0:00:00.000,0:00:15.000 (Music) 0:00:15.000,0:00:18.000 Somewhere out there in that vast universe 0:00:18.000,0:00:21.000 there must surely be countless other planets teeming with life, 0:00:21.000,0:00:24.000 but why don't we see any evidence of it? 0:00:24.000,0:00:28.000 Well, this is the famous question asked by Enrico Fermi in 1950: 0:00:28.000,0:00:31.000 "Where is everybody?" 0:00:31.000,0:00:35.000 Conspiracy theorists claim that UFOs are visiting all the time 0:00:35.000,0:00:37.000 and the reports are just being covered up, 0:00:37.000,0:00:40.000 but honestly, they aren't very convincing. 0:00:40.000,0:00:42.000 But that leaves a real riddle. 0:00:42.000,0:00:45.000 In the past year, the Kepler space observatory has found 0:00:45.000,0:00:48.000 hundreds of planets just around nearby stars, 0:00:48.000,0:00:50.000 and if you extrapolate that data, 0:00:50.000,0:00:53.000 it looks like there could be half a trillions planets 0:00:53.000,0:00:56.000 just in our own galaxy. 0:00:56.000,0:00:59.000 If any one in 10,000 has conditions 0:00:59.000,0:01:02.000 that might support a form of life, that's still 0:01:02.000,0:01:04.000 50 million possible life-harboring planets 0:01:04.000,0:01:06.000 right here in the Milky Way. 0:01:06.000,0:01:08.000 So here's the riddle. 0:01:08.000,0:01:13.000 Our Earth didn't form until about 9 billion years after the Big Bang. 0:01:13.000,0:01:16.000 Countless other planets in our galaxy 0:01:16.000,0:01:19.000 should have formed earlier and given life a chance to get underway 0:01:19.000,0:01:23.000 billions, or certainly many millions, of years 0:01:23.000,0:01:25.000 earlier than happened on Earth. 0:01:25.000,0:01:28.000 If just a few of them had spawned intelligent life 0:01:28.000,0:01:30.000 and started creating technologies, 0:01:30.000,0:01:33.000 those technologies would have had millions of years 0:01:33.000,0:01:36.000 to grow in complexity and power. 0:01:36.000,0:01:38.000 On Earth, 0:01:38.000,0:01:41.000 we've seen how dramatically 0:01:41.000,0:01:44.000 technology can accelerate in just 100 years. 0:01:44.000,0:01:48.000 In millions of years, an intelligent alien civilization 0:01:48.000,0:01:51.000 could easily have spread out across the galaxy, 0:01:51.000,0:01:54.000 perhaps creating giant energy-harvesting artifacts 0:01:54.000,0:01:57.000 or fleets of colonizing spaceships 0:01:57.000,0:02:00.000 or glorious works of art that fill the night sky. 0:02:00.000,0:02:03.000 At the very least, you'd think they'd be revealing their presence, 0:02:03.000,0:02:05.000 deliberately or otherwise, 0:02:05.000,0:02:08.000 through electromagnetic signals 0:02:08.000,0:02:11.000 of one kind or another. And yet we see no convincing evidence of any of it. 0:02:11.000,0:02:14.000 Why? 0:02:14.000,0:02:17.000 Well, there are numerous possible answers, 0:02:17.000,0:02:19.000 some of them quite dark. 0:02:19.000,0:02:22.000 Maybe a single, super-intelligent civilization 0:02:22.000,0:02:25.000 has indeed taken over the galaxy, 0:02:25.000,0:02:28.000 and has imposed strict radio silence 0:02:28.000,0:02:31.000 because it's paranoid of any potential competitors. 0:02:31.000,0:02:34.000 It's just sitting there ready to obliterate 0:02:34.000,0:02:37.000 anything that becomes a threat. 0:02:37.000,0:02:40.000 Or maybe they're not that intelligent, 0:02:40.000,0:02:43.000 or perhaps the evolution of an intelligence 0:02:43.000,0:02:45.000 capable of creating sophisticated technology 0:02:45.000,0:02:47.000 is far rarer than we've assumed. 0:02:47.000,0:02:52.000 After all, it's only happened once on Earth in 4 billion years. 0:02:52.000,0:02:55.000 Maybe even that was incredibly lucky. 0:02:55.000,0:02:58.000 Maybe we are the first such civilization in our galaxy. 0:02:58.000,0:03:02.000 Or perhaps civilization carries with it 0:03:02.000,0:03:04.000 the seeds of its own destruction 0:03:04.000,0:03:07.000 through the inability to control the technologies it creates. 