NARRATOR: In the beginning,
there was darkness, and then bang. [blasting] Giving birth to an endless
expanding existence of time, space, and matter. Every day, new discoveries
are unlocking the mysterious, the mind-blowing, the deadly
secrets of a place we call the universe. The past and the future,
the ultimate vacation destinations, but are
they within reach? DONALD MAROLF: That could
happen within a few years or a few decades. NARRATOR: When you
travel through time, strange things start to happen. You can imagine warping
things so dramatically that you can actually
visit yourself in the past. NARRATOR: Some humans have
already made the trip. You will have jumped into the
future while aging very level. That's really cool. NARRATOR: See how it's
possible as we unravel the mystery of time travel. [dramatic music] [blasting] [dramatic music] [whimsical music] Of all the riddles
of the universe, time travel may be
the most perplexing. Time itself has a lot
of fascination for us, and so we end up thinking
of ways of cheating time and things like that, going
back in time, changing things. [tape rewinding] NARRATOR: Time travel could
involve going back in time or speeding into the future. But for the moment, every one
of us is frozen in the present. [thudding] Yet science holds
out the possibility that we might loosen the
hold the time has on us. Einstein's theory of
relativity, in which time plays a central role, makes
time travel an open question. Our best theory of
time, which is relativity, doesn't explicitly forbid
time travel, per se. It might be that there are
things we yet don't understand that will improve the theory. But it seems that there are
ways of constructing scenarios within relativity that allow
you to go back in time. [blasting] NARRATOR: Traveling
into the past seems improbable because time
only goes one way, forward. Physicists call this
the arrow of time. The arrow of time
is just the fact that you can always orient
yourself moving from the past to the future. You remember the past. You don't remember the future. You can cause things to
happen in the future, but you can't cause things
to happen in the past. If you took a movie of things
going on in your everyday life like, mixing cream
into your coffee, then you played that
movie backwards, it would be perfectly obvious. Cream mixes into coffee. It doesn't un-mix. That's the arrow of time. [dramatic music] NARRATOR: The arrow makes
time a one-way street of irreversible events,
something we know intuitively from our everyday experience. On a pool table, you can break,
but don't expect the balls to realign on their own. You can scramble an egg,
but you can't unscramble it. The reason why time as an arrow
is a fundamental law of physics that says all things
in the universe move from orderly states-- [blasting] --to disorderly states. As the universe gets older,
as we move from the past to the future, all
the differences between the past and the
future can be summed up by saying that the
universe is winding down. The universe is going from being
orderly, very neatly arranged, to disorderly and messy. So if you had a plate that
was a nice plate that was put together an orderly, it breaks. It becomes more disorderly. That's very natural. NARRATOR: And if you
try to restore order by gluing the plate
back together, your actions release enough
energy into the surrounding environment to create more
disorder in the universe as a whole. [dramatic music] But the arrow of time can be
bent in extreme conditions. It all goes back to Einstein's
theory of relativity. Einstein showed that the
gravity of massive objects like planets, stars,
black holes can actually cause space itself to bend. More amazing than that, he
showed that space and time are actually linked into a
single something he called spacetime. This means that whenever
space is warped, so is time. And nothing in the
universe can bend spacetime more than the supergravity
of a black hole. SEAN CARROLL: As
you can imagine, the gravitational field is so
strong that space and time curl back on themselves. And you can start at one
point, go forward in time, and come back at the
point that you left. NARRATOR: When the arrow of time
bends around to meet its tail, it creates an endless loop in
which the same events happen over and over. So if this is time
curling back on itself and the universe just repeats
itself over and over again, every moment in time would
just repeat an infinite number of times. NARRATOR: An endless loop
would become pretty frustrating for anyone. But suppose a time traveler
can land in the past without the constant repetition? In that case, there
are other roadblocks. The most perplexing are the
inconsistencies or paradoxes that pop up when we start
meddling with the past. [whooshing] A famous example of the kind
of inconsistency you can get with time travel is called
the grandfather paradox, and this is where
someone goes back to the time of, for
