:12,070 --> 00:38:13,490 to put the heart in 749 00:38:13,490 --> 00:38:15,370 and it's gotta go uphill. 750 00:38:15,370 --> 00:38:20,370 And so I might put the heart higher up within the chest. 751 00:38:20,600 --> 00:38:21,780 The heart is just a simple 752 00:38:21,780 --> 00:38:24,630 pump that has to get blood around the body. 753 00:38:24,630 --> 00:38:26,833 And pumping uphill is harder work. 754 00:38:27,935 --> 00:38:31,040 So a giant human needs as short a distance 755 00:38:31,040 --> 00:38:33,163 between heart and brain as possible. 756 00:38:35,140 --> 00:38:37,830 The chances are, however large his heart, 757 00:38:37,830 --> 00:38:40,120 our giant human would be lonely 758 00:38:40,120 --> 00:38:42,600 and not just because to he way he looks. 759 00:38:42,600 --> 00:38:44,530 Another consequence of being large 760 00:38:44,530 --> 00:38:46,330 is that the population will be small 761 00:38:46,330 --> 00:38:48,905 because each one need a lot of food. 762 00:38:48,905 --> 00:38:52,313 And so giants would probably not be very numerous. 763 00:38:53,590 --> 00:38:55,192 Even with a four-legged friend, 764 00:38:55,192 --> 00:38:58,093 life as a giant would be no fairytale. 765 00:38:59,689 --> 00:39:02,770 It would have to be a very strange creature indeed 766 00:39:02,770 --> 00:39:04,380 to overcome all the problems 767 00:39:04,380 --> 00:39:07,033 that being big creates for a human being. 768 00:39:08,210 --> 00:39:12,050 That's because size is intrinsic to everything. 769 00:39:12,050 --> 00:39:14,630 Your size determines what shape you are, 770 00:39:14,630 --> 00:39:16,373 how you live, what you eat. 771 00:39:17,900 --> 00:39:19,350 Change it too much 772 00:39:19,350 --> 00:39:21,793 and you simply get a different species. 773 00:39:22,810 --> 00:39:26,500 So let's put things back to how they were. 774 00:39:32,393 --> 00:39:35,060 (alarm beeping) 775 00:39:37,360 --> 00:39:40,693 We've changed the size of the Earth and everything on it 776 00:39:40,693 --> 00:39:43,120 and it really didn't work 777 00:39:43,120 --> 00:39:46,023 but there's one last thought experiment we can try. 778 00:39:47,344 --> 00:39:50,180 Because if we're going to change the size of things, 779 00:39:50,180 --> 00:39:52,280 we can't miss out something massive 780 00:39:52,280 --> 00:39:54,793 that lies at the very heart of our solar system, 781 00:39:58,490 --> 00:40:01,203 the sun, our nearest star. 782 00:40:03,280 --> 00:40:05,290 But when it comes to stars, 783 00:40:05,290 --> 00:40:06,593 does size matter? 784 00:40:08,598 --> 00:40:13,290 Size is crucial to the work of astrophysicist Volker Bromm 785 00:40:13,290 --> 00:40:14,940 because the size of a star 786 00:40:14,940 --> 00:40:17,180 determines how it behaves. 787 00:40:17,180 --> 00:40:18,200 When you think about stars, 788 00:40:18,200 --> 00:40:21,000 then size is absolutely essential 789 00:40:21,000 --> 00:40:24,020 because you could say that the size of a star, 790 00:40:24,020 --> 00:40:27,347 or more precisely the mass of a star is destiny. 791 00:40:27,347 --> 00:40:30,650 If a star's size is its destiny, 792 00:40:30,650 --> 00:40:32,850 just how big is ours? 793 00:40:32,850 --> 00:40:36,570 Well, it's 109 times wider than planet Earth 794 00:40:36,570 --> 00:40:39,653 and 330,000 times as massive. 795 00:40:40,540 --> 00:40:43,300 It accounts for 99.86 percent 796 00:40:43,300 --> 00:40:45,703 of all mass in the solar system. 797 00:40:47,640 --> 00:40:48,970 As it turns out, 798 00:40:48,970 --> 00:40:51,383 just the right size for life on Earth. 