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These are the user uploaded subtitles that are being translated: 1 00:00:02,000 --> 00:00:07,000 The human eye - one of the most powerful instruments on Earth. 2 00:00:07,000 --> 00:00:13,040 On a clear day, we can spot the smallest detail in the widest view. 3 00:00:13,040 --> 00:00:18,280 But what the eye sees is not the full picture. 4 00:00:18,280 --> 00:00:22,400 Alongside the world we see is a very different world. 5 00:00:27,440 --> 00:00:32,560 An invisible world of hidden forces and powers. 6 00:00:32,560 --> 00:00:36,960 This shapes every aspect of life on Earth. 7 00:00:43,680 --> 00:00:48,320 Now, technology can open a door on that hidden world, 8 00:00:48,320 --> 00:00:53,680 revealing its mysteries, and showing us the true wonder of the world we live in. 9 00:01:16,600 --> 00:01:20,680 In our vibrant, hectic world, we think we spot everything. 10 00:01:25,920 --> 00:01:30,960 But right in the midst of this busy world, there's a whole other world going on, 11 00:01:30,960 --> 00:01:33,120 it's just that we can't see it. 12 00:01:33,120 --> 00:01:36,400 To us, it's invisible. 13 00:01:39,240 --> 00:01:44,800 Our eyes are too slow to see everything that's really going on. 14 00:01:44,800 --> 00:01:50,640 The world is full of things that happen too fast for us to notice. 15 00:01:52,800 --> 00:01:56,440 Things we miss in the blink of an eye. 16 00:02:08,600 --> 00:02:12,080 The blink of an eye takes about 15 milliseconds, 17 00:02:12,080 --> 00:02:17,280 and it takes the human brain about 150 milliseconds to process what we see. 18 00:02:17,280 --> 00:02:19,760 We're not aware of this time lag going on, 19 00:02:19,760 --> 00:02:23,000 but in those few milliseconds, there are things happening, 20 00:02:23,000 --> 00:02:25,520 extraordinary things that were never see. 21 00:02:29,440 --> 00:02:32,800 This is the invisible world of speed... 22 00:02:40,440 --> 00:02:42,600 ..where thin air... 23 00:02:42,600 --> 00:02:44,600 can shatter rock 24 00:02:44,600 --> 00:02:47,560 and water can tear through metal. 25 00:02:49,760 --> 00:02:53,960 Where the fastest thing on Earth is right beneath our feet. 26 00:02:57,680 --> 00:03:02,960 And where we'd see spectacular events that some thought were UFOs. 27 00:03:05,400 --> 00:03:11,800 If we could stretch time, we could solve some of the biggest mysteries of our planet. 28 00:03:15,360 --> 00:03:22,200 Now, using the latest camera technology, we CAN stretch time, making the invisible visible. 29 00:03:22,200 --> 00:03:26,280 We can overcome the limitations of our eyes to see whole new worlds. 30 00:03:36,560 --> 00:03:41,200 Lightning. A billion volts and hotter than the sun. 31 00:03:46,920 --> 00:03:50,720 But there's even more danger in what you CAN'T see. 32 00:03:53,000 --> 00:03:55,840 This is Rapid City, South Dakota. 33 00:03:55,840 --> 00:03:58,400 In the middle of America's lightning belt, 34 00:03:58,400 --> 00:04:00,600 it gets hundreds of strikes every year. 35 00:04:03,240 --> 00:04:06,760 But there is something strange about the lightning here... 36 00:04:08,400 --> 00:04:12,120 ..something that's becoming a bigger and bigger problem. 37 00:04:12,120 --> 00:04:14,240 Something too fast to see. 38 00:04:16,720 --> 00:04:19,680 Lightning travels at over 100,000 miles an hour. 39 00:04:23,280 --> 00:04:30,000 So only with super slow-motion cameras can experts begin to understand what's going on. 40 00:04:31,560 --> 00:04:35,080 When you view a flash in real time, it's like seeing a title of a book. 41 00:04:35,080 --> 00:04:38,440 You can see that there was a flash there that reached the ground, 42 00:04:38,440 --> 00:04:41,760 maybe it flickered a little bit, but that's all you know. 43 00:04:43,120 --> 00:04:46,760 You come and record this same flash with these high-speed cameras, 44 00:04:46,760 --> 00:04:48,440 it's like a novel. 45 00:04:48,440 --> 00:04:52,640 It tells a unique story every time you play it back. Incredible. 46 00:04:54,160 --> 00:04:59,960 In slow motion, we can see what gives lightning the shape that launched a thousand horror movies. 47 00:04:59,960 --> 00:05:03,440 Fingers of electricity hunting for the ground. 48 00:05:07,880 --> 00:05:12,640 And now, these high-speed cameras are allowing us to catch something 49 00:05:12,640 --> 00:05:15,360 completely invisible to the naked eye. 50 00:05:18,800 --> 00:05:25,520 The strange lightning that's found not in the plains, but right in the heart of Rapid City. 51 00:05:27,960 --> 00:05:29,800 There's a storm brewing. 52 00:05:33,560 --> 00:05:40,080 Specialist cameras set to record at nearly 300 times slow-motion are waiting to capture it. 53 00:05:44,440 --> 00:05:46,360 And there it is. 54 00:05:46,360 --> 00:05:49,760 At first it looks like a normal lightning strike 55 00:05:49,760 --> 00:05:53,240 but the technology reveals something else. 56 00:05:56,840 --> 00:06:02,680 Instead of lightning shooting downwards, this lightning is travelling upwards. 57 00:06:12,440 --> 00:06:15,800 When I played this for the first time, I was just blown away. 58 00:06:15,800 --> 00:06:17,520 It was just amazing to see it. 59 00:06:21,000 --> 00:06:28,800 And this strange, upside-down lightning is powerful, it carries more charge than normal lightning. 60 00:06:35,400 --> 00:06:41,320 But what's really extraordinary is that upward lightning is created by us. 61 00:06:42,840 --> 00:06:46,720 Because it's these tall transmission towers that are triggering 62 00:06:46,720 --> 00:06:50,920 the vast bolts of lightning firing up into the clouds. 63 00:06:56,520 --> 00:07:00,840 Now, you might think that because it is going away from the town, 64 00:07:00,840 --> 00:07:02,840 this lightning is harmless. 65 00:07:02,840 --> 00:07:05,280 Unfortunately not. 66 00:07:05,280 --> 00:07:09,560 When the upward bolt hits the storm clouds, it triggers more lightning 67 00:07:09,560 --> 00:07:12,920 that fires straight back down to the city. 68 00:07:14,960 --> 00:07:18,440 And it is not just here, in Rapid City. 69 00:07:18,440 --> 00:07:20,840 As we build more tall buildings, 70 00:07:20,840 --> 00:07:25,200 this new form of lightning is spreading across the world. 