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NARRATOR:
It's a mysterious force
that shapes our universe.
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It feels familiar,
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but it's far stranger
than anyone ever imagined.
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And yet, one man's
brilliant mind tamed it.
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Gravity.
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Using simple
thought experiments,
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Albert Einstein made
an astonishing discovery:
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time and space
are shaped by matter.
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CLIFFORD JOHNSON:
You get rid of this force
of gravity,
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and instead, we have
curvature of spacetime.
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JANNA LEVIN:
Right now, the space around me
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is being squeezed and stretched.
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NARRATOR:
He called it the "General Theory
of Relativity."
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How did one person,
working almost entirely alone,
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change everything we thought
we knew about the universe?
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DAVID KAISER:
Einstein is toiling
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as the world seems
to fall apart.
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ROBBERT DIJKGRAAF:
He was able with pure thought
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to solve the riddle
of the universe.
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NARRATOR:
"Inside Einstein's Mind,"
right now on NOVA.
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Major funding for NOVA is
provided by the following...
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Shouldn't what makes
each of us unique
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Supporting NOVA and promoting
public understanding of science.
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And the Corporation
for Public Broadcasting.
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And by PBS viewers like you.
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Thank you.
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Additional funding
from Roger and Vicki Sant.
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NARRATOR:
Gravity.
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The most familiar yet most
mysterious of nature's forces.
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100 years ago, Albert Einstein
made a mind-blowing discovery:
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what we feel as gravity
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is in fact the push and pull
of space and time itself.
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He called his idea
"general relativity."
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It is perhaps
the most remarkable feat
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of thinking about nature
to come from a single mind.
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CLIFFORD JOHNSON:
General relativity
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is undoubtedly one of the
greatest scientific theories
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ever conceived.
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It's a theory of space, time,
and gravity.
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JANNA LEVIN:
One mathematical sentence,
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and from it, you can derive
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the understanding
of the entire universe
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on the largest scales,
and that is beautiful.
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NARRATOR:
Only now, a century
after it was first proposed,
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do we have the technology
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to explore the extremes
of Einstein's great theory.
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Supermassive black holes
at the center of galaxies.
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Waves of gravity that
distort space and time.
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The evolution
of our entire universe.
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How did a concept
that explains so much
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come from the mind of one man?
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JOHN NORTON:
Einstein had a magical talent.
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He could take a hard,
physical problem
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and boil it down
to a powerful visual image,
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a thought experiment.
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SEAN CARROLL:
Suddenly he realizes,
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"This is how the world works.
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All this abstract nonsense is
the correct theory of reality."
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NARRATOR:
To gain an insight
into Einstein's mind
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and the true wonder
of general relativity,
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we need to trace
the crucial thought experiments
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that led to his great
breakthrough.
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The seeds for his ideas
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were planted
when he was just a child.
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Einstein grew up
in a small house in Munich,
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in southern Germany.
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His unique personality
was evident early on.
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WALTER ISAACSON:
Like many great innovators,
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Einstein was a rebel, a loner,
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but deeply curious.
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He was slow in learning to speak
as a child,
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so slow that his parents
consulted a doctor,
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but he later said that
that's maybe why he thought
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in visual thought experiments.
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His sister remembers him
building little card towers
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using playing cards.
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He was a daydreamer,
but he was deeply persistent.
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NARRATOR:
Einstein's father, Hermann,
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manufactured electrical
equipment.
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He nurtured his son's interest
in science.
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On one occasion,
he brought him a compass.
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ISAACSON:
Now, you and I maybe remember
getting a compass
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when we were kids,
and we were like,
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"Oh look, the needle twitches
and points north,"
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but then we're on
to something else,
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like, "Oh look,
there's a dead squirrel."
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But for Einstein,
after getting that compass,
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he developed a lifelong devotion
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to understanding how things
can be forced to move
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even though nothing's
touching them.
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NARRATOR:
The young Einstein
became gripped by a desire
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to understand the underlying
laws of nature.
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He developed a unique way
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of thinking
about the physical world
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inspired by his favorite book.
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ISAACSON:
The book Einstein loved
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told little stories,
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like what it'd be like
to travel through space
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or go through
an electrical wire.
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And it made Einstein think
visually.
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NARRATOR:
These imagined situations
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that we often call
"thought experiments"
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became a defining feature
of Einstein's thinking.
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DAVID KAISER:
One of the critical
thought experiments
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that Einstein began
to play with
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very young,
around the age of 16,
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was trying to imagine
what would happen
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if he could catch up
with a light wave.
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It's one thing to imagine
a light wave zooming past him
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at some seemingly
impossible speed,
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but what if he could somehow
just propel himself
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really quickly?
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What would it look like
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if he could catch up
with that light wave?
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What would he see?
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ISAACSON:
He said it caused him
to walk around in such anxiety,
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his palms would sweat.
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Now, you and I may remember
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what was causing our palms
to sweat at age 16,
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and it was not a light beam.
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But that's why he's Einstein.
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NARRATOR:
This dream-like thought
about the nature of light
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was Einstein's first step
on the path to his great theory.
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It stayed with him throughout
his time at school and college.
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KAISER:
He was extremely gifted
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in science and math
as a young person
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and very bad at other classes,
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mostly because
he kept cutting class
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and being very rude
to his teachers.
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Many teachers
from his high school days on
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were convinced he'd never amount
to anything.
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He was a discipline problem,
and he was bad news.
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ISAACSON:
He applies to the second best
university in Zurich,
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the Zurich Polytech,
and gets rejected.
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I'd love to meet
the admissions director
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who rejected Albert Einstein.
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But eventually he gets in,
and he does moderately well,
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but not good enough
to get a teaching fellowship.
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And so he ends up
at the Bern Swiss patent office
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as a third class examiner.
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NARRATOR:
Undaunted by his
university results,
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Einstein started work
at the patent office in 1902,
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age 23.
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Here, his job was to assess
the originality of new devices.
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KAISER:
He was immersed
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in the kinds
of technical details
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that he'd been fascinated by
as a very young kid.
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And here he was,
sitting in the kind of wave
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of the modern age.
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This was the era
of electrification.
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So all the latest clever ideas
for switching technology,
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for coordinating clocks
in particular,
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those were all
passing through his office.
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NARRATOR:
Time zones had recently been
introduced in central Europe,
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and accurately
synchronizing clocks
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was a major challenge
of the day.
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Switzerland was a world leader
in time technology.
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Dozens of patents to link clocks
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passed through
Einstein's office.
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ISAACSON:
He could whip through
these patent applications,
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and then out of his drawer,
he'd pull his physics notes,
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and his boss was very indulgent
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and would sort of turn
a blind eye
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as Einstein was doing
his theories in his spare time.
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SIMON SCHAFFER:
It's really important
to remember that
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theoretical physics was new
when Einstein was a young man.
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You could do quite a lot
of this work by reading
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a relatively small number
of science journals
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and making the calculations
yourself.
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Einstein's world in 1905
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was dominated
by two kinds of physics.
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One was about 200 years old,
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founded by Isaac Newton,
a British natural philosopher.
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For Newton, all there is
in the world is matter moving.
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NARRATOR:
Newton showed that the motion
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of falling apples
and orbiting planets
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are governed
by the same force:
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gravity.
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His equations are so effective,
we still use them today
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to send probes to the farthest
reaches of the solar system.
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The other important theory
of Einstein's day
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covered electricity
and magnetism.
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That branch of physics
had been revolutionized in 1865
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by the Scottish physicist
James Clerk Maxwell.
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Maxwell's theory describes light
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as an electromagnetic wave
that travels at a fixed speed.
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In Newton's world,
the speed of light is not fixed.
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SCHAFFER:
Einstein could see that
there's a contradiction
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between Newton and Maxwell.
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They just don't fit together.
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And one of the things
Einstein hated-- hated--
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was contradiction.
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If there's one kind of physics
that says this
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and another kind of physics
that says that
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and they're different,
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that's a sign that something's
gone wrong and it needs fixing.
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NARRATOR:
For months, Einstein wrestles
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with the problem.
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Eventually,
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00:11:20,013 --> 00:11:21,880
to resolve this contradiction,
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he focuses on a key element
of speed: time.
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ISAACSON:
He realized that
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any statement about time
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is simply a question
about what is simultaneous.
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For example, if you say
the train arrives at 7:00,
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that simply means that
it gets to the platform
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simultaneous with the clock
going to 7:00.
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NARRATOR:
In a brilliant
thought experiment,
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he questions what "simultaneous"
actually means
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and sees that the flow of time
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is different for an observer
that is moving
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versus one that is
standing still.
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00:12:07,894 --> 00:12:12,330
He imagines a man
standing on a railway platform.
