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Tonight, we want to celebrate a
simple activity we just don't do

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enough - going outside, looking up
and marvelling at the night sky.

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We're not just talking about
observing the stars,

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we are going to explore some of the
more surprising ways

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that the night sky can captivate us.

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We're at the
Royal Observatory, Greenwich,

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the spiritual home
of British astronomy,

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to find out how we can all enjoy
the majesty of the night sky.

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Welcome to The Sky At Night.

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Astronomy is of course the very
heart of The Sky At Night.

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But it's easy to overlook the sheer
variety of ways in which

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the night sky can inspire
and even provoke us.

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So, tonight, with Christmas only
weeks away,

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in a spirit of celebration,

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we are going to enjoy the many ways
the night sky can bring us pleasure.

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Chris learns about the ancient art
of navigation using just the sky.

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That's one of the most ridiculous
things anyone has ever said on an

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astronomy programme!

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Pete and Maggie take on an epic
challenge, trying to persuade

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a group of teenagers to fall in love
with stargazing.

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And Chris discovers how astronomy
can reveal a spectacular world

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of colour hidden in the sky above.

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But first, I'm going to Norway
in search of one of the greatest

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spectacles the night sky has to
offer -

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the Aurora Borealis.

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Perhaps the most surprising thing
about the Aurora is that there is

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much that, even now,
we don't understand.

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New discoveries are still being
made,

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and it's not just the scientists
who are making them.

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You can sometimes see the Aurora
from the UK.

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But to increase my chances of seeing
them and to learn more about them,

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I've come here to Tromso in Norway.

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Now, you might not believe this,

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but the sun has just set and
it's getting dark, but it's only

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two o'clock in the afternoon,
and it really is quite cold.

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Tromso nestles between the fields
of northern Norway.

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It's been a working port
for many years,

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but it's also a centre for Aurora
research

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because it has one of the most
reliable records for Aurora displays

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anywhere on Earth.

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Thank you. I just can't wait to see
them with my own eyes.

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What's the probability of us
seeing the Northern Lights tonight?

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I think it looks good tonight.

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The weather is clear, and that's
what we need.

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Tromso is probably one of the best
places on Earth

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to see the Northern Lights -
not just because I live here!

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We are placed straight
underneath the Aurora Oval,

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the imaginary oval of particles
surrounding the North Pole.

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We've been driving around for about
half an hour now and I'm beginning

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to see what might be the
Northern lights.

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It's quite hard to describe,
but there's sort of a wispy light

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in the sky, and I'm really hoping
that's it,

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so we can hopefully pull over
and check it out.

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Wow!

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It really is them.

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This band of colour across the sky.

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This is amazing. Anything that
usually gets between me

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and the stars is a bad thing but,

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at the moment, this is just
so glorious.

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It's so much better than I thought.

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So much more dynamic,
so much more colour.

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I'm just loving it,
loving every second.

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I can actually see a sheet
travelling across the sky.

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But what exactly are they? Well,
it turns out that they are not

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as well understood
as you might imagine.

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It's been thought that they were
caused by electrons

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from the solar wind, twisting along
the Earth's magnetic field,

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ionising gas in the atmosphere
which then shimmers and glows.

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But there are some fairly obvious
problems with this theory.

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Aurora expert Melanie Windridge
explains.

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Firstly, we know that,

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if charged particles were coming in
directly from the solar wind

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and hitting into our atmosphere,
they'd be hitting us on the day side

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of the planet, and we don't see
Aurora there.

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It's too light.
We see Aurora at night,

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so somehow the particles are getting
round to the back of the planet.

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Another thing is that we know that
if the particles were coming in

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directly from the sun,

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then they wouldn't have enough
energy to cause the bright,

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vibrant displays that we see
on the night side.

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New research has begun to suggest
an answer.

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The electrons coming from the solar
wind are receiving

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an unexpected boost in energy

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from a complex interaction
with the Earth's magnetic field.

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The Earth's magnetosphere is the
Earth's magnetic field

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but then modified by the solar wind,

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so the wind comes past and
it's deflected around it

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like a stone in a river or something
like that. I have seen that,

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so you've got sort of the Earth's
magnetic field and it would be

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sort of around the Earth, but it's
elongated. Yeah, it's stretched out.

