[MUSIC PLAYING]
Thank you.
So it's great to be
back at the RI again.
I spoke here last year and it's
such a fantastic auditorium.
I'm a professor of astrophysics
at the University of Sydney,
and as was mentioned there,
I'm a cosmologist, right.
My job is to try and
understand the forces that
have shaped the evolution
of the Universe,
from a time when the
Universe was basically
formless to the rich
structure of the Universe
that we see around us today.
So what I want to do
tonight is basically take us
all in a bit of a journey.
What we want to do
is not take a journey
through space but a
journey through time.
And we want to look
backwards first to see
how our Universe evolved from
its birth in the Big Bang
to the Universe with stars, and
planets, and galaxies today.
And then we want to turn around
and run the Universe forward
and ask what fate
holds for the Universe.
Just what is going to
happen as this Universe gets
older and older?
So every journey starts
with a single step,
and before we take a step
backwards into the past or step
forwards into the
future, I think
it's important to
understand where we are,
where we are today.
Just what kind of
Universe do we live in?
And, of course, the
starting point for that
is where are we now?
And we find ourselves
on the surface
of a small, rocky planet.
And it's a very special planet.
It's an extraordinary
planet, because out
of the thousands
of planets we know,
that we've discovered
in the Universe,
and the trillions
of planets we think
are out there in the
observable Universe,
this is the only
one where we have
complete and utter evidence that
there is life on this planet.
Sometimes it's a bit difficult
to see intelligent life
on this planet, but there
is life on this planet.
OK.
Now, I'm going to touch
upon life in the Universe
as we go out into the
future a little bit.
So it's important to
try and understand
what we mean when we say life.
And it turns out that defining
life is incredibly difficult.
When you get down to the
details, how you define
whether what's alive
and what's dead,
people set up rules and say,
this is my dividing line.
This is the living stuff,
that's the dead stuff.
Or this stuff on the dead side,
which just looks a bit alive.
And that happens all the time.
And there are arguments about
whether viruses are alive.
Or the prions are
alive, these things
even smaller than viruses.
And so defining life, that
would take another lecture
and probably a
few more lectures,
and we would be here until
almost the end of the Universe
trying to define what life is.
But what I'm going to touch
upon is an aspect of life
which, in my opinion, I think
is one of the key things
that life does if we're
going to define something
as a living organism.
And that's to do with energy.
All life processes energy.
So what we have in
this picture here,
we have a lovely sunflower.
That sunflower has
captured sunlight,
and that sunlight has
been stored as energy
in the chemical bonds
inside the plant.
Creatures come along
and they eat the plant,
and they can use that energy
to run their own chemical
processes in their body.
And, similarly, we
could eat the plants
or we could eat the animals
that ate the plants.
And so there's just a
continuous progression
whereby we use and
process energy,
and that is one of the defining
characteristics of life.
All life processes
energy of some sort.
And that energy not only
drives the chemical reactions
in your body, but it also drives
the sort of mental reactions
in your mind when
you think, right.
We all know that when
you have a sugar low,
it's very hard to
think about anything.
You need energy
to run your brain.
In fact, it uses up
a very large amount
of the energy that you take in.
So there's actually
a very strong link
between flows of energy and
processing of information.
And any time you
run your computer
and your computer is doing
very difficult calculations,
or updating Facebook,
or something,
it's processing
information, and you
can feel the heat that's
generated by that information
being processed.
So if any living creature is
going to be sentient and know
about its environment
and react to that,
it's going to need to have an
energy flow to drive that sort
of behaviour.
Now, the ultimate source of
energy on the Earth of course
is the Sun.
In the middle of the Sun,
every second 11 million tonnes
of hydrogen get
turned into helium.
That releases energy,
which takes 100,000 years
to percolate through the
Sun, and then 8 minutes
to get from the
surface of the Sun
to the Earth, where it's
absorbed by this sunflower,
or it lands on the
pavement outside in London
and makes the place even hotter.
So all life on Earth
exists because we
have a vast reservoir of
energy right next door to us
in the Universe.
And we can use that
energy, and that
has driven life and evolution
up until the present day.
Take away that source of
energy, you have no life.
What we'll be seeing
is that energy
will come to play a
critical role in what life
can do when we look at the
far future of the Universe.
It becomes the scarce resource.
It's the thing
that any life that
exists in the distant
future Universe
is going to need to seek if
it's going to continue to live.
But let's just try and remember
our place in the Universe.
As I said, we're on the
surface of this rocky planet.
Energy is given to
us by the Sun, which
is a very typical dwarf star.
And our Sun is not
alone in the universe,
but the Sun actually occupies
a small patch of the Universe
with roughly 300 billion
other suns in an object which
is known as the Milky Way.
When we look out
into the Universe,
we see that there are
possibly a hundred billion
to a trillion other
galaxies out there.
So there's a huge number of
stars, huge number of galaxies,
huge number of potential places
where there could be life.
But we have no idea what
the frequency of life
is in the Universe.
Life could be very common, or
life could be extremely rare.
And all of our
observational evidence
is quite consistent
with this being
the only place in
the Universe where
there is life at the moment.
So I said, this is
a special planet.
So before we play the game
of looking into the future,
let's work out how we understand
what happened in the past.
And what we know
is that people have
looked at the skies
for thousands of years
and you see patterns
of stars on the sky.
And people have
generally invented
stories of heroes,
and gods, and legends
to explain the various
patterns that we see.
For us here at
the RI, of course,
the important thing is
not just the stories
that people have
told but how they
came to apply science
to understanding
the evolution of the Universe.
And this all
happened, of course,
during the time of the
birth of modern science.
And I'll just pop
up this guy here.
This, of course, is probably
Britain's most famous
scientist, second famous if
you consider Stephen Hawking
as well.
