0:00 So, here’s a question.0:01 What does the end of EVERYTHING look like?0:05 Not just the end of a movie, or a book, but the end of the entire universe.0:12 Whoa.0:12 That’s a big question for a Tuesday.0:15 I mean, a giant explosion?0:18 A big crunch?0:19 That’s what people used to think!0:22 But the real answer is so much quieter, and honestly, so much stranger.0:28 Last week we talked about how looking at stars is a form of time travel into the past.0:35 Well, today, we're going to time travel into the far, far, FAR future.0:42 Okay, I'm strapped in.0:43 Where are we going?0:45 We're going to the Heat Death of the Universe.0:49 And it all starts with one simple idea: entropy.0:53 Uh oh.0:54 That’s one of those science words that sounds complicated.0:59 It sounds it, but it's not!1:01 I promise.1:02 Think about your bedroom.1:04 Does it naturally get cleaner or messier?1:08 Oh, messier.1:09 One hundred percent.1:11 Without question.1:12 Exactly!1:13 That's entropy.1:14 It’s the universe's fundamental tendency to go from a neat, orderly state to a messy, disordered one.1:23 Or think of it like this: you pour a cup of hot coffee in a cold room.1:29 The heat doesn't stay in the cup, right?1:33 It spreads out into the room until everything is the same lukewarm temperature.1:40 Right, the coffee gets cold.1:42 Yes!1:43 Energy wants to spread out.1:45 And that simple rule dictates the entire future of the cosmos.1:50 So, let's jump forward in time.1:53 A hundred trillion years from now.1:56 All the stars you can see in the sky?1:59 They've all burned out.2:01 All of them?2:02 Like, the sun, everything?2:05 Everything.2:06 The big, bright blue stars go first.2:09 Then the yellow ones like our sun.2:12 The last lights to go out will be the tiny, dim red dwarfs.2:17 They’ll sip their fuel for trillions of years, but eventually, they too will flicker and die.2:25 The age of stars will be over.2:28 So the universe is just… dark?2:30 Pitch black.2:31 It's called the Degenerate Era.2:34 The only things left are the corpses of stars—white dwarfs, neutron stars, and of course, black holes.2:43 For an almost unimaginable amount of time, the universe is just a cold, dark graveyard of these objects, slowly drifting apart as space continues to expand.2:57 Okay, that is a bleak picture.2:59 But at least the black holes are still there, right?3:04 They’re the ultimate survivors.3:07 Ah, but that’s the twist!3:09 They’re not!3:10 This is my FAVORITE part.3:12 For the longest time, we thought black holes were permanent.3:17 The final cosmic prisons.3:20 But the great physicist Stephen Hawking proved that they’re not.3:25 Wait—what?3:26 How can something escape a black hole?3:29 It doesn't, not really.3:31 Instead, the black hole itself...3:34 evaporates.3:35 No.3:36 How?3:36 It’s a process called Hawking Radiation.3:39 Over incredible amounts of time, black holes slowly leak their energy back out into space, particle by particle.3:49 They get smaller, and smaller, and smaller, until——they’re gone.3:55 You’re kidding me.3:56 So even a supermassive black hole at the center of a galaxy will just… disappear?4:04 It will!4:04 It just takes a while.4:06 We’re talking timescales like ten to the power of one hundred years.4:12 That's a one followed by a hundred zeroes.4:16 There isn’t a word in any language for a number that big.4:21 My brain just can't even hold that number.4:25 So...4:25 after the last star has died, and after the last black hole has evaporated...4:32 what's left?4:33 Almost nothing.4:34 The Black Hole Era gives way to the final act: the Dark Era.4:39 The universe will be a vast, cold, and almost perfectly empty space.4:45 So it’s just… gone?4:47 Not quite.4:48 It will be a thin, cold soup of leftover particles—photons, neutrinos, the most basic building blocks of matter—drifting aimlessly in the dark.5:00 The temperature everywhere will be just a fraction of a degree above absolute zero.5:08 And that’s it?5:09 That’s the end?5:10 That’s the end.5:12 All the energy has spread out as much as it possibly can.5:17 The coffee has gone completely cold.5:20 Entropy has reached its maximum.5:23 No more work can be done.5:25 No more stars can form.5:27 No more change can happen.5:29 The universe has reached its final state of equilibrium.5:34 Wow.5:34 It’s a little sad, isn't it?5:37 Is it?5:37 Or is it kind of beautiful?5:40 Think of it.5:41 The universe began in a flash of incredible energy and complexity, and it will end in a state of perfect, simple, quiet.5:51 It’s the longest, most epic story ever told, coming to its final, silent page.5:58 It’s not a violent end.6:00 It’s just… rest.