71 00:07:32,160 --> 00:07:38,400 In this high-speed world, there are surprises hidden in even the most everyday things we think we know. 72 00:07:38,400 --> 00:07:40,920 Take this, for example. 73 00:07:54,400 --> 00:08:00,520 On the face of it, that's just one small firework designed to make people go, "Ahh!" 74 00:08:08,160 --> 00:08:11,680 But in fact, there's an invisible force at work here, 75 00:08:11,680 --> 00:08:15,880 one hidden in all explosions, and it's powerful enough 76 00:08:15,880 --> 00:08:19,120 to destroy buildings or tear through solid rock. 77 00:08:20,680 --> 00:08:26,120 Even this little candle unleashes a force too fast for us to see, 78 00:08:26,120 --> 00:08:29,800 that reaches way beyond the pretty sparkle. 79 00:08:29,800 --> 00:08:32,800 And that's what this special camera shows, 80 00:08:32,800 --> 00:08:35,520 something our eyes can never see. 81 00:08:39,080 --> 00:08:40,560 It's a shockwave - 82 00:08:40,560 --> 00:08:46,920 super-fast, devastating, potentially deadly, and yet it's just thin air. 83 00:08:49,000 --> 00:08:52,880 I want to take a closer look at this devastating force in action. 84 00:08:52,880 --> 00:08:55,320 To do that, I need to blow something up. 85 00:08:55,320 --> 00:08:59,920 So, this rock face, it's about 100 metres long. 86 00:08:59,920 --> 00:09:01,880 That's what we're going to blow up, 87 00:09:01,880 --> 00:09:06,120 which will mean shifting about 20,000 tons of rock. 88 00:09:07,920 --> 00:09:15,360 Up here on the top, we're filling not one, but 20, separate holes with explosives. 89 00:09:15,360 --> 00:09:21,320 You see, our experiment is a bit more sophisticated than just creating one massive explosion. 90 00:09:21,320 --> 00:09:24,760 Each one of these 20 separate explosions needs to be 91 00:09:24,760 --> 00:09:29,200 choreographed to go off at 25 millisecond intervals. 92 00:09:29,200 --> 00:09:32,200 That way, each explosion will fragment the rock, 93 00:09:32,200 --> 00:09:35,720 and open up a face that can then be hit by subsequent explosions. 94 00:09:35,720 --> 00:09:37,440 At least, that's the theory. 95 00:09:37,440 --> 00:09:40,600 This whole event is going to be over in about half a second. 96 00:09:40,600 --> 00:09:42,960 So to stand a chance of seeing this, 97 00:09:42,960 --> 00:09:46,000 we're going to need to film it at high-speed. 98 00:09:47,880 --> 00:09:51,800 We're using a remote trigger with a short travel, 99 00:09:51,800 --> 00:09:57,560 so I need to be 100 metres away from the explosion - in that. 100 00:09:57,560 --> 00:09:59,280 Yeah, I know. 101 00:09:59,280 --> 00:10:03,480 But it does mean I'll get to experience very much at first hand 102 00:10:03,480 --> 00:10:07,760 the impact of 20 separate explosions detonating within half a second 103 00:10:07,760 --> 00:10:11,560 of one another to try and shift 20,000 tons of rocks. 104 00:10:11,560 --> 00:10:15,200 So in that sense, I'm lucky to be in there. 105 00:10:17,960 --> 00:10:19,240 Nice! 106 00:10:19,240 --> 00:10:21,080 Oh, yeah. 107 00:10:25,200 --> 00:10:27,400 I feel safe. 108 00:10:27,400 --> 00:10:29,800 So, I arm it with that. BEEP 109 00:10:29,800 --> 00:10:32,000 That means it's now armed. 110 00:10:32,000 --> 00:10:38,120 Counting down from five, four, three, two, one. 111 00:10:48,200 --> 00:10:52,280 20,000 tons of rock, gone in a second. 112 00:10:52,280 --> 00:10:55,840 And I'm still safe, which is a bonus. 113 00:10:55,840 --> 00:10:57,720 That was quite a rumble. 114 00:10:57,720 --> 00:10:59,800 I really felt that. 115 00:10:59,800 --> 00:11:03,360 Yeah, just to actually feel the earth move 116 00:11:03,360 --> 00:11:08,000 because of something you have just triggered, that's quite a sensation. 117 00:11:08,000 --> 00:11:09,200 Yeah. 118 00:11:09,200 --> 00:11:12,480 A little lie-down is needed. 119 00:11:12,480 --> 00:11:16,640 But it's only when we slow down in the film 40 times that 120 00:11:16,640 --> 00:11:18,680 we can see more of what just happened 121 00:11:18,680 --> 00:11:21,760 and why I wasn't turned into mush. 122 00:11:23,280 --> 00:11:26,800 There's a flash as the detonation cable ignites. 123 00:11:29,200 --> 00:11:34,120 And now we can see the blast going off. One every 25 milliseconds. 124 00:11:40,560 --> 00:11:43,920 But the real force is not the blast. 125 00:11:47,680 --> 00:11:50,920 It's the shockwaves that each blast releases. 126 00:11:56,280 --> 00:12:02,400 Deep in the quarry face, the shockwaves are forcing their way through sheer rock, 127 00:12:02,400 --> 00:12:04,760 eventually erupting at the top. 128 00:12:17,920 --> 00:12:21,080 The shockwaves keep on expanding outwards, 129 00:12:21,080 --> 00:12:23,320 powerful enough to crumble the rock 130 00:12:23,320 --> 00:12:27,080 and finally tear apart the entire face. 131 00:12:27,080 --> 00:12:29,760 But thankfully, not mine. 132 00:12:36,040 --> 00:12:38,240 By choreographing the explosions, 133 00:12:38,240 --> 00:12:42,560 we were able to drive and steer the shockwaves through the rock, 134 00:12:42,560 --> 00:12:45,680 rather than let them spill out into the air around, 135 00:12:45,680 --> 00:12:48,040 which is why I was able to get so close. 136 00:12:48,040 --> 00:12:50,720 Not sure I'd want to get much closer. 137 00:12:57,680 --> 00:13:02,320 So, how can a shockwave cause such awesome destruction? 138 00:13:03,160 --> 00:13:08,320 To find out, we're going to trigger one almighty explosion. 139 00:13:11,400 --> 00:13:14,680 We're going to attempt to see a shockwave. 140 00:13:14,680 --> 00:13:16,760 It'll be over in the blink of an eye, 141 00:13:16,760 --> 00:13:20,960 but high-speed cameras will capture every millisecond. 142 00:13:20,960 --> 00:13:23,360 At least, that's the plan. 143 00:13:23,360 --> 00:13:26,160 First, thousands of pounds of gunpowder are loaded. 144 00:13:26,160 --> 00:13:28,880 That's a lot of gunpowder. 145 00:13:29,880 --> 00:13:31,160 The fuse is set. 146 00:13:35,320 --> 00:13:39,600 To be safe, everyone needs to be over a mile away - 147 00:13:39,600 --> 00:13:43,480 that's why they're running away in pick-up trucks. 