But this is Isaac
Newton, who in my mind
should be Britain's
most famous scientist.
Isaac Newton was
around at the time
when there was just a
changing viewpoint on how
we understand the Universe.
And I like this picture.
This picture was taken off the
back of the old pound note.
There's people in this
room who clearly have never
seen an old pound note.
You're probably too young.
But in the old days there
used to be a pound note.
On the back of it was this
picture of Isaac Newton.
And I like this
picture because it's
a picture of Isaac Newton
with his telescope.
And he observed the Universe.
He used his telescope to
see what was going on.
Now, he was not the first
to look at the heavens.
It's reported that Galileo
was the first to look
at the heavens and see, when he
looked at the planet Jupiter,
that Jupiter had
companions, that there
were moons orbiting Jupiter.
And that led to
this general idea
that there must be some sort
of order to the heavens,
and then people wondering
whether the order
in the heavens is similar to
the order down here on Earth.
And if I understand how
things behave here on Earth,
maybe that will
tell me how things
are behaving in the heavens.
And so what you
start to do is you
start to dispel the
need for gods and heroes
in describing what's
going on in the Universe,
but what you want are
laws of science that
tell you how things behave.
Now, the other reason
that I like this picture
is that in Newton's lap there is
his book, the Principia, where
essentially he lay down
the key ideas which
became classical mechanics,
how things react to forces.
But also, in there he
described the law of gravity.
And the picture that we
have in the background there
is sort of Newton's description
of how gravity works
in basically holding
the Earth in its orbit
as it travels around the Sun.
And, of course, Newton's great
insight was to realise that
the force that takes an apple
and pulls it from the tree
and pulls it to the ground is
exactly the same force that
holds the Moon in its
orbit around the Earth,
the Earth in its
orbit around the Sun,
and Jupiter's moons in
their orbit around Jupiter.
So you could write down
mathematical equations
and you could make predictions.
You could predict
where Jupiter's moons
are going to be
because they are just
obeying the laws of science.
No need to introduce any gods
or mythical beings anywhere
because it's all there
in the equations.
Now, some people
don't like that.
That leads to a very
sterile universe of course,
where everything
is just governed
by mathematical equations.
But it at least means
it's predictable.
We know where things
are going to be.
Now, in the 400 years or
so since we had Newton,
the only thing that's changed
is that we've gotten deeper
into our physical laws.
We understand the
physical laws that
govern the Universe
in a lot more detail,
and we've peered more
deeply into the Universe.
And what we've done is
developed new telescopes
that can see further and further
out into the distant cosmos.
And this picture here,
this is a telescope
that's currently
being constructed
in the southern hemisphere.
This is the Square
Kilometre Array
which is being built in
South Africa and Australia.
It will be a radio telescopes,
so it can only see radio waves.
And it will basically
be a collecting area
of 1 square Kilometre.
So we'll be able to see some
of the faintest things that
are out there in the Universe.
But, as well as the
Square Kilometre Array,
we have lots of giant
optical telescopes.
You have telescopes
in space that
look at x-rays and
gamma rays, and look
at microwaves, et cetera.
And what they've
revealed is a universe
which is, in my humble
opinion, being a cosmologist,
quite exciting.
So what we've got
here, we have a picture
that was made by
the WMAP consortium.
WMAP is just a telescope
that's in space, the Wilkinson
Microwave Anisotropy Probe.
Its job was to look more
deeply into the universe
than any other telescopes.
But what we've got here is a
picture of our entire Universe
as we understand it, both
in terms of what we can see
and in terms of what
we can understand
in terms of the physics that's
going on in the Universe.
Now, because light travels
at a finite speed, when
you look at more and
more distant objects,
you're looking further
and further back in time.
And what we have is a picture of
our Universe from today as far
back as we can see,
and what we can see
is that the Universe has changed
and evolved over its lifetime.
The first important thing is
to realise that our Universe
hasn't been around forever.
The Universe appears to have
been born in an event now known
as the Big Bang that occurred
roughly 14 billion years ago.
So our Universe
has a finite age.
But looking back, we see
that the Universe in the past
was different to
the Universe today.
So today around us we see
all these stars and galaxies.
And as we look back in the past,
we also see stars and galaxies
but they're different
to the ones today.
They're less formed.
And as we push back further
and further, we get to a point
where there were
no galaxies at all.
And we can push
back even further
and we run into the very
start of the Universe.
So in terms of the
Universe's evolution,
you can go from left to right.
At this side, you
have the Big Bang.
The Universe was
filled with material
all smoothly distributed.
Then the laws of physics acted
over roughly 14 billion years
to give us the Universe
that we see today.
And so there are a
number of key features
that people like to talk about.
The very birth itself,
which is something
that we do not understand.
We do not yet have
the laws of physics
to understand the very
birth of the Universe.
But after that, the
evolution of the Universe
through this rapid expansion
known as inflation,
through the overall evolution of
matter into stars and galaxies,
that all seems to be
described very accurately
by the laws of physics.
So, in fact, one of
the things that we
like to do-- it's
actually a very
big part of modern
astrophysics--
is we like to build
our own universes.
And I have PhD
students working for me
that, they generate
universes before breakfast.
Well, generally not
because none of them
are ever up before
breakfast, right.
So early afternoon they'll
generate a universe.
So what do I mean by that?
What do I mean by
generate a universe?
Well, as I said, we think
all of the processes
underway in the Universe
are just governed
by the laws of science.
So if I take my laws of
science, my laws of physics,
my law of how gravity
works, how gases work,
how nuclear physics works, et
cetera, et cetera, et cetera,
and I translate those
equations into computer code,
and I give the equations
to a computer and say
to the computer solve
the equations for me--
because that's what
computers are good at--
I can actually generate
a synthetic universe.
