How the Universe Works

What is our universe made of?

It's the biggest unsolved mystery in science.

Despite the name, space is not an empty space at all.

Space itself is something.

There's a hidden structure

and a force that exists within space itself...

Space-time is something absolutely real.

It's absolutely fundamental.

It's really part of the fundamental architecture.

A force that connects everything in our universe.

It's an active player in the game of life.

It underpins our reality,

tying together all of space and time

since the very beginning.

We call it space-time.

It's everything.

Space-time is what the universe really is.

Space-time is how the universe works,

but what is it?

How does it control our past, present and future?

captions paid for by discovery communications

We can't see it.

We can't touch it,

but without space-time, we wouldn't be here.

Space-time is the fabric of our reality.

It shapes and governs our lives.

If we want to understand the story of the universe,

it's absolutely crucial we understand

how space-time behaves.

Space-time has been active

since the beginning of everything

and is the key to the evolution of everything.

We have to understand space-time

in order to understand the history of the universe,

to understand how the universe began,

how it evolved, and what's going to happen in the future.

The story of space-time

is the story of our universe.

To know how the story plays out, how it will end,

we need to go back to the very beginning...

...to a time when there was nothing, no stars, no space,

a time before there was time.

Then, all of a sudden...

Our entire universe was born in the big bang.

It started in a instantaneous moment

where, from nothing, our universe was created.

The very definition of the moment of the big bang

is that space and time were created at that instant.

It is, as far as we currently know,

the coming into existence of space and time itself.

The infant universe,

a tiny speck of energy and space-time,

materializes from nowhere.

Then... The universe suddenly expands.

The idea of inflation is that a very tiny region,

in an incredibly short amount of time,

far shorter than a second,

grew by many, many, many orders of magnitude,

so imagine myself suddenly becoming the size of a galaxy.

In a fraction of a second,

the universe grew from smaller than the size of an atom

to the size of a baseball.

In cosmic terms, that's like a grain of sand

growing almost to the size of the observable universe.

The universe, at the instant of inflation,

actually expanded faster than the speed of light.

It seems to be a violation

of everything you've heard in physics.

You may be thinking, "hey, hey, hey, Mr. Astronomy guy.

Nothing can move faster than the speed of light,"

and it turns out, that's kind of true.

But the rule is, nothing can move through the universe

faster than the speed of light.

In inflation, it's space itself that is expanding,

so there is no violation.

There is no paradox.

Inflating fast, the universe

went through a phenomenal growth spurt.

At the moment of the big bang, space-time was this entity

that was flying out in all directions.

It was space itself that was expanding.

But the universe didn't expand evenly.

One spot in the universe was ever so slightly more dense

than a spot right next to it,

and we're talking about a tiny, tiny fraction of a percent,

one part in 100,000, but that was enough.

Fluctuations in expanding space-time

created areas with higher density.

Inflation made these high-density regions larger...

...and this allowed our universe to take shape.

When parts of the universe didn't inflate

quite the same way as others,

all of a sudden, things could start to come together.

As the universe cooled,

energy turned into matter...

...and in the denser regions,

that matter started to clump together.

Crucially, these regions had more mass than others.

Mass bends space-time,

so anything that is made of matter bends space-time.

And the more matter you have in one place, the more you bend it.

In fact, I am bending space-time right now.

When I flex, I bend it even more

because of my incredibly high muscle density.

I don't bend at the maximum.

I don't want to destroy the earth and the solar system,

but, you know, it's an effect.

It's a real thing.

Space isn't constant.

It's not something that is always the same everywhere.

It actually bends, curves.

It warps depending on the matter inside of it.

We'd see a curving grid of space-time moving

and reacting to objects within it,

and we'd feel the curving of space-time

as the force we call gravity.

Gravity is different from all the other forces.

It is intimately connected with the curvature of space-time.

Something that can bend space and time has gravity.

That's what gravity is,

the bending of space and time itself.

It's hard to visualize this,

but a good analogy is a trapeze artist

and their safety net.

You can imagine a trapeze artist falling into a net on purpose.

That net is flat

and looks like a nice, orderly, evenly spaced grid,

but when they fall into it, they distort that grid.

Well, that's a lot like space.

If you have matter in space, it warps the framework.

When the trapeze artist is resting in the net,

they're bending that space-time grid a little bit.

If you had two trapeze artists in there,

double the mass in roughly the same volume,

you would get a bigger dip.

You have a bigger distortion, and that's how space-time works.

More mass equals a bigger curve in space-time

equals more gravity,

but understanding the nature of gravity and space-time

is no easy thing.

It's an idea developed by one of the greatest minds ever.

Einstein had the idea that space itself is something,

something that can be bent, something that can be stretched,

that we are all bound together by space-time.

Einstein says that space and time have a geometry.

They have a life of their own. They have dynamics.

Those dynamics are what we call gravity.

The more dense the region of matter,

the greater the gravity, the deeper the curve.

This connection is the foundation

of our physical reality.

It's the interaction between matter and energy and space-time

that created the universe that we see around us today.

But that doesn't mean we fully understand it.

There's much more that we don't know,

and that's frustrating.

With the laws of physics, I can talk about

how space-time behaves,

but it does appear to be something that stretches,

that contracts, and that gravity is the embodiment of space-time.

Born in the big bang, space, time, and energy

combined to create our infant universe.

These basic materials were the foundations,

but how did we get to the incredible,

complex structures we see today?

How did space-time build our majestic cosmos?

Our entire universe was created in the big bang

13.8 billion years ago.

Everything came from nothing,

but our modern universe is a complex mosaic of matter.

When we marvel through our telescopes

at the fantastic structure of our universe

and its galaxies,

you got to ask, "where'd that come from?"

Matter in the universe arranges itself

on a vast cosmic web.

Galaxies and galaxies' clusters

are strung out on sheets and filaments.

It seems this intricate web is organized

by a cosmic architect, space-time.

It shaped everything from planets to galaxies,

atoms to cities.

The universe is made of space-time.

Whatever the substance is, time and space bound together,

that's expanding and creating the universe we see around us.

It's everything.

Space-time is what the universe really is.

It's a hard concept to grasp

and even harder to visualize.

Scientists observe the universe

in different wavelengths of light.

This is the sun, invisible light, X-ray, and ultraviolet.

Now imagine if we could see it in the space-time spectrum.

We would see space-time

distorting as objects move through it.

Space-time can warp and push things around.

It can expand and pull things apart.

But it's the shape of space-time

that dictates how we experience it.

Imagine you're in your car.