When I was a boy, my dad used to
pick me up after school.

I was about 11 years old,
in Geneva, Switzerland,

and he'd drive me across town

to the site of the Large Hadron Collider,
in Geneva,

which was called the European
Center for Nuclear Research, at the time.

It's where they discovered
the Higgs boson a few years ago.

There was a remarkable man there,
Rafael Carreras,

who used to give weekly lectures
called in French

'Science Pour Tous' which means
'Science for Everybody'.

There were people from all walks of life
who attended these lectures.

There were school boys like me, 
janitors at CERN, professors, housewives.

A whole mix of people were attending
that stuff who gave up their lunch hour.

They were also working people.

There were two things that struck me
about these lectures.

The first thing was that people were
doing this not for any personal benefit,

there was no credit, no remuneration,

but they were just doing it
because it interested them.

I thought this was rather wonderful
and sort of put a light bulb in my head

that maybe you could go through life doing
what interests you rather than

what doesn't interest you in order to,
then, do what interests you.

You could short-circuit things. 
(Laughter)

The other thing I liked is, Dr. Carreras
was always encouraging.

I'd often go
and ask him questions and so on.

He never looked down on me as a kid.

There weren't any stupid questions.

You could go and ask him anything

and there was always stuff to be learned

and I liked this environment so much,

I think it set me on a path
to ending up here

where I am a professional scientist
talking to you.

Even before then, 
my dad used to read me stories

from the 'Winnie the Pooh' books

and there's a picture here 
of Winnie the Pooh and Piglet

searching for a Heffalump.

A Heffalump's a very rare 
and unusual thing

that had almost, maybe never, been seen.

But they got circumstantial evidence here.

They' ve seen footprints in the snow

and this has encouraging them,

maybe if we continue work 
a little bit harder,

maybe we could find this thing.

So the basic difference betweeen me 
and Winnie the Pooh in this picture

is that he's looking down
and I look up for a living.

So, we scientists, in particular,

the subject of this talk is to look for
the first stars

and galaxies to form after the Big Bang.

They're rare and unusual objects.
We think they are very different

to the stars and galaxies
that we can see around us today.

But we think they are there.

We have circumstantial evidence
that makes us think

that they are there 
so the quest is worth following.

So I've told you these two anecdotes
maybe a bit from my life

in order to give the idea 
of a timeline also

that I sit here today looking in my past

as we all can towards when I was born,

and you can see significant events
that shaped your life.

What's remarkable is that we can do
the same thing for the Universe.

So the Universe originated in a Big Bang.

We don't know exactly what banged
or how it banged,

although, a couple of weeks ago,
we had some indications

if you followed the science news.

But we know when it banged
to amazing accuracy.

So, we know the Big Bang was
the creation of time and space.

Matter and light happened
14 billion years ago.

We know the exact number to 1% accuracy.

As I was bouncing back into my past
at the start of this talk,

we can do the same thing here in astronomy

because light travels at finite speed.

So when we look up at the sky,

we' re actually looking into the past.

And for most cases it's not so relevant.

In the case of the moon 
it's like 2 seconds.

When you see the moon, 
you see it as it was 2 seconds ago

because that's how long it takes light
to reach us from the moon.

Naked eye stars that you can see

if you go out in the desert 
away from the street

that may be a few thousand years.

You see them as if 
they were a few thousand years ago.

But the most distant object 
you can see with your naked eye

which is the Andromeda galaxy

pictured here seen through a telescope,

is actually 2.4 million years ago.

So the light has taken 2.4 million years
to reach you.

Even without the aid of the telescope
you can see this object.

If you wanted to know
what it looked like today,

you'd have to wait another 2.4 million years.

So, the history of Astronomy 
has really been the history of developing

telescopes and technology to be able 
to push further out into space

and see even more distant 
and remarkable things.

This is a picture of an object
known as a comet cluster,

many thousands of galaxies
like the Milky Way.

It's so far away that it's seen
250 million years ago, roughly speaking.

So 250 million years ago,

here there was a deep sea, 
a deep inland sea.

We know this because we see
the Kaibab limestones of Red Rock.

We see these also, just downstream
from Glen Canyon down at Lee's Ferry.

These tell us the idea of what 
was happening here was very different.

It wasn't a desert. It was an inland sea.

But we don't see the thing itself.

We have circumstantial evidence,
the rocks.

But here we're seeing the thing itself

as it was 250 million years ago.

So I've drawn sort of a timeline

on the slide we have today 
on the Big Bang.

The green arrow shows you
when the Earth formed.

So the Earth is a relatively recent
addition to the Universe.

It's only been there for a third
of the existence of the Universe.

For two thirds of the time 
our solar system wasn't even there.

So how far back can we actually look
with our technology?

I've drawn here a little red square
on the slide

which shows the field of view

of the best instrument that we built
to be able to do this --

you've certainly heard of it --
it's the Hubble Space Telescope.

The Hubble Space Telescope
has a very small field of view.

In other words, it takes
a very small picture of the sky at a time,

about 100th of the size of the moon.

If you want to picture that, it's like
coding a grain of sand at arm's length.

It's a very, very small part of the sky.

And scientists had the idea 
to try and probe back in time

would be to take a picture of the sky

but to take two weeks 
to observe one part of the sky.

This was a remarkable idea to look 
at a nondescript, not a part of the sky

we'd thought
it wasn't anything interesting,

but just to see what's out there.

What we found was remarkable.

Here's one of the most famous images
ever taken in astronomy.