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Two bolts of lightning strike
on either side of him.
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(lightning strike)
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00:12:19,306 --> 00:12:22,807
The man is standing
exactly halfway between them
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and the light from each strike
reaches his eyes
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at exactly same moment.
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00:12:28,982 --> 00:12:32,450
For him, the two strikes
are simultaneous.
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(thunder rumbling)
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Then Einstein imagines a woman
on a fast-moving train,
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Traveling at close to the speed
of light,
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what would she see?
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00:12:57,878 --> 00:13:01,112
As the light travels out
from the strikes,
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00:13:01,114 --> 00:13:07,018
the train is moving towards one
and away from the other.
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00:13:07,020 --> 00:13:11,656
Light from the front strike
reaches her eyes first.
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For the woman on the train,
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time elapses
between the two strikes.
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(thunder rumbling)
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For the man on the platform,
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there is no time
between the strikes.
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(thunder rumbling)
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This simple thought
has mind-blowing significance.
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Simultaneity,
and the flow of time itself,
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depends on how you're moving.
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If there's no such thing
as simultaneity,
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00:13:50,330 --> 00:13:52,330
then there's no such thing
as absolute time everywhere
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throughout the universe,
and Isaac Newton was wrong.
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NARRATOR:
This concept that time,
and space as well, are relative
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became known as
special relativity.
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00:14:06,346 --> 00:14:09,914
It led to remarkable results,
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00:14:09,916 --> 00:14:15,887
such as the famous equation
relating energy to mass.
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00:14:15,889 --> 00:14:17,956
Einstein published
this article in 1905
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00:14:17,958 --> 00:14:19,357
to exactly no acclaim.
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00:14:19,359 --> 00:14:20,592
Most people ignored it.
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00:14:20,594 --> 00:14:23,728
This was not setting the world
on fire.
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00:14:23,730 --> 00:14:27,332
Two years go by
before a very eminent physicist,
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00:14:27,334 --> 00:14:29,801
Johannes Stark,
invites Einstein
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00:14:29,803 --> 00:14:32,003
to write a review article
on Einstein's own work,
250
00:14:32,005 --> 00:14:33,705
precisely because no one
was paying attention.
251
00:14:33,707 --> 00:14:37,542
And he begins thinking
about ways to generalize
252
00:14:37,544 --> 00:14:39,344
and to push his own results
from 1905.
253
00:14:39,346 --> 00:14:41,880
What if he considers
not only a train
254
00:14:41,882 --> 00:14:44,182
moving at a fixed speed
past the platform?
255
00:14:44,184 --> 00:14:46,251
What if that train begins
to speed up or slow down?
256
00:14:46,253 --> 00:14:48,019
What if there's acceleration?
257
00:14:48,021 --> 00:14:52,490
NARRATOR:
Adding acceleration to the
equations was his first task.
258
00:14:52,492 --> 00:14:58,363
Then there was that mysterious
Newtonian force of gravity
259
00:14:58,365 --> 00:15:00,164
to contend with.
260
00:15:00,166 --> 00:15:01,933
In Newton's theory,
261
00:15:01,935 --> 00:15:05,536
gravity is a force
that acts instantaneously.
262
00:15:05,538 --> 00:15:08,006
But special relativity says
that's impossible--
263
00:15:08,008 --> 00:15:12,944
nothing can travel
faster than light.
264
00:15:12,946 --> 00:15:14,812
ELEANOR KNOX:
What Newton's theory
tells you is that
265
00:15:14,814 --> 00:15:17,482
suppose the sun
were to disappear,
266
00:15:17,484 --> 00:15:20,551
the orbit of the earth should
change at that very moment.
267
00:15:20,553 --> 00:15:22,787
But the notion of
"at that very moment"
268
00:15:22,789 --> 00:15:25,890
in two different places
is exactly one of these notions
269
00:15:25,892 --> 00:15:27,425
that special relativity
has told you
270
00:15:27,427 --> 00:15:28,826
isn't a good physics notion.
271
00:15:28,828 --> 00:15:34,132
So you've now got this challenge
of trying to work out
272
00:15:34,134 --> 00:15:36,200
how to take the success
of Newton's theory of gravity
273
00:15:36,202 --> 00:15:39,304
but fit it into this new
special relativistic picture.
274
00:15:39,306 --> 00:15:43,675
NARRATOR:
It was only when Einstein
began to understand the link
275
00:15:43,677 --> 00:15:46,010
between gravity and acceleration
276
00:15:46,012 --> 00:15:50,281
that things began
to fall into place.
277
00:15:52,185 --> 00:15:54,686
We all know that
when we are accelerated,
278
00:15:54,688 --> 00:15:57,622
and of course now we have cars
and airplanes
279
00:15:57,624 --> 00:16:01,626
to give us the physical feeling,
280
00:16:01,628 --> 00:16:03,962
if you're in an airplane
and it's taking off,
281
00:16:03,964 --> 00:16:05,763
you are pushed back
in your chair,
282
00:16:05,765 --> 00:16:07,966
you feel actually kind of
a force pushing you back,
283
00:16:07,968 --> 00:16:10,935
which feels very similar
to the force of gravity.
284
00:16:10,937 --> 00:16:13,604
But you need the brilliance
of Einstein
285
00:16:13,606 --> 00:16:16,607
to explain why they are related.
286
00:16:17,978 --> 00:16:20,511
NARRATOR: Suddenly, he hits
upon what he describes as
287
00:16:20,513 --> 00:16:24,582
the happiest thought
of his life.
288
00:16:24,584 --> 00:16:28,252
If gravity and acceleration
feel the same,
289
00:16:28,254 --> 00:16:32,957
perhaps they are the same.
290
00:16:32,959 --> 00:16:36,494
Again, he examines the idea
291
00:16:36,496 --> 00:16:39,597
in a beautiful
thought experiment.
292
00:16:39,599 --> 00:16:42,066
He imagines a man in a box
293
00:16:42,068 --> 00:16:45,570
floating weightlessly
in a distant region of space
294
00:16:45,572 --> 00:16:46,904
in zero gravity.
295
00:16:50,143 --> 00:16:51,909
Suddenly, the man stops floating
296
00:16:51,911 --> 00:16:57,348
and accelerates downward
until he's standing in the box.
297
00:16:57,350 --> 00:17:00,451
What has happened?
298
00:17:02,555 --> 00:17:05,390
Either the box
is now close to a planet
299
00:17:05,392 --> 00:17:11,829
and the force of gravity
has pulled the man to the floor,
300
00:17:11,831 --> 00:17:15,033
or someone has attached a rope
301
00:17:15,035 --> 00:17:18,336
and the box is now
being pulled continuously
302
00:17:18,338 --> 00:17:20,705
and accelerated upwards.
303
00:17:24,477 --> 00:17:27,612
So which is it?
304
00:17:27,614 --> 00:17:30,348
Gravity?
305
00:17:30,350 --> 00:17:33,618
Or acceleration?
306
00:17:33,620 --> 00:17:37,321
Without being able
to see outside,
307
00:17:37,323 --> 00:17:41,359
the man can't tell what's
causing his fall to the floor.
308
00:17:41,361 --> 00:17:43,327
CARROLL:
Einstein realized
309
00:17:43,329 --> 00:17:46,064
there is no way
to tell the difference
310
00:17:46,066 --> 00:17:48,066
between sitting
in a gravitational field
311
00:17:48,068 --> 00:17:49,567
and being accelerated.
312
00:17:49,569 --> 00:17:51,936
These are equivalent situations
313
00:17:51,938 --> 00:17:54,272
JOHNSON:
The fact that these two effects
are the same,
314
00:17:54,274 --> 00:17:55,807
give the same result,
315
00:17:55,809 --> 00:17:58,443
means that gravity
is acceleration.
316
00:17:58,445 --> 00:18:00,078
It's not just like acceleration;
317
00:18:00,080 --> 00:18:02,346
it's the same thing.
318
00:18:02,348 --> 00:18:06,584
NARRATOR:
It's a big breakthrough.
319
00:18:06,586 --> 00:18:11,689
Einstein's theory
of special relativity worked
320
00:18:11,691 --> 00:18:15,560
for motion at a constant speed.
321
00:18:15,562 --> 00:18:18,162
By extending his ideas
to acceleration,
322
00:18:18,164 --> 00:18:22,100
he could begin to formulate
a new theory of gravity.
323
00:18:38,051 --> 00:18:43,054
In 1912, Einstein is living
in Zurich with his wife Mileva
324
00:18:43,056 --> 00:18:45,490
and two young sons,
Hans and Eduard.
325
00:18:45,492 --> 00:18:49,927
The academic world had realized
the importance
326
00:18:49,929 --> 00:18:53,898
of special relativity,
and his career had taken off.