And so in the next
sort of animation,
I'm going to show you
the results of one
of the big simulations
of the Universe
that was done by a
group called Illustris.
Essentially, what
you do is you just
say I'm going to take a
big volume of the Universe.
This volume is
billions of light years
across, much bigger
than our own galaxy.
I'm going to put matter in
there, nice and smoothly
distributed like it
was after the Big Bang.
And then I'm going
to hit Go and you
can solve all of the
difficult equations,
and you can tell me what
the Universe looks like.
So one of the best things
about giving astronomy talks,
you can just put on the
movies and you can dip out,
have a cup of coffee.
Come back when the
movie ends and just say,
wasn't that lovely?
So what we're seeing
here, this is matter
moving in the early Universe.
So it was originally
smoothly distributed.
Gravity started acting and
pulling matter together.
And the matter just doesn't
fall into one big lump,
but it falls into
several lumps connected
by this structure which is
known as the cosmic web.
Inside these lumps,
gas can pool together,
and when that gas pools,
it can form stars.
So where you get
these big lumps,
that's where you
form your galaxies.
So inside these galaxies
we have stars burning away.
But stars evolve over time,
and eventually the giant stars,
they basically run out of
fuel and then they explode.
And hopefully we should have
an explosion any time now.
There we are.
Right on cue.
What you've got
there is a giant star
that is being burning elements
in its core-- hydrogen
to helium, helium
into carbon, carbon
into oxygen, da da da da.
All of those elements are caught
up in the heart of the star.
But for life, having those
elements in the heart of a star
is pretty pointless.
What you need them is
spread out through the rest
of the intergalactic medium--
or interstellar medium,
I should say--
and for that material to be
recycled in the next generation
of stars.
So that's what happens
when massive stars explode.
These stars explode and they
spit out the heavy elements
that are needed for life.
So it's kind of sobering
to think about this,
that you look at yourself
and you think, this is me.
I am [MUMBLES]
years old, but I'm
made of water, mostly water.
The hydrogen in that
water, that hydrogen
was formed in the Big Bang.
That hydrogen is 14
billion years old.
The oxygen in the
water, that oxygen
was formed in the
heart of a big star.
And, in fact, the
elements that make up me
have probably been through
the hearts of several stars
through several generations
of being formed,
material spat out,
recycled, being spat out,
and being recycled.
And the one that I
always like to mention
is that elements like this--
I was told by the
jeweller it's gold.
It might be.
But gold.
Stars don't create
gold when stars burn.
Gold is only created
when stars die.
That gives you the conditions
that can squeeze atoms together
so hard to give you gold.
So I said, if you want
to be romantic then
you should say that a star had
to die to give us this ring.
But we are implicitly tied
through that evolution
of stars.
There's no way we could have
had life in the early Universe
with just hydrogen and helium.
There's just not the
complexity there to have life.
So what we have got of course is
we've got our picture of today.
This is today.
This is a lovely
picture taken in Chile.
This is the VLT, the
Very Large Telescope.
We are not very imaginative
in naming telescopes.
The ELT is coming--
Extremely Large Telescope.
I kid you not.
There's also OWL, which is
Overwhelmingly Large telescope.
We should spend more time
when think of these names.
But anyway, the VLT exists.
It's in Chile.
It's four 8-metre telescopes.
All the good
telescopes in the world
are now in Chile because they've
got some of the clearest skies
and you can get up very high.
And this is a beautiful view of
the centre of our own Milky Way
galaxy.
So if we were in
Chile, your eyes
do not see quite as good
as this but the view
is quite spectacular.
But we find ourselves on
a rocky planet orbiting
a fairly typical smallish star
in a reasonably big galaxy,
which is one of many
hundreds of billions
or trillions of other
galaxies in the Universe.
Now, one of the
issues about when
you think about evolution--
let's go back to the
evolution of humans--
is that we often
make the mistake,
is that here we are,
here we are now,
and therefore we are the
pinnacle of evolution.
This must be the end point.
How can it get better than this?
Right?
But of course we're wrong.
Humans are still evolving,
still changing all the time.
Evolution hasn't stopped
because we've suddenly
discovered the iPhone.
We are still evolving.
And there are
different pressures
on how things evolve but
we are still evolving.
And it's the same
with the Universe.
You might think, well, this
planet is quite comfortable
and this Universe looks kind
of pretty and photogenic.
Maybe this is the
pinnacle of the Universe.
This is the way that it's
always going to be from now on.
How can it get any better?
Unfortunately, this is not
the pinnacle of the Universe.
And at some level this is
the start of a long decline.
So on that happy note, let's
now turn the picture around
and start looking at the future.
Now, in understanding the
future history of the Universe,
we have some
limitations that we're
going to have to acknowledge.
Studying the Universe's
evolution from the Big Bang
to now, you can have
a telescope and you
can see what's happened
in the Universe
to guide you in what
processes were important.
But unfortunately, we
don't have any telescopes
that can receive
light from the future.
It would be beautiful to see
what the future Universe is
going to do because that would
help you make a prediction
because you can see it.
So we don't.
So at some level we're
working in the dark.
We're going to make
predictions, and there
will be some level
of uncertainty
because we don't know everything
about our current state
of the Universe perfectly.
But there's a bigger problem,
and the bigger problem
is that we don't know our
laws of physics perfectly.
We know that we have some
very good laws of physics.
We have quantum mechanics.
If your iPhone wants to work,
it relies on quantum mechanics.
We know that to a very
high degree of accuracy.
We also have a really good
description of gravity
given to us by Einstein.
Again, GPS works.
It gets you down to a centimetre
on the surface of the Earth.
You need to worry about
Einstein's theory of gravity
to make GPS work.
