What will happen to us when the Sun turns into a red giant?
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00:00 Five billion years from now,
00:06 the Sun will expand and become a red giant.
00:10 And the Earth might just be in the way.
00:14 If humans were still around then,
00:16 would we leave the Earth?
00:18 Or would we move it?
00:21 This is WHAT IF,
00:23 and here's what would happen
00:24 if we moved the Earth.
00:29 What's the Sun's problem anyway?
00:31 Well, like any other star,
00:33 it has an expiration date.
00:35 The beginning of its end
00:37 will feature our Sun swelling into a red giant,
00:40 wiping out everything that happens to be orbiting it too closely,
00:44 like the Earth.
00:46 If we wanted to survive,
00:48 we'd need to take action long before the Sun started going on a rampage.
00:54 It would take a billion space shuttles
00:56 to evacuate about 7.5 billion Earthlings.
00:59 Even if we could launch 1,000 space shuttles every day,
01:03 it would take over 2,700 years
01:05 to move everyone off the doomed planet.
01:08 Maybe we could save ourselves some trouble
01:11 by moving our whole planet instead.
01:14 That's actually quite possible.
01:16 We'd only need to give the Earth one big boost in the right direction,
01:19 and keep it on course.
01:21 And there are a few ways to do that.
01:25 To move the planet out of danger,
01:27 we'd have to change its velocity by 1,200 m/s (3,000 ft/s).
01:31 That would require about 7,000 of the most powerful rockets ever built.
01:36 But this plan has one big flaw.
01:39 To escape the Sun's expanding flames,
01:41 we'd need to escape pretty far.
01:43 At least move into the orbit of Mars.
01:47 Moving something as bulky as the Earth to a safe zone there
01:50 might take us billions of years.
01:52 And for every billion years that passed,
01:55 we'd use up about a third of the Earth's mass as propellant.
01:58 That's not very efficient, is it?
02:01 To move the Earth more efficiently,
02:03 we'd have to consider electric propulsion.
02:07 Unlike the chemical one used in most rockets,
02:10 electric propulsion doesn't require a lot of mass.
02:14 We could get away with sacrificing only 2% of the Earth's mass every billion years.
02:19 You'd hardly notice the difference.
02:21 But this option would require a lot of power,
02:25 about 800 times more than what's produced here on Earth right now.
02:30 Plus, it would take some careful engineering to make this work.
02:34 Because the Earth is spinning,
02:36 a rocket placed in one location would not always point in the right direction.
02:41 We'd need to place rockets all around the Earth,
02:43 and have each of them fire only for a certain amount of time.
02:47 That would keep the Earth on course.
02:50 It would take a billion years to move the planet out of the danger zone.
02:54 Any miscalculation could mean extinction.
02:58 There is a better way,
03:00 and it involves asteroids.
03:03 Aerospace engineers use something called a gravitational slingshot
03:07 to alter a spacecraft's path without using too much propellant.
03:12 When a spacecraft approaches the Earth and then leaves its gravitational pull,
03:17 it receives some of the Earth's orbital energy.
03:20 We could use the same effect to redirect our planet.
03:24 First, we'd have to make comets or asteroids pass close to the Earth,
03:28 transferring some of their energy in the process.
03:31 Next, engineers would redirect the asteroids close to Jupiter and Saturn,
03:36 where they would pick up some of the gas giant's energy.
03:40 From there, the asteroids would bring that energy back to Earth.
03:44 We'd repeat the process over and over again until it got us to a safe orbit.
03:49 Of course, that would be quite dangerous too.
03:54 The slightest miscount might redirect a gigantic asteroid right into the planet,
03:59 and destroy all life as we know it.
04:03 Now, we wouldn't be taking the Moon on our road trip around the Solar System.
04:08 Most likely, we'd ditch our celestial partner
04:10 the moment we pushed Earth's orbit away from the Sun.
04:14 Now, the big risk here is that moving the Earth might disrupt the whole planetary system.
04:20 It could easily destabilize Mercury or Venus,
04:24 setting them on the path of destruction.
04:26 And there's no one living on those planets that can save them.
04:30 At least, not that we know about.
04:32 Maybe we'd be better off terraforming another planet to use as our new home.
04:37 But that's a story for another WHAT IF.
04:41 [ ♪ Outro ]