In our night sky, you can see space -
big, mysterious, and frankly a bit scary.
I sometimes look up at it and ask those big questions.
Such as, how do stars work?
How did it all begin?
And, what is Madonna doing in space?
For the answers, stick with me,
as we uncover the things you need to know about the universe.
Right, let's get this show on the road,
and the beginning is as good a place to start as any.
So, how did the universe begin?
Everyone knows the universe started with a bang -
a bang so big, it's called the Big Bang.
It happened everywhere in the universe at the same time,
and was the beginning of everything we know -
space, matter and even time itself.
The Big Bang is the most important event in history.
In fact, without it, there wouldn't be any history.
Even so, the biggest brains in science don't really know
why it happened, only that it did.
And they know it did because there are clues out there in space.
In 1929, astronomer Edwin Hubble discovered that
distant galaxies are moving away from us,
and the furthest are moving away faster than the closer ones.
So, logically, all these galaxies came from one tiny central point -
the Big Bang.
Further proof was found by two young scientists in the 1960s,
when their new radio telescope seemed to be faulty,
due to a constant annoying hiss.
Hmm? Grr!
They checked the telescope and pinned the blame
on some resident pigeons and their droppings.
GUN COCKS
SHOT FIRES
They swept the dish and evicted the birds, but the hiss was still there.
This hiss was in fact cosmic microwave background radiation,
or CMB, which is the heat and light left over from the Big Bang.
It's travelled over 270,000 billion, billion miles to reach us,
and has slowly cooled on its long journey.
In fact, we've all seen the Big Bang.
About 1% of the static on your untuned TV is this CMB radiation.
And scientists have used this static to calculate the age
of the universe, which is roughly 13.7 billion years old.
That's a seriously long time ago,
so perhaps we may never know what caused the Big Bang.
But we do know that the universe apparently came from nothing,
but is now everything. So if it came from nothing,
what is the universe made from?
You might be surprised to learn that we don't really know.
All the matter and energy we can see only accounts for
about 5% of the universe's total mass,
and a whopping 97% of all this visible stuff is made up
of just two elements - hydrogen and helium.
So, everything heavier here on Earth,
like carbon, oxygen, water, baboons, jet planes and clowns,
is very rare indeed.
And as for the remaining 95% that's invisible,
well, unsurprisingly, that's a bit of a mystery.
Scientists think that a quarter of all this missing stuff is
comprised of dark matter. It's divided into two theoretical types -
weakly-interacting massive particles, or WIMPs for short,
and massive compact halo objects, or MACHOs, to you and me.
WIMPs are tiny particles of exotic matter.
And by exotic, scientists mean
they are different from ordinary particles.
Not that they dance for money.
But so far, they've proven undetectable.
There could be WIMPs flying through you right now,
only you can't see or feel them.
And we can't see MACHOs, as they don't reflect or emit light.
They could be everything from failed stars to black holes.
Although it only exists theoretically, scientists think
dark matter is important, as it seems to binds galaxies together.
Otherwise they would simply fly apart -
which might be fun to watch, but not so good for us.
But even with dark matter,
that still leaves about 70% of the universe simply missing.
Scientists have called what's left dark energy,
which is even more puzzling.
In 1998, astronomers discovered that
the universe's rate of expansion is actually increasing.
Something seems to be overpowering gravity,
which scientists thought would
eventually slow the universe's expansion.
They now think that this is due to dark energy.
So, if our greatest thinkers had to take an exam
in what the universe is made from,
they'd have to tick the "Don't know" box.
But it's definitely made from something, and if we look at
the night sky, what we can actually see are stars, billions of them.
So many, in fact, that it sort of makes your brain hurt a bit.
So, how do stars work?
There are hundreds of billions of stars in our galaxy alone.
And they come in a dazzling variety of colour, size and brightness.
All stars, including our own Sun, work in roughly the same way.
They harness the power of nuclear reactions -
specifically, a process we call fusion.
Humans have also harnessed nuclear power,
but this is fission, not fusion.
Fission is the splitting of atoms to unleash vast amounts of energy,
as in the original atomic bomb.
But during fusion, the opposite occurs.
In the deep core of a star,
hydrogen atoms collide and fuse together, creating helium.
These shiny new helium atoms have slightly less mass
than the hydrogen atoms that created them.
And this lost mass is released as gamma radiation.
