Cosmos: Possible Worlds - First Season

We inhabit a cosmos of undiscovered dimensions

and paradoxical realities.

We live on one level of perception,

but there are others.

Every once in a while, a searcher happens upon

the doorway to one of these other levels.

One of them discovered a paradox about reality that

proved to be so profound, we have yet to understand

how it could be possible.

The universe, or perhaps we should say,

universes have never been the same.

Nature writes her most intimate secrets in light.

The light from our star that powers all life on this world.

The light that plants eat to make sugar.

The light that is the yardstick of the universe,

stitching diamonds into the fabric of space and time.

The imprisoned light that defines black holes.

The absence of light that prevents us from knowing

what dark matter and dark energy are.

"Seeing the light" usually refers to a religious epiphany,

but no one is more light-obsessed than astronomers.

And as soon as they began studying light,

it challenged even the very best of them.

Take Isaac Newton, for example.

He was so desperate to understand the nature of light and colors,

he was willing to stick needles in his eyes.

No, I mean literally.

Newton was only in his mid-20s,

but he had already laid the foundations of a new branch of mathematics called "calculus,"

and he was conducting a series

of experiments that led him to conclude that color was an aspect of light.

Newton wanted to find out which of the things we see

are properties of light and which are caused by our nerves.

Was color hiding inside the light?

Or was it in our eyes?

With a burning desire to know,

he took a needle called a bodkin and

Newton carefully noted that if he conducted

the experiment in a room filled with light,

even with his eyes shut, some light would pass through

his eyelids and he would see a great, broad blue-ish circle.

It may not sound like much of a result considering the pain,

but it was with simple homemade experiments such

as this one that Isaac Newton became the first person to explain rainbows,

and how white light hides a whole

palette of colors inside itself.

Most people thought of the events Newton studied as

being just the way things were.

The way an apple falls.

The way a ray of light shines through a window.

Newton's greatness stemmed from his questioning of the

"why" and "how" of ordinary things.

Newton asked, what was light made of?

If you could break light apart into its tiniest components,

what would you see?

Newton noticed that light moved in straight lines.

How else to explain the edges of shadows?

Or the straightness of the inspiring rays of sunlight

that poke through a cloud?

Or the darkness that resulted from a total solar eclipse?

From these observations, Newton reasoned that light

must consist of a stream of particles,

or corpuscles as he called them,

that a ray of light was like a stream of bullets striking

the retina of the eye.

But there was one man over in Holland,

who vigorously disagreed with Newton's particle theory of light.

Christiaan Huygens shared Isaac Newton's insatiable curiosity,

and when it came to changing the world,

he was no slouch himself.

Despite a lifelong struggle with depression,

he managed to get a lot done.

While looking through a telescope that he designed and built himself,

he discovered Saturn's moon, Titan.

Huygens invented the pendulum clock.

He worked out the mathematical formulas necessary to create

a pendulum with an arc that would accurately and

consistently measure out uniform increments of time.

Huygens sketched a prototype for a new machine

that he thought might have some promise.

It was what he called a "magic lantern."

A few hundred years would pass before it evolved into

a working motion picture projector.

But back in the 17th century,

Christiaan Huygens already had an idea for a movie,

possibly influenced by his gloomy disposition.

Huygens, like Newton,

also invented his own new branch of mathematics,

a predictive theory of the outcomes of games of chance,

probability theory.

A way to call heads or tails.

And like Newton, Christiaan Huygens had his own theory of light,

but it was very different.

He didn't think light consisted of particles like

bullets firing along a single path.

Huygens saw light as a wave,

spreading out in all directions.

It was already known in that time that sound must travel as a wave.

How?

Because a voice could be heard around a door when it was slightly ajar,

so sound must travel around the door as water would,

like a wave.

Huygens thought that light moved the same way sound did,

spreading out as waves.

So, which genius was right?

The answer to that question of whether light was a particle

or a wave would prove to be complicated.

Now enter Thomas Young.

The man who exposed the enigma at the heart of light

and unraveled the fabric of the cosmos that we thought we knew.

Come with me to one of the greatest mysteries in the history of science.

It's a story about a man who could do just about anything,

and Thomas Young did.

For 1500 years, no one had been able to decipher Egyptian hieroglyphics.

By identifying six major sounds that the hieroglyphics represented,

he was able to decrypt six of the symbols,

which led to the complete translation of the ancient

Egyptian language by others.

He was the first to chart the family tree of the Indo-European languages.

As a physician, he identified a deformity in the shape of the eye,

the defective vision he named astigmatism.

But it was Young's design of an experiment that sent

physics down the rabbit hole we still live in.

It looks simple, right?

How could three sheets of cardboard set such a catastrophe in motion?

A green glass shade like this one will only allow the green light through,

so that only a single color,

or frequency of light will pass through the slits.

Why was that important?

Because he assumed that the many overlapping colors would

result in the same light wave that Huygens imagined,

called an interference pattern.

He forced that single color of light to travel through

two separate slits to see what kind of pattern the light

would make on that last piece of cardboard.

If light was a particle, you'd expect to see two distinct

clumps of light on the opposite wall,

where the individual particles of light ended up

after they passed through the slits.

But that's not what happened.

Instead, a completely unexpected pattern.

The one that two waves would make when they overlapped,

or interfered with each other.

That's why they're called an interference pattern.

Young had demonstrated that light was actually a wave.

That Newton, the greatest genius in the history of science was half wrong.

That light was not a particle as he confidently proclaimed.

There's a reason that arguments from authority

hold little weight in science.

Nature and nature only settles the argument.

And she has so many tricks up her sleeve,

only a fool would ever consider our understanding of nature complete.

Newton had missed something fundamental.

Surprising, but we haven't gotten to the really disturbing part yet.

Thomas Young left a time bomb with a long fuse.

One that took 100 years to burn down before it exploded.

It wasn't until the end of the 19th century that science

developed the necessary tools to find an opening to a hidden universe,

a realm of deeper mystery.

You can hear the discoverer's astonishment in his own account.

Could anything, at first sight,

seem more impractical than a body which is so small that

its mass is an insignificant fraction of the mass of an atom of hydrogen?

Which itself is so small that

the crowd of these atoms equal

in number to the population of the whole world would be too small

to have been detected by any means then known to science.

That voice, that particular organization of

sound waves frozen in time nearly 100 years ago,

belongs to J.J. Thomson.

He's remembering his discovery of the electron in his cathode ray experiment.

He had heated up a metal electrode until it spit out an electron.

And another, and another.

For the first time, an elementary particle of

the atom was made visible.

Science was breaking into nature's vault where she had

kept her most closely held secrets,

and that's when things got really crazy.

If even the smallest units of matter, atoms say,

had even smaller components, such as an electron,

then could the same thing be true of light?

Scientists, in their never-ending fascination with light,

set out to devise ways of isolating smaller

and smaller units of it.

It proved to be the passage way through the looking glass.

It was the crossing of a threshold into a wonderland

where the known rules of physics do not apply.

For the first time, they were able to isolate the tiniest unit of light,

a single photon.

And to perform Young's double slit experiment on a whole new level,

tracing its precise path either through the right slit or the left slit.

We'll pull over to the side of the road for the best possible view of which slit,

the right or the left,

the photon passes through to get to the far wall.

Left slit, right slit.

Another right slit.

Left slit.

If we watched them all day long,

the pattern would be random.

About half would go through either slit.