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)