327
00:18:53,900 --> 00:18:55,566
He's now a professor
328
00:18:55,568 --> 00:18:58,136
at the esteemed Swiss Federal
Institute of Technology,
329
00:18:58,138 --> 00:19:04,308
but spends as much time as
possible working on his theory.
330
00:19:04,310 --> 00:19:06,410
He needs mathematics
331
00:19:06,412 --> 00:19:10,348
that describes how objects move
in space and time
332
00:19:10,350 --> 00:19:14,051
and soon realizes that
the best tool for the job
333
00:19:14,053 --> 00:19:20,324
is a strange but powerful
concept called "spacetime."
334
00:19:20,326 --> 00:19:22,326
LEVIN:
If I think of space,
335
00:19:22,328 --> 00:19:25,630
I know that I can find anything
if I know where it is
336
00:19:25,632 --> 00:19:29,300
north-south, east-west,
and up-down, three points.
337
00:19:29,302 --> 00:19:31,035
But that doesn't mean
I can find it,
338
00:19:31,037 --> 00:19:33,204
because I also have to know
where it is in time.
339
00:19:33,206 --> 00:19:35,006
And so if we start to think,
340
00:19:35,008 --> 00:19:38,109
to know everything
about an event in the universe,
341
00:19:38,111 --> 00:19:41,078
I have to know not just
its spatial coordinates,
342
00:19:41,080 --> 00:19:43,080
but also its time coordinate.
343
00:19:43,082 --> 00:19:46,050
I can begin to think
about where it is in spacetime.
344
00:19:48,755 --> 00:19:51,989
NARRATOR:
Imagine a camera
filming an action,
345
00:19:51,991 --> 00:19:58,963
capturing each moment in time
as a single frame.
346
00:20:06,172 --> 00:20:09,307
DIJKGRAAF:
Einstein basically tells us,
"Think of the movie reel."
347
00:20:09,309 --> 00:20:14,478
So you have
all these little pictures.
348
00:20:14,480 --> 00:20:16,914
Now, cut them apart one by one
349
00:20:16,916 --> 00:20:18,416
and stack them on top
of each other,
350
00:20:18,418 --> 00:20:21,352
you get this pile.
351
00:20:21,354 --> 00:20:24,755
And if you go up in the pile,
you go up in time.
352
00:20:24,757 --> 00:20:29,594
And now kind of glue them
all together into one big block,
353
00:20:29,596 --> 00:20:35,099
and that block
has both space and time,
354
00:20:35,101 --> 00:20:39,470
and that's the spacetime
continuum.
355
00:20:39,472 --> 00:20:43,207
It's almost looking at a movie
not frame by frame,
356
00:20:43,209 --> 00:20:45,610
but seeing the whole movie
at once.
357
00:20:45,612 --> 00:20:49,213
They would now be
kind of two strands
358
00:20:49,215 --> 00:20:51,949
going up in space and time,
359
00:20:51,951 --> 00:20:55,253
and they would be
kind of spaghetti strands.
360
00:20:55,255 --> 00:20:58,189
In fact, we all are
spaghetti strands
361
00:20:58,191 --> 00:21:00,291
moving in this spacetime.
362
00:21:04,097 --> 00:21:08,933
NARRATOR:
Einstein feels that spacetime
is the natural arena
363
00:21:08,935 --> 00:21:11,969
in which his theory
of relativity should play out.
364
00:21:11,971 --> 00:21:17,675
But now he needs
sophisticated mathematics.
365
00:21:17,677 --> 00:21:20,144
By your standard or mine,
Einstein was good at math.
366
00:21:20,146 --> 00:21:21,412
He was Einstein.
367
00:21:21,414 --> 00:21:23,881
But he was not really
a mathematician per se.
368
00:21:23,883 --> 00:21:26,217
He didn't prove theorems,
he didn't pore over math books.
369
00:21:26,219 --> 00:21:27,351
He was a physicist.
370
00:21:27,353 --> 00:21:28,819
He did thought experiments.
371
00:21:28,821 --> 00:21:31,489
He thought of very tangible,
concrete situations
372
00:21:31,491 --> 00:21:32,923
and what would happen.
373
00:21:32,925 --> 00:21:35,459
So when it came time for him
to really bear down
374
00:21:35,461 --> 00:21:37,728
to the absolute cutting edge
mathematics of his day,
375
00:21:37,730 --> 00:21:39,530
he required help.
376
00:21:39,532 --> 00:21:45,936
NARRATOR:
At university, Einstein had
skipped the geometry classes,
377
00:21:45,938 --> 00:21:50,474
letting his friend Marcel
Grossman take notes for him.
378
00:21:50,476 --> 00:21:53,177
Grossman had excelled
in geometry
379
00:21:53,179 --> 00:21:56,647
and was now chairman
of the math department.
380
00:21:56,649 --> 00:22:01,319
He suggests Einstein
uses advanced mathematics
381
00:22:01,321 --> 00:22:06,624
in which the shape of space
and time could be curved.
382
00:22:06,626 --> 00:22:08,926
CARROLL:
Because spacetime
has a geometry,
383
00:22:08,928 --> 00:22:11,195
he thinks to himself,
384
00:22:11,197 --> 00:22:13,597
"Well, maybe it's the actual
shape of spacetime itself
385
00:22:13,599 --> 00:22:15,366
that is giving rise to gravity."
386
00:22:15,368 --> 00:22:24,542
NARRATOR:
After months of work, Einstein
has an extraordinary idea.
387
00:22:24,544 --> 00:22:31,015
"What if spacetime
is shaped by matter,
388
00:22:31,017 --> 00:22:33,984
and that's what we feel
as gravity?"
389
00:22:33,986 --> 00:22:38,322
JOHNSON:
In struggling to figure out
what causes gravity then,
390
00:22:38,324 --> 00:22:40,691
Einstein has this great insight.
391
00:22:40,693 --> 00:22:42,526
It is simply that a mass
392
00:22:42,528 --> 00:22:45,830
distorts the shape of spacetime
around it.
393
00:22:45,832 --> 00:22:49,166
So you get rid of this force
of gravity,
394
00:22:49,168 --> 00:22:53,537
and instead we have
curvature of spacetime.
395
00:22:53,539 --> 00:22:55,139
In Einstein's universe then,
396
00:22:55,141 --> 00:22:57,875
if space were empty,
it would be flat.
397
00:22:57,877 --> 00:22:59,210
There'd be nothing going on.
398
00:22:59,212 --> 00:23:01,345
But as soon as you
put objects down,
399
00:23:01,347 --> 00:23:04,615
they warp the space and time
around them,
400
00:23:04,617 --> 00:23:08,285
and that causes a deviation
of the geometry
401
00:23:08,287 --> 00:23:11,088
so that now things start moving.
402
00:23:14,494 --> 00:23:17,828
DIJKGRAAF:
Everything wants to move
as simple as possible
403
00:23:17,830 --> 00:23:20,531
through space and time.
404
00:23:20,533 --> 00:23:26,103
But Einstein tells us that mass
sculpts space and time,
405
00:23:26,105 --> 00:23:29,206
and it's the curved motion
through this sculpture
406
00:23:29,208 --> 00:23:30,841
that's the force of gravity.
407
00:23:33,513 --> 00:23:35,079
KNOX:
We have this feeling that
408
00:23:35,081 --> 00:23:37,481
the reason I can feel pressure
on the soles of my feet,
409
00:23:37,483 --> 00:23:39,717
that the reason things are going
to drop when I throw them,
410
00:23:39,719 --> 00:23:41,051
are because there's a force
411
00:23:41,053 --> 00:23:43,287
attracting us down
to the center of the earth.
412
00:23:43,289 --> 00:23:46,390
What general relativity tells
you is that's not the right way
413
00:23:46,392 --> 00:23:48,025
to think about
what's going on there.
414
00:23:48,027 --> 00:23:54,064
What's really going on is that
your natural path in spacetime
415
00:23:54,066 --> 00:23:55,933
would take you to the center
of the earth,
416
00:23:55,935 --> 00:23:58,002
and what's actually happening is
the floor is getting in the way,
417
00:23:58,004 --> 00:23:59,737
it's pushing you upwards.
418
00:23:59,739 --> 00:24:04,508
CARROLL:
When we look at it, we go,
"Ah, the force of gravity"
419
00:24:04,510 --> 00:24:07,077
But Einstein says, "No, no, no,
the curvature of spacetime."
420
00:24:11,984 --> 00:24:16,353
NARRATOR:
It's a stunning insight.
