Placeholder Image

字幕表 動画を再生する

  • "This is a planetary emergency evacuation.

  • Please remain calm,

  • and board your space shuttles."

  • Even though humanity might not have to

  • leave the Earth in your lifetime,

  • we should start preparing early on.

  • Not only could it take centuries

  • to set up the relocation program,

  • it would take generations to move

  • to a potential new home.

  • That, right there, is Proxima Centauri b,

  • or just Proxima b.

  • It's the closest potentially

  • habitable planet out there.

  • Its temperatures are in the bearable range,

  • and it could have just the right

  • breathable atmosphere.

  • We only have to get there.

  • When astronomers started finding planets

  • outside our Solar System, or exoplanets,

  • we realized that there are

  • many worlds out there.

  • That meant that Earth

  • doesn't have to be our home forever.

  • And that we don't have to die with our planet

  • when the Sun engulfs it

  • some 5 billion years from now.

  • Now that we've found over 4,100 exoplanets,

  • we've learned something rather disappointing.

  • Not all exoplanets are good for humans to live on.

  • Most of the worlds we've encountered

  • are either ice giants like Neptune,

  • or gas giants like Jupiter and Saturn.

  • Only 161 of those planets

  • are terrestrial, like Earth.

  • And when it comes to sustaining human life,

  • being terrestrial isn't quite enough.

  • Proxima b is very promising.

  • It orbits a red dwarf star called Proxima Centauri

  • in a system with three stars in it.

  • Proxima Centauri is small.

  • It only has between 7.5% and 50% of our Sun's mass.

  • That's a good thing.

  • Because the red dwarf Proxima Centauri

  • is so much smaller than our yellow dwarf Sun,

  • it burns at a lower temperature.

  • It takes stars like Proxima Centauri

  • much longer to burn through all of their hydrogen supply.

  • Because of that, Proxima Centauri

  • has a lifetime of trillions of years,

  • while our Sun has a 10-billion-year expiration term.

  • That alone makes Proxima b

  • a good candidate for relocation.

  • That and the fact that its orbit

  • lies in Proxima Centauri's habitable zone.

  • That means there's the potential for liquid water

  • and comfortable surface temperatures.

  • If we're lucky, Proxima b would

  • have an atmosphere that we could breathe.

  • If it does, the surface temperatures

  • would be in the range of 30°C (86°F).

  • I don't know about you, but

  • I'd move there right now.

  • I just need to warn you that

  • there are a few problems.

  • A trip to Proxima b would be long

  • and very dangerous.

  • Proxima b might be the closest

  • habitable exoplanet we've got, but

  • that doesn't mean it's close.

  • The red dwarf star, Proxima Centauri,

  • is about 4.3 light-years away.

  • That means that if you could travel at the speed of light,

  • it would take you 4.3 years to get there.

  • Nothing we've built so far can reach that kind of speed.

  • Realistically, a trip to Proxima Centauri in a space shuttle

  • would take 165,000 years, give or take.

  • That's right, some of the colonists

  • would be born in transit.

  • Some of them would never see the Earth.

  • Some of them would never see Proxima b.

  • They'd just live their lives aboard the spaceship

  • and die in space.

  • According to some calculations,

  • 98 people would be just enough.

  • Their descendants would arrive at Proxima b with

  • enough genetic diversity

  • to populate the entire planet.

  • And that's accounting for possible cases of infertility,

  • inbreeding and sudden deaths.

  • In those calculations, the crew would be traveling

  • on something faster than a space shuttle.

  • Their mission to Proxima b

  • would take only 6,300 years.

  • But don't be surprised.

  • Technology is constantly improving.

  • Right now, a scientific and technological

  • program called Breakthrough Initiatives

  • is looking at how we can get in the neighborhood

  • of Proxima Centauri within one generation.

  • Their Project Starshot is working on

  • an ultra-light, unmanned probe

  • that would reach the star system in just 20 years.

  • Now I definitely need to sign up.

  • But, again, Proxima b is really far away.

  • It's so far that we can't even see if it has an atmosphere.

  • It might just happen that

  • we would arrive at a frozen planet

  • with surface temperatures of -40°C (-40°F).

  • And even if it has an atmosphere,

  • it might not be the right one.

  • We might still enjoy warm temperatures, but

  • we'd be doing that in space suits with oxygen tanks.

  • Or, Proxima b could be tidally locked to Proxima Centauri,

  • meaning one of the planet's sides would

  • always face its star,

  • and the other side would be plunged into darkness.

  • Space flight itself could bring some unpleasant surprises.

  • Spending an entire lifetime

  • in a zero-gravity environment

  • would lead the crew members to lose

  • muscle and bone density.

  • They'd be constantly exposed to space radiation.

  • Their microbiomes, immune systems and

  • physiology would all be different from ours.

  • They wouldn't be the same

  • kind of humans as we are.

  • They would change their values and culture.

  • They might forget all the farming techniques

  • we'd teach them to sustain themselves

  • in space and on their new planet.

  • They might change their mind

  • about the mission altogether

  • and just turn their spaceship in a different direction.

  • Who knowsthey might even come back to Earth

  • and take revenge for all those years

  • they were forced to spend in space.

  • If that happens, I'll be asking for a refund.

  • Sending anyone on a mission like this is a huge risk.

  • We'd need to design and build a vehicle,

  • choose the space travelers very carefully,

  • supply them with all the food and water,

  • and make sure they could become self-sustaining.

  • We'd have to design new propulsion,

  • navigation, hibernation and

  • life support systems.

  • And we have no way of knowing

  • if Proxima b is actually habitable.

  • Now I don't really feel like going there. Do you?

  • Maybe a better idea would be

  • to build a megastructure

  • somewhere closer to the Solar System.

  • But that's a story for another What If.

"This is a planetary emergency evacuation.

字幕と単語

動画の操作 ここで「動画」の調整と「字幕」の表示を設定することができます

B1 中級

もし人類をプロキシマBに移転させたら? (What If We Relocated Humanity to Proxima B?)

  • 0 0
    林宜悉 に公開 2021 年 01 月 14 日
動画の中の単語