799 00:40:52,740 --> 00:40:55,980 The sun is, for us, the essential star. 800 00:40:55,980 --> 00:40:59,110 The sun really provides us with a perfect cosmic environment 801 00:40:59,110 --> 00:41:01,520 to enable life on Earth. 802 00:41:01,520 --> 00:41:04,200 How do we know the sun is so perfect? 803 00:41:04,200 --> 00:41:05,084 One way to find out 804 00:41:05,084 --> 00:41:07,890 is to visit our parallel universe, 805 00:41:07,890 --> 00:41:09,200 make the sun bigger 806 00:41:09,200 --> 00:41:11,023 and see if the world survives. 807 00:41:13,060 --> 00:41:15,193 Let's start by imagining our sun 808 00:41:15,193 --> 00:41:18,093 but with exactly double the amount of gas. 809 00:41:23,080 --> 00:41:25,267 You might imagine it would be twice as bright 810 00:41:25,267 --> 00:41:26,503 but you'd be wrong. 811 00:41:32,140 --> 00:41:34,100 How a star reacts to increasing the mass 812 00:41:34,100 --> 00:41:36,320 is highly nonintuitive. 813 00:41:36,320 --> 00:41:37,920 So you double the mass 814 00:41:37,920 --> 00:41:41,033 and you increase the energy output tenfold. 815 00:41:43,050 --> 00:41:43,970 On Earth, 816 00:41:43,970 --> 00:41:45,713 the effects would be staggering. 817 00:41:47,290 --> 00:41:49,250 The equilibrium temperature on Earth 818 00:41:49,250 --> 00:41:51,490 would go up by a significant factor. 819 00:41:51,490 --> 00:41:52,500 So we would have a much hotter Earth 820 00:41:52,500 --> 00:41:54,130 which would then suddenly 821 00:41:54,130 --> 00:41:56,453 become completely inhospitable. 822 00:41:57,660 --> 00:42:00,483 First, the ice caps would melt. 823 00:42:06,263 --> 00:42:08,903 Then the oceans and rivers would dry up. 824 00:42:09,870 --> 00:42:12,330 The surface of the Earth would eventually stabilize 825 00:42:12,330 --> 00:42:14,233 at over 200 degrees centigrade. 826 00:42:20,010 --> 00:42:21,520 But all is not lost. 827 00:42:21,520 --> 00:42:24,463 There is one way we could get things back to normal. 828 00:42:25,770 --> 00:42:28,870 A key question in modern astronomy 829 00:42:28,870 --> 00:42:32,470 is that we think about the region around any star 830 00:42:32,470 --> 00:42:36,069 where life, in principle, could be sustained. 831 00:42:36,069 --> 00:42:38,820 For life as we know it to exist, 832 00:42:38,820 --> 00:42:41,090 the temperature of a planet needs to be right 833 00:42:41,090 --> 00:42:43,800 for water to exist as a liquid. 834 00:42:43,800 --> 00:42:46,870 The area around any star where this could happen 835 00:42:46,870 --> 00:42:48,473 is called the goldilocks zone. 836 00:42:49,480 --> 00:42:51,990 You basically have a very, very special region 837 00:42:51,990 --> 00:42:52,920 around any star 838 00:42:52,920 --> 00:42:55,555 and this goldilocks zone of not too hot, not too cold, 839 00:42:55,555 --> 00:42:57,650 what we call the habitable zone 840 00:42:57,650 --> 00:43:00,680 is a very precious, precarious zone 841 00:43:00,680 --> 00:43:02,900 because if you play with the conditions in the central star 842 00:43:02,900 --> 00:43:04,540 everything changes. 843 00:43:04,540 --> 00:43:07,450 As a double mass sun burns so much hotter, 844 00:43:07,450 --> 00:43:10,423 this means the goldilocks zone is now further away, 845 00:43:11,260 --> 00:43:13,003 three times further away. 846 00:43:14,062 --> 00:43:16,580 So we just need to move planet Earth 847 00:43:17,500 --> 00:43:19,360 to its new resting place, 848 00:43:19,360 --> 00:43:20,680 well past Mars, 849 00:43:20,680 --> 00:43:24,823 450 million kilometers from the bigger sun. 850 00:43:26,010 --> 00:43:28,760 Here, life would not be in immediate danger. 851 00:43:28,760 --> 00:43:30,370 But it's far from ideal. 