How humanity can reach the stars

Could we exit our solar system, and enter another? Astrophysicist Philip Lubin discusses the awesome potential of using lasers to propel small spacecraft, enabling humanity's first interstellar missions. Learn how this transformative technology could help us reach Proxima Centauri, the nearest star to our own -- and fundamentally alter our understanding of the universe along the way.

We're here at the University
of California, Santa Barbara

to discuss a dream of humanity:

the ability to exit our solar system

and enter another solar system.

And the solution is literally
before your eyes.

So I have two things on me
that you have -- I have a watch,

and I have a flashlight,

which, if it's not on you,
it's on your phone.

So the watch keeps time,

and my flashlight
just illuminates my environment.

So like art, to me,
science is illuminating.

I want to see reality in a different way.

When I turn on the flashlight,

suddenly the dark becomes bright,
and I suddenly see.

The flashlight and its light,

which you can see coming out --

the light on my hand
is not only illuminating my hand,

it's actually pushing on my hand.

Light carries energy and momentum.

So the answer is not to make a spacecraft
out of a flashlight,

by having the exhaust come out this way

and the spacecraft goes that way --

that's what we do today with chemistry.

The answer is this:

Take the flashlight and put it
somewhere on the Earth,

in orbit or on the Moon,

and then shine it on a reflector,

which propels the reflector to speeds
which can approach the speed of light.

Well, how do you make a flashlight
that's big enough?

This isn't going to do it,

my hand doesn't seem to be going anywhere.

And that's because the force
is very, very low.

So the way that you can solve this problem

is taking many, many flashlights,
which are actually lasers,

and synchronizing them in time,

and when you gang them all together
into a gigantic array,

which we call a phased array,

you then have a sufficiently
powerful system,

which, if you make it roughly
the size of a city,

it can push a spacecraft,
which is roughly the size of your hand,

to speeds which are roughly
25 percent the speed of light.

That would enable us to get
to the nearest star, Proxima Centauri,

which is a little over
four light years away,

in less than 20 years.

Initial probes would be
roughly the size of your hand,

and the size of the reflector
that you're going to use

is going to be roughly human size,

so not a whole lot larger than myself,

but a few meters in size.

It only uses the reflection of light
from this very large laser array

to propel the spacecraft.

So let's talk about this.

This is a lot like sailing on the ocean.

When you sail on the ocean,
you're pushed by the wind.

And the wind then drives the sail
forward through the water.

In our case, we're creating
an artificial wind in space

from this laser array,

except the wind is actually the photons
from the laser itself,

the light from the laser becomes the wind

upon which we sail.

It is a very directed light --

it's often called directed energy.

So why is this possible today,

why can we talk about
going to the stars today,

when 60 years ago,

when the space program began in earnest,

people would have said,
"That's not possible"?

Well, the reason it's possible today
has a lot to do with the consumer,

and the very fact that you're watching me.

You're watching me
over a high-speed internet,

which is dominated by the photonics
of sending data over fiber optics.

Photonics essentially allow
the internet to exist

in the way it does today.

The ability to send vast amounts
of data very quickly

is the same technology
that we're going to use

to send spacecraft
very quickly to the stars.

You effectively have an infinite
supply of propellent,

you can turn it on and off as needed.

You do not leave the laser array
that produces the light on

for the entire journey.

For small spacecraft,
it's only on for a few minutes,

and then it's like shooting a gun.

You have a projectile
which just moves ballistically.

Even if we, as humans,
are not on the spacecraft,

at least we have the ability
to send out such spacecraft.

You want to remotely view,

or have remote imaging and remote sensing,

of an object.

So when we go to Jupiter, for example,

with a flyby mission,

we are taking pictures of Jupiter,

we're measuring the magnetic field,

the particle density,

and we're basically exploring remotely.

The same way that you are looking at me.

And all of the current missions
that are beyond the Moon

are remote-sensing missions.

What would we hope to find
if we visited an exoplanet?

Perhaps there's life on an exoplanet,

and we would be able to see
evidence of life,

either through atmospheric biosignatures

or through, you know, a dramatic picture,

we would be able to see something
actually on the surface.

We don't know if there's life
elsewhere in the universe.

Perhaps on the missions that we send out,
we will find evidence for life,

perhaps we will not.

And while economics may seem
like an inappropriate thing

to bring into a talk
on interstellar capability,

it is in fact one of the driving issues
in achieving interstellar capability.

You have to get things to the point
where they're economically affordable

to do what we want to do.

So currently,

we have systems in the lab

which have achieved the ability
to synchronize over very large scales,

out to about 10 kilometers
or roughly six miles.

We've been able to achieve
synchronization of laser systems,

and it's worked beautifully.

We've known how to build lasers
for many decades,

but it's only now that the technology
has gotten inexpensive enough,

and become mature enough

that we can imagine
having huge arrays, literally,

kilometer-scale arrays,
much like solar farms,

but instead of receiving light,
they transmit light.

The beauty of this type of technology
is it enables many applications,

not just relativistic flight
for small spacecraft,

but enables high-speed spacecraft,

high-speed flight in our solar system,

it enables planetary defense,

it enables space debris removal,

it enables powering of distant assets
that we may want to send power to,

such as spacecraft or bases
on the Moon or other places.

It's an extremely versatile technology,

it's something that humanity
would want to develop

even if they didn't want
to send spacecraft to the stars,

because that technology
allows so many applications

that are currently not feasible.

And therefore, I feel
it's an inevitable technology,

because we have the ability,

we just need to fine-tune the technology

and in a sense, wait for economics
to catch up with us

so that it becomes cheap enough
to build the large systems.

The smaller systems are affordable now.

And we've already started building
prototype systems in our lab.

So while it's not
going to happen tomorrow,

we've already begun the process,

and so far, it's looking good.

This is both a revolutionary program,

in terms of being
a transformative technology,

but it's also an evolutionary program.

So personally,
I do not expect to be around

when the first
relativistic flight happens.

I think that's probably 30-plus years off
before we get to that point,

and perhaps more.

But what inspires me

is to look at the ability
to achieve the final goal.

Even if it does not happen in my lifetime,

it can happen in the lifetime
of the next generation

or the generation beyond that.

The consequences are so transformative

that we literally, in my opinion,
must go down this path,

and must explore what the limitations are,

and then how do we overcome
the limitations.

The search for life on other planets

would be one of humanity's
foremost explorations,

and if we're able to do so,

and actually find life on another planet,

it would change humanity forever.

Everything is profound in life.

If you look deep enough,

you'll find something incredibly complex
and interesting and beautiful in life.

And the same is true
with the lowly photon

that we use to see every day.

But when we look outside
and we imagine something vastly greater,

an array of lasers that are synchronized,

we could imagine things
which are just extraordinary in life.

And the ability to go to another star

is one of those
extraordinary capabilities.

(Birds chirping)