421
00:24:16,355 --> 00:24:20,891
Just as an ant might feel forces
pulling it left and right
422
00:24:20,893 --> 00:24:22,993
as it walks over crumpled paper
423
00:24:22,995 --> 00:24:27,264
when it's simply the shape
of a surface dictating its path,
424
00:24:27,266 --> 00:24:31,635
Einstein saw that what we feel
as the force of gravity
425
00:24:31,637 --> 00:24:36,707
is in fact the shape of the
spacetime we're moving through.
426
00:24:40,780 --> 00:24:44,081
Einstein now has
everything he needs
427
00:24:44,083 --> 00:24:47,318
to formulate his final theory
of gravity.
428
00:24:47,320 --> 00:24:51,055
But he makes a critical mistake.
429
00:24:51,057 --> 00:24:54,024
He misinterprets
one of his equations,
430
00:24:54,026 --> 00:24:56,093
and unaware of his error,
431
00:24:56,095 --> 00:25:00,531
continues working
on incorrect ideas.
432
00:25:00,533 --> 00:25:03,534
NORTON:
The point at which Einstein
is going to give
433
00:25:03,536 --> 00:25:05,469
the most essential equations
of the theory,
434
00:25:05,471 --> 00:25:07,771
Einstein considers
something like them
435
00:25:07,773 --> 00:25:10,341
and then says,
"Ah, but these don't work,"
436
00:25:10,343 --> 00:25:12,076
and then writes down
the wrong equations.
437
00:25:16,816 --> 00:25:21,852
What follows are alternations
of confidence and despair
438
00:25:21,854 --> 00:25:24,522
as he convinces himself
that everything was fine
439
00:25:24,524 --> 00:25:26,524
with this theory,
and then he realizes
440
00:25:26,526 --> 00:25:28,459
that things aren't so good
with the theory.
441
00:25:32,298 --> 00:25:36,200
It is a long, dark period
for Einstein
442
00:25:36,202 --> 00:25:38,402
as he struggles
to reconcile himself
443
00:25:38,404 --> 00:25:41,605
with a theory
that is just not working.
444
00:25:46,245 --> 00:25:50,214
NARRATOR:
Two years later,
Einstein is in Berlin.
445
00:25:50,216 --> 00:25:53,584
At just 36 years old,
he has one of the most
446
00:25:53,586 --> 00:25:56,620
prestigious positions
in physics.
447
00:25:56,622 --> 00:25:59,657
But he is still struggling
with his theory.
448
00:26:06,832 --> 00:26:10,267
ISAACSON:
By 1915, he'd reached
the pinnacle of the profession.
449
00:26:10,269 --> 00:26:12,269
He's in the Prussian Academy
450
00:26:12,271 --> 00:26:14,338
and a professor
at the University of Berlin.
451
00:26:14,340 --> 00:26:16,307
But his marriage
is falling apart,
452
00:26:16,309 --> 00:26:19,577
his wife and his two kids
have moved back to Switzerland,
453
00:26:19,579 --> 00:26:22,746
so he's pacing around
almost all alone
454
00:26:22,748 --> 00:26:24,315
in this apartment in Berlin.
455
00:26:26,652 --> 00:26:28,819
NARRATOR:
And now he has a competitor.
456
00:26:32,525 --> 00:26:35,292
Einstein had enthusiastically
shared his ideas
457
00:26:35,294 --> 00:26:38,062
with the brilliant mathematician
David Hilbert.
458
00:26:38,064 --> 00:26:41,398
Hilbert was so impressed,
459
00:26:41,400 --> 00:26:44,535
he decided to work
on the theory himself.
460
00:26:46,105 --> 00:26:48,339
Einstein is now
in a race to the finish
461
00:26:48,341 --> 00:26:53,477
with one of the world's
best mathematicians.
462
00:26:55,715 --> 00:26:57,214
KAISER:
This is unfolding
463
00:26:57,216 --> 00:27:00,551
in a remarkably dramatic period
in history.
464
00:27:00,553 --> 00:27:04,555
World War I has begun
to ravage central Europe.
465
00:27:04,557 --> 00:27:08,492
Einstein is not just toiling
in the abstract;
466
00:27:08,494 --> 00:27:11,161
he's toiling as the world
seems to fall apart.
467
00:27:15,901 --> 00:27:21,105
NARRATOR:
By November 1915, Einstein
is scheduled to present his work
468
00:27:21,107 --> 00:27:23,774
in a series
of four weekly lectures
469
00:27:23,776 --> 00:27:25,743
at the esteemed
Prussian Academy.
470
00:27:25,745 --> 00:27:30,881
But he's struggling
to formulate his ideas.
471
00:27:30,883 --> 00:27:33,183
In the midst
of these challenges,
472
00:27:33,185 --> 00:27:35,352
letters arrive
from his wife in Zurich
473
00:27:35,354 --> 00:27:37,187
pressing the issue
474
00:27:37,189 --> 00:27:39,790
of his financial obligations
to his family
475
00:27:39,792 --> 00:27:42,593
and discussing contact
with his sons.
476
00:27:45,197 --> 00:27:47,798
As his lectures begin,
477
00:27:47,800 --> 00:27:52,136
his theory is still
far from complete.
478
00:27:52,138 --> 00:27:55,039
The pressure on Einstein
is huge.
479
00:27:58,244 --> 00:28:02,846
SCHAFFER:
He would give a lecture,
revise it, give it again.
480
00:28:02,848 --> 00:28:06,684
Spot mistakes, correct them,
get up on the podium,
481
00:28:06,686 --> 00:28:09,253
explain what was wrong
in the previous week's lecture,
482
00:28:09,255 --> 00:28:11,655
correct it and then move on,
483
00:28:11,657 --> 00:28:15,292
and then do that again and again
for four weeks running.
484
00:28:17,830 --> 00:28:22,766
His work to convince them
of the truth
485
00:28:22,768 --> 00:28:27,538
of this absolutely radical
new theory of relativity
486
00:28:27,540 --> 00:28:29,339
that he was proposing
487
00:28:29,341 --> 00:28:31,809
is one of the most intense
periods of work
488
00:28:31,811 --> 00:28:33,177
in the history of science.
489
00:28:42,855 --> 00:28:45,756
NARRATOR:
Somehow, he's able
to focus on his theory
490
00:28:45,758 --> 00:28:51,228
with an incredible intensity,
and he makes his breakthrough.
491
00:28:51,230 --> 00:28:54,565
He tests his equations
on a problem
492
00:28:54,567 --> 00:28:58,702
that Newton's theory of gravity
couldn't solve:
493
00:28:58,704 --> 00:29:02,072
the orbit of Mercury.
494
00:29:02,074 --> 00:29:06,477
Mercury's path around the sun
has an anomaly
495
00:29:06,479 --> 00:29:09,113
that Newton's theory
can't explain:
496
00:29:09,115 --> 00:29:12,015
it deviates slightly
each time it goes round.
497
00:29:15,121 --> 00:29:19,690
Einstein calculates the orbit
with his new equations.
498
00:29:19,692 --> 00:29:22,326
The answer is correct,
499
00:29:22,328 --> 00:29:26,597
exactly what astronomers
had observed.
500
00:29:26,599 --> 00:29:29,500
He'd found the final equations
501
00:29:29,502 --> 00:29:32,269
for his general theory
of relativity.
502
00:29:43,249 --> 00:29:45,115
CARROLL:
You have to think about the
hubris of being Albert Einstein.
503
00:29:45,117 --> 00:29:47,584
He had already thrown out
Newtonian mechanics
504
00:29:47,586 --> 00:29:49,620
with special relativity,
and then he had gone off
505
00:29:49,622 --> 00:29:51,989
on his little personal quest
to incorporate gravity.
506
00:29:51,991 --> 00:29:55,726
And at the end of the day,
he boils it down to a prediction
507
00:29:55,728 --> 00:29:57,828
for a number
that had been observed:
508
00:29:57,830 --> 00:29:59,730
the procession
of the orbit of Mercury.
509
00:29:59,732 --> 00:30:02,332
And, miraculously,
when the pages of algebra
510
00:30:02,334 --> 00:30:05,169
work out to their end,
you get the right answer.
511
00:30:05,171 --> 00:30:07,738
And suddenly, it's not just
playing with equations anymore;
512
00:30:07,740 --> 00:30:10,307
he realizes
this is how the world works.
513
00:30:10,309 --> 00:30:14,645
All this abstract nonsense is
the correct theory of reality.
514
00:30:16,582 --> 00:30:21,318
SCHAFFER:
Einstein is at last able
to present a successful theory.
515
00:30:21,320 --> 00:30:23,253
That's a triumphant moment,
516
00:30:23,255 --> 00:30:25,656
one of the great moments
in the history of physics,
517
00:30:25,658 --> 00:30:32,196
and, for Einstein, a victory
very much against the odds,
518
00:30:32,198 --> 00:30:34,097
and he'd won.