852 00:43:30,370 --> 00:43:34,840 The new longer orbit means a year is much longer. 853 00:43:34,840 --> 00:43:36,400 And so are the seasons. 854 00:43:36,400 --> 00:43:39,200 In fact, winter would last 16 months 855 00:43:39,200 --> 00:43:41,843 which would make growing crops very difficult. 856 00:43:43,000 --> 00:43:45,853 So could Earth survive around an even bigger sun? 857 00:43:46,989 --> 00:43:48,770 Before we can answer that, 858 00:43:48,770 --> 00:43:51,836 we need to know just how big stars get. 859 00:43:51,836 --> 00:43:54,586 (dramatic music) 860 00:43:56,090 --> 00:43:59,410 Since mankind first invented the telescope, 861 00:43:59,410 --> 00:44:02,613 we have wondered just how big the stars really are. 862 00:44:04,680 --> 00:44:05,780 This is what we found. 863 00:44:08,000 --> 00:44:10,807 We think of our sun as pretty big 864 00:44:10,807 --> 00:44:13,370 but in the universe's hall of fame, 865 00:44:13,370 --> 00:44:14,767 it's just a nobody. 866 00:44:28,470 --> 00:44:30,480 The biggest star by radius 867 00:44:30,480 --> 00:44:32,250 that mankind has every observed 868 00:44:32,250 --> 00:44:35,250 is known as UY Scuti. 869 00:44:35,250 --> 00:44:40,029 It's more than 1,700 times the width of our sun. 870 00:44:40,029 --> 00:44:42,050 But there are stars even bigger 871 00:44:42,050 --> 00:44:44,170 if we look far enough away. 872 00:44:44,170 --> 00:44:46,833 Not just in distance but in time. 873 00:44:47,890 --> 00:44:48,760 In astronomy, 874 00:44:48,760 --> 00:44:51,680 we have a great privilege. 875 00:44:51,680 --> 00:44:54,230 We can do something that historians and archeologists 876 00:44:54,230 --> 00:44:55,300 only dream of. 877 00:44:55,300 --> 00:44:59,100 We can directly take images of the distant past. 878 00:44:59,100 --> 00:45:01,210 And we do this by looking at objects 879 00:45:01,210 --> 00:45:03,063 that are far away in the universe. 880 00:45:04,337 --> 00:45:05,630 Objects that are far away, 881 00:45:05,630 --> 00:45:07,040 they have sent out the light 882 00:45:07,040 --> 00:45:10,110 that we receive billions of years later 883 00:45:10,110 --> 00:45:12,087 and light travels with a limit of speed, 884 00:45:12,087 --> 00:45:13,110 the speed of light. 885 00:45:13,110 --> 00:45:15,950 And therefore looking far out into space 886 00:45:15,950 --> 00:45:18,683 means also looking far back into time. 887 00:45:20,967 --> 00:45:22,810 When they looked far enough away 888 00:45:22,810 --> 00:45:24,760 and far enough back in time, 889 00:45:24,760 --> 00:45:28,160 scientists found that the biggest stars to ever exist 890 00:45:28,160 --> 00:45:30,650 were born in the very early universe. 891 00:45:30,650 --> 00:45:32,740 If one thinks about the early universe, 892 00:45:32,740 --> 00:45:35,620 then you also discover possibilities 893 00:45:35,620 --> 00:45:38,703 of really pushing star formation to the extreme. 894 00:45:42,467 --> 00:45:44,310 Professor Volker Bromm 895 00:45:44,310 --> 00:45:46,240 has built theoretical models 896 00:45:46,240 --> 00:45:47,450 that show just how big 897 00:45:47,450 --> 00:45:49,093 these early stars could've been. 898 00:45:50,140 --> 00:45:51,810 His visualization lab 899 00:45:51,810 --> 00:45:53,990 simulates how massive clouds of gas 900 00:45:53,990 --> 00:45:55,930 in the early universe collapsed 901 00:45:55,930 --> 00:45:58,050 to form giant stars. 902 00:45:58,050 --> 00:46:00,320 So there are special regions in the universe 903 00:46:00,320 --> 00:46:01,420 where conditions arrive 904 00:46:01,420 --> 00:46:04,067 that you can have extraordinary large 905 00:46:04,067 --> 00:46:06,006 clouds of primordial gas 906 00:46:06,006 --> 00:46:08,573 collapsing in one go if you like. 907 00:46:10,138 --> 00:46:13,150 So then we have a very, very extreme case 908 00:46:13,150 --> 00:46:14,230 of visualized star formation. 