148 00:13:45,440 --> 00:13:48,720 Except for these guys - 149 00:13:48,720 --> 00:13:51,040 the detonators. 150 00:13:51,040 --> 00:13:55,360 They'll be less than half a mile from the blast zone, 151 00:13:55,360 --> 00:13:58,080 which is why they get the armoured car. 152 00:14:01,640 --> 00:14:03,640 Everybody ready? Are you ready, sir? 153 00:14:06,840 --> 00:14:12,400 Range control to security checkpoint, are you clear? 'All clear.' 154 00:14:12,400 --> 00:14:16,400 Obs one, are you clear? 'We're all clear.' 155 00:14:18,520 --> 00:14:22,920 10/4, stand by for counting. I'll say it again, stand by for counting. 156 00:14:22,920 --> 00:14:27,440 Five, four, three, two, one... 157 00:14:43,320 --> 00:14:47,960 In an instant, thousands of pounds of gunpowder explode. 158 00:14:47,960 --> 00:14:51,800 But the shockwave is completely invisible. 159 00:14:53,320 --> 00:14:56,200 So we need to slow it down over 100 times, 160 00:14:56,200 --> 00:15:00,240 and then watch it back repeatedly - from several angles. 161 00:15:00,240 --> 00:15:03,880 Stand by for counting. I'll say it again, stand by for counting. 162 00:15:05,400 --> 00:15:09,760 Five, four, three, two, one... 163 00:15:11,760 --> 00:15:14,520 The fuse races towards the site. 164 00:15:17,160 --> 00:15:21,200 In a thousandth of a second, the gunpowder ignites. 165 00:15:25,360 --> 00:15:29,880 In one millionth of a second it changes from solid to gas. 166 00:15:38,840 --> 00:15:43,080 And there it is. Finally, we can see the shockwave. 167 00:15:59,240 --> 00:16:03,200 A wall of intense high pressure in the air. 168 00:16:20,280 --> 00:16:24,840 It's travelling at over 300 metres every second. 169 00:16:24,840 --> 00:16:29,240 So fast that anything in its path is punched aside. 170 00:16:35,600 --> 00:16:38,920 And now we can see amazing detail. 171 00:16:38,920 --> 00:16:44,600 The shockwave reignites unburnt fuel, triggering a secondary shockwave at the tip. 172 00:16:51,720 --> 00:16:56,720 It's the shockwave, not the explosion itself, that causes devastation. 173 00:17:18,840 --> 00:17:24,880 In the high-speed world, thin air can create brute force and destruction. 174 00:17:26,560 --> 00:17:30,480 But it can also allow us to do some pretty amazing things. 175 00:17:43,520 --> 00:17:45,440 OK, right, so go for the off, yeah. 176 00:17:45,440 --> 00:17:49,240 A nice bit of back pressure as you take-off, plenty of left pedal. 177 00:17:49,240 --> 00:17:51,320 And a bit more. 178 00:17:51,320 --> 00:17:52,480 That's it. 179 00:17:54,320 --> 00:17:56,000 There she goes. 180 00:17:57,040 --> 00:18:00,080 Now, bear with me, I am still learning this. 181 00:18:00,080 --> 00:18:03,920 Now, it's something that we take for granted, but essentially 182 00:18:03,920 --> 00:18:07,960 nearly two tons of helicopter and me are being held up by air. 183 00:18:07,960 --> 00:18:10,760 Just very, very fast-moving air. 184 00:18:10,760 --> 00:18:16,800 The rotor above pushes air downwards, that creates the lift that keeps me up in the sky. 185 00:18:16,800 --> 00:18:19,560 It's one of the basic principles of aerodynamics. 186 00:18:21,640 --> 00:18:23,800 But step into the world of the invisible, 187 00:18:23,800 --> 00:18:28,280 and this benign and useful force suddenly looks very different. 188 00:18:44,680 --> 00:18:49,480 These planes are flying close to the speed of sound. 189 00:18:50,880 --> 00:18:54,240 But at this speed, the air moves so fast 190 00:18:54,240 --> 00:18:57,720 it's about to become a potentially dangerous force. 191 00:19:05,520 --> 00:19:12,160 Slowed down by nearly 200 times, just watch what happens on the wing. 192 00:19:13,680 --> 00:19:19,720 At these super high-speeds, the moisture in the air suddenly condenses into water. 193 00:19:21,320 --> 00:19:23,160 A cloud forms. 194 00:19:30,200 --> 00:19:33,760 I know that doesn't sound very scary - a cloud - 195 00:19:33,760 --> 00:19:38,560 but that cloud is like suddenly dumping the weight of a car on the wings. 196 00:19:41,200 --> 00:19:46,360 Only the most skilled pilots, like these, can cope. 197 00:19:56,000 --> 00:19:58,880 We may think that we've conquered flight, 198 00:19:58,880 --> 00:20:01,080 but compared to the natural world, 199 00:20:01,080 --> 00:20:04,920 our mastery of the air is basically rubbish. 200 00:20:14,200 --> 00:20:17,360 Engineers have been wrestling with the problem of flight 201 00:20:17,360 --> 00:20:20,800 since the Wright brothers first got airborne 100 years ago. 202 00:20:20,800 --> 00:20:24,920 But it is only now, with the advent of ultra-high-speed filming 203 00:20:24,920 --> 00:20:27,960 that we can really begin to understand some of the secrets 204 00:20:27,960 --> 00:20:30,320 of the natural world, which has, after all, 205 00:20:30,320 --> 00:20:34,560 been working on the same problem for over 350 million years. 206 00:20:36,640 --> 00:20:39,680 Now, come on, you've worked it out now. 207 00:20:39,680 --> 00:20:41,920 It's a lot of practice, it's a lot of years. 208 00:20:45,640 --> 00:20:48,600 Yep, got there in the end. 209 00:20:50,600 --> 00:20:54,760 The first creatures to fly weren't birds, 210 00:20:54,760 --> 00:20:56,240 they were insects. 211 00:20:57,160 --> 00:21:00,160 For centuries, their secrets were invisible. 212 00:21:00,160 --> 00:21:03,640 Wing movements lost in a blur of motion. 213 00:21:03,640 --> 00:21:07,720 We're only now starting to get the full picture. 214 00:21:10,320 --> 00:21:15,960 The hummingbird hawk-moth is revealed to be a model of flying finesse. 215 00:21:19,160 --> 00:21:25,000 With amazing control, it can hover at a complete standstill, 216 00:21:25,000 --> 00:21:27,880 perfectly poised to gather nectar. 217 00:21:30,040 --> 00:21:34,360 But not all insects are quite so elegant. 218 00:21:35,880 --> 00:21:40,520 The bumble bee is an aerodynamic mystery that had scientists baffled. 219 00:21:44,000 --> 00:21:48,520 A big, fat body, supported only by tiny wings. 