example, their grandfather. So imagine that I go back in
time with the time machine and meet my grandfather in 1937. He's just about to go on a
blind date with my grandmother. They've never met before. But actually, I convince
him not to go on that date. He's actually
interested in the races, and so I tell him that
there's an exciting race with Seabiscuit that's coming
up at the Santa Anita track. And so we go off
together to that race. He never meets my grandmother. So what happens to me? How is it possible that I
could have been born, and then been able to go back in time,
meet him, and stop myself from being born? So there's an example
of an inconsistency. It's a loop in time that
really doesn't make sense. NARRATOR: But if time
travel is possible, nature must have a way
around the contradiction. One thing that physicists
are quite certain of is that the universe
ultimately makes sense. In all of physics and all
the science more generally, consistency, self-consistency,
common sense, if you like, is something that is a
fundamental principle. NARRATOR: Physicists have come
up with at least three ways that nature might act to
prevent time travel paradoxes. The first is simple. Nature prevents paradoxes
by making time travel into the past impossible. In other words,
it can't be done. A different alternative
is the strange idea of multiple universes. One way of dealing
with travel back in time is to say that
you actually enter a different parallel
universe after having made the journey back in time. So you don't affect the
history of the universe from which you came. In effect, anything that
can happen will happen. But the way it happens is by
entering a parallel universe. Pretty bizarre thought. NARRATOR: A third solution
to the paradox problem is the notion that if
time travel is possible, you just won't be able to change
the past when you get there. The science behind
this can be illustrated by reducing the problem to
the simplest situation you can think of. For example, balls
on a pool table. Let's set up a pool table
that's like a time machine. If a ball enters one pocket,
it travels through a wormhole and can exit another
pocket before it entered the first pocket. So it's a time machine. So now, suppose the
ball really does go through the first pocket,
emerges before it entered, and then hits itself before
it entered the first pocket. That would deflect
it, preventing it from entering the first pocket. And thus, preventing it from
having exited the second pocket and done the deflection
in the first place. So it's a paradox. However, the idea of
self-consistent solutions gives us a way out
of this paradox. Suppose that the ball
exiting the second pocket can only hit itself
in such a way as to deflect it into
the first pocket. Then the whole loop
is self-consistent. There is no paradox. We think that nature
always somehow manages to choose the solution that
provides self-consistency. In other words, you always
get a solution that does not produce a paradox. [whooshing] NARRATOR: If that's the case
and Clifford Johnson were able to travel to
the year 1937, he might be able to
meet his grandfather. But despite his best
efforts, nothing he does would alter the fact that
somehow his grandfather will meet his grandmother to
allow Clifford to be born. Hi. How are you? How you doing? NARRATOR: One way or
another, the universe will prevent him from
changing history. But we don't have to worry
about paradoxes when we travel forward, taking the arrow
of time into the future. SCOTT CARROLL: Traveling
forward in time is the easiest
thing in the world. Every minute, you move one
minute forward in time. One thing we can do to
change how we move forward in time relative
to each other is to actually move at
different velocities compared to each other. NARRATOR: A time machine
that takes us into the future is based on Einstein's
discovery about time and speed. The faster you move
in space, time for you slows down as compared
to people standing still. And as mind-bending
as this seems, it's actually been
proven by experiments. [whooshing] Clocks have been placed
on rapidly moving airplanes and rocket ships, and they've
moved over some distance at a very rapid speed. And when the atomic
clocks were measured after the end of
the journey, they had progress forward in
time a little bit less than similar clocks which had
remained at rest on Earth. NARRATOR: The effect is
called time dilation, and we can use it to
travel into the future. In fact, it's already been done. [clock ticking] Russian cosmonaut
Sergei Kirkalev has logged more than
803 days in orbit, traveling 17,000 miles an hour,
making him the world's record holder in time travel,
though you'd hardly know it to look at him. What's actually
happened is that he's about a 50th of a second
slower in the amount of time that has passed for him compared
to everyone else who stayed on Earth. NARRATOR: But
dilation really begins to pay off as a time machine
