tend to spend a lot of our time focused on the future.

But just like people in every other profession with every other passion,

we're well served by remembering the lessons of history.

And lately, there's been one moment in history

that's really been bouncing around my brain quite a bit,

and I'm not referring to that one from a long time ago in a galaxy far far away.

I'm referring to something a little bit closer to home.

It is September, 1962.

President John F. Kennedy is addressing America

to tell them what he'd already told Congress a few months earlier,

which is that he believed

we should dedicate ourselves as a nation to the goal

of sending human beings to the moon and bringing them back safely

before the decade of the 1960's had ended.

Now if you remember a line from this speech,

it almost certainly goes like this, and I'm not going to do the accent

because my JFK really sounds more like Mayor Qiumby,

but you have to imagine. He says,

"We choose to go to the moon and do these other things in this decade

not because they are easy but because they are hard."

Now I wasn't in the audience that day, I wasn't alive on that day.

I like to think if I had been there and he'd said,

"We go to the moon not because it was easy but because it was hard,"

I would have said, "Really,

you want us to spend a decade and a hundred billion dollars

doing something just because it's hard?

That's the best explanation you can give?"

Our most charismatic and eloquent president,

that's the explanation he came up with?

But who am I to complain

because 2500 days later a half a billion of us

were watching live as Neil and Buzz

took those famous small steps and that giant leap.

It actually worked.

A president had told us to go somewhere by a certain deadline,

and we believed him and because we believed him,

we did it.

But I'll mention also, you know, along the way,

we showed the real reason why President Kennedy

and why congress wanted us to go.

It was not because it was hard

it was because by leaving boot prints and flags,

we could show the bad guys that our rockets were bigger than theirs.

But by the time the final Apollo crew

left the service of the moon in December 1972,

a decade after JFK gave that famous speech --

I'll note, by the way, only on the final mission did we actually take a scientist

-- by the time we left, we had spent the equivalent

of a 135 billion with a B, billion dollars in today's money

on these missions.

135 billion, to me that number is overwhelmingly large.

In fact, I'm so overwhelmed that I cannot put that number into context.

I don't exactly walk around with 135 billion dollars in my wallet.

I don't know what else you could do with that money.

I don't know. It's hard for me to say,

was it worth it unless you can compare it to something else.

So doing my homework in finding some other things

that we were spending money on at the same time,

or that we spend money on now,

when I can make that comparison,

that 135 billion dollar starts to look quite different.

If you ask me which was more valuable to the nation and to our species,

going to the moon or a year in Vietnam?

The answer to me is fairly clear.

I'm among the camp that thinks the Apollo program

is the greatest thing we, as a species, have ever done.

So, it's pretty easy; but nevertheless, it's important to ask this question,

"Was it worth it?"

You know, from Yuri Gagarin in April 1961 until today,

542 human beings have been in outer space.

And I can guarantee you that everyone of those 542,

plus all of the hard working men and women who have helped put them up there,

all the people who work on the great robots like Mars Curiosity,

like the hubble space telescope,

every single one of us has been asked at some point by a friend,

or by a loved one why,

why is it worth it? Why do we go to outer space?

Why is it worth spending even one dollar?

We live in a world so full of social injustice,

of problems, of poverty, and disease.

Why is it worth spending even one dollar up there,

when there are still so many problems down here?

People ask me that question all the time,

and I find something a little weird about it.

It's not weird that they asked me the question,

it's a really good question.

We need to ask that question we need to have a good answer to that question.

The weird thing to me is that when people ask me that question,

maybe it's because of the cultural memories of JFK in that famous speech,

they expect me to be able to answer that question in a sound bite,

or actually now in a tweet.

And they expect if they ask any person working in the space industry

that we will all give the same answer.

And if we can't express that answer in an elevator speech,

it means we lack conviction in our beliefs.

Now I'd like you to participate in a thought experiment with me.

Imagine right after you watch this talk,

you leave here and you go to the closest airport

and you park yourself at LAX for an hour,

and you ask everyone getting off a plane,

"Why did you choose to spend your money to come to Los Angeles?"

Would you ever expect them to all give the same answer?

Would you ever expect any of them to be able to sum up that answer

in a tweet or a sentence?

Would you expect if they came back again next month

that they would give the same answer?

Would you expect that even one of them would say, "I came here

because President Obama said I should be here by the end of the year?"

(Laughter)

Right, it's ridiculous for us to think that

because Los Angeles is a big wonderful diverse city with so many things to do,

and everyone on that plane should have a different reason.

Well, if you think Los Angeles is big,

you do not know the definition of big.