220 00:21:48,520 --> 00:21:51,080 Now, how's that supposed to work? 221 00:21:52,560 --> 00:21:56,520 The confusion started over 70 years ago, when a French entomologist 222 00:21:56,520 --> 00:22:01,240 calculated that bee flight was aerodynamically impossible. 223 00:22:01,240 --> 00:22:04,560 Ever since, scientists have struggled to understand just how 224 00:22:04,560 --> 00:22:09,040 a bee's apparently random flapping can possibly keep it airborne. 225 00:22:09,040 --> 00:22:11,160 And, at first, even seen in slow motion, 226 00:22:11,160 --> 00:22:13,720 the mystery doesn't get any clearer. 227 00:22:15,720 --> 00:22:18,280 Here she is, lurching through the air. 228 00:22:18,280 --> 00:22:22,440 She even has to use her legs to balance herself - 229 00:22:22,440 --> 00:22:24,880 elegant it's not. 230 00:22:26,440 --> 00:22:30,440 The only way she's staying up is by furiously flapping 231 00:22:30,440 --> 00:22:34,120 at an extraordinary 200 beats every second. 232 00:22:35,640 --> 00:22:37,200 That's why she's so round, 233 00:22:37,200 --> 00:22:41,680 her chest is a mass of muscle to power the wings. 234 00:22:46,560 --> 00:22:49,200 No, I'm not trying to set fire to them, 235 00:22:49,200 --> 00:22:53,120 this smoke should help us see what's happening. 236 00:22:53,120 --> 00:22:54,920 As the bee beats its wings, 237 00:22:54,920 --> 00:22:58,360 air, or in this case, smoke, is pulled downwards. 238 00:23:00,080 --> 00:23:01,800 This generates lift, 239 00:23:01,800 --> 00:23:06,000 but not enough to keep the stripy buffoon airborne. 240 00:23:06,000 --> 00:23:12,400 Only in super slo-mo can we see she's actually rather clever. 241 00:23:12,400 --> 00:23:15,160 At the end of each downstroke, 242 00:23:15,160 --> 00:23:17,480 she twists her wings over. 243 00:23:23,680 --> 00:23:28,040 So, even on the upstroke, the smoke is still pulled downwards, 244 00:23:29,560 --> 00:23:32,000 giving her double the amount of lift. 245 00:23:35,120 --> 00:23:38,200 And you don't get that with an aeroplane. 246 00:23:45,120 --> 00:23:48,080 By looking into the invisible world of high-speed, 247 00:23:48,080 --> 00:23:51,960 human engineers are discovering a range of animal secrets 248 00:23:51,960 --> 00:23:55,720 they can use to develop even better flying machines. 249 00:24:03,800 --> 00:24:07,200 So, why do we miss so much of what's around us, 250 00:24:07,200 --> 00:24:13,160 when it's perfectly obvious to other creatures? 251 00:24:13,160 --> 00:24:18,360 A fly, for example, can see 100 images a second, 252 00:24:18,360 --> 00:24:24,280 allowing it to zoom around at top speed and not crash into things. 253 00:24:26,000 --> 00:24:31,720 To a fly, our world appears incredibly slow... 254 00:24:36,320 --> 00:24:40,800 ..which is why, annoyingly, I'm never going to catch it. 255 00:24:46,120 --> 00:24:51,120 But what the fly has in speed, it loses in detail. 256 00:24:51,120 --> 00:24:53,560 Everything it sees is a blur. 257 00:25:02,520 --> 00:25:08,680 We, on the other hand, have evolved to see very fine detail. 258 00:25:08,680 --> 00:25:13,720 But there's a trade-off - our eyes can't do speed. 259 00:25:14,880 --> 00:25:19,040 We process a lot of information in any one scene, 260 00:25:19,040 --> 00:25:23,080 but it does take time. So much time, in fact, that the best we can do 261 00:25:23,080 --> 00:25:26,880 effectively is take snapshots of the world around us. 262 00:25:26,880 --> 00:25:29,440 We take a look, process the information, 263 00:25:29,440 --> 00:25:32,960 take another look, process that information, and so on. 264 00:25:35,000 --> 00:25:38,560 Each snapshot lasts just 100 milliseconds. 265 00:25:41,480 --> 00:25:46,120 And unlike the fly, our snapshots are very detailed. 266 00:25:48,120 --> 00:25:51,080 So it takes time to process each one. 267 00:25:57,320 --> 00:26:02,960 Anything that happens in those milliseconds while we're processing information remains hidden. 268 00:26:02,960 --> 00:26:04,880 It's as thought it's not there. 269 00:26:04,880 --> 00:26:07,680 So, right now, everything's fine. 270 00:26:07,680 --> 00:26:11,160 I can deal with all the information coming my way, I can see colour, 271 00:26:11,160 --> 00:26:14,080 yellow track, I can see the curve, the shape of it. 272 00:26:14,080 --> 00:26:17,480 I can even see the chain moving to pull my little cart long. 273 00:26:17,480 --> 00:26:20,440 No problem...at normal speeds. 274 00:26:20,440 --> 00:26:23,800 But it's surprising how quickly you reach the point beyond which 275 00:26:23,800 --> 00:26:27,880 I can't process the information, because as things get faster, 276 00:26:27,880 --> 00:26:31,040 so strange things begin to happen to our vision. 277 00:26:35,200 --> 00:26:38,720 Now, it's not that I'm missing stuff 278 00:26:38,720 --> 00:26:41,040 cos I'm looking the wrong way. 279 00:26:41,040 --> 00:26:43,840 I just can't deal with the information as it comes in. 280 00:26:43,840 --> 00:26:46,880 There's just too much going on! 281 00:26:47,960 --> 00:26:50,400 I can't work out what's what. 282 00:26:50,400 --> 00:26:54,480 My vision hasn't suddenly gone faulty, this is as good as it is. 283 00:26:59,040 --> 00:27:00,360 The faster things move, 284 00:27:00,360 --> 00:27:03,720 the less time we have to process all the detail in the picture. 285 00:27:05,400 --> 00:27:09,520 But as things speed up, eventually the rate of incoming information 286 00:27:09,520 --> 00:27:16,120 exceeds the speed of our neural processors, and you can't see! 287 00:27:18,320 --> 00:27:21,000 I'm not too sure my stomach can process it either. 288 00:27:23,800 --> 00:27:28,000 And when it gets too fast, we simply can't see it at all. 289 00:27:32,800 --> 00:27:36,040 Did you spot this? 290 00:27:48,520 --> 00:27:53,640 When we start to see the things that are usually invisible, 291 00:27:53,640 --> 00:27:56,960 it shows us how extraordinary our world really is. 292 00:27:59,320 --> 00:28:02,640 Water becomes thick, elastic. 293 00:28:04,160 --> 00:28:08,280 It even contains a powerful force that can tear through sheet metal. 294 00:28:12,560 --> 00:28:17,840 Nothing is quite what it seems, even stuff we think is familiar. 