when you pump your speed to just under the
speed of light. The idea is to let
clocks on Earth move at their normal speed
while you're off in space, and your clock is
moving more slowly. When you get back,
you're in the future. Suppose, for example you
wanted to go 500 years into the future. CLIFFORD JOHNSON: To move
500 years into the future, you'd have to move at 99.99%
of the speed of light for seven years. [upbeat music] NARRATOR: When you
get back, you'll have aged only seven years,
but everything on Earth will have aged 500. But one of the biggest problems
with building a time machine for travel into the future
is finding enough fuel to boost a spaceship
to speeds that high. There's no law of
physics that says you can't go close to
the speed of light, but your rocket ship
becomes heavier and heavier as you go closer and
closer to light speed. So you require
more and more fuel to accelerate you smaller
and smaller amounts, and then you need more than
an infinite amount of energy to actually break the
light speed barrier. NARRATOR: But high
speed isn't the only way to zip into the future. Einstein's theory of relativity
says high gravity also slows down your clock,
the kind of gravity you might find
near a black hole. Let's say you're in
a spaceship, and you go and you park yourself
just outside a black hole for a while. Once you return to
Earth, you will notice that many, many years
may have passed on Earth, but only a few weeks or
months will have passed in your own frame of reference. You will have jumped into the
future while aging very little. That's really cool. [dramatic music] NARRATOR: But spending years at
high speed or near a black hole is a slow kind of time travel. For more impatient
voyagers, there may be an instantaneous
version by way of a shortcut through space called a wormhole. It could also become a
corridor through time. [buzzing, whooshing] [dramatic music] [blipping] To conquer time travel, we have
to tread a long path that takes us through bizarre theories and
incredibly complex technology toward a goal that will one
day make starships into time machines. [engine humming, blipping] Starships, in fact,
may be our best bet to shoot off in a
ship at super speed and let our own time slow down
while the rest of the world moves on. [blasting] We have a vested interest in
these kinds of adventures. The high speeds that
result in time travel are also our only way of
smashing a time barrier that keeps us from
traveling to the stars because the distances
are so huge. We would really like
to be able to traverse giant distances in a
short amount of time in order to explore the
universe on a human timescale. NARRATOR: Even the
nearest stars to Earth seem impossibly far away. Alpha Centauri is the closest. But in this case, close amounts
to 4.3 light-years away, 25 trillion miles, 100 million
times farther than the moon. Today's speediest rockets would
need 80,000 years to get there, so the challenge is
to get there faster. But if we're going to use
high-speed star missions as our way to get to
the future, it still doesn't satisfy our dream
of getting there in a flash. [whooshing] Achieving time travel by
moving fast and so slowing your clock down relative
to everyone else is a way of achieving
time travel. It's a little bit like Rip Van
Winkle did by going to sleep, and then waking up later,
and it's the future. But some might think of
that as cheating in a way. It's not really the time travel
that we think of where we, perhaps, go through a portal,
or flick a lever on a machine, and then end up at
a different time. NARRATOR: Physicists did
important theoretical work on instantaneous time
travel in the 1980s while helping Carl Sagan,
who was writing his novel, "Contact." [dramatic music, whooshing] The book imagines space
travel faster than light through a corridor
in space called a wormhole. A wormhole is a kind
of shortcut between two different parts of space,
which can be very far away, or they can actually
be close to each other. But the key idea is that you can
traverse the wormhole by simply going in through the
entrance, one side of it, and coming out the other side. NARRATOR: In "Contact" and
many other science-fiction scenarios, wormholes
are used as tunnels to travel huge distances across
the universe to other stars. But a wormhole with
openings close together is a much better starting
point for a time machine. Suppose I have a
wormhole right next to me. If I put my arm
into it like this, then it would emerge over there. A wormhole is a great ingredient
for constructing a time machine. [whooshing] NARRATOR: A wormhole
time machine would use the same
Rip Van Winkle trick as the very fast spaceship. Super speed makes your clock
slow down while everyone else keeps on going. It works because both
ends of the wormhole always have the same date and
time, no matter what happens to them. CLIFFORD JOHNSON: You can
take one into the wormhole and put it on a rocket