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Away from the solar wind. Exactly,
like a windsock as the wind

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is deflected past the Earth.

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And so you have this long tail,
this long windsock-like tail,

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behind the Earth and,
in that region,

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you get a lot of magnetic field
built up and pushing down

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behind the Earth and, eventually,

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these magnetic field lines get so
close,

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but magnetic field lines can't cross
and so that's when they get pushed

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close, close, close, close, close
and then, bang!

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They snap. And when they snap,

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they catapult back towards the Earth
and they catapult particles,

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electrons, down the field lines into
the Earth's atmosphere at the poles,

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and that's what's causing
the Aurora.

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It's that acceleration of particles,
it's giving them a lot of energy,

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and that means that they can
interact with our atmosphere

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and cause the bright lights
that we see in the night side.

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Just looking up here tonight,

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there's so many different phenomena
happening.

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We don't fully understand the causes
of the movements or the dynamism.

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We are beginning to understand
pieces of it now because we have

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better technologies available to us
now, we have satellites up in space,

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and that's really useful because we
can fly through space and we can

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measure things like particle
densities or particle speeds or what

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the conditions are like out there.

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And the Aurora act as a kind of
window onto the processes

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that are happening in space. Or,
if you like, the atmosphere is

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the screen on which the Aurora
plays out, but it's playing out

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cos of things that are happening
out in space. But I suppose we have

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many more cameras than we used to
because we had the professionals,

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but I guess we have amateurs doing
some amazing stuff and taking some

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amazing images which we can relate
to what's happening up there.

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Exactly, and that's a really good
point because we are now able to get

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many more pictures than we ever
used to be able to get.

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Just recently, in the last year
or so,

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there has been a new feature
identified in the Aurora which is

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quite amusingly called Steve

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because they didn't really know
what to call it, perhaps!

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Dave was taken! Exactly, so Steve!

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And Steve is like a ribbon aurora,
it's like a pinky-white ribbon,

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it's quite different to the normal
green arcs or bands that you see

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across the sky. And it happens at
a slightly different orientation,

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so a little bit more towards the
equator than the main auroral band.

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And I think people have actually
been seeing it for a while,

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but it's fairly rare and so
it wasn't seen very often.

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But now that more and more people
are taking photographs,

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it was popping up in these
photographs more and more.

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So what do they think's causing it?

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They know now that it's happening
about 300km up in the atmosphere,

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it's about 25km wide, but they
don't know what's causing it.

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I can see some more developing
just behind us, actually.

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Oh, yes, it's looking lovely up
there. So it's still a mystery.

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But a mystery that we're solving
slowly but surely with the help

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of citizen scientists, so it is
a fantastic thing to observe.

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Thank you so much for explaining.
You're welcome.

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CHRIS: Although the Aurora
is full of colour,

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it's easy to assume that the rest of
the night is a monochrome world,

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one with an inky black sky
and a sprinkle of white stars.

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But there's plenty of colour
up there to enjoy,

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if only you know where to look.

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To explore this hidden universe,

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I met up with astronomer Jen Gupta
at the Royal Observatory, Greenwich.

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So, Jen, we are here to talk about
colour in the night sky,

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and that's odd because people think
of the night-time world as

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black-and-white. Yeah,
so if we look up at the stars,

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and we can see some stars here
tonight,

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you think of stars being kind of
these white pinpricks of light,

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you don't think of much colour being
out there.

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But, actually, every star in the
night sky has its own colour,

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and a classic example I think at
this time of year are some of the

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stars in the constellation of Orion.

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So Orion is just rising here
in the east at the moment.

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The classic stars you want to look
for are Betelgeuse, his top left,

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as we look, shoulder or armpit.

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The other one that you want to look
out for is Rigel,

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which is his bottom right foot,
as we look at it.

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And if you look closely at those
stars, you'll see that Betelgeuse

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looks a kind of orangey-reddish
colour whereas Rigel looks white

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to us but it's actually
more kind of whitey-blue.

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So why is that? Why are those
two stars different colours?

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This is all to do with their
temperatures,

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and it's a little bit confusing to
start off with because it's actually

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because Betelgeuse
is cooler than Rigel,

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and it's the physics
that's driving the stars.