0:03:07.000,0:03:12.000 But there are numerous more hopeful answers. 0:03:12.000,0:03:16.000 I mean, for a start, we're not looking that hard. And we're spending a pitiful amount of money on it. 0:03:16.000,0:03:20.000 Only a tiny fraction of the stars in our galaxy 0:03:20.000,0:03:23.000 have really been looked at closely for signs of interesting signals. 0:03:23.000,0:03:26.000 And perhaps we're not looking the right way. 0:03:26.000,0:03:29.000 Maybe as civilizations develop, 0:03:29.000,0:03:32.000 they quickly discover communication technologies 0:03:32.000,0:03:35.000 far more sophisticated and useful than electromagnetic waves. 0:03:35.000,0:03:38.000 Maybe all the action takes place 0:03:38.000,0:03:42.000 inside the mysterious recently discovered dark matter, 0:03:42.000,0:03:46.000 or dark energy, that appear to account for most of the universe's mass. 0:03:46.000,0:03:50.000 Or maybe we're looking at the wrong scale. 0:03:50.000,0:03:53.000 Perhaps intelligent civilizations come to realize 0:03:53.000,0:03:56.000 that life is ultimately just complex patterns of information 0:03:56.000,0:03:58.000 interacting with each other in a beautiful way, 0:03:58.000,0:04:01.000 and that that can happen more efficiently at a small scale. 0:04:01.000,0:04:04.000 So, just as on Earth clunky stereo systems 0:04:04.000,0:04:07.000 have shrunk to beautiful, tiny iPods, maybe intelligent life itself, 0:04:07.000,0:04:10.000 in order to reduce its footprint on the environment, 0:04:10.000,0:04:12.000 has turned itself microscopic, 0:04:12.000,0:04:15.000 so the Solar System might be teeming with aliens, and we're just not noticing them. 0:04:15.000,0:04:19.000 Maybe the very ideas in our heads are a form of alien life. 0:04:19.000,0:04:22.000 Well, okay, that's a crazy thought. 0:04:22.000,0:04:24.000 The aliens made me say it. 0:04:24.000,0:04:27.000 But it is cool that ideas do seem to have a life all of their own 0:04:27.000,0:04:30.000 and that they outlive their creators. 0:04:30.000,0:04:35.000 Maybe biological life is just a passing phase. 0:04:35.000,0:04:40.000 Well, within the next 15 years, 0:04:40.000,0:04:42.000 we could start seeing real spectroscopic information 0:04:42.000,0:04:46.000 from promising nearby planets that will reveal just how life-ready they might be. 0:04:46.000,0:04:49.000 And meanwhile SETI, the Search for Extra-Terrestrial Intelligence, 0:04:49.000,0:04:52.000 is now releasing its data to the public 0:04:52.000,0:04:55.000 so that millions of citizen scientists, maybe including you, 0:04:55.000,0:04:58.000 can bring the power of the crowd to join the search. 0:04:58.000,0:05:01.000 And here on Earth, amazing experiments are being done 0:05:01.000,0:05:04.000 to try to create life from scratch, 0:05:04.000,0:05:07.000 life that might be very different from the DNA forms we know. 0:05:07.000,0:05:09.000 All of this will help us understand 0:05:09.000,0:05:12.000 whether the universe is teeming with life 0:05:12.000,0:05:16.000 or whether, indeed, it's just us. 0:05:16.000,0:05:20.000 Either answer, in its own way, 0:05:20.000,0:05:23.000 is awe-inspiring, 0:05:23.000,0:05:25.000 because even if we are alone, 0:05:25.000,0:05:29.000 the fact that we think and dream and ask these questions 0:05:29.000,0:05:33.000 might yet turn out to be one of the most important facts about the universe. 0:05:33.000,0:05:37.000 And I have one more piece of good news for you. 0:05:37.000,0:05:40.000 The quest for knowledge and understanding never gets dull. 0:05:40.000,0:05:43.000 It doesn't. It's actually the opposite. The more you know, 0:05:43.000,0:05:46.000 the more amazing the world seems. 0:05:46.000,0:05:49.000 And it's the crazy possibilities, the unanswered questions, 0:05:49.000,9:59:59.000 that pull us forward. So stay curious.