ship or something and send it off at very
high speed and then back. [blasting] So what happens is that when
it returns, it's in the future. NARRATOR: A traveling wormhole
opening from the year 2010 might end up returning to
Earth in the year 2510. Because its clock was so
slow, it aged very little while the rest of the
world aged 500 years. So now if I walk into the
end of the wormhole that's in the past, the end that
didn't go on the rocket ship, I can come out the other end,
and I'd be in the future. Although each step
of this scenario might be really hard to
achieve with any technology we can imagine,
it's all internally consistent in the laws of
gravity, and space, and time that we understand so far. So that wormhole time
machine is, we would say, a consistent solution of the
equations of space and time. NARRATOR: "The wormhole time
machine would work in reverse, too, making time
travel theoretically possible from the future
back into the past, where you started. [buzzing, humming] [helicopter blades whirring] Well, let's face it. Most people are interested in
the idea of going backwards in time because they
want to fix things. [siren wailing] The interesting
thing is, though, that we can, using the
laws of physics, at least explore what it would be like
to travel backwards in time. [whooshing] NARRATOR: And although we're
preoccupied with time machines, it may be that time travel is
possible through wormholes that are natural in origin. [whooshing] Another possibility, if
we can't make time machines, is that maybe nature
has already made them, and we just have
to discover them. What could have happened is
that in the very early universe, the nature of space and
time was already twisted up in such a way that some of that
got frozen in, leaving time loops that we might be able
to use as time machines sometime in the future. So it's an interesting
possibility that we don't actually have
to create these things. NARRATOR: But what if we are
left to our own resources? Can we build a time
machine at all? If theory says a wormhole
is the way to go, then what does it take to make one? Wormholes are
speculative ideas. We can write down the
equations that describe them. We don't expect to bump into
one in astronomy or anything like that, but we
could be surprised. Where we do expect
wormholes to exist as at the submicroscopic
level, where space and time are fluctuating wildly. So what people
imagine is somehow capturing a microscopic
wormhole and growing it to a larger size. We don't know if
that's possible. We have no idea how to do
that, but that's probably what it would take if you
wanted a big sized wormhole. NARRATOR: The technology we need
to manipulate a wormhole may seem impossibly remote. But for those willing to
let their imaginations roam, there is a glimmer of hope
in at least one place. It's where spacetime and the
nature of existence itself meet in head-on collisions inside the
biggest, most complex machine ever created by man. [dramatic music] Where does the universe hide
the secrets that might tell us how to travel in time? [whooshing] Our exploration has taken us
through the world of wormholes and their possibilities
as time machines. And now, we're in search
of the technology that might make space travel
and time travel two sides of the same coin. If there's nothing on Earth
that comes close to being a time machine now, there is something
that might one day lead us to new laws of physics that
help us determine if it's at least possible. It explores the universe not
in the realm of the cosmic web and its galaxies, but in the
domain of quantum physics, involving particles sizes
more than a million times smaller than the smallest atom. It's the newest tool at the
frontier of physics called the Large Hadron Collider. The Large Hadron Collider is
the largest, most complicated machine ever created
by humankind. And its role is to help us
study the frontier of particle physics. What it actually does is it
accelerates protons in two directions around the ring, one
way around and the other way around, to nearly the speed of
light and then collides them. NARRATOR: The Collider went
operational in November 2009. And as scientists
ramped up the power, the energy and its collisions
was increased almost tenfold by March 2010. And it will double that
sometime after 2013. Today's theories of space, time,
gravity, and quantum physics are still incomplete, and tools
like the Large Hadron Collider will help fill in the
ever-puzzling blanks. [dramatic music, whooshing] This is where we expect that
if there's some missing physics that we need to understand
spacetime in a way that will tell us whether time travel
is possible or restricted in various ways, this
is where we expect the new results to come from. NARRATOR: The goal is to
figure out how rules governing the tiniest particles
in existence also apply to the biggest
things like stars, galaxies, and the expanding
universe itself. Without understanding this,