519
00:30:38,537 --> 00:30:44,541
NARRATOR:
On the 25th of November 1915,
Einstein lays out his findings
520
00:30:44,543 --> 00:30:50,280
in his climactic fourth lecture
at the Prussian Academy.
521
00:30:50,282 --> 00:30:55,452
He presents general relativity.
522
00:30:55,454 --> 00:30:58,956
The theory can be written
as a single equation.
523
00:30:58,958 --> 00:31:02,259
It condenses
sprawling complexities
524
00:31:02,261 --> 00:31:06,129
into a beautifully compact set
of symbols.
525
00:31:08,634 --> 00:31:12,102
So the formula is really simple:
G-mu-nu equals...
526
00:31:12,104 --> 00:31:15,105
NARRATOR:
G for the shape of spacetime
527
00:31:15,107 --> 00:31:19,810
and T for the distribution
of mass and energy.
528
00:31:19,812 --> 00:31:23,013
So this very simple formula
529
00:31:23,015 --> 00:31:26,149
captures all of Einstein
general relativity.
530
00:31:26,151 --> 00:31:28,018
It's a beautiful,
simple equation
531
00:31:28,020 --> 00:31:30,988
but it's a lot of work
to unpack the symbols,
532
00:31:30,990 --> 00:31:32,856
the mathematical symbols,
533
00:31:32,858 --> 00:31:35,492
and see how
in this very simple formula,
534
00:31:35,494 --> 00:31:38,128
the whole geometry
of the universe is hidden.
535
00:31:38,130 --> 00:31:43,300
It's kind of an acquired taste
to see the beauty.
536
00:31:43,302 --> 00:31:46,403
It's also a signature formula
for Einstein.
537
00:31:46,405 --> 00:31:50,674
The true mark of his genius
is that he combines two elements
538
00:31:50,676 --> 00:31:53,243
that actually live
in different universes.
539
00:31:53,245 --> 00:31:56,079
The left hand side lives
in the world of geometry,
540
00:31:56,081 --> 00:31:57,481
of mathematics.
541
00:31:57,483 --> 00:31:59,816
The right hand side lives
in the world of physics,
542
00:31:59,818 --> 00:32:01,551
of matter and movement.
543
00:32:01,553 --> 00:32:06,790
And so perhaps the most powerful
ingredient of the equation
544
00:32:06,792 --> 00:32:10,060
is this very simple
equal sign here,
545
00:32:10,062 --> 00:32:13,563
these two lines that actually
are connecting the two worlds,
546
00:32:13,565 --> 00:32:15,499
and it's quite appropriate
they're two lines
547
00:32:15,501 --> 00:32:17,200
because it's two-way traffic.
548
00:32:17,202 --> 00:32:21,972
Matter tells space and time
to curve,
549
00:32:21,974 --> 00:32:25,609
space and time tells matter
to move.
550
00:32:37,056 --> 00:32:39,489
NARRATOR:
When Einstein presented
his great theory,
551
00:32:39,491 --> 00:32:41,758
few people understood it.
552
00:32:41,760 --> 00:32:44,895
He needed a way
to prove to the world
553
00:32:44,897 --> 00:32:48,532
that the counterintuitive
features of his theory
554
00:32:48,534 --> 00:32:50,500
were real.
555
00:32:53,906 --> 00:32:56,807
SCHAFFER:
The general theory of relativity
556
00:32:56,809 --> 00:33:00,744
made predictions of things
which looked really strange.
557
00:33:03,015 --> 00:33:06,216
For example,
the idea that light bends
558
00:33:06,218 --> 00:33:09,119
when it passes near
a very heavy body.
559
00:33:09,121 --> 00:33:10,587
No one had ever looked for that.
560
00:33:10,589 --> 00:33:13,156
No one had ever observed it.
561
00:33:13,158 --> 00:33:14,958
Einstein was desperate,
562
00:33:14,960 --> 00:33:19,429
desperate to get astronomers
to make that test.
563
00:33:19,431 --> 00:33:21,898
NARRATOR:
Einstein's theory predicts that
564
00:33:21,900 --> 00:33:25,702
when light from a distant star
travels close to the sun,
565
00:33:25,704 --> 00:33:31,975
the warped space around the sun
bends the light's path.
566
00:33:31,977 --> 00:33:37,647
In May 1919, the English
astronomer Arthur Eddington
567
00:33:37,649 --> 00:33:41,451
traveled to the African island
of Principe to record images
568
00:33:41,453 --> 00:33:46,390
that would show this phenomenon.
569
00:33:46,392 --> 00:33:48,058
KAISER:
What Eddington
had been able to do
570
00:33:48,060 --> 00:33:50,060
was take photographs of stars
571
00:33:50,062 --> 00:33:51,895
during a total eclipse
of the sun
572
00:33:51,897 --> 00:33:55,032
so the moon blocked most
of the brightness of the sun
573
00:33:55,034 --> 00:33:57,901
and little pinpricks of light
could be seen around the sun--
574
00:33:57,903 --> 00:34:00,070
otherwise, it would be lost
in the glare--
575
00:34:00,072 --> 00:34:02,339
and Eddington and his colleagues
were able to measure
576
00:34:02,341 --> 00:34:05,776
that the appearance
of those stars had been shifted
577
00:34:05,778 --> 00:34:07,310
compared to where
they would have been
578
00:34:07,312 --> 00:34:09,846
had that big mass of the sun
not been deflecting that light
579
00:34:09,848 --> 00:34:12,282
from far away.
580
00:34:12,284 --> 00:34:15,519
SCHAFFER:
So Eddington's able to show
581
00:34:15,521 --> 00:34:19,389
that Einstein's general
relativity theory is right
582
00:34:19,391 --> 00:34:24,094
and a revolution in science
has been accomplished.
583
00:34:32,504 --> 00:34:36,139
ISAACSON:
When the eclipse experiments
prove Einstein's theory right,
584
00:34:36,141 --> 00:34:39,543
he rockets to fame.
not just because he's explained
585
00:34:39,545 --> 00:34:41,778
a new way of looking
at the universe,
586
00:34:41,780 --> 00:34:43,880
but at the end of World War I,
587
00:34:43,882 --> 00:34:48,351
you had the predictions
of a German scientist
588
00:34:48,353 --> 00:34:51,154
be proven right
by some British astronomers,
589
00:34:51,156 --> 00:34:53,190
and it becomes headlines
across the world.
590
00:34:53,192 --> 00:34:54,458
The New York Times says,
591
00:34:54,460 --> 00:34:57,194
"Lights all askew
at the heavens,
592
00:34:57,196 --> 00:34:59,996
men of science
more or less agog."
593
00:34:59,998 --> 00:35:01,398
This is back when newspapers
594
00:35:01,400 --> 00:35:03,033
knew how to write
great headlines.
595
00:35:03,035 --> 00:35:05,669
But Einstein kind of loves
this fact
596
00:35:05,671 --> 00:35:07,904
that he is now an icon
of science.
597
00:35:11,877 --> 00:35:15,512
NARRATOR:
Einstein becomes
a worldwide celebrity,
598
00:35:15,514 --> 00:35:20,016
the icon of genius
we still recognize today.
599
00:35:20,018 --> 00:35:24,921
SCHAFFER:
The only person
who was more widely known
600
00:35:24,923 --> 00:35:26,723
was Charlie Chaplin,
601
00:35:26,725 --> 00:35:29,626
and they got on
like a house on fire.
602
00:35:29,628 --> 00:35:33,497
Chaplin said, "The reason
they all love me
603
00:35:33,499 --> 00:35:36,099
"is because they understand
everything I do,
604
00:35:36,101 --> 00:35:37,601
"and the reason they love you
605
00:35:37,603 --> 00:35:39,402
"is that they don't understand
anything you do.
606
00:35:39,404 --> 00:35:40,570
Can you explain that?"
607
00:35:40,572 --> 00:35:42,272
And Einstein said...
608
00:35:46,545 --> 00:35:52,549
NARRATOR:
But in 1930s Berlin,
the Nazi party is gaining power.
609
00:35:52,551 --> 00:35:56,820
As a Jewish scientist, Einstein
becomes increasingly caught up
610
00:35:56,822 --> 00:36:00,323
in the political turmoil.
611
00:36:00,325 --> 00:36:02,425
KAISER:
Einstein's theories
became a target.
612
00:36:02,427 --> 00:36:04,194
They were deemed
aesthetically repugnant
613
00:36:04,196 --> 00:36:06,863
to a kind of Aryan sensibility.