Space is pretty big.

Space is the closest thing that we can conceive up to the infinite.

I love this picture from the Hubble,

because every little one of those specs of confetti

is not a city, or a nation, or a continent, it's not a planet or a star,

it is a galaxy or a cluster of galaxies.

Our universe is enormous, it is mind-bogglingly big and diverse.

Our reasons for going there are correspondingly large.

(Applause)

We've become, thanks to the internet, a culture of Buzzfeed listicles,

and a "Top 10 Reasons Why We Go To Space."

I don't think you can give the top 10 reasons why we go to space,

because after all there are seven billions of us

and God knows, how many planets and stars and reasons out there.

You just can't summarize it all.

I think the only question that makes sense is,

"What do you think it's worth it for you to spend your time and your money?

Whether you're a taxpayer, and if you're a US taxpayer,

you contribute about one dollar a week to the Nasa budget,

whether you are an innovator and entrepreneur in the space community,

whether you're an engineer who decided to take that job at Nasa

instead of going into the biomedical field,

or any of the number of other worthy fields?

Why did you choose to do that?"

Well, I have a lot of reasons, not just one, and I'm only one person.

My reasons to go to space don't start with Tang and Velcro.

(Laughter)

Nasa has a million wonderful spinoffs and there are things

that have been discovered in the pursuit of space exploration that made my life

and all your lives better every day, but of course you could say,

"Well, if we had spent 135 billion dollars on some other scientific project

we would have a lot of the same spinoffs as well."

So that's not my reason, even though that's important.

If I'm being really honest, the reason I fell in love with space as a kid

and I'm just as in love with it today is because going to space

really looks like fun. It looks like fun!

(Applause)

If you've ever had the chance to experience weightlessness,

you will want to do it more.

When Ed White, pictured here,

became the first American to walk in space,

he didn't want to go back into his capsule.

When mission control finally talked him back in, he said,

"This is the saddest moment of my life."

I can understand that. How couldn't it be?

How can you look at that picture or this picture?

Whether it's from the 60's, or from today,

how can you look at that picture of Tracy Caldwell Dyson

just chilling out on the International Space Station,

and think anything other than, "God, what I wouldn't give to be there?

To float around like that?

To see that view. That view. This kind of view."

The view that was brought back to us from the Apollo astronauts,

the views that we continue to see today.

I see this picture and to me it's beautiful,

but it's more than that, it's important.

Other have argued, and I believe that you can draw

a very straight line from this picture to a fundamental change

in the way that we, as humans, think about ourselves,

and our role in the universe. After all, how can you look at a picture like that?

How can you see that with your own eyes

and not realize we live on a small world?

That we need to be good stewards of our environment.

That we need to be good neighbors to the other seven billion people

trapped here on this pale blue dot.

We all know -- (Applause) -- at some intellectual level

that the borders we draw on maps are usually imaginary lines,

but seeing it with your own eyes means something very different.

And because of photographs like this, because we send astronauts,

and we send satellites and telescopes,

we now have multiple generations of children

who are weaned on images like this,

because now you can't turn on your smartphone or your laptop

without seeing a picture just like this one or like this one.

Because we have space, "the ultimate high ground,"

we are able not just to look outwards

but to look inwards back on our own planet

and to recognize threats as they're coming our way.

This is typhoon Haiyan just two weeks ago

bearing down on the Philippines. You want to ask me this question,

"Why is it worth spending even one dollar to explore space

when there's suffering and pain and loss here on earth?"

Look at the pictures from the Philippines.

Look at the photographs from superstorm Sandy,

or from Hurricane Katrina, or any of a number of other storms.

You will see suffering. You will see pain, loss, and devastation.

What you will not see is all the lives that were spared and the damage

that was averted, because we knew these things were coming.

Because our eyes in the sky, whether they're robotic or humans,

were telling us, "Hey everybody, look out, you need to do something about this."

And, of course, as we explore more, we have learned

that those threats don't just come from within, they can come from with-out.

You saw the Russian dash cam videos of the meteorites

coming down in February of this year.

An asteroid not much bigger than that could wipe out a city.

An asteroid the size of the one pictured here could wipe out a country,

not much bigger than that could wipe out civilization as we know it.

In the aerospace industry we have an old joke that says

that asteroids are just Mother Nature's Way of saying,

"So, how's that space program coming?'" (Laughter)

Because we dare to -- (Applause)

Because we and the generations just before us have dared to explore,

we had this unique opportunity throughout all of life as we know it

to maybe do something about that. To see our doom coming, to say,