building a time machine might be harder than trying to
build a radio without knowing about the existence
of electricity. There are many physicists
in the world who believe that this understanding is, in
fact, right around the corner, that it could happen within
a few years or a few decades. On the other hand, it could be
that this problem is, in fact, much harder than we think and
that human civilization will simply not live long enough
to figure out how it works. NARRATOR: The Large
Hadron Collider might also reveal extra dimensions that
could play a role in time travel. We live in three
dimensions of space. If we lived in only
two dimensions, our universe would
be a flat sheet. A sphere would look
like a circle to us. The third dimension would
be there, but just hidden from our view. If dimensions other
than our familiar three are really there,
they, too, are hidden. [dramatic music, whooshing] If we were to find
experimental evidence for the existence
of other dimensions, and if we were to
be able to explore the meaning of these
other dimensions and see how they come
about, it could be that far, far in the future,
this new physics would be utilized to come up
with some new form of travel that allows us to
at least get close to the speed of light
barrier, if not surpass it. NARRATOR: Getting
close to light speed may be the most promising way to
travel in time by slowing down our clocks. In this respect, the
Large Hadron Collider is leading the way, even if
its first step is an extremely small one. The Large Hadron Collider
is 17 miles around, and it accelerates protons
to nearly the speed of light. If you wanted to do that
but with human beings, a rough calculation shows
you'd have to scale it up to 1,000 light-years around
in order to do the same thing. NARRATOR: This is like
saying that the spacecraft, powerful enough to carry us
to the stars at that speed, would be bigger than the
distance we need to travel. Big enough, in fact, to enclose
the nearest 100,000 stars. [dramatic music, whooshing] Back on Earth, the physics
of light speed and beyond meets surf culture on the
beach at Malibu, California. Richard Obousy is one of
the few physicists who have worked on the concept of
faster-than-light warp drive. A warp ship, he says,
rides a wave-like ripple of warped space, almost as a
surfer rides a wave of water. A great analogy is with
that of a surfer riding a wave of seawater. So just as the wave behind it
sort of rises up and pushes this surfer through
the ocean, I think it's a great analogy with how
a spacecraft is mutually pulled and pushed through
the fabric of space. [dramatic music, whooshing] NARRATOR: The idea is
based in part on the fact that space and the
universe is expanding. If we can make it
expand at will, we may be able to
propel a warp ship. We make space expand
behind the ship and make it contract in front. The wave of warped space moves
through the universe faster than light. While inside a
so-called "warp bubble," the ship is a passenger, never
violating Einstein's rule against exceeding
the speed of light. [dramatic music] While warp drive is mostly
science fiction at this point, there is some physics behind it. Mexican physicist
Miguel Alcubierre worked out the complex
math to support it in 1994. Unfortunately, there's nothing
in the math that tells us how to do it. And though most scientists
have major doubts, not all the skeptics are writing
off warp drive completely. Warp bubbles may be
impossible, they say. But what about super-advanced
beings building faster-than-light warp drive
bullet trains to the stars and through time? [dramatic music] In searching for the
secrets of time travel, we inevitably meet the
idea of warp drive, or other strategies for
traveling faster than light. It's the most
sought-after solution to the dream of star
travel and potentially, turning any spaceship
into a time machine. The most optimistic
views of the future paint a picture of spaceships
writing warp bubbles as easily as expert surfers catch waves
off the beaches of Earth. But even optimistic physicists
must face some harsh realities. [dramatic music] If surfing is an analogy for
how a warp ship might work, then watching a beginning surfer
drives home a better point. Achieving warp drive
is very difficult. This morning, I had
my first surfing lesson. I had this idea
that in some sense, we were going to be
able to manipulate, in some sense, nature,
and that I was going to be able to ride this wave. And it was going to carry
me at great velocities across the ocean. But the reality is that
the ocean manipulated me. It was far harder to control
than I originally anticipated. [dramatic music] NARRATOR: And control
is a real problem because science says a warp ship
just can't make its own warp field. [buzzing, whooshing] One of the often cited
problems with the warp drive model is the ship would be what
we call causally disconnected from the bubble. That is, it could