This is explained by Einstein's famous E = mc2 equation,
which states that mass and energy are effectively
two sides of the same coin.
In fact, if you could measure it accurately enough,
a hot cup of tea would weigh more than an identical cold one,
because it has more energy.
Mmm. Now, just try to imagine this -
every single second, 600 million tons of hydrogen collide
inside the Sun, and this creates new helium,
and that releases four million tons of energy.
Or, to put it another way, while I've been speaking,
the Sun has lost the equivalent of 500 aircraft carriers in mass.
Can I have another cup of tea, please?
Fusion is the beating heart of all stars in the universe.
And it's pretty handy for us down here on Earth,
as it provides the visible light we depend on.
Wow! Cool! Ow! My frickin' eyes!
In fact, the light from the Sun only takes eight minutes to reach us,
but can be up to a million years old,
as it takes so long to journey out of the Sun's dense interior.
Mmm.
Makes you think about sunbathing in a whole new light, really.
But anyway, stars are actually just like you and me.
Apart from them being great flaming balls of fire.
But like you and me, they are born, they live and then they die -
often with spectacular results.
So, what happens when a star dies?
As the Sun grows old, it will become smaller, brighter and hotter.
In three billion years, it will be 40% brighter,
and so hot, it will evaporate our oceans.
In another two billion years, its core will collapse,
and it will expand to form a red giant -
so massive, it will engulf the Earth.
When this red giant Sun finally dies,
it will throw off most of its mass in a huge nebula of gas and dust.
And all that will remain is a dense core, called a white dwarf,
which will slowly cool over billions of years.
However, not all stars behave like the Sun.
Other stars, called red dwarfs, use their fuel so economically,
they may last for a trillion years or more.
And at the other end of the spectrum, the biggest stars,
hundreds of times bigger than the Sun, burn their fuel very quickly -
they live fast and die young.
It's these biggest stars that produce
the strangest results when they die.
They literally go out with a bang, exploding in violent supernovas,
amongst the most spectacular events in the universe.
Supernova explosions might be spectacular,
but they could also be very dangerous for us humans.
If one occurred within 25 light years of earth,
it would kill all life on the planet.
The ozone layer would be destroyed,
bathing us in lethal doses of radiation.
Probably best to stay indoors if this happens.
These supernova explosions can have two outcomes.
Firstly, the material left behind can collapse
to form a superdense neutron star.
A neutron star is only about the size of a city like London,
but can weigh twice as much as our Sun.
But when the largest stars of all explode,
the remaining neutron core is compressed
in a fraction of a second into a singularity.
This is infinitely small, smaller even than an atom,
and its gravitational pull is so massive,
nothing can escape from it, not even light.
This is a stellar black hole.
They are the strangest and most destructive forces in nature -
anything straying near a black hole will be sucked in and destroyed.
The universe sounds like a pretty violent place,
what with innocent stars exploding
and being eaten by rogue black holes.
But if stars are continually being destroyed,
surely they're at risk of becoming an endangered species?
So, why aren't stars extinct?
Across the universe, stars are dying all the time, so you might think
the night sky would slowly dim as their lights are snuffed out.
This isn't happening - but why?
Well, the answer is recycling.
All the mass and energy that exists today
was created during the Big Bang.
And that's it, that's all there'll ever be.
Therefore, the universe needs an efficient recycling scheme,
and this relies on the humble atom.
Atoms consist of a tiny central nucleus
surrounded by a cloud of orbiting electrons.
If an atom was the size of a football pitch,
the nucleus would be smaller than a single blade of grass.
The vast majority of an atom is empty space,
which means most of everything is actually empty space.
Atoms are also remarkably durable.
No-one knows how long a single atom can survive, but it could be
as long as 100 billion, trillion, trillion years.
So long, in fact, that they can be reused almost endlessly.
When a star dies, most of its mass is thrown out into space.
This is when the recycling process can begin.
Over time, a dead star's atoms condense and compact,
until they become so hot, they ignite, forming a new star.
You could say this is stellar reincarnation.
Our Sun is thought to be a third-generation star,
so every atom here on Earth has passed through
two long-dead stars already.
Not only that, but as atoms are
constantly recycled here on Earth too,
millions of your atoms once belonged to Shakespeare,
Genghis Khan and Julius Caesar.
It's weird to think that all of the atoms in our body might once have
been part of ancient stars or planets, or even aliens.
We are really just a series of cosmic hand-me-downs.