295 00:28:21,440 --> 00:28:25,280 It's not exactly a rare thing for most of us, rain. 296 00:28:27,600 --> 00:28:34,560 But venture into the invisible realm, and suddenly the world as we think we know it changes. 297 00:28:36,600 --> 00:28:38,640 Take a simple raindrop, for example. 298 00:28:38,640 --> 00:28:41,640 We all know that they form a tear-shape, 299 00:28:41,640 --> 00:28:45,200 fall through the air, and then land on the ground. 300 00:28:45,200 --> 00:28:49,240 Except they don't necessarily do any of those things. 301 00:28:53,400 --> 00:28:59,680 Looking at this downpour with specialist cameras reveals the surprising story of rain. 302 00:29:03,160 --> 00:29:06,560 Every raindrop begins as a perfect sphere. 303 00:29:08,080 --> 00:29:12,320 As they fall, air resistance causes the drops to flatten. 304 00:29:12,320 --> 00:29:14,440 Real footage slowed down 305 00:29:14,440 --> 00:29:18,240 shows that they're really, well, wet hamburgers. 306 00:29:18,240 --> 00:29:23,080 In fact, they never, ever form the classic teardrop we imagine. 307 00:29:27,160 --> 00:29:30,160 So much for the raindrops' tear shape. 308 00:29:30,160 --> 00:29:35,840 High-speed filming shows what happens next to these airborne hamburgers. 309 00:29:39,080 --> 00:29:43,960 This rare sequence reveals something quite extraordinary - 310 00:29:43,960 --> 00:29:46,600 rain that simply vanishes. 311 00:29:51,280 --> 00:29:54,680 Bigger raindrops can swell and inflate like balloons 312 00:29:54,680 --> 00:29:58,960 until they burst, exploding into smaller and smaller drops. 313 00:30:17,720 --> 00:30:20,960 Some of these tiny drops never actually hit the ground, 314 00:30:20,960 --> 00:30:24,400 they're just dispersed into the air. 315 00:30:24,400 --> 00:30:28,440 But there are still enough big drops left to land on us. 316 00:31:29,000 --> 00:31:32,840 In the high-speed world, water becomes thick... 317 00:31:36,480 --> 00:31:38,000 ..dense... 318 00:31:40,040 --> 00:31:43,840 ..an alien environment that we struggle to get through. 319 00:31:46,640 --> 00:31:51,320 Over time, a strong swimmer can manage about two miles an hour. 320 00:31:54,120 --> 00:31:58,480 But that's a crawl compared to other mammals, like this fella, 321 00:31:58,480 --> 00:32:02,320 the dolphin, who speeds through five times faster. 322 00:32:10,880 --> 00:32:13,160 But it's only in slow motion that we can see 323 00:32:13,160 --> 00:32:16,000 why the dolphin is so much at home here... 324 00:32:33,920 --> 00:32:37,120 ..and why we aren't. 325 00:32:37,120 --> 00:32:40,560 Water is 800 times thicker than air. 326 00:32:44,360 --> 00:32:50,040 So thick that it pulls and distorts our soft bodies as we swim, 327 00:32:50,040 --> 00:32:54,000 causing drag, which holds us back. 328 00:32:58,080 --> 00:33:01,520 Now watch what happens to Mr Dolphin here. 329 00:33:07,000 --> 00:33:12,480 The water doesn't distort his body at all, passing smoothly over it. 330 00:33:12,480 --> 00:33:17,440 That's because the dolphin has much thicker skin, like rubber, 331 00:33:17,440 --> 00:33:20,120 that stops his blubber flapping. 332 00:33:21,800 --> 00:33:25,480 So, while we struggle to make headway, 333 00:33:25,480 --> 00:33:29,240 a dolphin is barely trying. 334 00:33:29,240 --> 00:33:34,680 And when it needs to swim even faster, the dolphin makes it look easy. 335 00:33:37,120 --> 00:33:38,640 Slowed down 40 times, 336 00:33:38,640 --> 00:33:42,480 we can suddenly see things invisible to the naked eye... 337 00:33:45,520 --> 00:33:50,400 ..like the way the water flows cleanly around its torpedo-shaped body 338 00:33:50,400 --> 00:33:54,280 so the dolphin can speed through effortlessly, 339 00:33:54,280 --> 00:33:58,680 saving his energy for, well, showing off, basically. 340 00:34:11,000 --> 00:34:12,720 Yes, yes, very good. 341 00:34:12,720 --> 00:34:14,320 Have a fish. 342 00:34:16,120 --> 00:34:18,920 And if he can't be bothered with all this, 343 00:34:18,920 --> 00:34:21,440 he can hitch a ride on the surf. 344 00:34:32,200 --> 00:34:35,600 But there's something really strange about water, 345 00:34:35,600 --> 00:34:37,840 and it's hiding beyond our sight. 346 00:34:37,840 --> 00:34:42,560 Lurking in these warm, clear waters, is an invisible force... 347 00:34:45,560 --> 00:34:48,440 ..capable of tearing through metal. 348 00:34:50,680 --> 00:34:53,200 A force that is, even now, 349 00:34:53,200 --> 00:34:55,760 destroying this boat. 350 00:34:55,760 --> 00:35:00,640 To see this force in action, we're going to need some help. 351 00:35:00,640 --> 00:35:04,960 In this tank is a tiny creature, 352 00:35:04,960 --> 00:35:06,520 but it's armed. 353 00:35:10,680 --> 00:35:14,720 Hiding under the rock is a pistol shrimp, 354 00:35:14,720 --> 00:35:17,520 and it's packing a lethal weapon. 355 00:35:17,520 --> 00:35:21,920 This crab is heading into trouble. 356 00:35:27,600 --> 00:35:30,320 Our shrimp is ready for a scrap. 357 00:35:34,000 --> 00:35:38,720 At first sight, it looks like he's punching the intruder with his claw. 358 00:35:41,080 --> 00:35:44,680 But, in fact, something much stranger is going on. 359 00:35:48,440 --> 00:35:51,960 Its weapon isn't exactly the claw itself, not directly. 360 00:35:51,960 --> 00:35:54,000 The weapon is invisible, 361 00:35:54,000 --> 00:35:58,120 as I shall now demonstrate with this paint brush. 362 00:35:58,120 --> 00:36:00,840 I'm not getting in there with it, it's armed. 363 00:36:00,840 --> 00:36:02,280 Right... 364 00:36:04,400 --> 00:36:06,680 Come on. SNAP! 365 00:36:06,680 --> 00:36:08,840 Oh! Did you hear that? 366 00:36:09,920 --> 00:36:10,960 SNAP! 367 00:36:10,960 --> 00:36:13,520 That noise is a big clue as to what's going on. 368 00:36:13,520 --> 00:36:18,920 It's too fast to see, so let's have a look at it again in slow motion. 369 00:36:21,120 --> 00:36:25,000 The sound we hear is not from the claw itself 370 00:36:25,000 --> 00:36:28,840 but from an amazing invisible force. 