never find a way to communicate with the bubble. And so it could never turn the
bubble off once it had started. NARRATOR: But what would
happen if the starship did not have to worry about turning
its bubble on and off? What you might imagine
for a sufficiently advanced civilization and given
sufficient new laws of physics would be some kind of warp
drive escalator or corridor. And then when you would drop a
ship into the prearranged warp tube, if you will, it might be
able to ride some wave along to the end. NARRATOR: It would be like
a bullet train to the stars. Its passenger cars might
travel faster than light, but whoever invents it would
need thousands of years at sub-light speeds to build it
and use more energy than we can imagine. [whooshing] You would probably need to
harness at least the energy output of an entire star,
it's not a lot more than that. So these are things we can
talk about hypothetically, but no one has an engineering
program to make it happen. NARRATOR: When astronomers
recently discovered that the expansion of the
universe is accelerating, they reasoned it was driven by
a mysterious dark energy that is part of space everywhere. A few people have suggested that
dark energy can be harnessed as a power source
for exotic devices like starships or time machines. We don't really know
what the dark energy is, so it's not clear that we will
never be able to harness it. However, the leading models
suggest that it's either a property of space itself
that can't be changed, or some sort of an energy field
which is of such low density. There's so little of
it per unit volume that harnessing
interesting amounts of it will essentially be impossible. NARRATOR: The bottom line
when it comes to warp drives, wormholes, or time machines
leads many scientists to reject them out of hand. Can we be sure
that they're right? Though we think we know a lot
about the universe right now, and we do, there have been many
times in the history of physics when we've been burned by having
too much of a self-assured sense of knowing at all. There really are laws of
physics that we can't violate, but there's also technology. You say, well, this
is just too hard. We'll never be able to do it. And there, when scientists
say things like that, they're almost always wrong. It's much safer
for us to say, here are what the laws of physics
allow us to imagine doing. Hopefully someday
in the future, we'll build the technology
that makes it happen. [buzzing] [dramatic music] NARRATOR: And as we've
seen, that future may confront us very soon as
astronomers search for planets around stars outside
the solar system. The closest star system to Earth
has a binary pair of stars. Is that a good place
to search for planets? That's just what Nicole
of Oklahoma City, Oklahoma wanted to ask the universe
when she wrote, "Can planets exist in a binary star system?" Nicole, that's a
really cool question. It turns out that a
planet in a binary system can orbit either one of
the two stars very closely, or it can orbit both of
them from very far away. But it can't orbit among them. It can't do a figure-eight
among them, for example. That trajectory is unstable,
and the planet would quickly get ejected. NARRATOR: We may be on
the verge of discovering an Earth-sized planet
around one of the two stars in the Alpha Centauri system,
the sun's nearest neighbor. It would be a more
compelling reason than ever before to explore the exotic
science of high-speed space voyages and the time
travel that goes with them. [dramatic music, whooshing] Alpha Centauri
is very exciting because it now appears from a
variety of different computer simulations that it's quite
possible that there could be terrestrial mass
planets orbiting both components of the Alpha
Centauri binary system. NARRATOR: Alpha Centauri
A and B are so distant, they look like a
single star from Earth, but they're actually
a binary pair. A third member of the system is
Proxima Centauri, a red dwarf loosely bound to the main pair. If you're sitting on a
planet in the Alpha Centauri A system or the Alpha
Centauri B system, Proxima Centauri wouldn't even
be visible in your night sky. It's that dim. NARRATOR: Alpha Centauri A
and B orbit around each other. At their closest point,
they're about 20% farther than the distance
from the sun to Saturn. At their farthest,
they're 20% more distant than the sun is from Neptune. Each has a habitable zone
similar to the sun, where life-bearing
planets could exist. And that, after all, is a
Holy Grail in astronomy. Well, a trip to
the nearest stars-- for example, Alpha Centauri-- that we can do
within our lifetimes would be immensely exciting. One of the great
goals of science is to find life elsewhere
in the universe. What better place to start,
other than our solar system, than the nearest star? [gentle music] NARRATOR: But now, space
travel becomes time travel, as we set our sights on a
mission that can be done under the laws of