614
00:36:06,865 --> 00:36:09,833
So people attacked not just
Einstein the Jewish scientist,
615
00:36:09,835 --> 00:36:11,434
but they would actually
have people
616
00:36:11,436 --> 00:36:12,936
denouncing general relativity.
617
00:36:16,808 --> 00:36:19,442
NEWS ANNOUNCER:
In January, Nobel Prize
mathematician Albert Einstein
618
00:36:19,444 --> 00:36:20,810
visited California...
619
00:36:20,812 --> 00:36:23,013
NARRATOR:
He begins to make trips
to America,
620
00:36:23,015 --> 00:36:26,516
where he is welcomed
with open arms.
621
00:36:26,518 --> 00:36:30,153
NEWS ANNOUNCER:
Germany's loss, America's gain.
622
00:36:30,155 --> 00:36:33,490
NARRATOR:
And in 1933,
he settles in Princeton
623
00:36:33,492 --> 00:36:36,026
with his second wife Elsa,
624
00:36:36,028 --> 00:36:38,595
taking up a position at the
Institute for Advanced Study.
625
00:36:41,800 --> 00:36:47,337
Today, the Institute is headed
by Professor Robbert Dijkgraaf.
626
00:36:47,339 --> 00:36:51,341
DIJKGRAAF:
He basically was still
very much by himself,
627
00:36:51,343 --> 00:36:53,577
just actually
as he was in Berlin,
628
00:36:53,579 --> 00:36:57,013
just concentrating
on his deep ideas
629
00:36:57,015 --> 00:37:00,784
and struggling
with understanding the universe.
630
00:37:00,786 --> 00:37:03,153
Of course, his office was here.
631
00:37:03,155 --> 00:37:05,989
NARRATOR:
At the Institute,
632
00:37:05,991 --> 00:37:08,825
Einstein worked to unify
his theory of gravity
633
00:37:08,827 --> 00:37:12,262
with the other laws of physics.
634
00:37:14,900 --> 00:37:16,666
DIJKGRAAF:
With Einstein,
you see this phenomena
635
00:37:16,668 --> 00:37:18,235
you see with many great
scientists--
636
00:37:18,237 --> 00:37:21,771
that they climb
this very high mountain
637
00:37:21,773 --> 00:37:26,810
and instead of celebrating
their success,
638
00:37:26,812 --> 00:37:30,146
they're privileged to see
a much wider landscape,
639
00:37:30,148 --> 00:37:32,782
and they see all these mountains
behind it.
640
00:37:32,784 --> 00:37:35,118
And I think he was
very much aware
641
00:37:35,120 --> 00:37:39,022
how much still there was
to be done.
642
00:37:39,024 --> 00:37:41,891
Till the very last days
of his life,
643
00:37:41,893 --> 00:37:44,294
he was trying to push
these equations
644
00:37:44,296 --> 00:37:49,099
and find a description
of nature, all of nature,
645
00:37:49,101 --> 00:37:54,671
in terms of the geometry
of space and time.
646
00:37:54,673 --> 00:38:00,143
NARRATOR:
But general relativity was
fading from mainstream science.
647
00:38:00,145 --> 00:38:02,746
Physics was now focused
648
00:38:02,748 --> 00:38:07,250
on the quantum theory
of atoms and tiny particles,
649
00:38:07,252 --> 00:38:11,388
a theory incompatible
with Einstein's ideas,
650
00:38:11,390 --> 00:38:14,991
but one that could be tested
in the lab.
651
00:38:14,993 --> 00:38:17,527
Most of general relativity
652
00:38:17,529 --> 00:38:21,398
was then beyond the reach
of experiment.
653
00:38:21,400 --> 00:38:26,469
When Einstein died in 1955,
age 76,
654
00:38:26,471 --> 00:38:29,839
his theory was seen as one
655
00:38:29,841 --> 00:38:33,376
with little hope
of future discovery.
656
00:38:33,378 --> 00:38:36,813
CARROLL:
The best theories in physics
always take us to places
657
00:38:36,815 --> 00:38:38,715
where the people who invented
them didn't imagine.
658
00:38:38,717 --> 00:38:41,618
And a truly wonderful theory
like general relativity
659
00:38:41,620 --> 00:38:43,320
predicts all sorts of things
660
00:38:43,322 --> 00:38:45,822
that Einstein
didn't conceive of.
661
00:38:45,824 --> 00:38:47,457
The theory has a life
of its own.
662
00:38:47,459 --> 00:38:50,694
We understand general relativity
much better right now
663
00:38:50,696 --> 00:38:52,829
than Albert Einstein ever did.
664
00:38:52,831 --> 00:38:54,798
(engines roaring)
665
00:38:54,800 --> 00:38:58,168
NEWS ANNOUNCER:
Liftoff of space shuttle
Discovery
666
00:38:58,170 --> 00:39:01,838
with the Hubble space telescope,
our window on the universe.
667
00:39:01,840 --> 00:39:03,940
NARRATOR:
Today, 100 years
after general relativity
668
00:39:03,942 --> 00:39:05,408
was first presented...
669
00:39:05,410 --> 00:39:08,011
ASTRONAUT:
Telescopes released,
okay, thank you.
670
00:39:08,013 --> 00:39:11,381
NARRATOR:
...new technology
is allowing us to explore
671
00:39:11,383 --> 00:39:14,851
the most remarkable predictions
of the theory:
672
00:39:14,853 --> 00:39:16,553
an expanding universe,
673
00:39:16,555 --> 00:39:22,625
black holes,
ripples in spacetime,
674
00:39:22,627 --> 00:39:27,630
and perhaps the most bizarre,
675
00:39:27,632 --> 00:39:31,301
the idea that not just space,
but time itself
676
00:39:31,303 --> 00:39:35,171
is distorted by heavy objects.
677
00:39:35,173 --> 00:39:38,842
To prove it,
a team of physicists
678
00:39:38,844 --> 00:39:40,443
is carrying out
a remarkable experiment.
679
00:39:43,281 --> 00:39:48,118
They're using two atomic clocks
that are in near perfect sync,
680
00:39:48,120 --> 00:39:51,154
accurate to a billionth
of a second.
681
00:39:51,156 --> 00:39:54,257
The master clock
remains at sea level
682
00:39:54,259 --> 00:39:57,627
while they take the second clock
683
00:39:57,629 --> 00:40:00,330
to the top of New Hampshire's
Mount Sunapee.
684
00:40:00,332 --> 00:40:04,033
General relativity tells us that
as you move away
685
00:40:04,035 --> 00:40:10,774
from the mass of the planet,
time should speed up.
686
00:40:13,311 --> 00:40:16,746
After four days
at the top of the mountain,
687
00:40:16,748 --> 00:40:19,616
the test clock is taken back
to the lab for comparison.
688
00:40:22,821 --> 00:40:27,290
There, they compare it
to the sea level master clock.
689
00:40:27,292 --> 00:40:29,058
We'll put that one
into Channel A.
690
00:40:29,060 --> 00:40:32,028
NARRATOR:
Four days ago,
they were ticking in unison.
691
00:40:32,030 --> 00:40:33,463
Master clock
in Channel B.
692
00:40:33,465 --> 00:40:34,631
NARRATOR:
But what about now?
693
00:40:34,633 --> 00:40:35,765
You guys ready?
694
00:40:35,767 --> 00:40:36,933
This is it right here.
695
00:40:36,935 --> 00:40:38,435
The time interval counter
is gonna show us
696
00:40:38,437 --> 00:40:41,504
the time difference
between these two clock ticks.
697
00:40:43,141 --> 00:40:44,908
20 nanoseconds.
698
00:40:44,910 --> 00:40:47,444
You can see the time
difference between them
699
00:40:47,446 --> 00:40:49,312
represented here
graphically
700
00:40:49,314 --> 00:40:51,614
of the clock that was up
at the mountain for four days
701
00:40:51,616 --> 00:40:53,850
and our master clock.
702
00:40:53,852 --> 00:40:58,121
NARRATOR:
Gravity, the distortion
of space and time,
703
00:40:58,123 --> 00:41:01,658
becomes weaker as you move away
from the surface of the planet.
704
00:41:01,660 --> 00:41:05,728
So while the test clock
was up the mountain,
705
00:41:05,730 --> 00:41:08,298
time sped up.
706
00:41:08,300 --> 00:41:13,136
It's now 20 nanoseconds,
707
00:41:13,138 --> 00:41:17,373
20 billionths of a second,
ahead of the sea level clock,
708
00:41:17,375 --> 00:41:18,608
This is really awesome.
709
00:41:21,913 --> 00:41:26,616
NARRATOR:
This distortion of time
has surprising consequences.
710
00:41:26,618 --> 00:41:29,152
The Global Positioning System,
711
00:41:29,154 --> 00:41:32,188
something we all take
for granted,
712
00:41:32,190 --> 00:41:36,259
wouldn't work without
taking this into account.