371 00:36:30,360 --> 00:36:34,840 The claw snap happens so fast it causes a high-speed water jet 372 00:36:34,840 --> 00:36:38,240 which shoots forward at almost 60 miles an hour, 373 00:36:38,240 --> 00:36:43,320 fast enough to vaporise the water and form a bubble. 374 00:36:48,720 --> 00:36:54,160 And that's a lot more dangerous than it sounds. 375 00:36:54,160 --> 00:36:59,040 The temperature inside the bubble reaches over 4,000 degrees, 376 00:36:59,040 --> 00:37:03,400 and, as it collapses, this massive energy is released 377 00:37:03,400 --> 00:37:10,920 like a superheated shockwave, stunning, or even killing, its prey. 378 00:37:13,920 --> 00:37:18,080 The knockout punch comes not from the claw 379 00:37:18,080 --> 00:37:21,280 but from the super-hot power of a bubble. 380 00:37:28,360 --> 00:37:32,600 This incredible force is called cavitation. 381 00:37:32,600 --> 00:37:37,560 It happens whenever water is forced to move at extreme speeds, 382 00:37:37,560 --> 00:37:40,560 and it can do a lot more than scare off a little crab. 383 00:37:51,600 --> 00:37:54,480 Up to now, it's been completely invisible. 384 00:37:59,160 --> 00:38:04,440 Using ultra high-speed cameras, we can finally see it in action. 385 00:38:11,320 --> 00:38:17,080 This propeller is spinning so fast it vaporises the water around the tips of the blades... 386 00:38:19,120 --> 00:38:22,680 ..creating streams of super-hot bubbles. 387 00:38:23,720 --> 00:38:27,560 As they collapse, they release a massive wave of energy... 388 00:38:30,240 --> 00:38:32,360 ..bombarding the propeller blades. 389 00:38:43,360 --> 00:38:46,240 It's so powerful, 390 00:38:46,240 --> 00:38:50,000 it can destroy the metal itself. 391 00:38:51,240 --> 00:38:54,520 Cavitation ruined this propeller 392 00:38:54,520 --> 00:38:58,520 after a single journey across the Atlantic. 393 00:39:12,720 --> 00:39:18,600 Our everyday world, familiar, ordinary, even a bit boring. 394 00:39:21,320 --> 00:39:25,080 But hidden beyond the timescale of our eyes 395 00:39:25,080 --> 00:39:27,720 lie truly amazing phenomena. 396 00:39:27,720 --> 00:39:33,160 And some of the fastest of all happen not in the air 397 00:39:33,160 --> 00:39:37,640 or in the water, but right under our feet. 398 00:39:44,840 --> 00:39:50,360 The plant world lives according to an entirely different time-frame to ours, 399 00:39:50,360 --> 00:39:54,960 which is why this all looks very peaceful, calm, relaxing, even. 400 00:39:54,960 --> 00:39:58,880 But, in fact, there's a war going on. It's just that we can't see it. 401 00:40:06,400 --> 00:40:09,320 By squeezing weeks into seconds, 402 00:40:09,320 --> 00:40:13,440 we see plants locked in a battle for survival, 403 00:40:13,440 --> 00:40:19,480 competing for sunlight, space, and for the attention of insects. 404 00:40:25,000 --> 00:40:27,960 But plants don't just do slow. 405 00:40:31,240 --> 00:40:36,080 This timescale according to which the plant world lives is exactly that, a scale. 406 00:40:36,080 --> 00:40:39,520 And plants can exploit the extremes at either end of it, 407 00:40:39,520 --> 00:40:44,360 so when they need something to happen fast, they can do fast. 408 00:40:44,360 --> 00:40:45,600 Watch this. 409 00:40:48,560 --> 00:40:50,800 You see? 410 00:40:50,800 --> 00:40:54,960 No, you won't have done, because it happens too fast to see. 411 00:40:54,960 --> 00:40:58,160 We'll have to slow it down to see what's actually happening. 412 00:41:07,240 --> 00:41:13,720 This Himalayan balsam is firing out seeds at an astonishing six metres a second. 413 00:41:17,720 --> 00:41:21,800 Flinging them in all directions like a toddler with a plate of peas. 414 00:41:30,880 --> 00:41:35,680 Sending them far enough to keep its own patch free from competition. 415 00:41:39,680 --> 00:41:46,120 OK, so what do you think is the fastest accelerator on the planet? 416 00:41:46,120 --> 00:41:47,320 A rocket? 417 00:41:48,240 --> 00:41:49,640 A jet fighter? 418 00:41:51,160 --> 00:41:52,760 A missile? 419 00:41:52,760 --> 00:41:56,040 Nope. Thanks to the latest in high-speed cameras, 420 00:41:56,040 --> 00:41:59,320 we now know it's something else entirely. 421 00:42:01,920 --> 00:42:05,240 And it's found right here in the British countryside. 422 00:42:08,560 --> 00:42:14,440 The fastest living thing on the planet is in this field right now. 423 00:42:14,440 --> 00:42:19,000 It's not some supersonic species of falcon, or a cheetah. 424 00:42:19,000 --> 00:42:22,200 We're in Herefordshire, they don't have them here anyway. 425 00:42:22,200 --> 00:42:26,160 It's not those two, either. But it's got something to do with them. 426 00:42:26,160 --> 00:42:29,880 What it is, is right here. 427 00:42:29,880 --> 00:42:32,320 Down, it's smaller, 428 00:42:32,320 --> 00:42:36,480 it's down...it's right here. 429 00:42:36,480 --> 00:42:41,120 Yeah, this. Well, not actually this, 430 00:42:41,120 --> 00:42:46,000 but this horse poo is home to hundreds of tiny fungi 431 00:42:46,000 --> 00:42:50,600 and it is literally the speediest thing on the planet, 432 00:42:50,600 --> 00:42:52,160 in there. 433 00:42:55,280 --> 00:43:00,440 Well, not exactly the fungi themselves, but their spores. 434 00:43:00,440 --> 00:43:03,480 Here they are, just starting to appear now. 435 00:43:03,480 --> 00:43:06,720 When these grow up, 436 00:43:06,720 --> 00:43:11,520 they will be capable of feats of acceleration that the mind can barely comprehend. 437 00:43:13,520 --> 00:43:16,080 These little beauties, pilobolus, 438 00:43:16,080 --> 00:43:21,240 can do 0-20 in two millionths of a second, 439 00:43:21,240 --> 00:43:26,320 and pull 20,000G, which is a lot. 440 00:43:26,320 --> 00:43:29,240 Astronauts on a space shuttle have to cope with four. 441 00:43:29,240 --> 00:43:34,080 Get anything past five G, pretty much, and people start passing out. 442 00:43:35,120 --> 00:43:37,280 Now watch the spores. 443 00:43:37,280 --> 00:43:39,280 They're the black bits on the top. 444 00:43:41,480 --> 00:43:44,560 At normal speed, they seem to simply vanish... 445 00:43:45,880 --> 00:43:49,800 ..because they have one of the speediest lift offs on the planet. 446 00:43:51,800 --> 00:43:54,920 It's so fast that it's invisible. 