physics we know now, a mission that can cross more
than four light-years of space in just 45 days. [dramatic music] Our quest to unravel
the mysteries of time now point us again to Alpha
Centauri, the sun's closest neighbor. It is the most likely first
destination for a starship from Earth, a starship whose mission
cannot avoid a component of time travel. We have no idea what
kind of technology would actually take us from
here to Alpha Centauri and back. Therefore, we might as well be
optimistic and say that we just move at 99.99%
the speed of light all the way there and
then all the way back. NARRATOR: The ship seems
surprisingly small for one that has to make such a long trip. How can it hold enough
supplies to support a crew for the duration? It can because it is
not only a starship. It is also a time machine. It would take about 8.6 years
because Alpha Centauri is 4.3 light-years away. But to the people
on the ship, it would take less than two months. It would take about 45 days
because they're traveling close to the speed of light. [dramatic music, whooshing] NARRATOR: The
astronauts would also have to overcome the problem
of killer acceleration in quickly reaching
the speed of light. Otherwise, they'd have to
speed up slowly, adding time to the total trip. Alpha Centauri is
the go-to destination for Earth-bound beings hoping
for a toehold in star travel. It's no accident that James
Cameron chose it as home to his fictional moon,
Pandora, in the movie "Avatar." The reason we would
go to Alpha Centauri has to do with today's
intensive telescope search for Earth-like planets
around Alpha Centauri B, one of two stars in the
system's main binary pair. Alpha Centauri
B, it turns out, is by far the best star in
the entire sky for searching for low-mass,
Earth-like planets. But to carry out
that kind of search requires a very
dedicated effort. It's not something
that you can accomplish in a few nights at a telescope. [beeping] NARRATOR: It's hard enough to
separate the two main stars of Alpha Centauri in
a space photograph. Trying to see an Earth-sized
planet around one of them is, at the moment, impossible. The best shot we have
is to find the planet by the wobble method, detecting
a star's subtle back and forth motion caused by the tiny
gravitational tug any planet would have on it. Like time travel, it
seems almost undoable. The back and forth wobble
that we need to detect is incredibly small. I'm here at the Rose Bowl. And if the Rose Bowl were
the size of Alpha Centauri, then the amount of wobble
that we need to detect is about this much,
about 3.3 inches. And we need to detect that
from 4.3 million miles away. [thudding] [beeping, dramatic music] NARRATOR: Alpha Centauri B
is slightly smaller than A, and the planet hunt
is concentrated there, mostly because a smaller
star will show more wobble, and detection will
be that much easier. In three to five years,
we should have an answer. [gentle music] I think that if we were
to discover that there is an Earth-mass planet orbiting
the very nearest star, then there would be a great deal
of excitement to somehow either build a large telescope to
try to observe that planet, or perhaps in the far future,
to design a mission that could actually go there. [gentle music] NARRATOR: With the goal of our
time travel quest identified, we can imagine our
spacecraft in Earth orbit about to leave on the first
mission to Alpha Centauri. [blasting] [gentle music] The ship's high speed propels
it into a time machine mode, slowing its clock so
its passengers approach Alpha Centauri in
three to four weeks, seeing things up close no
human has ever seen before. First up, a stellar flare from
the red dwarf Proxima Centauri. On the outskirts of
the triple system, it is the closest of
the three to the sun. Proxima Centauri is prone
to these sudden outbursts that can cause it to brighten up
by a factor of four or five over the course of just a day,
and then fade back just as quickly. So you might be in for
some real fireworks as you pass by Proxima Centauri. As we come within
the triple-star system, we might imagine swinging past
Alpha Centauri A and using gravity assist to send us in the
direction of Alpha Centauri B. [gentle music, whooshing] NARRATOR: The sister Earth,
the ship's destination, is the ultimate goal. And the travelers will
be anxious to explore it and search for life. [gentle music] [blasting] Although the trip has taken a
little more than a few months for the travelers,
the high speed will slow down their clocks
so much that when they return, nearly a decade will
have passed on Earth. The realization of star
travel at high speed is a dream for the far future. On an Earth where technology
is so advanced and changing so fast, the difference of 8
or 10 years could be dramatic. This kind of time
travel may become routine to a new generation
of star travelers taking mankind on the next
giant leap in its epic journey through the universe. [blasting]
