0:00 The Milky Way galaxy may contain forty billion Earth-sized planets orbiting in the habitable zones of their stars.0:08 It’s a number so large it’s almost meaningless, and yet, we have found zero confirmed evidence of intelligent life anywhere but here.0:17 It’s another one of those fundamental asymmetries, isn't it?0:21 Last week we were talking about why time seems to only flow forward, and here we are again, staring at another profound imbalance in the universe.0:32 An imbalance is the perfect word for it.0:35 All that potential real estate, and nobody home.0:38 That's the Fermi Paradox, right?0:40 That’s the heart of it.0:42 The physicist Enrico Fermi supposedly asked it over lunch back in 1950.0:47 Given the age of the universe, and the sheer number of stars, the math says the sky should be full of ships, signals, evidence.0:56 So...0:57 where is everybody?0:58 My first instinct is just...1:00 space is big.1:01 It takes a long, long time to get anywhere.1:04 It is, but the numbers don't work out even then.1:07 A civilization only slightly more advanced than ours could build self-replicating probes and colonize the entire galaxy in about ten million years.1:18 The galaxy is over ten BILLION years old.1:21 Someone should have done it by now.1:23 So the silence itself is the signal.1:26 The silence is the data.1:28 Exactly.1:28 And that leads to the proposed solutions, which are really just a collection of unsettling possibilities.1:36 The most famous is the Great Filter.1:38 The idea that there's some wall that life has to get past.1:42 A wall so high that almost no one makes it over.1:46 The terrifying question is, is that wall in our past, or in our future?1:51 Okay, walk me through that.1:53 If it's in our past...1:54 Then we are incredibly lucky.1:56 It means some step, like the jump from non-living chemicals to life, or from single-celled organisms to complex ones like us, is almost impossible.2:07 We won the cosmic lottery, and we are likely the first and only ones to do it.2:12 We're alone.2:13 And if the filter is in our future?2:16 That’s a much darker thought.2:18 That’s the thought that keeps astronomers up at night.2:22 It would mean that civilizations regularly arise, but they all discover something—nuclear weapons, runaway AI, a technology we can't even imagine—that inevitably destroys them.2:34 In that scenario, the silence isn't a mystery.2:38 It’s a graveyard.2:39 So we’re either a miracle or we’re doomed.2:42 Not a lot of great options there.2:44 This feels like a pattern we’ve seen before, though.2:48 The way we look for answers is constrained by the tools we have.2:52 It’s very similar to the age of exploration on Earth.2:56 When European ships first mapped the world, they’d label vast sections of continents "terra incognita"—unknown land.3:04 They assumed it was empty, but of course it wasn't.3:08 It was just unknown to them.3:10 Which leads to the Zoo Hypothesis.3:12 That they’re out there, and they know we're here, but they have a strict 'look, don't touch' policy.3:20 The Prime Directive, for Star Trek fans.3:22 We're a protected nature preserve.3:25 They're waiting for us to mature, to stop fighting wars and solve our own problems before they make contact.3:33 I can’t decide if that’s the most hopeful answer or the most condescending one.3:38 So we’re left with these possibilities.3:41 We’re alone.3:42 We’re next in line for extinction.3:44 Or we’re an exhibit.3:46 And every attempt to solve the paradox just seems to make it deeper.3:51 Because you can’t prove any of them.3:53 All you can do is keep listening to the static.3:57 It's the question itself that seems to matter more than any potential answer.4:02 I think so.4:03 It forces us to confront our own place in the cosmos.4:07 It’s a mirror.4:08 When we ask "Where is everybody?" we’re really asking, "Who are we?4:12 And what are we going to become?" The search for them is really about what we hope for ourselves.4:19 And whether we can be the one species to finally make it past the filter.4:25 If there is one.4:26 We might just be the ones to finally fill the silence.
