so do aliens exist that's a huge question to answer so to start off let's start with our
solar system in our solar system we've got the sun in the center that's our star and orbiting around
we've got eight planets and we live we live in one of them the earth and we think around some
of those planets like jupiter the moons that orbit around jupiter some of them could have
alien life on them but that would be very simple like bacteria so if we want to find intelligent
aliens that maybe we'd be able to talk to we need to look outside our solar system and we're not
the only place with a star and planets there's actually we think hundreds of billions that's a
hundred thousand million other stars in our milky way galaxy alone and we think each of those stars
probably has at least a planet just one planet orbiting around it and so i think the chances of
alien life existing out there in space is really really huge because there's hundreds of millions
and billions of planets that they could be on but we need evidence to prove it as scientists
and we use sometimes the level telescope outside here at georgia bank we use it we point it towards
some of these planets to look for these radio these radio wave signals and we haven't found
any over the last 50 years nothing so it's not looking great but in the future when we get bigger
and better telescopes we think our chances will increase and we should eventually spot
alien life i think we will discover it one day will we ever be able to talk to them probably not
hi i'm sarah bosman and i'm an astrophysicist at ucl i study mostly the early universe
space is really enormous it's so big and it's kind of hard to imagine and the units we use on earth
like kilometers or miles don't even make sense to apply to space because you just get too many zeros
if you try to think of it that way so astronomers have to come up with a whole new unit to measure
distances in space which is a light year so for instance our galaxy is a hundred thousand light
years from one edge to the other that means if you are traveling at the speed of light which is the
fastest you can ever go it will still take you a hundred thousand years from one edge to the other
and that's only how big one galaxy is so if we look outside of our galaxy to how
many other galaxies there are we just study small patches of the sky and count how many
there are in each small patch and the amount of galaxies we think are in the universe it's about
two trillion galaxies which is a ridiculous number so if you took all these galaxies and
split them among everyone on earth each person would have about 250 galaxies all to themselves
and and that's only the space we know about now beyond that there could be even more space
so when light travels through a vacuum that's as fast as anything can go and a vacuum means
that it's just empty space so the light isn't traveling through air or dust or anything else
when it does travel through these things it will slow down slightly
but when it's just traveling through a vacuum that is its top speed and we've measured that that's
about 300 000 kilometers a second which means that light could go around the whole earth
seven and a half times a second when it comes to other things traveling faster than light it
gets a little bit more complicated so a scientist called albert einstein came up with an equation
that tells us anything that has mass will get heavier and heavier the faster it goes
so if you keep speeding something up it's going to get more and more mass it's going to keep getting
heavier until it reaches a speed of light and at that point it has to have infinite mass which is
impossible something can't weigh infinity it can't have infinite mass so that tells us that nothing
can ever travel at the speed of light the speed of light is the top speed anything can ever travel
stars there are loads of them but how do we count them on your fingers
with pen and paper pulling a random number out of a hat maybe not
counting stars takes a lot of time and a lot of effort the first thing you should worry about
if you look at the night sky and try and you're trying to count every single star is that you
don't count the same one twice so what we do to avoid that is give every single point on the sky
a unique address so in the same way as on the globe you have longitude and latitude to find
a place on earth we have the same for the sky so once you have addresses like this and you're
sure you're not counting each star twice uh you divide the entire sky into tiny little squares
and then what you're going to do is take a picture of each of these squares a very very good picture
and then look at that picture and count how many stars you see and you do this over and over and
over back in the days we used to attach cameras directly on the end of telescopes to take pictures
but that was often ruined by bad weather and other such things so now we have sent a specialized
satellite in space called the gaia satellite whose only job is to count all the stars it can
see and how bright they are and how fast they're moving gaia has only been going for a few years
and it's already counted 1.1 billion stars just around the sun in our small part of the galaxy
so counting all of those by hand and making a list would take a bit too long
now imagine this an asteroid hurtling towards earth and you have to come up with a plan to
stop it so what do you do how about crashing a spacecraft into the asteroid to knock it out
the way now it might sound a bit crazy but that's actually nasa's plan the asteroid nasa want to hit
is called didimos and will be approaching earth in october 2022 and then again in 2024 it's
made up of two different parts dilemmas a and a smaller asteroid orbiting it called didimos b
but they only need to target the smaller asteroid to stop the earth being hit it's the first ever
mission to change the direction of an asteroid called the double asteroid redirection test
or if you want to be quicker darts plans for the spacecraft got the thumbs up and they're about to
start designing it so how will this all work well it's expected to be about the size of a fridge
the spacecraft will shoot itself at the asteroid deliberately crashing into it at
50 times the speed of a racing car the force of the crash would physically knock the asteroid off
in a different direction it could be a space tacular moment in history
you