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So we've got an example here.
This could be my star.

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We are going to start lighting up
this light bulb,

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and what's happening is we're going
to make the wire inside glow,

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and you can see here it's kind of
glowing an orangey colour. Right.

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As we increase the power through it
and we make it heat up

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even further, you can see the colour
starting to change through to a kind

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of yellow and, if we kept going,
and I don't want to do that,

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it would get a little bit too hot,

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but it would end up glowing very
white, basically. And so, just by

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looking at the colour of the light
bulb, I can work out the temperature

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of the filament. Yeah, exactly.

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And the same's true with the stars
but for different reasons. Yes.

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It's a different process that's
going on. What's happening in stars

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is actually a process called
nuclear fusion.

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It's mostly hydrogen - the most
abundant element in the universe -

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hydrogen atoms smashing together
to form a helium atom,

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and that's the process that's
powering the sun, the process

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powering all these stars. And this
is true for most stars

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but because they're different
temperatures,

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we get these different colours.
Exactly. And so, when we look at

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Betelgeuse we're looking at a star
where the surface temperature

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is around about 3,500 degrees

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for Betelgeuse compared to about
11,000 degrees for Rigel,

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so you've got a big difference
in temperatures.

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But there aren't many green stars
in the sky. That seems weird.

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No, but there are other things in
the night sky. If you're desperate

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to see something that's green in the
night sky, we do have other options

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and, in fact, there's one in the
Orion constellation again.

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So, if you find Orion's sword
hanging down from his belt,

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there's the Orion nebula in sight
there,

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that kind of fuzzy looking star.

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But if you zoom in on that
with a telescope,

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you'll actually see that it's
glowing with colours.

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What's happening in the Orion nebula
is that the gas is being lit up by

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some young stars that are forming
in this cloud of gas,

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and that's doing what we call an
emission spectrum

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coming out of them.
So the gas is getting excited?

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Yeah, we are giving energy to the
gas, we are giving lots of energy,

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we are making it glow, and we've
actually got these three lamps here
which can do exactly the same thing.

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So if I flip this one on, can you
see that it starts to glow?

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The exact same thing is happening.

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We're putting energy into the gas
inside that tube and we're making it

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glow a kind of pinky-purple colour.

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So this gas actually inside there is
hydrogen. If I switch this one on,

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this will maybe be more familiar to
people, this is neon, so your neon

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signs work in the exact same way.

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And then finally here
we've got helium.

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And the different colours are just
because there's different gases.

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Exactly, so that's what you will
immediately notice. They are all
glowing in different colours

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because of the different atoms that
are inside this gas, and so we can
work out what is inside our nebulae

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by looking at the colours
coming from them.

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And so, when I see Orion as green,
what does that tell me?

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That's actually oxygen in the
nebula, but what you'll notice

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if you see photos of the Orion
nebula maybe taken

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00:12:46,360 --> 00:12:49,120
with the Hubble Space Telescope,
you'll notice they are actually

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00:12:49,120 --> 00:12:51,760
much more like this colour,
they are more kind of pinky-purpley,

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00:12:51,760 --> 00:12:54,520
and that's because there's a lot of
hydrogen in the nebula as well.

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00:12:54,520 --> 00:12:57,760
But it is amazing that, just with
the stars and even with the nebula,

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we can tell so much from
a very simple observation,

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00:13:00,680 --> 00:13:03,040
just by asking what colour
something is.

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00:13:03,040 --> 00:13:06,480
Exactly, and this was kind of a
revolution,

235
00:13:06,480 --> 00:13:09,320
the end of the 19th century,
early 20th century,

236
00:13:09,320 --> 00:13:11,040
this technique of spectroscopy,

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00:13:11,040 --> 00:13:13,840
being able to identify what's going
on in these gases,

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00:13:13,840 --> 00:13:16,800
in these elements,
just from their colours.

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00:13:16,800 --> 00:13:20,160
And it's really the birth
of modern astrophysics.

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All this, just from looking at
colour! Jen, thank you very much.

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00:13:23,720 --> 00:13:25,600
Thank you.

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00:13:25,600 --> 00:13:28,800
Coming up, we'll be exploring the
ancient art

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00:13:28,800 --> 00:13:30,680
of navigating by the sky.