The only problem that
we have is that, when
we have conditions where we
have to worry about quantum
mechanics and gravity
together, they just do not
fit together mathematically.
So there will be places
where we go into the future
that this uncertainty of
how these sort of mesh
together are going
to cause problems.
So as we go out into
the far future Universe,
we're going to get a
bit more speculative,
and I'll try and flash a
speculation metre as we go.
But nearby times, pretty good.
Distant times, things are going
to get a little more ropy.
So what's the first thing
that's going to happen?
So what we're going to do is
we're going to go forward.
And we'll go forward
in steps, but the steps
will get bigger, because
the Universe will
have different epochs
where things are important
and they tend to be spaced out
at larger and larger steps.
All we're going to worry
about at the moment
are the next few billion years.
So as was mentioned, Brexit
might be solved in that time
scale or it might not.
But what's going to happen?
Well, the first thing that
we need to think about
is essentially the end
of our Milky Way galaxy.
Now, again, look at
that lovely picture.
In a few billion
years it will be gone.
So what do I mean?
Well, here's our
Milky Way galaxy.
It's a spiral galaxy.
There's a bulge in the middle.
Stars going around the outside.
Our Sun is one of those
stars going around outside.
The Sun takes 250 million
years to do one orbit around
the centre of the Milky Way.
The problem is the Milky Way
is not alone in the universe.
It inhabits this
patch of the universe
with two other big galaxies.
One of them is called
M33 or Triangulum.
It's a tenth the mass
of the Milky Way.
We don't care.
The other one,
M31, is Andromeda,
which is about the same
size as the Milky Way.
And Andromeda is approaching
us at half a million kilometres
per hour, which, if we
do the maths quickly,
which says in about 4 billion
years it will be here.
So what's going to happen is
that Andromeda and the Milky
Way are going to collide.
So you saw there, that
was the initial collision.
Stars started to get ripped off.
So gravity pulls the stars,
starts to fling them outwards.
Now, the Sun might be
one of those stars that
ends up being thrown out
of the Milky Way galaxy.
So the collision
is just starting.
Now, before I proceed,
I should point out
I've got a little
time scale up there,
and I've tried to use words
to describe the times.
So a billion years,
that makes sense.
We all know what a billion is.
We all know what the national
debt is, et cetera, et cetera
et cetera.
So we can understand trillions.
But we're going to have
to go to bigger numbers.
So there's scientific notation.
5 times 10 to the 9 years.
All that means is 5
followed by nine zeros.
That's 5 billion.
So you will see numbers
to the power of something.
Just add that many zeros
on to the end, and just
say, wow, that's a lot of time.
So we had this
initial collision.
So if you saw on that
collision, the two galaxies
approached each other,
some stars got thrown off,
but then they separated.
So it's going to get
kind of exciting.
Why?
Because in the collision, the
Milky Way galaxy gets shaken.
It gets vigorously shaken by the
Andromeda Galaxy coming close.
And what that shaking
does is it causes
gas clouds inside the
Milky Way to collapse.
Now, that gas is the stuff
that gives you lots of stars.
But if you shake it and make it
all collapse at the same time,
then what happens is you produce
lots of very massive stars,
very giant stars.
So massive stars are hot.
They glow blue.
And so for a little
while our Universe,
our local patch of
the Universe is going
to look like a Christmas tree.
Our sky will be
completely filled
with these hot blue
stars glowing away.
But the collision isn't over.
Gravity started doing its thing.
Galaxies will come
back together and they
will smack each other again.
And notice that as they smack,
they get closer and closer.
They're losing energy because
stars are being thrown out.
But they are now
merging together.
The other thing that happens
is that some of that gas,
instead of getting
turned into stars,
swirls down into the centre
of the resultant galaxy
that's formed from the Milky
Way merging with Andromeda.
I'm going to have
apologise in advance.
This object is
known as Milkomeda.
I hate the name with a passion.
I have to use it.
Sorry.
It's part of my
union card, I think.
So there's going to be a
big black hole in the centre
of this remnant galaxy.
Gas is going to go and fall
in towards that black hole.
And that gas, as
it falls in, starts
to swirl around and crash
into other bits of gas
and get very hot.
So the centre of this Milkomeda
or Milkdromeda galaxy will
start to glow.
It will glow very,
very brightly.
So we will not only
have this Christmas tree
of bright blue stars
across the sky.
We will also have this
very active region
around the black hole glowing
brightly and shooting out
matter.
Here you can see there's a
big jet of matter coming out.
So that's all very exciting.
So that would be nice to see.
I'd like to hang around
for a few billion years
to see this collision.
But there's a problem.
And the problem is
that it's all going
to be over way too quickly.
What do I mean by that?
Well, the massive stars that
we have in the Milky Way,
they are James Dean stars.
Some people know
who James Dean was?
Live fast, die young.
Amy Whitehouse.
Other than that, my cultural
references are out the window,
I'm afraid.
So giant stars live
fast, die young.
So they burn for
10 million years,
and then, bang, they're gone.
So that Christmas tree
effect will go away.
Similarly, that gas which is
swishing around in the middle,
well, that eventually gets
eaten up by the black hole.
So the active galaxy, the part
which glows really brightly,
that goes away.
And what we're left with is--
the rest of the crash
is really boring.
The two beautiful spiral
galaxies, Andromeda
and the Milky Way, which
were there at the start
are now completely gone.
We are left with
this amorphous blob
with a rather horrible name.
So that's kind of sad.
One of the nice things
about being an astronomer
is looking up at the sky
and seeing that structure
of the Milky Way.
In this future galaxy
after the collision,
either we will be
inside and we'll just
have a uniform spread of
stars all over the sky,
or we'll be outside
from being spat out
and we're looking back
at an amorphous blob.
But there's more
things to worry about.
So now we've moved on.