447 00:44:01,080 --> 00:44:05,000 It's only recently, with the development of ultra high-speed cameras, 448 00:44:05,000 --> 00:44:11,920 that we've had any idea of the incredible high-speed performers hidden in humble horse poo. 449 00:44:17,560 --> 00:44:22,760 Slowed down 10,000 times, we can see them hurtling through the air. 450 00:44:27,560 --> 00:44:34,520 It's so fast, it's like us being catapulted to 100 times the speed of sound. 451 00:44:40,000 --> 00:44:43,520 All of which begs the question, why? 452 00:44:43,520 --> 00:44:47,040 Why does a fungi that lives in poo 453 00:44:47,040 --> 00:44:51,000 need to be the speediest thing on the planet? Why? 454 00:44:52,520 --> 00:44:54,960 Well, for our fungal family to survive, 455 00:44:54,960 --> 00:44:59,520 their spores need to get gobbled up by a friendly grass eater. 456 00:44:59,520 --> 00:45:02,160 This horse, for example. 457 00:45:04,440 --> 00:45:07,680 But he won't eat grass from an area around any pile of poo, 458 00:45:07,680 --> 00:45:11,960 known, rather charmingly, as, "the zone of repugnance". 459 00:45:11,960 --> 00:45:13,080 Which it kind of is. 460 00:45:13,080 --> 00:45:16,200 So the fungus has to launch spores beyond that, 461 00:45:16,200 --> 00:45:20,200 which means clearing over two metres. 462 00:45:20,200 --> 00:45:22,200 But there's a problem. 463 00:45:22,200 --> 00:45:24,280 The air's too thick. 464 00:45:24,280 --> 00:45:28,320 You see, the smaller you are, then, relatively speaking, 465 00:45:28,320 --> 00:45:30,960 the thicker the air gets. Imagine this coin 466 00:45:30,960 --> 00:45:34,200 were a tiny pilobolus spore. 467 00:45:36,320 --> 00:45:38,040 There it goes. 468 00:45:41,560 --> 00:45:46,720 But, to the tiny spore, the air is thick, like honey. 469 00:45:48,840 --> 00:45:50,840 And would stop it in its tracks. 470 00:45:53,920 --> 00:45:56,720 The only solution is to go fast enough 471 00:45:56,720 --> 00:46:02,400 to power through the thick air into the fresh, poo-free grass beyond. 472 00:46:02,400 --> 00:46:07,320 And that's exactly what the fungal spores do. 473 00:46:08,840 --> 00:46:15,840 Underneath each tiny head, an explosive bubble of liquid pressure builds up 474 00:46:15,840 --> 00:46:18,440 until, finally, it bursts, 475 00:46:20,200 --> 00:46:24,960 launching the spore at its tip more than two metres away. 476 00:46:36,800 --> 00:46:40,600 I know, it's impressive. 477 00:46:40,600 --> 00:46:43,240 Yep, your head's really heavy. 478 00:46:43,240 --> 00:46:47,080 Close-up, you're quite ugly, you know that, don't you? Get off. 479 00:46:57,080 --> 00:47:00,200 By looking into the invisible world of high-speed, 480 00:47:00,200 --> 00:47:03,120 we discover extraordinary events, 481 00:47:03,120 --> 00:47:06,600 even in something as ordinary as a garden pond. 482 00:47:08,600 --> 00:47:11,720 These little creatures, water striders, 483 00:47:11,720 --> 00:47:15,880 had long been a bit of a mystery. Nobody could work out quite how 484 00:47:15,880 --> 00:47:21,800 they could propel themselves across the surface of the water so quickly. 485 00:47:23,800 --> 00:47:28,600 They can scoot forward nearly two metres every second. 486 00:47:35,520 --> 00:47:39,040 And they're achieving something of biblical proportions, 487 00:47:39,040 --> 00:47:45,320 actually walking on water, skating across the surface without sinking. 488 00:47:47,360 --> 00:47:51,680 Only by seeing what time usually renders invisible to us 489 00:47:51,680 --> 00:47:54,360 can we understand what's really going on, 490 00:47:54,360 --> 00:47:58,160 and it's got something to do with what's about to happen here. 491 00:48:07,400 --> 00:48:10,560 Normally, this is too fast to see. 492 00:48:10,560 --> 00:48:13,440 But watch what happens in slow motion, 493 00:48:13,440 --> 00:48:16,800 as the droplet of milk hits the water surface. 494 00:48:39,840 --> 00:48:43,240 Instead of breaking, the water surface stretches, 495 00:48:43,240 --> 00:48:46,840 bouncing the milk drop back up into the air. 496 00:49:20,560 --> 00:49:26,320 The water behaves as if it has a thin elastic film on the surface. 497 00:49:26,320 --> 00:49:28,720 It's called surface tension. 498 00:49:33,920 --> 00:49:37,640 And it's this elastic membrane that allows the water strider 499 00:49:37,640 --> 00:49:42,400 to stand on the water, rather than sinking into it. 500 00:49:45,720 --> 00:49:49,640 He's also using that elastic surface tension 501 00:49:49,640 --> 00:49:56,120 to catapult himself across the pond at the equivalent of about 600mph. 502 00:50:07,560 --> 00:50:12,000 In coloured water, we can see the force 503 00:50:12,000 --> 00:50:15,720 of the strider's legs as they push across the surface. 504 00:50:18,400 --> 00:50:22,000 The high-speed artist of the invisible world. 505 00:50:32,040 --> 00:50:34,560 To us, this is just a pond. 506 00:50:34,560 --> 00:50:38,960 But to the water strider, it's a giant trampoline. 507 00:50:52,520 --> 00:50:57,120 Now we're going even further, looking far above us 508 00:50:57,120 --> 00:51:01,960 to reveal the invisible secrets on the very edges of our world. 509 00:51:03,760 --> 00:51:07,440 At the edges of our world, high above our heads, 510 00:51:07,440 --> 00:51:10,160 are even more astonishing events. 511 00:51:10,160 --> 00:51:14,720 The night sky might look calm, tranquil, the silvery moon, 512 00:51:14,720 --> 00:51:19,000 a few stars, all of that, but there are other things up there, 513 00:51:19,000 --> 00:51:23,880 things so strange we weren't even sure they existed. 514 00:51:29,560 --> 00:51:32,760 Our final journey takes us on the hunt 515 00:51:32,760 --> 00:51:36,320 for one of the most elusive events of the invisible world. 516 00:51:40,160 --> 00:51:43,520 We're attempting to find a spectacular lightning formation 517 00:51:43,520 --> 00:51:50,360 50 miles wide, but so fast it's virtually invisible. 518 00:51:50,360 --> 00:51:54,320 Centre 6775 with you at flight level 4-0-0. 519 00:51:54,320 --> 00:51:57,960 'Take off from 6775 Centre.' 