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00:13:32,160 --> 00:13:36,320
But first, most regular viewers
already know that the night sky

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00:13:36,320 --> 00:13:38,920
is full of wonders.

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00:13:38,920 --> 00:13:42,640
But there are plenty of people out
there who have yet to be initiated.

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00:13:42,640 --> 00:13:46,760
So we set Maggie and Pete
a challenge.

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00:13:46,760 --> 00:13:49,720
Could they convince a group of young
people, who've never had the chance

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00:13:49,720 --> 00:13:52,080
to appreciate the beauty
of the night sky,

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00:13:52,080 --> 00:13:54,640
to take a look at astronomy?

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00:13:54,640 --> 00:13:59,160
We're here at the Ashton on Mersey
Sixth Form School in Manchester,

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00:13:59,160 --> 00:14:02,440
but we are on a mission to inspire
the next generation of astronomers

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00:14:02,440 --> 00:14:04,640
with the wonders of the night sky.

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00:14:04,640 --> 00:14:06,240
The weather's a bit challenging.

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00:14:06,240 --> 00:14:08,640
We've got lots of cloud scudding
through.

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00:14:08,640 --> 00:14:10,640
But we are going to give it
our best shot.

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00:14:13,280 --> 00:14:15,920
So what are your experiences
with the night sky?

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00:14:15,920 --> 00:14:18,360
Have you done much stargazing
in the past?

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00:14:18,360 --> 00:14:19,800
ALL: No!

260
00:14:19,800 --> 00:14:22,120
Do you notice the stars and the moon
and stuff?

261
00:14:22,120 --> 00:14:24,280
Yeah. OK. That's good.

262
00:14:24,280 --> 00:14:27,160
Have any of you looked through
a telescope before?

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00:14:27,160 --> 00:14:28,680
Yeah, from Argos!

264
00:14:28,680 --> 00:14:30,360
LAUGHTER

265
00:14:30,360 --> 00:14:32,280
Didn't see much. OK. Oh, right, yes!

266
00:14:32,280 --> 00:14:36,240
Do you know how many planets
are in the solar system? Is it 12?

267
00:14:37,680 --> 00:14:40,920
That's slightly high! Does
anyone else have a guess?

268
00:14:40,920 --> 00:14:42,560
Three.

269
00:14:42,560 --> 00:14:45,240
That's a bit low now! Six. Nine.

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00:14:45,240 --> 00:14:49,560
You're getting really close. Eight.
Eight, yes. Pluto was demoted.

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00:14:49,560 --> 00:14:52,280
So it used to be nine,
but Pluto was demoted.

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00:14:52,280 --> 00:14:55,520
OK, so we've got the moon,

273
00:14:55,520 --> 00:14:59,040
but I've set the telescope up
so that that's pointing at it.

274
00:14:59,040 --> 00:15:01,040
There's a bit of cloud down there,

275
00:15:01,040 --> 00:15:04,240
but if you want to have a look
through the eyepiece.

276
00:15:04,240 --> 00:15:06,080
Go on, have a go.

277
00:15:06,080 --> 00:15:08,560
The eyepiece is there,
so you're looking in the side.

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00:15:09,760 --> 00:15:11,360
Can you see it?

279
00:15:15,600 --> 00:15:19,680
It might be tricky.
I'm, like, seeing bits of it!

280
00:15:19,680 --> 00:15:23,120
Oh, yeah. I can see it. Can you see
it? Can you see any craters on it?

281
00:15:23,120 --> 00:15:24,480
What's a crater?

282
00:15:24,480 --> 00:15:26,960
It's sort of like where something's
hit it and it's left

283
00:15:26,960 --> 00:15:31,520
some indentations on it.
Like cheese. Yeah, yeah, yeah.

284
00:15:31,520 --> 00:15:35,600
Those craters are caused by lumps of
rock in space hitting the moon,

285
00:15:35,600 --> 00:15:37,760
and it's what leaves an impact
crater.

286
00:15:37,760 --> 00:15:40,800
Those craters you're looking at
there are about 100 miles across.

287
00:15:40,800 --> 00:15:42,440
Oh, my gosh!

288
00:15:42,440 --> 00:15:45,320
You wouldn't think it has all that
in it, would you? It's incredible.