It's a Hubble Ultra-Deep Field.

In an area the size of the grain of sand
held at arm's length,

you see ten thousand galaxies here.

They're not stars in our Milky Way.

They're separate individual galaxies,
like our Milky Way.

In this image, about ten of them
are seen as they were

13.3 billion years ago,

which is to say
the light started on this journey

long before the solar system ever formed.

For most of that journey,
the Sun and the Earth didn't exist.

You know, the Sun and the Earth formed
and then life evolved and so on,

we built telescopes and boom,
we capture this light.

It's utterly remarkable.

But those are not the first galaxies.

Remember, we are looking
for the first stars and galaxies.

This is one of the major
scientific adventures, I think,

of the 21st century

which is going to play out
in the next ten years.

So we sit here and we look
at this Hubble Deep Field.

How do we select then the ten galaxies,

the one in a thousand galaxies
that are the most distant.

It's so simple that I thought
I'd just tell you today.

What we do is not a technical description.

We take a picture at visible wavelengths
of the Hubble-Deep Field

and one at infrared wavelengths.

The galaxies which can be seen
in the infrared image,

but cannot be seen in the visible image,
those are the ones.

There's just a few of them,
there's just ten of them.

Those are the ones that are seen
13.3 billion years ago.

To summarize my story so far --

if I can get the next slide, there it is.

We sit here in the Milky Way
and we look further and further back

with more sophisticated telescopes.

And we look further and further 
back in time

13.3 billion years so far with the Hubble.

But we have another piece of information

which is the cosmic background radiation.

The cosmic background radiation
which is seen at radio wavelengths

tells us what was happening
in the Universe

only roughly half a million years 
after the Big Bang.

We know there was a time from the staff,

the outermost shell that's colored
green and yellow and blue there,

that there was a time when there were 
no stars and galaxies in the Universe.

That's what that tells us.

But it tells us another important thing,

which is that on its journey,
the slide on its way to us

was modified by stars and galaxies,

the first generation of stars and galaxies

that we haven't yet detected.

That's a sort of Heffalump effect.
The footprints.

We see the footprints
of the things we're looking for

but we haven't seen the thing itself yet.

So in order to find these things that
we're looking for,

we need to devise new tools.

The history of astronomy has been
the remarkable improvements

we've been added for 400 years
with the telescope.

Galileo's telescope 
had a lens about this big

and this is a next generation
of telescopes being built in Chile.

This is a European
Extremely Large Telescope --

running out of names for telescopes now. 
(Laughter)

But the mirror --

The mirror is about the size of this room

so it's a gigantic tool for looking back
into space ever further.

As you saw from before, 
we need visible and infrared light

in order to study these objects.

In the infrared, we' re building

what is the successor to the Hubble
Space Telescope

which is what's called
the James Webb Space Telescope.

This is just one sixth of it shown here.

So it's a gigantic instrument.

It's so big that it won't fit
into a rocket.

So they are going to have to fold it up
like insect wings or something,

put it in there, send it out into space,
take it out, unfold it

and then it's going to take what we hope

are the images 
of the first stars and galaxies.

It's also going to explore planets

and other things
that are of great interest to us.

So, what do we expect to find?

The way we do astronomy
is illustrated in this video here,

is astronomy and science 
is a constant dialogue, really,

between theories or our conjectures 
about the way things ought to be,

which is shown in the movie here,

and the way they actually are,
which is shown in the stills.

So in the movie here, 
you can see two galaxies,

like the Milky Way and Andromeda
that are on a collision.

This is a calculation done in a computer.

Once in a while, they freeze the movie

and because it's a computer simulation

you can view it any way you like,

and then they try and compare it,

to actual images of galaxies nearby

to see how good a job we have

at understanding interactions
between galaxies.

In the case of the most distant 
stars and galaxies,

we've only done half of this.

We have our conjectures,
but we don't have the observations.

So what can we expect to see?
How is this going to play out?

Based on the history of astronomy,

I think I can best tell it 
with an anecdote.

Howard Carter, when they discovered
Tutankhamun's tomb,

they were in a sort of narrow corridor

and he was the first to see the tomb
in modern times,

and he had a candle 
and in the flickering light he could see

this vast array of treasures of gold 
and statues of animals and things.

The others behind him -- 
he didn't say anything,

and they were like: 'What do you see?'

And he said, 'Wonderful things',
'Wonderful things'.

And I think that's what we can expect

in our science in the future.

But as well as learning about the Universe

which is going to be tremendously exciting,

I think, science teaches a lot about
our humanity, ourselves as human beings.

For those of you 
who don't know the Pooh story,

the punchline to this one is

they actually didn't find the tracks
of the Heffalump, unfortunately.

They were looking at
their own tracks in the snow.

But they learned something 
about themselves in this adventure

and about what they were.

We do this too, when we do science.

We learn our position in the Universe,
but we also learn about ourselves.

And the European Center for Nuclear Research
which has many --

several Nobel prizes 
have been awarded there.

I didn't tell you this far,
it was built really

out of the ashes of Europe after WWII.
Europe had been at war.

I am an immigrant from Europe.

For most of the 20th century
for reasons that weren't clear,

but all these countries, 
for religious, cultural, ethnic reasons

were at each other's throats.

And the idea is 
maybe there is another way.

What if we work together?

What if people from these countries
that had been at war

showed that by working together, 
overcoming their prejudice,

we can do good science?

And history of CERN has shown

that when you do this 
you can achieve wonderful things.

Wonderful things!

Thank you.

(Applause)