713
00:41:36,261 --> 00:41:38,595
The engineers who built
the GPS system
714
00:41:38,597 --> 00:41:40,730
we use every day
to pinpoint locations
715
00:41:40,732 --> 00:41:44,968
had to ensure it adjusted
for the time difference
716
00:41:44,970 --> 00:41:49,506
between clocks on satellites
and receivers on the ground.
717
00:41:49,508 --> 00:41:55,011
If they didn't, GPS would be off
by six miles every day.
718
00:41:55,013 --> 00:41:57,046
JIM GATES:
Your GPS units
719
00:41:57,048 --> 00:41:59,983
use the results
of general relativity.
720
00:41:59,985 --> 00:42:02,452
When you navigate in your car,
721
00:42:02,454 --> 00:42:04,921
you perhaps should give a word
of thanks to Uncle Albert.
722
00:42:10,629 --> 00:42:13,463
NARRATOR:
Of all general relativity's
predictions
723
00:42:13,465 --> 00:42:16,499
that new technology
has allowed us to explore,
724
00:42:16,501 --> 00:42:21,838
there's one that's
straight out of science fiction:
725
00:42:21,840 --> 00:42:23,740
a black hole.
726
00:42:27,612 --> 00:42:31,347
Everything that we're
familiar with in ordinary life
727
00:42:31,349 --> 00:42:33,216
is made from matter.
728
00:42:33,218 --> 00:42:34,817
But not black holes.
729
00:42:34,819 --> 00:42:39,088
Black holes are made
from warped space and time
730
00:42:39,090 --> 00:42:43,326
and nothing else.
731
00:42:43,328 --> 00:42:47,530
A black hole is an object
that is spherical,
732
00:42:47,532 --> 00:42:50,233
like a star or like the Earth,
733
00:42:50,235 --> 00:42:53,102
with a sharp boundary
called the horizon
734
00:42:53,104 --> 00:42:57,307
through which nothing
can come out.
735
00:42:57,309 --> 00:43:01,678
So it casts a shadow
on whatever is behind it.
736
00:43:01,680 --> 00:43:07,116
It's just a black, black shadow,
unbelievably black.
737
00:43:07,118 --> 00:43:12,555
NARRATOR:
This simulation shows
the distortion of starlight
738
00:43:12,557 --> 00:43:15,358
around a black hole.
739
00:43:15,360 --> 00:43:19,062
Even though Einstein knew his
theory predicted black holes,
740
00:43:19,064 --> 00:43:24,167
he found it hard to believe they
would really exist in nature.
741
00:43:24,169 --> 00:43:27,704
In the 1960s,
Professor Kip Thorne
742
00:43:27,706 --> 00:43:31,741
worked on the mathematical
concept of black holes.
743
00:43:31,743 --> 00:43:34,544
The idea made sense on paper,
744
00:43:34,546 --> 00:43:38,915
and he began to feel that these
science fiction-like objects
745
00:43:38,917 --> 00:43:41,551
might actually be real.
746
00:43:41,553 --> 00:43:44,654
THORNE:
Must be here somewhere,
it's in one of these piles.
747
00:43:44,656 --> 00:43:48,424
NARRATOR:
Kip Thorne made a bet with
fellow physicist Stephen Hawking
748
00:43:48,426 --> 00:43:51,461
about whether or not
a strong source of x-rays
749
00:43:51,463 --> 00:43:55,264
known as Cygnus X-1
was in fact a black hole.
750
00:43:55,266 --> 00:43:56,866
THORNE:
I think it's in here.
751
00:43:56,868 --> 00:44:01,070
Yeah, here we go, relativity,
stars and black holes.
752
00:44:01,072 --> 00:44:03,072
Yeah, there it is.
753
00:44:03,074 --> 00:44:07,010
So that is a copy
of the famous bet.
754
00:44:07,012 --> 00:44:09,312
"Stephen Hawking
bets a one-year subscription
755
00:44:09,314 --> 00:44:11,080
"to Penthouse magazine
756
00:44:11,082 --> 00:44:13,249
"against Kip Thorne's wager
of a four-year subscription
757
00:44:13,251 --> 00:44:16,753
"to a political magazine called
Private Eye
758
00:44:16,755 --> 00:44:19,489
"that Cygnus X-1 does not
contain a black hole of mass
759
00:44:19,491 --> 00:44:21,557
"above the Chandrasekhar Limit.
760
00:44:21,559 --> 00:44:25,895
It's witnessed this 10th day
of December 1974."
761
00:44:25,897 --> 00:44:30,033
Stephen Hawking had
a terribly deep investment
762
00:44:30,035 --> 00:44:32,368
in it actually being
a black hole,
763
00:44:32,370 --> 00:44:38,541
and so he made the bet against
himself as an insurance policy
764
00:44:38,543 --> 00:44:40,543
that at least he would get
something out of it
765
00:44:40,545 --> 00:44:43,479
if Cygnus X-1 turned out
not to be a black hole.
766
00:44:43,481 --> 00:44:46,349
The evidence mounted thereafter
767
00:44:46,351 --> 00:44:48,484
over the period
of the '70s and '80s,
768
00:44:48,486 --> 00:44:51,821
and in June 1990,
769
00:44:51,823 --> 00:44:56,059
Stephen snuck into my office
and signed off on the bet,
770
00:44:56,061 --> 00:44:58,661
that finally, the evidence
was absolutely overwhelming
771
00:44:58,663 --> 00:45:01,664
that Cygnus X-1
really is a black hole.
772
00:45:01,666 --> 00:45:05,168
And Penthouse magazine arrived.
773
00:45:05,170 --> 00:45:06,969
He sent me the British version
of Penthouse,
774
00:45:06,971 --> 00:45:09,038
which was ever
so much more raunchy
775
00:45:09,040 --> 00:45:10,673
than the American Penthouse,
actually.
776
00:45:10,675 --> 00:45:14,677
Enough to make my face turn red
when I received it at first.
777
00:45:20,618 --> 00:45:23,519
NARRATOR:
Today, we have evidence
suggesting that
778
00:45:23,521 --> 00:45:28,191
there are millions of black
holes in our galaxy alone.
779
00:45:28,193 --> 00:45:32,595
But perhaps the most profound
prediction of general relativity
780
00:45:32,597 --> 00:45:37,033
is that our universe
had a hot, dense beginning
781
00:45:37,035 --> 00:45:40,069
that we call the big bang.
782
00:45:44,709 --> 00:45:48,511
The discovery that distant
galaxies are moving away from us
783
00:45:48,513 --> 00:45:53,549
and that there's a background
radiation permeating space
784
00:45:53,551 --> 00:45:56,152
provided evidence
for the big bang
785
00:45:56,154 --> 00:45:59,055
and a universe that's growing.
786
00:45:59,057 --> 00:46:01,791
SAUL PERLMUTTER:
With this picture
of an expanding universe,
787
00:46:01,793 --> 00:46:03,693
there were natural questions.
788
00:46:03,695 --> 00:46:06,562
Is the universe slowing down
as it expands?
789
00:46:06,564 --> 00:46:09,499
Is it so dense that someday,
790
00:46:09,501 --> 00:46:11,501
it will come to a halt
and collapse?
791
00:46:11,503 --> 00:46:13,202
Will the universe come
to an end?
792
00:46:13,204 --> 00:46:15,004
These seemed like
good questions.
793
00:46:15,006 --> 00:46:20,710
NARRATOR:
To find answers, in the 1990s,
Saul Perlmutter and his team
794
00:46:20,712 --> 00:46:24,847
observed exploding stars,
called supernovae,
795
00:46:24,849 --> 00:46:28,317
to track the growth
of the universe.
796
00:46:28,319 --> 00:46:31,554
PERLMUTTER:
When we made the measurement,
we discovered that the universe
797
00:46:31,556 --> 00:46:33,356
isn't slowing down enough
to come to a halt.
798
00:46:33,358 --> 00:46:35,391
In fact,
it's not slowing at all;
799
00:46:35,393 --> 00:46:36,959
it's speeding up!
800
00:46:36,961 --> 00:46:39,328
The universe is expanding
faster and faster.
801
00:46:39,330 --> 00:46:41,664
NARRATOR:
But what's pushing it?
802
00:46:41,666 --> 00:46:45,601
PERLMUTTER:
In order to explain
the acceleration of the universe
803
00:46:45,603 --> 00:46:47,904
within Einstein's theory
of general relativity,
804
00:46:47,906 --> 00:46:51,507
we're considering an energy
spread throughout all of space
805
00:46:51,509 --> 00:46:52,842
that we've never seen before.