289
00:15:45,320 --> 00:15:48,320
The moon is amazing when you
really get in close to it.

290
00:15:50,360 --> 00:15:54,320
Right, if you have a look through
there at the two stars.

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00:15:54,320 --> 00:15:55,600
Do you want to have a go?

292
00:15:56,880 --> 00:15:58,720
Look at them carefully. Can you see

293
00:15:58,720 --> 00:16:02,240
the difference in colour between
them? It looks like an aeroplane.

294
00:16:05,000 --> 00:16:06,920
One is yellowy in colour.

295
00:16:06,920 --> 00:16:10,080
The other one's tiny. One's yellow
and one's blue. Is that right?

296
00:16:10,080 --> 00:16:11,600
That's right, yeah.

297
00:16:11,600 --> 00:16:13,960
This is a star, it's called Albireo,

298
00:16:13,960 --> 00:16:16,480
and they are thought to be
gravitationally linked.

299
00:16:16,480 --> 00:16:22,280
They look beautiful because one of
them is yellow and the other one is

300
00:16:22,280 --> 00:16:23,760
a bluer star.

301
00:16:25,560 --> 00:16:28,320
Oh, look. There are some stars up
there.

302
00:16:28,320 --> 00:16:31,040
We should be able to see the W
of Cassiopeia.

303
00:16:31,040 --> 00:16:33,440
It's right up there above us.

304
00:16:33,440 --> 00:16:35,960
And if you've got the W of
Cassiopeia,

305
00:16:35,960 --> 00:16:37,960
you might get the Pleiades,

306
00:16:37,960 --> 00:16:40,760
you know, coming in.
The Pleiades would be nice.

307
00:16:42,600 --> 00:16:45,840
So the Pleiades, or the Seven
Sisters, is something that we call

308
00:16:45,840 --> 00:16:49,040
an open cluster, and these are
sort of like stellar nurseries,

309
00:16:49,040 --> 00:16:51,440
so it's where stars are born.

310
00:16:51,440 --> 00:16:54,360
How do you feel about that?
That's the best I've seen.

311
00:16:56,440 --> 00:16:59,440
Well, when we started off, you
hadn't looked through a telescope

312
00:16:59,440 --> 00:17:00,880
or seen anything in the night sky,

313
00:17:00,880 --> 00:17:04,360
but now you have seen a few things,
what do you think now?

314
00:17:04,360 --> 00:17:06,160
Fascinating.

315
00:17:06,160 --> 00:17:09,280
It's amazing that there's so much
out there that we don't know about.

316
00:17:09,280 --> 00:17:12,640
What's the best thing
you've seen tonight?

317
00:17:12,640 --> 00:17:15,800
Probably the moon.
Yeah, looking close at it.

318
00:17:15,800 --> 00:17:18,520
I just want to find out more now,
though.

319
00:17:18,520 --> 00:17:20,560
That's always good to hear, yeah.

320
00:17:20,560 --> 00:17:23,640
Right, OK. I never knew that stars
are different colours, either.

321
00:17:23,640 --> 00:17:27,040
Right. That was interesting.
We've done a good job here tonight.

322
00:17:27,040 --> 00:17:28,680
I think our work here is done.

323
00:17:28,680 --> 00:17:32,040
Yeah, definitely.
Go forth and buy telescopes!

324
00:17:36,600 --> 00:17:38,400
If all our talk about the beauty

325
00:17:38,400 --> 00:17:40,920
of the night sky has whet your
appetite,

326
00:17:40,920 --> 00:17:43,680
then you might want to get some
astronomy equipment of your own.

327
00:17:44,960 --> 00:17:47,880
So what do you need to dip your toe
in the water?

328
00:17:47,880 --> 00:17:49,800
Pete Lawrence has the answers.

329
00:17:51,960 --> 00:17:53,480
Now, it's great to be outside,

330
00:17:53,480 --> 00:17:55,720
looking up at the night sky
with just your eyes,

331
00:17:55,720 --> 00:17:59,760
but you'll get to a point where you
want to go a bit closer to them,

332
00:17:59,760 --> 00:18:04,360
you want to see more detail
and have a bit more magnification.

