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  • Five billion years from now,

  • the Sun will expand and become a red giant.

  • And the Earth might be just in the way...

  • If humans were still around then...

  • What is the Sun's problem anyway?

  • Like any other star, it has an expiration date.

  • The beginning of its end will feature

  • our Sun swelling into a red giant,

  • wiping out everything that happens to be orbiting it too closely.

  • Like the Earth.

  • If we wanted to survive,

  • we'd need to take action long before

  • the Sun started going on a rampage.

  • It would take a billion space shuttles

  • to evacuate about 7.5 billion Earthlings.

  • Even if we could launch 1,000 space shuttles every day,

  • it would take over 2,700 years to move everyone off the doomed planet.

  • Maybe we could save ourselves some trouble

  • by moving our whole planet instead.

  • We'd only need to give the Earth one big boost in the right direction -

  • and keep it on course.

  • And there are a few ways to do that.

  • To move the planet out of danger,

  • we'd have to change its velocity

  • by 1,200 meters per second (3,937 feet per second).

  • That would require about 7,000

  • of the most powerful rockets ever built, but...

  • this plan has one big flaw.

  • To escape the Sun's expanding flames,

  • we'd need to escape pretty far -

  • at least move into the orbit of Mars.

  • Moving something as bulky as the Earth to a safe zone there

  • might take us billions of years.

  • And for every billion years that passed,

  • we'd use up about a third of the Earth's mass as propellant.

  • That's not very efficient, is it?

  • To move the Earth more efficiently,

  • we'd have to consider electric propulsion.

  • Unlike the chemical one used in most rockets,

  • electric propulsion doesn't require a lot of mass.

  • We could get away with sacrificing only 2%

  • of the Earth's mass every billion years.

  • You'd hardly notice the difference.

  • But this option would require a lot of power -

  • about 800 times more than what's produced here on Earth right now.

  • Plus, it would take some careful engineering to make this work.

  • Because the Earth is spinning,

  • a rocket placed in one location

  • would not always point in the right direction.

  • We'd need to place rockets all around the Earth,

  • and have each of them fire only for a certain amount of time.

  • That would keep the Earth on course.

  • It would take a billion years to move the planet

  • out of the danger zone.

  • Any miscalculation could mean extinction.

  • It involves asteroids.

  • Aerospace engineers use something called a gravitational slingshot

  • to alter a spacecraft's path without using too much propellant.

  • When a spacecraft approaches the Earth,

  • and then leaves its gravitational pull,

  • it receives some of the Earth's orbital energy.

  • We could use the same effect to redirect our planet.

  • First, we'd have to make comets or asteroids pass close to the Earth,

  • transferring some of their energy in the process.

  • Next, engineers would redirect the asteroids

  • close to Jupiter and Saturn,

  • where they would pick up some of the gas giants' energy.

  • From there, the asteroids would bring that energy back to Earth.

  • We'd repeat the process over and over again until it got us to a safe orbit.

  • Of course, that would be quite dangerous too.

  • The slightest miscount might redirect a gigantic asteroid right into the planet,

  • and destroy all life as we know it.

  • We wouldn't be taking the Moon on our road trip around the Solar System.

  • Most likely, we'd ditch our celestial partner

  • the moment we pushed Earth's orbit away from the Sun.

  • The big risk here is that

  • moving Earth might disrupt the whole planetary system.

  • It could easily destabilize Mercury or Venus,

  • setting them on the path of destruction.

  • And there is no one living on those planets that can save them -

  • at least, not that we know about.

  • Maybe we'd be better off terraforming another planet to use as our new home.

  • But that's a story for another WHAT IF.

Five billion years from now,

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地球を移動させたら? (What If We Moved Earth?)

  • 7 1
    林宜悉 に公開 2021 年 01 月 14 日
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