We're now getting to roughly 7
billion years into the future.
As I mentioned, these
galaxies collide,
but one thing is
kind of interesting,
is that stars are actually
very small compared
to the separation between them.
So you're going to take
200 billion stars, 200
billion stars,
smash them together,
and not one star will
collide with another star.
So our Sun will
survive the collision.
The Sun will sail past
all the other stars.
I said it might end up
somewhere interesting,
and it might end up
somewhere not so interesting.
But we're now getting towards 7
billion years into the future.
The problem is that the sun is
currently 5 billion years old.
It was formed 5
billion years ago.
And what I mean by the
Sun is 5 billion years,
I mean for 5 billion years the
Sun has been turning hydrogen
into helium at the
core of the Sun.
And we know how much
hydrogen there is in the Sun,
and so we can estimate
how long the Sun has
got until it exhausts all of
its hydrogen. And it's roughly 5
to 6 billion years.
So while the Sun might
survive this collision,
it's going to run out
of its hydrogen fuel.
Now that's, I've said,
the death of the Sun.
It's not quite the death.
The Sun doesn't die
nice and quietly.
When the sun runs
out of hydrogen,
it sort of rearranges
its internal pieces
and tries to start burning
helium into heavier
elements rather than hydrogen.
That causes the sun to swell.
It swells and cools.
So it goes from being
a typical yellow star
into being a red giant.
But it continues to swell
and swell and swell.
It eats Mercury.
It eats Venus.
It gets brighter and brighter.
And by this point, the
energy flow from the sun
strips the atmosphere off the
Earth, boils away the ocean,
and completely
sterilises the surface.
This is reasonably unavoidable.
This is what's going to
happen when the Sun runs out
of hydrogen.
So, eventually, we're
not quite sure how big
the Sun is going to get.
There are some that think
that the Sun is actually
going to get larger than
the orbit of the Earth
and completely
swallow the Earth,
so the Earth will be completely
and utterly obliterated.
And the Sun might even swell
out towards the orbit of Mars.
After that point,
the Sun then goes
through a rather sort of
middle age crisis, whereby
it sort of shrinks
and grows, and shrinks
and-- we all know what happens
when you get to middle age,
right?
Shrinks and grows.
And then, eventually, the Sun
becomes unstable and it blows
off its outer layers
and the Sun is gone.
Now, if this is the only
planet in the Universe
where there is life and
we haven't gotten off
the surface by then,
then that's the end
of life in the Universe.
The Earth will not survive.
Now, there's 7
billion years to go,
so we sort of hope,
on that time scale,
that we can put our
differences between us
and work together
and think maybe it
would be a good idea
to get off the planet
before the Sun
completely evaporates it.
It may take a few
billion years of arguing
to get to that point, but
this is going to be necessary.
If life is going to continue,
it cannot hang around a single
star, because stars just
don't live for long enough.
Life is going to have to move
from one star to the other.
And so what we're going to have,
hopefully, fingers crossed,
is that life will--
humans or descendants of humans,
or maybe the cockroaches,
will develop
technology that allows
them to travel to other stars.
That's the only way
that life is going
to be able to protect itself
as the universe evolves.
Now, the technology required
for travelling to stars is hard.
We know we can't do
it at the moment.
We just do not have
the technology.
But, as I said, there's
a lot of time between now
and a few billion years, so
hopefully that kind of thing
can be developed.
But you might sort
of think, well,
if I'm going to travel
between the individual stars
in our own Milky Way galaxy,
then how about I go large?
How about, instead of just
roaming the stars around here,
I think of jumping
between galaxies?
So I've got billions of
galaxies in the Universe.
They're quite a
large distance away,
but, again, as
technology evolves
it might become possible that
we could travel from one galaxy
to the next galaxy.
And the more life
spreads, of course,
the more chance it
has of surviving
into the future Universe.
The big problem is that,
if you're going to do that,
you better start
relatively nowish.
Why?
Well, because it's not
going to be possible when
we get up to the next steps.
So now we're out to
about 100 billion years.
Why is that?
Well, as I mentioned
at the start,
what we've realised is that
our Universe today is dominated
by this strange stuff that we
don't really know what it is
called dark energy.
We know it exists because we see
the expansion of the Universe
accelerating.
So something is there
that's causing the Universe
to do that, but we
don't know what it is.
But it's dominating.
70% of all energy
in the universe
appears to be in
this dark energy.
And as time goes on that
percentage increases,
until very close to--
not too far into the future it's
going to be effectively 100%.
What that does is drive the
expansion faster and faster
and faster, which means that
distant objects move away
from us faster and faster.
Until eventually they're moving
so fast that any light signals
that they try to send
us never reach here
because the Universe
is expanding
so quickly in between the
distant object and us.
And that means that,
basically, by the time
we get to roughly
100 billion years,
then what's going to happen
is that our distant Universe
is going to start
to fade from view.
So, firstly, the most
distant galaxies we see
will basically freeze and
then become invisible,
and then the more
nearby galaxies,
until at 100 billion years,
the only thing we can see
are stars near us in
our leftover galaxy.
Everything else is now
accelerating away from us
so fast that we will
never see it again.
So any species or
civilization that
arises in this time
in the Universe
will never come
to the conclusion
that we live in an
expanding universe.
Why?
Well, they'll take
their telescopes,
they'll look at the sky and
they'll say what do we see?
Oh, we just see stars
in the nearby universe
and everything else
is inky blackness.
No evidence that
there's expansion.
There will be no
future Edwin Hubble
who measures the
redshift of galaxies
because there will be
no galaxies to see.
That also means that
life, then, is isolated.
It's now stuck here on
this galaxy, Milkomeda,
or any other
galaxies, but now they
are separated that
they will never ever
have contact ever again.