But how did the atoms of some ancient star end up
as part of you or me or even a geranium?
Just how did the solar system form?
Our solar system began life as a huge cloud of gas and dust
called the solar nebula.
About 4.6 billion years ago,
this giant cloud started to coalesce under the force of gravity.
It also began to spin itself into a flattened disk shape.
At the centre of this spinning nebula,
99% of all its mass compressed into a protosun.
This was a baby star, not yet ready to ignite.
All the remaining matter in the huge cloud around the new protosun
slowly formed itself into rings.
These rings would eventually become the planets we know today.
Close to the protosun, the higher temperatures meant
only rocky materials and metals could survive the heat.
Therefore, the closest planets to the Sun -
Mercury, Venus, Earth and Mars -
are mostly composed of heavier elements, like iron.
But in the distant, colder regions, big lumps of rock and ice managed
to capture vast clouds of gas around them.
These would become the gas giants - Jupiter, Saturn, Uranus and Neptune.
Eventually, the protosun became dense enough
to begin fusion in its core, and - drum roll, please -
our Sun finally became a fully-fledged star.
But for Earth, the story was really just beginning.
When our planet was just 100 million years old, a huge object
the size of Mars collided with us,
throwing vast amounts of rock into space.
This stray rock eventually reassembled itself into the Moon.
That huge collision that formed the Moon
also knocked the Earth off its axis by 23.5 degrees,
and that was very handy for us, because that created the seasons.
In its youth, Earth is thought to have been volcanic and inhospitable.
But over time, it came to be covered in a vast ocean of water,
perhaps carried here by icy comets and asteroids.
However it got here, it was this water that allowed life to thrive.
We all know our place in the solar system -
the third rock from the Sun,
one of eight planets orbiting our nearest star.
But, if there is anyone or anything else out there,
how will they be able to find us?
Where are we?
If there's some sort of intergalactic postal system,
then our address might look something like this.
Planet Earth, the solar system, local fluff,
the Milky Way, local group, local supercluster, the universe.
For most of human history,
we have placed our planet slap bang at the centre of the universe.
But since astronomer Nicolaus Copernicus realised that
the Earth actually orbits the Sun,
every new discovery has highlighted the fact
that we're not particularly special at all.
Actually, it seems as though we live in a rather unimportant cul-de-sac,
in the grand scheme of things.
We are just an insignificant dot in the vastness of space.
But don't get depressed about this -
because that assumption is, in fact, the cornerstone of modern astronomy,
what is sometimes known as the cosmological principle.
The cosmological principle states that,
when viewed on a sufficiently large scale,
the universe actually looks the same,
in all places and in all directions.
So when we look out into space at the other stars and galaxies,
they might seem haphazard and irregular,
but in fact, they are all laid out in a very symmetrical way.
So, if we send out a galactic calling card,
there's a distinct possibility that aliens wouldn't be able
to find us, even with directions, due to the cosmological principle
and the sheer size of the universe.
We humans are obsessed with the idea
that there could be other life in the universe.
From books to films to people who claim to have been abducted,
we all have our own take on what else might be out there.
But is there any fact behind any of this fiction?
Or are we alone?
If there is life out there, then scientists believe
it will probably be found in the Goldilocks zone.
This has nothing to do with bears and porridge,
but describes a planet that's just right,
the perfect distance from a star
and warm enough for water to be found on its surface.
In our solar system, only the Earth fits the bill.
Our nearest neighbours, Venus and Mars, are just too close
or too far away from the Sun.
However, this doesn't mean there couldn't be life
somewhere else in our solar system.
It's just that it would probably be simple bacteria,
and unlikely to provide intelligent conversation.
I can't say I have much confidence in your opinion!
There's bacteria here on Earth that can live in poisonous environments,
suggesting creatures on other worlds may evolve
in ways we can barely imagine.
And instead of being carbon-based, as on Earth,
life elsewhere could have evolved
using other elements, such as silicon.
Such creatures could withstand much higher temperatures than us,
so planets too hot for humans could still support life.
In fact, the hunt for life
beyond our solar system is already in full swing.
NASA's Kepler Mission has identified over 1,000 potential planets
worthy of more investigation, and of these,
15 have been confirmed as lying in the Goldilocks zone.
In the 1960s, a scientist named Frank Drake developed an equation
designed to calculate the number of other civilizations
in our own galaxy, the Milky Way.