909 00:46:14,230 --> 00:46:17,512 A million solar mass cloud collapsing in one go. 910 00:46:17,512 --> 00:46:19,570 And again, this is a very special condition 911 00:46:19,570 --> 00:46:21,540 and we believe this only could've happened 912 00:46:21,540 --> 00:46:22,640 in the early universe. 913 00:46:24,493 --> 00:46:27,040 Volker's work tells us 914 00:46:27,040 --> 00:46:28,870 that back in the early universe, 915 00:46:28,870 --> 00:46:30,020 there may have been stars 916 00:46:30,020 --> 00:46:32,603 a million times more massive than our own, 917 00:46:33,630 --> 00:46:37,063 far, far bigger than anything around in the modern universe. 918 00:46:39,830 --> 00:46:42,603 Our sun would just be speck compared with this. 919 00:46:50,020 --> 00:46:51,940 The question is could the Earth 920 00:46:51,940 --> 00:46:53,930 survive orbiting a star 921 00:46:53,930 --> 00:46:55,760 that is possibly the biggest object 922 00:46:55,760 --> 00:46:56,933 that has ever existed? 923 00:46:59,529 --> 00:47:00,917 Let's find out. 924 00:47:04,820 --> 00:47:09,000 As the sun grows to the size of a super massive early star, 925 00:47:09,000 --> 00:47:10,963 it would envelope the inner planets. 926 00:47:13,435 --> 00:47:16,543 So the Earth needs to move to a safe distance. 927 00:47:23,680 --> 00:47:26,650 To the outer edge of our solar system, 928 00:47:26,650 --> 00:47:28,173 far beyond Neptune. 929 00:47:30,340 --> 00:47:31,680 Then we would have our planet 930 00:47:31,680 --> 00:47:33,350 sitting our at this huge distance 931 00:47:33,350 --> 00:47:34,183 and you can also ask then 932 00:47:34,183 --> 00:47:36,200 how long would then one orbit take? 933 00:47:36,200 --> 00:47:37,230 And then you would calculate 934 00:47:37,230 --> 00:47:39,713 that one orbit would roughly take 30,000 years. 935 00:47:42,090 --> 00:47:44,290 Not great for getting birthday presents. 936 00:47:44,290 --> 00:47:45,280 And New Years Eve 937 00:47:45,280 --> 00:47:46,620 would be something to be enjoyed 938 00:47:46,620 --> 00:47:49,497 only once every 1,200 generations. 939 00:47:49,497 --> 00:47:51,670 But there's a twist in this tale 940 00:47:51,670 --> 00:47:53,893 that means none of that really matters. 941 00:47:54,992 --> 00:47:56,332 The big problem then 942 00:47:56,332 --> 00:48:00,020 that such a hypothetical planet would encounter 943 00:48:00,020 --> 00:48:01,830 is that the host star, 944 00:48:01,830 --> 00:48:05,920 the supermassive star would have a very short lifetime 945 00:48:05,920 --> 00:48:09,240 because our sun lives for another five billion years. 946 00:48:09,240 --> 00:48:12,460 But the total lifetime of the supermassive stars 947 00:48:12,460 --> 00:48:14,030 is just a few hundred thousand years, 948 00:48:14,030 --> 00:48:15,630 maybe up to a million years. 949 00:48:15,630 --> 00:48:18,010 So this is in astronomical terms, 950 00:48:18,010 --> 00:48:19,283 a blink of an eye. 951 00:48:21,708 --> 00:48:23,330 Put simply, 952 00:48:23,330 --> 00:48:26,203 if our sun had been a massive early star, 953 00:48:26,203 --> 00:48:29,053 life as we know it would never have existed. 