So life is going to have to
deal with what's going on here
if it's going to
survive into the longer
distant future of the Universe.
So what's next?
So we're going to now
take another big jump.
We're going to move
from 100 billion years
out to roughly 10
trillion years.
So the Universe
sits there evolving.
What we're going
to see now is we're
going to see that remnant galaxy
of the Milky Way and Andromeda
as they merged.
And, as I said, when
they merge, they
create lots of hot
blue stars that
live for a very short
time before exploding.
So all the blue stars
live for 10 million years
and then explode,
and they're gone.
Then stars like our Sun
reach the end of their lives.
So they too are getting
older and older and they die.
Now, unlike the Milky
Way, which has lots of gas
and can produce new stars,
this leftover object,
that used up all its
gas in that one burst
during the interaction.
So there's no new stars born.
And all you have is
this continuous death
of stars as they get
older and older and older.
And, in fact, an interesting
relationship with stars
is that the bigger the
star, the shorter it lives.
So the big stars live
for a few million years.
Stars the size of the Sun
live for a few billion years.
And tiny stars, these
little red dwarf
stars, they live for
trillions of years.
So what we're going to have is
the stars continuously dying,
and our patch of the
Universe is going
to become redder and redder,
as these little faint
red dwarf stars are
the only things left.
They too, of course,
will be getting older
and the galaxy will
continuously fade over time.
Now, you might say, well, OK.
This object that collided,
it produced many hundreds
of billions of stars
all moving around.
You've still got lots
of these red dwarfs.
You think, oh, that's
not so bad for life.
But red dwarfs are
not friendly stars.
What we've come to realise
quite recently is that red dwarf
stars, even though they look
nice, and quiet, and sedate,
are actually quite
violent and active places.
These stars, instead of just
sitting there and nicely
putting our energy over
their trillions of years,
what they do is they often
have big solar flares.
They have big bursts of energy.
And it's thought that
those bursts of energy
continuously sterilise
any planets that
are orbiting that star.
So it's going to be
very hard for life
to evolve afresh on planets
orbiting red dwarf stars.
But if life has
survived from our period
into this distant
part of the Universe,
they're going to have to
rely on the energy that's
generated by these red dwarf
stars to keep them going.
Now, as I mentioned,
these stars are small.
These stars are
faint, and so they
don't put out a lot
of energy compared
to a star like the Sun.
So any life in the future
part of the Universe
is going to have to
work very hard to become
very efficient at collecting
energy and using that energy.
And there's been a
number of suggestions
on what you would do.
I'll just put up this picture
because I think it's pretty.
This is a Dyson sphere.
Now, a Dyson sphere
is a simple idea.
You have a future
civilization that can
do lots of difficult things.
We won't talk about
how they do it.
We'll just pretend
that they can.
And they find a
star and they want
to be very efficient in
using the energy of the star,
so instead of
sitting on a planet,
you build a big sort of
enclosure around the star.
That way, you capture
all of the starlight.
You can use that starlight
to run your life,
and you can expend waste
heat out into the universe.
So that's essentially what
you would probably want
to do with a red dwarf star.
You have a red dwarf star.
It's got a very little
amount of energy,
but if you can try and
capture all of that energy
in one of these
Dyson spheres then
maybe you can continue to
power life into the future.
The next thing that
you might need to do
is possibly a
little more radical.
And the big problem is that
this is highly inefficient.
I don't mean just me.
I mean all of us.
Human living biological
life is highly inefficient.
Given the thought processes
that we generate--
all the energy we
need to take in
and all of the various things
we need to do to keep us alive
is wasteful in terms of energy.
So energy is now becoming the
rare commodity in the Universe,
and you might
decide, essentially,
that you may want to do away
with biological forms of life
and move into a more efficient
form of life, which effectively
is a computational
electronic form of life.
Now, of course, there's a few
problems with all of that.
Number one, we don't know
what consciousness is,
so how you could take
consciousness and plunk
on a computer and say there
I am is an unsolved problem.
But people think that
this is a possibility.
Once computers get smart
enough and fast enough
that maybe you could have the
equivalent of consciousness
on a computer.
And that consciousness,
compared to the amount
of energy we need
to keep going, would
be highly energy efficient.
You would need a lot less energy
to run a computer with you
on it rather than having you.
So there might be a move away
from the actual physical life
into more electronic life.
This is a realm loved
by philosophers.
They love talking
about this stuff.
They point that, if this is
the case, that in the future
we move on to an electronic
form of life which
is much more energy
efficient, then
it would be very
easy to generate
a huge number of individual
conscious life forms
on your computer,
because they're
so cheap compared to having
biological life forms.
And they say that, over the
entire history of the Universe,
then the most numerous
life form might
be computational life
somewhere near the time
we're talking about here where
the Universe is now dominated
by red dwarfs, and
that we effectively
are just at the start of life
and most life is yet to come.
And then people
counter and say, well,
maybe we are the
computational life
running on a computer
around a red dwarf star.
Which makes me think that if
this is a synthetic reality,
what must real reality be like?
Let's not worry about
that too much now.
Anyway, so life will have to
do something kind of radical
if it's going to be able
to efficiently use energy
and survive into the future.
But, again, there's a problem.
We're going to go on a factor
of 10 out 10 trillion years.
And there will come
a time when there
will be the last star in
the observable universe.
There will be one star left.
And that one star, once it gets
to around 100 trillion years
old, it will run out
of hydrogen in its core
and it will again
go through this sort
of like internal sort of ridge
again and try to burn helium.
But these stars are small.
So they settle down
for a very brief period
and they become
a blue dwarf star
for a very, very short period
of time, until, after a century,
they just go, oh, this
is too hard and give up.
So the nuclear reactions that
power the star basically stop.
And what happens
then is that the star
shrinks because gravity wins.