333
00:18:04,360 --> 00:18:07,920
And the best way to start doing that
is to use something like a pair of

334
00:18:07,920 --> 00:18:10,960
binoculars. And binoculars are
defined by two numbers.

335
00:18:10,960 --> 00:18:13,680
For example, these are
7 x 50.

336
00:18:13,680 --> 00:18:17,240
The first number indicates the
magnification of the binoculars.

337
00:18:17,240 --> 00:18:20,040
The second number indicates the
diameter of the front lens

338
00:18:20,040 --> 00:18:21,520
in millimetres.

339
00:18:21,520 --> 00:18:24,320
And that's really important because
the larger that value,

340
00:18:24,320 --> 00:18:28,200
the more light-gathering power
a pair of binoculars have got.

341
00:18:28,200 --> 00:18:32,720
Now, binoculars are wonderful
instruments to give you an overview

342
00:18:32,720 --> 00:18:35,840
of the night sky. They are wide
field instruments,

343
00:18:35,840 --> 00:18:39,400
so big clusters will look beautiful
through them.

344
00:18:39,400 --> 00:18:43,240
But there are occasions where you
want to get a bit more magnification

345
00:18:43,240 --> 00:18:45,240
and a bit more light grasp,

346
00:18:45,240 --> 00:18:47,720
and that's when you start to move
to a telescope.

347
00:18:47,720 --> 00:18:52,200
Now, the simplest type of telescope
is a lens-based telescope,

348
00:18:52,200 --> 00:18:56,320
known as a refractor. Here,
I've got a fairly basic refractor.

349
00:18:56,320 --> 00:19:00,120
This one's got a lens at the front,
which is 90 millimetres in diameter,

350
00:19:00,120 --> 00:19:03,200
so that's the light-gathering power
of this telescope,

351
00:19:03,200 --> 00:19:05,400
it's larger than these binoculars.

352
00:19:05,400 --> 00:19:08,440
So the light passes through the lens
at the front of the telescope,

353
00:19:08,440 --> 00:19:10,880
it's brought to a focus
at the end down here,

354
00:19:10,880 --> 00:19:13,960
and an eyepiece is used
to magnify the image.

355
00:19:13,960 --> 00:19:16,160
You can get different types
of eyepieces,

356
00:19:16,160 --> 00:19:19,280
and they can give you different
types of magnification.

357
00:19:19,280 --> 00:19:22,600
But this is a great telescope to
start picking up things like

358
00:19:22,600 --> 00:19:26,520
the craters on the moon, the rings
around Saturn and detail in some

359
00:19:26,520 --> 00:19:29,320
of the lovely deep
sky objects up there.

360
00:19:29,320 --> 00:19:31,600
But the amount of money you have to
spend,

361
00:19:31,600 --> 00:19:34,760
as you start moving up the scale
in refractor size,

362
00:19:34,760 --> 00:19:36,880
starts to become prohibitive.

363
00:19:36,880 --> 00:19:41,760
And that is where a second type of
basic telescope comes into play,

364
00:19:41,760 --> 00:19:45,280
which is known as a reflecting
telescope. Instead of using a lens

365
00:19:45,280 --> 00:19:48,000
at the front, this one uses
a mirror at the back,

366
00:19:48,000 --> 00:19:50,520
so the light comes in through
the front of the telescope,

367
00:19:50,520 --> 00:19:52,400
it hits the mirror at the back,

368
00:19:52,400 --> 00:19:55,760
and that mirror focuses the image
at the top of the telescope.

369
00:19:55,760 --> 00:19:58,800
You can't put your head there,
because you would block the light,

370
00:19:58,800 --> 00:20:02,760
so there is a small, 45-degree
mirror in the way

371
00:20:02,760 --> 00:20:06,200
which deflects the focusing light
off to the side of the tube.

372
00:20:06,200 --> 00:20:08,600
And that is where you stick the
eyepiece,

373
00:20:08,600 --> 00:20:10,600
and that is where you get your view.