954 00:48:34,140 --> 00:48:36,450 Before life had a chance to evolve, 955 00:48:36,450 --> 00:48:38,280 the star would come to an end, 956 00:48:38,280 --> 00:48:40,963 perhaps in a most spectacular way. 957 00:48:44,790 --> 00:48:48,800 If these early super stars were to explode, 958 00:48:48,800 --> 00:48:49,633 the supernova explosion, 959 00:48:49,633 --> 00:48:52,496 then we could say that these would be the biggest explosions 960 00:48:52,496 --> 00:48:55,040 ever to happen in the history of the universe 961 00:48:55,040 --> 00:48:55,873 since the big bang. 962 00:48:55,873 --> 00:48:56,706 The big bang, of course, 963 00:48:56,706 --> 00:48:57,950 would still beat everything else. 964 00:48:57,950 --> 00:48:58,783 But otherwise, 965 00:48:58,783 --> 00:49:01,643 those would be truly colossal explosions. 966 00:49:05,200 --> 00:49:08,020 In their lives and even in their deaths, 967 00:49:08,020 --> 00:49:09,337 these giant early stars 968 00:49:09,337 --> 00:49:10,630 were the limit, 969 00:49:10,630 --> 00:49:13,750 the very end of the scale of big. 970 00:49:13,750 --> 00:49:16,243 But they just don't work for planet Earth. 971 00:49:17,100 --> 00:49:20,050 We've tried changing the size of the planet, 972 00:49:20,050 --> 00:49:21,313 the size of our sun, 973 00:49:21,313 --> 00:49:23,750 and even the size of living things 974 00:49:23,750 --> 00:49:26,080 but nothing works quite as well 975 00:49:26,080 --> 00:49:27,303 as what we started with. 976 00:49:32,270 --> 00:49:34,760 We are our size. 977 00:49:34,760 --> 00:49:38,403 Change it, and we risk changing who and what we are. 978 00:49:39,560 --> 00:49:42,010 So does size matter? 979 00:49:42,010 --> 00:49:42,963 What do you think? 980 00:49:43,830 --> 00:49:45,410 It matters hugely 981 00:49:45,410 --> 00:49:47,540 and it depends on what you're looking at. 982 00:49:47,540 --> 00:49:49,984 If you're looking at the brain, yes. 983 00:49:49,984 --> 00:49:52,793 If you're looking at bodies, 984 00:49:52,793 --> 00:49:57,700 just sustaining life in different thermal habitats, 985 00:49:57,700 --> 00:50:00,413 so size matters tremendously. 986 00:50:03,220 --> 00:50:04,970 Size doesn't matter. 987 00:50:06,020 --> 00:50:07,690 I've met the shortest people in the world 988 00:50:07,690 --> 00:50:09,967 and also some of the tallest. 989 00:50:09,967 --> 00:50:13,884 (speaking in foreign language) 990 00:50:16,270 --> 00:50:18,550 I even once met something taller than me. 991 00:50:18,550 --> 00:50:19,400 It was a giraffe. 992 00:50:22,160 --> 00:50:25,000 Today, Ian and Stuart produced a pumpkin 993 00:50:25,000 --> 00:50:29,595 weight 2,252.3 pounds. 994 00:50:29,595 --> 00:50:31,771 That's a new UK record. 995 00:50:31,771 --> 00:50:32,604 Woo! 996 00:50:33,940 --> 00:50:35,576 Size is the only thing that matters. 997 00:50:35,576 --> 00:50:36,923 Don't have to be pretty, 998 00:50:36,923 --> 00:50:38,170 don't have to look nice. 999 00:50:38,170 --> 00:50:39,770 Only thing that matters is size. 1000 00:50:42,620 --> 00:50:45,240 So size definitely matters for the redwood forest. 1001 00:50:45,240 --> 00:50:49,740 I think it really creates the structure, the scaffolding, 1002 00:50:49,740 --> 00:50:51,110 that makes the redwood forest 1003 00:50:51,110 --> 00:50:53,700 such a beautiful place to spend time. 1004 00:50:53,700 --> 00:50:56,010 So despite what some believe, 1005 00:50:56,010 --> 00:50:58,303 bigger isn't always better. 1006 00:50:59,570 --> 00:51:01,388 Bigger is hotter, 1007 00:51:01,388 --> 00:51:02,483 weaker, 1008 00:51:04,270 --> 00:51:05,363 more dangerous. 1009 00:51:06,840 --> 00:51:08,410 Bigger is grander, 1010 00:51:10,930 --> 00:51:11,763 slower, 1011 00:51:13,976 --> 00:51:15,559 and more fantastic. 1012 00:51:16,457 --> 00:51:19,777 And size really does matter. 1013 00:51:21,225 --> 00:51:24,142 (planet exploding) 1014 00:51:29,687 --> 00:51:32,520 (uplifting music)