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 knows — they 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.