374
00:20:10,600 --> 00:20:13,200
And the beauty of a reflecting
telescope is that,

375
00:20:13,200 --> 00:20:15,320
because they are less expensive,

376
00:20:15,320 --> 00:20:19,400
you can go for larger apertures and
that is more light-gathering power,

377
00:20:19,400 --> 00:20:23,000
and that means you can see fainter
objects in the night sky,

378
00:20:23,000 --> 00:20:27,320
so something like this is ideal
for looking at beautiful galaxies,

379
00:20:27,320 --> 00:20:30,560
nebulae, clusters, stuff like that,

380
00:20:30,560 --> 00:20:33,520
stuff which has got really faint
light, which you really need to grab

381
00:20:33,520 --> 00:20:37,480
and throw down the tube
of the telescope.

382
00:20:37,480 --> 00:20:41,040
To find out more about telescopes
and binoculars and the mounts

383
00:20:41,040 --> 00:20:44,000
they rest on, have a look at the
longer version of my review

384
00:20:44,000 --> 00:20:46,360
on the website.

385
00:20:46,360 --> 00:20:50,840
Remember, the best type of telescope
is the one that gets used.

386
00:20:53,920 --> 00:20:56,120
Our final Christmas treat

387
00:20:56,120 --> 00:21:00,040
is a very different way
to enjoy the night sky.

388
00:21:00,040 --> 00:21:03,960
For many thousands of years,
the sky has been our compass,

389
00:21:03,960 --> 00:21:07,960
our weather forecast, and our
calendar. But most of us have now

390
00:21:07,960 --> 00:21:12,960
lost that knowledge. So Chris took
a crash course when he met author

391
00:21:12,960 --> 00:21:16,080
and natural navigator
Tristan Gooley.

392
00:21:16,080 --> 00:21:19,160
So we are here in this field because
you are a natural navigator.

393
00:21:19,160 --> 00:21:20,760
What is that?

394
00:21:20,760 --> 00:21:24,480
Natural navigation is the wonderful
art of working out where we are

395
00:21:24,480 --> 00:21:27,200
and how to get to where we
want to be, just using nature,

396
00:21:27,200 --> 00:21:30,880
just what is around us.
And how does that link to astronomy?

397
00:21:30,880 --> 00:21:34,520
Well, the night sky has always been
one of nature's best compasses,

398
00:21:34,520 --> 00:21:38,320
and we have got fantastic cultural
records, from the Pacific Ocean,

399
00:21:38,320 --> 00:21:40,520
the Vikings, the Arab navigators,

400
00:21:40,520 --> 00:21:43,160
and all of those techniques
can still be used today.

401
00:21:43,160 --> 00:21:44,760
The sun is going down over there.

402
00:21:44,760 --> 00:21:47,640
We have got sunset. We have already
got the moon up there.

403
00:21:47,640 --> 00:21:50,360
And it is part of our national
navigation tool kit,

404
00:21:50,360 --> 00:21:52,800
if we look at the crescent moon
there,

405
00:21:52,800 --> 00:21:55,800
imagine a line touching the two
horns of the moon and then

406
00:21:55,800 --> 00:21:59,360
extend that down to your horizon and
you will be looking roughly south.

407
00:21:59,360 --> 00:22:02,880
It is not perfect, but it is giving
you the southern horizon.

408
00:22:05,240 --> 00:22:07,120
The first stars are coming out.

409
00:22:07,120 --> 00:22:09,200
It is a bit hazy, but we can see
them.

410
00:22:09,200 --> 00:22:12,360
How do we get ourselves oriented
in the landscape?

411
00:22:12,360 --> 00:22:16,920
Well, the best place for us to start
is nearly always the Plough,

412
00:22:16,920 --> 00:22:20,760
and I think we can just make it out,
just above those trees there.

413
00:22:20,760 --> 00:22:24,480
And we use the Plough
to find the North Star.

414
00:22:24,480 --> 00:22:27,000
And that is really our anchor
for night navigation.

415
00:22:27,000 --> 00:22:30,920
So how do we do that? Well, we have
got seven stars in the Plough,

416
00:22:30,920 --> 00:22:33,480
and we have got three
that make up the handle,

417
00:22:33,480 --> 00:22:36,720
and then four that make up the pan,
and as we look at it here,

418
00:22:36,720 --> 00:22:39,720
it is the two on the right
that form the pointers,

419
00:22:39,720 --> 00:22:42,520
and we go from the bottom
to the top one,

420
00:22:42,520 --> 00:22:44,480
and then five times that distance,

421
00:22:44,480 --> 00:22:46,400
in the direction they are pointing,

422
00:22:46,400 --> 00:22:49,040
and that takes us up
to the North Star.