806
00:46:52,844 --> 00:46:54,076
We don't know what it is.
807
00:46:54,078 --> 00:46:55,812
We call it dark energy.
808
00:46:55,814 --> 00:46:59,182
And, if so, it would require
809
00:46:59,184 --> 00:47:02,652
something like 70%
of all the stuff of the universe
810
00:47:02,654 --> 00:47:05,555
to be in this form of previously
unknown dark energy.
811
00:47:05,557 --> 00:47:08,424
So this is a lot to swallow,
812
00:47:08,426 --> 00:47:10,359
and you might imagine that
at that point,
813
00:47:10,361 --> 00:47:11,861
you should go back
and revisit your theory.
814
00:47:11,863 --> 00:47:14,430
The problem is that Einstein's
theory is so elegant,
815
00:47:14,432 --> 00:47:18,534
and it predicts many, many,
many digits of precision,
816
00:47:18,536 --> 00:47:21,270
that it's very, very difficult
to come up
817
00:47:21,272 --> 00:47:23,472
with any other theory.
818
00:47:26,244 --> 00:47:30,713
NARRATOR:
There is one final prediction
of general relativity
819
00:47:30,715 --> 00:47:36,352
that remains untested:
gravitational waves.
820
00:47:36,354 --> 00:47:41,090
LEVIN:
There are huge things
in the universe happening,
821
00:47:41,092 --> 00:47:44,026
like black holes colliding
or stars exploding,
822
00:47:44,028 --> 00:47:46,696
and they create these
gravitational waves--
823
00:47:46,698 --> 00:47:49,599
waves in the shape
of space and time
824
00:47:49,601 --> 00:47:52,268
that travel through the universe
at the speed of light.
825
00:47:52,270 --> 00:47:54,971
And so right now,
the space around me
826
00:47:54,973 --> 00:47:57,974
is being squeezed and stretched
by gravitational waves
827
00:47:57,976 --> 00:48:01,444
just getting here
from, let's say, two black holes
828
00:48:01,446 --> 00:48:03,913
colliding a billion
light years away.
829
00:48:07,218 --> 00:48:09,819
But the squeezing and stretching
is so minute,
830
00:48:09,821 --> 00:48:12,755
I absolutely could not
personally detect it.
831
00:48:12,757 --> 00:48:16,425
And so what we're trying to do
is build an instrument that can.
832
00:48:16,427 --> 00:48:19,896
NARRATOR:
In Louisiana
and Washington state,
833
00:48:19,898 --> 00:48:22,865
a vast experiment called LIGO
834
00:48:22,867 --> 00:48:24,901
is in the final phases
of calibration.
835
00:48:24,903 --> 00:48:30,406
It's hoped that laser beams
traveling two-and-a-half miles
836
00:48:30,408 --> 00:48:32,742
between precisely aligned
mirrors
837
00:48:32,744 --> 00:48:34,877
will measure
the squeezing of space
838
00:48:34,879 --> 00:48:38,247
caused by gravitational waves.
839
00:48:38,249 --> 00:48:43,920
This could open up an entirely
new window on the universe.
840
00:48:50,361 --> 00:48:54,664
For 100 years,
general relativity
841
00:48:54,666 --> 00:48:57,967
has been proven to be correct
time and time again.
842
00:48:57,969 --> 00:49:02,838
But Einstein himself knew that
his great theory had limits.
843
00:49:02,840 --> 00:49:04,707
It remains incompatible
844
00:49:04,709 --> 00:49:09,845
with the quantum world
of tiny atomic particles.
845
00:49:09,847 --> 00:49:12,281
Here at the Institute
for Advanced study,
846
00:49:12,283 --> 00:49:13,983
where Einstein worked,
847
00:49:13,985 --> 00:49:16,919
the world's leading
theoretical physicists
848
00:49:16,921 --> 00:49:21,257
are trying to solve the problem
Einstein never could:
849
00:49:21,259 --> 00:49:23,793
finding a single set of rules
850
00:49:23,795 --> 00:49:27,730
that applies to both the cosmic
and atomic scales.
851
00:49:27,732 --> 00:49:31,667
A unified theory.
852
00:49:31,669 --> 00:49:34,603
The Holy Grail of physics.
853
00:49:34,605 --> 00:49:38,975
We are now in what at this time
is the school of physics.
854
00:49:38,977 --> 00:49:41,143
So here,
people are still struggling
855
00:49:41,145 --> 00:49:43,980
with many of the same issues
that Einstein would struggle
856
00:49:43,982 --> 00:49:49,418
and are still trying to capture
the laws of the universe
857
00:49:49,420 --> 00:49:54,423
from the very small to the very
large in a single equation.
858
00:49:54,425 --> 00:49:59,862
And it's still blackboards
that are the weapon of choice.
859
00:49:59,864 --> 00:50:04,834
The brightest minds of the world
are coming here
860
00:50:04,836 --> 00:50:07,837
to work 24 hours,
seven days a week,
861
00:50:07,839 --> 00:50:13,342
struggling to grasp the great
mysteries of the universe.
862
00:50:13,344 --> 00:50:16,112
And I think we are still driven
by the same dream:
863
00:50:16,114 --> 00:50:17,980
that at some point,
864
00:50:17,982 --> 00:50:20,950
we can capture everything
in elegant mathematics.
865
00:50:20,952 --> 00:50:23,652
NARRATOR:
100 years after Einstein
866
00:50:23,654 --> 00:50:27,123
transformed our understanding
of nature,
867
00:50:27,125 --> 00:50:31,427
the stage is set
for the next revolution.
868
00:50:31,429 --> 00:50:34,330
CARROLL:
When we finally move
beyond Einstein,
869
00:50:34,332 --> 00:50:36,465
it might be another singular
genius that comes along--
870
00:50:36,467 --> 00:50:39,702
someone struggling in a poor
school in Kenya right now
871
00:50:39,704 --> 00:50:41,037
that we don't know about.
872
00:50:41,039 --> 00:50:42,838
Or it might be
20 different people
873
00:50:42,840 --> 00:50:44,407
with 20 different
points of view
874
00:50:44,409 --> 00:50:45,908
gradually building
brick-by-brick
875
00:50:45,910 --> 00:50:48,944
to finally figure out
a more comprehensive view
876
00:50:48,946 --> 00:50:51,447
that includes general
relativity in it.
877
00:50:58,456 --> 00:50:59,989
DIJKGRAAF:
I think the most important thing
878
00:50:59,991 --> 00:51:03,025
that you learn from Einstein
is just the power of an idea.
879
00:51:03,027 --> 00:51:05,928
If it's correct, you know,
it's just unstoppable.
880
00:51:09,067 --> 00:51:12,635
It's extremely encouraging that
he was able with pure thought
881
00:51:12,637 --> 00:51:15,304
to solve the riddle
of the universe.
882
00:51:19,577 --> 00:51:22,078
LEVIN:
Once we had general relativity,
883
00:51:22,080 --> 00:51:23,979
the world changed completely.
884
00:51:23,981 --> 00:51:25,948
Our point of view on the world
changed completely.
885
00:51:25,950 --> 00:51:28,217
I mean, the origin
of the universe
886
00:51:28,219 --> 00:51:30,586
is a prediction straight out
of general relativity.
887
00:51:30,588 --> 00:51:33,456
We didn't have that before.
888
00:51:33,458 --> 00:51:36,659
GATES:
I often wonder
what Einstein would make
889
00:51:36,661 --> 00:51:39,261
of today's theoretical physics.
890
00:51:39,263 --> 00:51:41,564
I think he would really be
saying, you know,
891
00:51:41,566 --> 00:51:43,432
"Get on with it, get the right
story, get the details right."
892
00:51:47,171 --> 00:51:50,706
DIJKGRAAF:
You know, you have
the huge universe,
893
00:51:50,708 --> 00:51:52,508
and it obeys
certain laws of nature,
894
00:51:52,510 --> 00:51:56,378
but where in the universe are
these laws actually discovered?
895
00:51:56,380 --> 00:51:59,081
Where are they studied?
896
00:51:59,083 --> 00:52:01,851
And then you go
to this tiny planet
897
00:52:01,853 --> 00:52:04,620
and there's this one individual,
Einstein, who captures this.
898
00:52:04,622 --> 00:52:07,089
And now there's
a small group of people
899
00:52:07,091 --> 00:52:10,359
walking in his footsteps
and trying to push it further.
900
00:52:10,361 --> 00:52:12,361
And I often feel,
901
00:52:12,363 --> 00:52:13,996
well, it's this small part
of the universe
902
00:52:13,998 --> 00:52:16,432
that actually is reflecting
upon itself,
903
00:52:16,434 --> 00:52:16,432
that tries
to understand itself.