These factors include the rate of new stars forming in the galaxy,
the proportion of these stars that have planets,
the percentage of these planets that are habitable,
and the length of time any civilization might last.
At the moment, we can only hypothesise
about most of these numbers,
but conservative estimates suggest that there might be
900 advanced civilizations in the Milky Way at any one time,
and our galaxy is just one of billions.
So, there's a very good chance that we're not alone.
Unfortunately, the distances involved are so huge
that we may never make contact with anybody out there.
However, that doesn't mean our nearest neighbours
haven't already discovered us, or at least our taste in pop music.
So, just what is Madonna doing in space?
The furthest any human has ventured from Earth is to our own Moon,
which in space terms is barely beyond our own doorstep.
Look at me, I'm flying!
Oh, no, wait, maybe not.
However, humanity has in fact travelled much further than that,
far beyond the furthest reaches of our solar system.
Madonna, Hitler and the Dalai Lama -
they're all out there in deep space,
thanks to the power of radio waves.
Since the early 20th century, our broadcasts have
leaked out into space, almost like a three-dimensional ripple on a pond.
All electromagnetic waves, including radio waves,
travel at the same speed -
some 300 million metres per second, what we call the speed of light.
Therefore, TV and radio signals transmitted 50 years ago have
journeyed 50 light years into space by now,
ample time to have reached hundreds of neighbouring stars.
So, if there are alien civilisations out there listening in,
the first they might know about life on Earth is
a speech by Martin Luther King, or an episode of EastEnders,
or even what I'm saying now.
But it's not just us broadcasting radio waves.
They're also being emitted by galaxies and even black holes,
which can be a bit confusing.
In 1967, a young Cambridge astronomy student noticed
a strange radio signal from space
that pulsated exactly every 1.337 seconds.
It was so precise and regular, it didn't appear natural.
Therefore, the object emitting the signal was dubbed LGM-1.
LGM stood for Little Green Men.
However, it wasn't a friendly alien, but a pulsar,
one of the strangest natural phenomena in the universe.
Pulsars are spinning neutron stars that emit beams of radiation -
almost like intergalactic lighthouses.
When you're just sitting at home,
it's comforting to think that the universe will be around for ever.
But don't get too comfortable,
because observations by cosmologists suggest that it probably won't.
So, the final question is really very obvious -
when will the universe end?
Scientists have developed three plausible theories
as to what might happen at the end of it all.
Currently, the most likely is the Big Chill.
This is what will happen
if the universe continues to expand forever.
Firstly, galaxies would move away from each other.
Then stars, and everything else, would slowly drift apart and die.
Finally, only giant black holes will remain,
each separated by distances 100 times greater
than the current size of our universe.
Eventually, even these black holes will evaporate,
and the universe will be still, cold and effectively dead.
But before you start to panic, you should probably know that
we have around 100 trillion years to wait
before even the beginning of the end, when stars start to disappear.
And that's about 10,000 times as long
as the universe has existed already.
And in any case, by that time,
we humans will probably have long since disappeared.
Another possible end is called the Big Rip.
This would be the spectacular and rapid destruction of the universe.
But this will only occur if, in the future,
the mysterious force of dark energy somehow supersedes gravity.
First galaxies, and then literally everything,
right down to tiny atoms, would be torn apart.
Lastly, the Big Crunch.
Not a breakfast cereal, but what will happen
if the Big Bang slows down and is thrown into reverse.
The universe would implode in an almighty crash,
crunching down to a tiny singularity.
It might seem morbid to think about the death of the universe,
but some scientists think that the end might not be the end at all.
Some believe that there might even be
parallel universes that exist alongside our own.
This is called multiverse theory.
It could be that, beyond the observable horizon of our universe,
there are other universes out there,
each existing separately like the bubbles inside a Swiss cheese.
Or perhaps other universes occupy a space
that we cannot even comprehend,
existing in extra dimensions we are, as yet, unaware of.
The universe is magnificently, mind-blowingly weird -
so strange, in fact, that we may never fully understand
how or why it came to be, or what dark energy is,
or if we're the only sentient beings in it.
And every new discovery or theory by beard-tugging boffins in white coats
has the potential to completely rewrite every book on the subject.
So for now, I'm off to contemplate my part
in the grand cosmological scheme of everything,
knowing only one thing for certain -
that my part - and yours, I'm afraid - is very, very small.
Subtitles by Red Bee Media Ltd
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