There's no radiation
pushing outwards.
So the star shrinks
down and down and down,
and what you're left
with is a white dwarf.
And a white dwarf
is a dead star.
It's not generating new energy.
All it does is sit
there and cool.
So it cool through from
white, through visible,
into the infrared,
into the radio,
and then effectively disappears.
So what we've got is that
we will get to a period
where our Universe will just
have these dead hearts of stars
floating around.
And there will be
billions of them,
but there will be
no more starlight.
The only energy that we get will
be from these dead star hearts.
Life is going to struggle.
Even a Dyson sphere
around a dead star
is going to pick up
very little energy.
And here we run into realms
of rampant speculation.
If you're going to have
life in this Universe,
it's going to have to seek out
energy wherever it can find it.
And maybe instead of
having life concentrated
into a single Dyson
sphere, you spread it
out into something that
looks like a cloud.
Now, this is actually
an interstellar cloud
in our own Milky Way.
This is not a depiction of a
cloud of life in the future.
But this is an idea
people have had,
is that maybe life is
distributed and grabs
bits of energy where it can and
it uses that to power itself.
And it's not a new idea.
There's a book by Fred Hoyle--
who is one of the
greatest astronomers
of the last century,
a British astronomer--
called The Black Cloud, where
he had this idea that these
clouds of interstellar gas,
they could be thinking beings.
They have very slow
processes where they somehow
send information back and
forth, and they power themselves
in our time by going close
to stars, which is how
the problems start in the book.
This black cloud comes to our
Sun to get some more energy.
But it might be
that in the future
our life could be
spread out and grab
all the little bits
of energy spread
around and continue
to drive itself.
So maybe that's it.
We get to a point now where
all our stars are dead.
What's left for the Universe?
Well, now we have to worry about
something kind of fundamental,
and that's the
stability of matter.
This table seems pretty solid.
I think we would all be rather
amazed if this table suddenly
evaporated into nothingness
in front of our eyes.
We think of matter as being
a solid, long-lived object.
Now, we know that matter
isn't purely stable
because we have radioactivity
and you can have one element
change into another element.
So uranium can decay
into other elements
through radioactive decay.
But what if the bits
that make up atoms,
are they stable on
very long time scales?
So what we're going to
do now is we're going
to take a really big jump.
So here we are at
100 trillion years.
We're going to jump out to
100 nonillion years, which
apparently is a word.
So we're jumping out
to 10 to the 32 years.
And what we're going to
do is think about an atom.
So what we're going
to do is we're just
going to zoom in on
a single atom here.
So everyone remembers
their high school chemistry
and high school physics, yes?
That was not very enthusiastic.
Anyway, let's try and recap.
What we've got in an
atom, we have electrons
moving around the outside.
So we have clouds of
electrons zipping around
at very high speeds.
Electrons are tiny things.
They weigh almost nothing.
But if we keep going
down deeper and deeper
and deeper and deeper into
the heart of an atom, what
we eventually find is
the atomic nucleus.
Now, the scales
here are incredible.
The scale of an atom to
the scale of a nucleus
is the same as the
scale of a cathedral
to the scale of a fly.
That's how big the nucleus
of each of your atoms are.
And the rest of your
atoms are empty space.
So most of you is
just empty space.
Your mass is in all of
the nuclei in your atoms.
When we look at an
atom, we see that it's
made up of a few particles.
We have two of them.
We have the neutron,
coloured blue,
so named because it's neutral,
and the proton, coloured red,
which carries a positive charge.
And it's the protons and
the electrons interacting
which hold the atom together.
What holds the nucleus
together is that yellow stuff.
That's the strong force.
And so the strong force holds
all those protons in this very
tight bundle at the
centre of the atom.
Now, if I take a neutron and I
put it to the side and I wait,
after about 15 minutes
the neutron decays.
The neutron will turn into
a proton, an electron,
and a neutrino.
So it will decay.
And it can do that through
Einstein's E equals m
c squared.
Neutrons are more
massive than protons,
so there's enough energy
there for the neutron
to turn into the proton
plus a few other things.
Now, if we take a proton
and put it to the side,
protons have less mass.
And if we do the
calculations and worry
about quantum
mechanics, it looks
like protons should be stable.
If I put a proton there it
should stay there forever.
Except, again, there's
a problem with that.
And the problem is that there
is matter in the universe.
Why is that a problem?
Well, when we use
our laws of physics
to predict the early Universe,
when the Universe was born
there should have
been equal amounts
of matter and antimatter.
As the Universe cooled down,
the matter and antimatter
annihilate, leaving no
matter in the Universe today.
Yet when I look around this
room, I see lots of matter.
When I look through a
telescope I see lots of matter.
I don't see a lot of antimatter.
So something happened
in the early Universe
which meant there was more
matter than antimatter.
And so what we
think is that there
was an additional force, one
that we don't quite understand,
that sort of treated matter
different to antimatter,
which made more matter in
the Universe than antimatter.
That's all well and good.
The big thing is that if
that force still exists,
then it has a consequence,
and that consequence
is that protons should
eventually decay.
And we've tried to
look for proton decay.
And we don't look at
it by taking one proton
and looking because that
would take a long time.
You take lots of protons
and you stare at them
and you look for any
of them decaying.
We haven't seen it
yet, but it's thought
that on this time scale
of 10 to the 32 years,
protons will decay.
I'll just give you a
little illustration.
So this is what a
proton looks like.
It's not a fundamental particle.
It's got quarks
buzzing around inside.
But after around 10 to the
32 years, two of those quarks
will interact via
this unknown force.
So we have to wait a long time.
Eventually, this force kicks in.
Two of the quarks will interact.
The proton then
goes into a state
that it's never been in
before, and it decays.
It decays into two photons,
which fly off in one direction,
and a positron, which
flies off in another.