520 00:51:57,960 --> 00:52:02,320 Brief glimpses have been mistaken for UFOs. 521 00:52:02,320 --> 00:52:04,320 They're called sprites. 522 00:52:04,320 --> 00:52:09,880 Now a team of scientists is heading high above the clouds, trying to 523 00:52:09,880 --> 00:52:16,280 catch them in the air on high-speed cameras for the first time. 524 00:52:16,280 --> 00:52:18,840 We're closer to the sprites, which is good, 525 00:52:18,840 --> 00:52:22,920 but since we're closer and we don't know where they're going to happen, 526 00:52:22,920 --> 00:52:25,280 that makes it a little harder. 527 00:52:25,280 --> 00:52:27,880 Conditions have to be just right. 528 00:52:27,880 --> 00:52:32,520 After years of planning, tonight is the night. 529 00:52:32,520 --> 00:52:34,360 No pressure then(!) 530 00:52:40,440 --> 00:52:44,680 1,000 miles away, a massive storm is brewing. 531 00:52:44,680 --> 00:52:47,440 This little plane's flying right into it. 532 00:52:47,440 --> 00:52:50,600 We're headed to Meridian, Mississippi now, and past that, 533 00:52:50,600 --> 00:52:53,920 we're going to head over toward Little Rock, Arkansas, and then 534 00:52:53,920 --> 00:52:56,920 we're going to go straight up toward Des Moines, Iowa. 535 00:52:56,920 --> 00:52:58,840 About two hours to get there. 536 00:52:58,840 --> 00:53:02,400 We'll have four hours to loiter around the storms 537 00:53:02,400 --> 00:53:06,520 for the sprite pictures in the back, and then two hours back home. 538 00:53:06,520 --> 00:53:09,200 So we'll be airborne about eight hours tonight. 539 00:53:10,320 --> 00:53:14,240 The mission takes place in almost total darkness. 540 00:53:14,240 --> 00:53:17,720 Any stray light makes it harder to detect sprites. 541 00:53:17,720 --> 00:53:22,680 A low-light camera and image intensifiers will help us see in the dark. 542 00:53:22,680 --> 00:53:25,400 I've also packed some carrots. 543 00:53:26,400 --> 00:53:30,240 Sprites are electrical discharges like normal lightning, 544 00:53:30,240 --> 00:53:32,560 but very different. 545 00:53:32,560 --> 00:53:35,880 The real difference is how brief the sprites last. 546 00:53:35,880 --> 00:53:38,000 Normal lightning can last, 547 00:53:38,000 --> 00:53:41,880 if you count all the strokes together, maybe half a second. 548 00:53:41,880 --> 00:53:44,680 Sprites are a lot shorter in duration. 549 00:53:47,480 --> 00:53:50,360 The plane's flying higher and higher. 550 00:53:50,360 --> 00:53:55,320 Now at 50,000 feet, close to the border with space. 551 00:54:00,040 --> 00:54:02,040 See that? That's Jupiter. 552 00:54:03,560 --> 00:54:07,760 With flying at this altitude, it's the clarity of the air. 553 00:54:07,760 --> 00:54:09,960 The visibility is forever. 554 00:54:13,000 --> 00:54:14,800 Getting close now. 555 00:54:14,800 --> 00:54:18,360 There's a storm building way below. 556 00:54:18,360 --> 00:54:21,640 It looks to me like we're getting all the lightning 557 00:54:21,640 --> 00:54:26,360 on our back side right now, so is it possible to turn ten degrees to the left? 558 00:54:28,480 --> 00:54:33,680 As the plane turns, the storm unleashes its fury. 559 00:54:39,400 --> 00:54:42,040 These are perfect sprite conditions. 560 00:54:42,040 --> 00:54:44,080 There's no time to lose. 561 00:54:44,080 --> 00:54:46,760 Do you think we should go up? Don't know. 562 00:54:49,000 --> 00:54:50,680 It won't hurt the intensifier. 563 00:54:50,680 --> 00:54:54,880 The high-speed cameras and image intensifiers are prepared. 564 00:54:54,880 --> 00:54:59,120 10,000 frames a second, 50 micro-second integration time. 565 00:54:59,120 --> 00:55:02,840 They're fixed on an area just above the storm itself. 566 00:55:02,840 --> 00:55:04,840 Gain is 60,500, 567 00:55:04,840 --> 00:55:08,880 the aspect is zero, elevation is minus four. Do we go again? 568 00:55:08,880 --> 00:55:13,640 Trying to catch one of the most elusive phenomena in the natural world. 569 00:55:17,320 --> 00:55:19,720 A sprite. There's something. 570 00:55:19,720 --> 00:55:23,120 I think that was probably outside the field of view, I'm not sure. 571 00:55:23,120 --> 00:55:25,200 It could have been a sprite. 572 00:55:29,120 --> 00:55:31,960 And the storm's about to die. 573 00:55:34,240 --> 00:55:37,520 We're now at minus four degrees elevation. 574 00:55:40,000 --> 00:55:43,000 And then... Sprite. We're looking. Yeah, we got it. 575 00:55:46,400 --> 00:55:49,480 It looks like there's two of them. I think he got them. 576 00:56:05,480 --> 00:56:10,520 A vast column of light, 20 miles tall. 577 00:56:10,520 --> 00:56:13,160 It dwarfs the city below. 578 00:56:17,560 --> 00:56:22,360 A spectacular formation, trailing globes of light. 579 00:56:22,360 --> 00:56:24,920 Each one is as bright as Jupiter. 580 00:56:28,880 --> 00:56:34,840 These amazing high-speed images have been captured from the air for the very first time. 581 00:56:34,840 --> 00:56:39,480 You and I live on seconds or minutes or maybe even years of timescales. 582 00:56:39,480 --> 00:56:44,080 And sprites are one one-thousandth of a second. 583 00:56:44,080 --> 00:56:47,000 It makes you realise how different the world can be. 584 00:56:49,080 --> 00:56:53,240 This vast display happens in our skies all over the world, 585 00:56:53,240 --> 00:56:56,720 but we're completely unaware of it. 586 00:57:00,320 --> 00:57:04,160 Although it is reckoned that some reports of UFOs 587 00:57:04,160 --> 00:57:09,200 might actually be glimpses of these vast, super-bright round flashes. 588 00:57:14,800 --> 00:57:17,320 Sprites aren't just spectacular. 589 00:57:17,320 --> 00:57:22,320 They're also one of the greatest secrets of the invisible world. 590 00:57:43,320 --> 00:57:48,920 Thanks to high-speed cameras, we've been able to see things we never even dreamed of. 591 00:57:48,920 --> 00:57:51,560 But of course, that is not the end of the line. 592 00:57:51,560 --> 00:57:55,480 Who knows what else is going on right now that we can't see - yet. 593 00:58:38,960 --> 00:58:42,160 Subtitles by Red Bee Media Ltd 594 00:58:42,160 --> 00:58:45,280 E-mail subtitling@bbc.co.uk 52220

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