Translator: Leonardo Silva
Reviewer: Ruy Lopes Pereira A century ago, Albert Einstein
revolutionized our understanding of space, time, energy and matter. We are still finding exciting
confirmations of his predictions, like the gravitational waves observed
last year by the LIGO experiment. When I think of the theme
of today's event, "Ingenuity," Einstein springs to mind. Where did his ingenious ideas come from? A blend of qualities: perhaps intuition,
originality, brilliance. Einstein had the ability
to look beyond the surface to reveal the underlying structure. He wasn't daunted by common sense, the idea that things must be
the way they seemed. He had the courage to pursue ideas
that seemed absurd to others and that set him free to be ingenious, a genius of his time and every other. A key element for Einstein
was imagination. Many of his discoveries
came from his ability to reimagine the universe
through thought experiments. At the age of 16, when he visualized
riding on a beam of light, he realized that, from this vantage,
light would appear as a frozen wave. That image ultimately led
to the theory of special relativity. One hundred years later, physicists know far more
about the universe than Einstein did. Now, we have greater tools for discovery,
such as particle accelerators, supercomputers, space telescopes
and experiments such as LIGO. Yet, imagination remains
our most powerful attribute. With it, we can roam
anywhere in space and time. We can witness
nature's most exotic phenomena while driving in our car, snoozing in bed, or pretending to listen
to someone boring at a party. Much of my own life has been spent
exploring the nature of black holes, their geometry, evolution and the fate
of those unlucky enough to fall in. These greedy monsters
are not easy travel destinations, but they fascinate me
and I keep going back. This year, Andy Strominger, Malcolm Perry
and I have reimagined black holes, examining the energy states
of their vacuums and the information stored
on their boundaries, with potentially
deep implications for physics. So, if our minds, helped by data
from telescopes and experiments, can cross the universe
making discoveries along the way, why go anywhere for real? Should we be content
to be cosmic couch potatoes, enjoying the universe
from the comfort of our home planet? No, we should not, for two reasons. The first is that the universe
is a violent place. Stars engulf planets, supernovas fire lethal rays across space, asteroids hurtle around
at hundreds of miles a second. Granted, these phenomena
do not make space sound very inviting. Yet, these are reasons
why we should venture out into space, instead of staying put, because, if we wait long enough,
they will reach us here. I am not doomsaying. It is guaranteed by the laws
of physics and probability. Furthermore, we know there's at least
one advanced civilization with a propensity for destroying
species, ecosystems, atmospheres and weather patterns,
perhaps entire planets, and it happens to live on Earth. Spreading out may be the only thing
that saves us from ourselves. The second reason is that we are,
by nature, explorers. The same curiosity that sends us
to the stars at the speed of thought urges us to go there in reality. And whenever we make a great new leap
like the moon landings, we elevate humanity,
bring people and nations together, usher new discoveries
and new technologies. So far, such journeys have been limited
to our local cosmic neighborhood. Forty years on, our most intrepid explorer, Voyager,
has just made it to interstellar space, but that is still a very long way
from reaching the stars. At Voyager's speed, 11 miles a second, it would take about 70,000 years to reach
our nearest star system, Alpha Centauri. It is 4.37 light years away,
25 trillion miles. If beings on Alpha Centauri are receiving
television transmissions from Earth, they are still blissfully ignorant
of the rise of Donald Trump. (Laughter) In fact, the distance
to Alpha Centauri is so great that to reach it in a human lifetime,
a spacecraft would have to carry fuel with roughly the mass
of all the stars in the galaxy. In other words, with current technology, interstellar travel
is utterly impractical, but we have a chance to change that,
thanks to imagination and ingenuity. Last month, I joined Yuri Milner
to launch "Breakthrough Starshot," a long-term research
and development program aimed at making
interstellar travel a reality. If we succeed, we will send
a probe to Alpha Centauri within the lifetime
of some of you watching today. Breakthrough Starshot
brings together three concepts: miniaturized spacecraft, light propulsion
and phase-locked lasers. A starship, a fully functional space probe reduced to a few centimeters
in size and grams in mass, will be attached to a light sail. Made from metamaterials, the light sail weighs
no more than a few grams. The starship and light sail,
together known as a nanocraft, will be placed in orbit. Meanwhile, on the ground,
an array of lasers set at kilometer scale will combine into a single,
very powerful light beam. The beam is fired through the atmosphere, striking the sail in space
with tens of gigawatts of power. The idea is that a nanocraft rides,
like Einstein, on the light beam. Not quite at the speed of light,
but to a fifth of it, or 100 million miles an hour, such a system could reach Mars in an hour, reach Pluto in days,
pass Voyager in under a week and reach Alpha Centauri
in just over 20 years. Once there, it could image
any planets discovered in the system, test for magnetic fields
and organic molecules and send the data back to Earth
in another laser beam. This tiny signal would be received
by the same array of dishes that was used to transmit the launch beam. This would not be
human interstellar travel. Even if it could be scaled up
to a crude vessel, it would be unable to stop, but it would be the moment
when human culture goes interstellar, when we finally reach out into the galaxy. And if it should send back images
of a habitable planet orbiting our closest neighbor, it could be of immense importance
to the destiny of our civilization. Of course, there are
major challenges to overcome. How to combine hundreds of lasers
through the motion of the atmosphere? How to propel the sail
without incinerating it and aim it in precisely
the right direction? How to keep the starship functioning
for 20 years in the frozen void, and send a signal back
across four light years with tiny lasers? But these are not limitations
set by the laws of physics. They are engineering problems. The word "engineer" comes from the same
root as the word "ingenuity." Engineering challenges
tend, eventually, to be solved. As it progresses to a mature technology, other highly exciting missions
are envisaged. Even with less powerful laser arrays, journey times to other planets, the outer
solar system or interstellar space could be vastly reduced. If we find a planet
in the Alpha Centauri system, its image, captured by a camera
traveling at a fifth of light speed, will be slightly distorted,
due to the effects of special relativity. It would be the first time a spacecraft
has flown fast enough to see such effects. In fact, Einstein's theory
is central to the whole mission. Without it, we would have neither lasers nor the ability to perform
the calculations necessary for guidance, imaging and data transmission
over 25 trillion miles, at a fifth of light speed. So, there is a direct path
between that 16-year-old boy, dreaming of riding on a light beam, and our dream, which we hope
will become a reality, of riding a light beam to the stars. Thank you for listening. (Applause)