What that means is that, on
this time scale of 10 to the 32
years, matter will melt.
All of the atoms in here
will just steadily
disintegrate away.
So if I waited long enough,
this desk would evaporate.
I'd have to wait
10 to the 32 years.
And that's quite a long
time, but that's ultimately
the fate of what's
going to happen
to the matter in the Universe.
Now, life could try and
grab onto that energy
and continue going,
but things are now
starting to get
difficult. You can pick up
these teeny bits
of energy and you
can use it to drive your life.
But then you realise that your
own protons are also decaying,
so then you've got to come up
with a way to make new protons
because they will
last a long time.
But to make new protons
you need more energy.
So where do you get the energy?
So there's one source left.
We haven't really
mentioned them very much,
but that's black holes.
I mentioned that there was a
big black hole at the centre
of the Milky Way, and that other
black holes are formed when
stars die.
So you create these black holes,
these completely collapsed
massive objects,
down into points.
They've got very strong
gravitational fields
and so you can extract
energy from them.
You could drop things into them.
Think about it this way.
If you've got a black hole,
I've got a fishing rod.
I've got a rock on the
end a fishing line.
I drop that rock in.
In it falls.
The spindle spins around.
I could extract that
energy and run the TV
and watch the cricket,
or something like that.
But there are lots of
ways of extracting energy
from black holes.
And they will still
be there in the dark,
so you might be able to
come up with a method
to use that extra energy
to keep life going.
Except, of course,
there's a problem.
And the problem is the
ghost of Stephen Hawking.
Why?
Well, what's Stephen
Hawking famous for in terms
of his scientific work?
He's famous for
looking at black holes
and linking black holes
with quantum mechanics.
And what he showed is that
black holes aren't really black.
If you take quantum
mechanics into account
at the edge of the
black hole, they
emit teeny bits of
energy, tiny amounts.
But, over time, that
energy which is emitted
takes away some of the mass from
the central of the black hole.
Now, over immense time
scales, 10 to the 100 years,
a big black hole, like the one
in the centre of the Milky Way
galaxy, will start to lose
enough energy that it actually
starts to shrink very rapidly.
And what you get is
that, if you have
black holes in
the Universe, they
undergo what's known
as Hawking radiation.
As they shrink they
emit more energy.
And as they emit more energy,
they shrink even more.
So they get this runaway
feedback, which essentially
drives them down to a
point, and then they explode
and all of their final mass
is released in a burst.
And this will happen
to all the black holes.
All the black holes will
be emitting this Hawking
radiation.
So there will be these
continuous random bursts
of energy in the Universe.
Now, if you are a
creature and you
are living in this distant
part of the Universe,
maybe you can harness this
energy as black holes wink out
of existence.
But I think it's going to
be very, very hard work,
very, very hard work.
And, effectively,
what you're doing is
you're only putting
off the inevitable.
Because once these black
holes have evaporated
and they're gone, once
all the stars are dead
and their stellar
hearts have dissolved,
there is nothing left.
There's no matter in
the form of stars.
There's only electrons and
positrons buzzing around.
There are no sources of energy,
only this soup of photons
bubbling through the Universe.
So the Universe reaches this
rather lovely named state
known as the heat
death of the Universe.
And what that means is we've
got to a point where there's
no usable energy left for life.
This is probably it.
This is probably
as far as life is
going to be able to push
it into the Universe.
Now, we don't want to
finish on a sad note, do we?
We have also entered
the realm of speculation
and speculative physics.
So let's be speculative on
the positive side, shall we?
We can't really be positive
about life in this Universe,
but we can be positive
about the Universe itself.
And there are a lot of
ideas that if we really
stretch the age of the Universe
out 10 to the 2,000 plus years,
that the Universe might actually
manage to change its spots.
I mentioned there's this
dark energy of the Universe,
that this material is there
and this energy associated
with space.
There are lots of ideas
that that energy might
be able to decay and go
from one energy state
down to another energy state.
And if it does that, then
that release of energy
as the Universe essentially
changes its energy state,
will give a new burst to the
expansion of the Universe.
So it will be like when you
open a bottle of fizzy water,
you get all these sites where
the bubbles form nucleation
sites.
That's what they think will
happen to the Universe,
that in individual
places of the Universe
there will be this
change of energy
and you'll get these
rapidly expanding
patches of the Universe.
And these rapidly
expanding patches
would effectively
be new universes.
Now, again,
speculation runs free.
We don't know what
kind of universes
are going to be created.
They might be universes
completely different to our own
in terms of the laws
of physics and how
the universe is composed
of matter and radiation.
Or they could be
just like our own
and the cycle could start again.
You could get matter forming
from this reborn universe
falling together, giving us
stars, the stars evolving
and giving us new burst of
life in whatever universe
follows this one.
Which is a reasonably
happy ending, isn't it?
Anyway, I'm going to finish
essentially with a quote from
one of my favourite authors.
So this is Douglas Adams.
"There is a theory which states
that if ever anyone discovers
exactly what the Universe
is for and why it is here,
it will instantly disappear and
be replaced by something even
more bizarre and inexplicable."
We may never actually answer the
deep philosophical questions,
but we may live in
a universe which
is replaced by something bizarre
and even more inexplicable.
But the line that really
got me when I read this
was the next one.
"There is another theory that
this has already happened,"
and that this
universe itself could
have been born from the
death of a previous universe.
And we may have this endless
cycles of universes and life
going on from infinity in the
past to infinity in the future.
So this almost sounds like
a Buddhist finish in there.
But that was a
semi-positive note.
I'll finish, though,
by putting up
a picture of what the Earth is
going to look like in roughly 7
billion years' time.
I'll finish there.
So thank you.
[AUDIENCE APPLAUDS]
