Katie Mack: The death of the universe -- and what it means for life | TED Fellows

[SHAPE YOUR FUTURE]

I love the universe.

The vastness, the mystery,

the astonishing beauty of the stars.

I love everything about it,

and I've devoted my life to studying it.

From atoms to galaxies,

from beginning to end.

But lately, I've gotten stuck on that last bit.

The fact that the universe is dying.

I know this may come as a shock.

I mean, it's the universe, it's everything.

It's supposed to be eternal, right?

But it isn't.

We know the universe had a beginning

and everything that begins ends.

The start of the story is a familiar one.

In the beginning, there was light.

We know that because we can see it directly.

The cosmos today is filled with low-energy background radiation

left over from a time

when the whole universe was an all-encompassing inferno.

In its first 380,000 years, space wasn't cold or dark.

It was thick with a churning, humming plasma.

It was hot and dense.

It was loud.

But it was also expanding.

Over time, the fire dissipated and space cooled.

Clouds of gas pulled together by their own gravity

formed stars and galaxies and planets and us.

And one day,

astronomers using a microwave receiver detected a bit of static

coming from every direction in the sky,

the leftover radiation from that primordial fire.

We can now map out the cosmos

to the farthest reaches of the observable universe.

We can see distant galaxies

whose light has taken billions of years to reach us.

So by looking at them, we are looking deep into the past.

We can watch how the expansion of the universe has slowed down

since that hot early phase 13.8 billion years ago.

We can see collisions of entire galaxies

and watch the bursts of star formation,

that result from the sudden conflagration of all that cosmic hydrogen.

And we can see that these collisions are happening less and less.

The expansion of the universe isn't slowing down anymore.

A few billion years ago, it started speeding up.

Distant galaxies are getting farther apart

faster and faster.

Star formation has slowed.

In fact, we can calculate exactly how much.

And when we do, we find something shocking.

Of all the stars that have ever been born or that ever will be,

around 90 percent have already come into being.

From now until the end of time,

the universe is working on just that last 10 percent.

The end of the universe is coming.

There are a few ways it could happen,

but the most likely is called the heat death,

and it's an agonizing, slow languishing of the cosmos.

Stars burn out and leave smoldering ash.

Galaxies become increasingly isolated in their own dim pools of light.

Particles decay.

Even black holes evaporate into the void.

Of course, we still have some time.

The heat death is so far in the future, we hardly have words to describe it.

Long past a billion years,

when the sun expands and boils off the oceans of the Earth.

Long past 100 billion years,

when we lose the ability to see distant galaxies

and that faint trace of Big Bang light.

Long after we are left alone in the darkness

watching the Milky Way fade.

It's OK to be sad about it,

even if it is trillions of years in the future.

No one wants to think about something they love coming to an end.

As disconnected as it may be to us here and now,

it is somehow more profound than personal death.

We have strategies for accepting the inevitability of that.

After all, we tell ourselves, something of us will live on.

Maybe it will be our great works.

Maybe it will be our children, carrying on our genetic material

or perhaps our basic outlook on life.

Maybe it will be some idea worth spreading.

Humanity might venture out into the stars and evolve and change,

but something of us will survive.

But if the universe ends,

at some point we have no legacy.

There will come a time when, in a very real sense,

our existence will not have mattered.

The slate will be wiped clean completely.

Why should we spend our lives

seeking answers to the ultimate questions of reality

if eventually there will be no one left to tell?

Why build a sandcastle when you can see that the tide is coming in?

I've asked a dozen other cosmologists

and they all had different answers.

To some, the death of the cosmos just seems right.

It's freeing to know that we are temporary.

"I very much like our blipness," one told me.

To others, the question itself motivates the search for some alternative theory.

There must be some way to carry on.

The slow fade to black just cannot be how our story ends.

One found comfort in the possibility of the multiverse.

"It's not all about us," he said.

Personally, I feel lucky.

Our cosmos existed for billions of years before us

and it will carry on long after we are gone.

For this brief moment, we are here.

We may be insignificant to the cosmos as a whole,

but we have an immense power to understand it,

to see the beginning,

to contemplate the end,

to look up into the sky

and see ourselves reflected in every tiny point of light.

There is a kind of luxury in the freedom to look beyond our own little lives

and contemplate the end of everything.

We, fragile, doomed humans

carry within us a sense of discovery and wonder.

It will persist as long as there are thinking beings in the cosmos.

And we can decide how to use it.

Thank you.