423
00:22:52,440 --> 00:22:55,480
Tristan has planned a natural
navigation challenge.

424
00:22:56,640 --> 00:22:58,880
We'll head north into the woods

425
00:22:58,880 --> 00:23:02,040
and then try to find our way back
using the stars.

426
00:23:04,920 --> 00:23:09,520
Tristan's first trick was to pick a
feature, which he calls a handrail,

427
00:23:09,520 --> 00:23:11,760
which will help guide us back
to our starting point.

428
00:23:12,880 --> 00:23:14,440
So that is our handrail.

429
00:23:14,440 --> 00:23:17,880
A handrail is just a line that you
know what direction it runs...

430
00:23:17,880 --> 00:23:20,760
OK. ..and that you will recognise
easily. So it could be a river,

431
00:23:20,760 --> 00:23:23,880
it could be a road. Right. Lots of
things could be our handrail.

432
00:23:23,880 --> 00:23:25,720
It is going to be the woods tonight.

433
00:23:25,720 --> 00:23:28,440
The technique of the handrail
is nice and simple.

434
00:23:28,440 --> 00:23:31,400
You do not need to find an exact
point. If you understand where

435
00:23:31,400 --> 00:23:33,800
a line is, in this case the line
of the woods...

436
00:23:33,800 --> 00:23:36,280
Right. ..and using the North Star
and other stars,

437
00:23:36,280 --> 00:23:40,520
we can see that the edge of this
wood runs from west to east,

438
00:23:40,520 --> 00:23:42,160
and once we have got our handrail,

439
00:23:42,160 --> 00:23:45,000
it allows us to kind of be a little
bit, you know, roam a bit, instead

440
00:23:45,000 --> 00:23:48,000
of having to be really worried,
we know exactly where we are. Sure.

441
00:23:48,000 --> 00:23:51,440
We are able to go into the woods
and even if we start to feel that

442
00:23:51,440 --> 00:23:53,280
we do not know exactly where we
are...

443
00:23:53,280 --> 00:23:56,200
We know this edge is east-west.
Exactly. Good, all right.

444
00:23:56,200 --> 00:23:59,440
Well, I'm confident. Let's go and
give it a go. Let's go for it.

445
00:24:01,160 --> 00:24:04,440
Spotting the Plough gave us
an early confidence boost,

446
00:24:04,440 --> 00:24:07,680
and so we headed north from
the handrail into the woods.

447
00:24:09,080 --> 00:24:11,920
Right now I would like some more
clear sky. That would be helpful.

448
00:24:11,920 --> 00:24:14,520
I am a bit worried we are going to
get lost now. Without the stars,

449
00:24:14,520 --> 00:24:16,600
I have lost my comfort blanket.

450
00:24:19,200 --> 00:24:23,000
OK, well, I can see a path
heading down this way,

451
00:24:23,000 --> 00:24:27,400
and that looks like a good bet for
us to head if not back home then we

452
00:24:27,400 --> 00:24:31,640
are going to venture off in a new
direction. All right, let's do that,
this way, then. Yeah. Let's go.

453
00:24:33,400 --> 00:24:36,440
This new path seemed to take us
west,

454
00:24:36,440 --> 00:24:38,960
and so I knew home
was still roughly south.

455
00:24:40,320 --> 00:24:42,360
So we have come into the woods,

456
00:24:42,360 --> 00:24:44,960
but so far it has been pretty easy
going.

457
00:24:44,960 --> 00:24:47,920
We have been on paths, we had a path
took us north into the woods,

458
00:24:47,920 --> 00:24:50,920
and then one that we turned
left down, roughly west,

459
00:24:50,920 --> 00:24:53,920
we don't know exactly where, we
haven't totally lost our bearings,

460
00:24:53,920 --> 00:24:56,400
although we can only see
the odd star at the moment.

461
00:24:56,400 --> 00:24:58,800
Yeah. Things are about to get a lot
more challenging.

462
00:24:58,800 --> 00:25:01,040
Oh, are they? Good.
I'm glad to hear that.

463
00:25:01,040 --> 00:25:04,880
We are going to head into the woods,
off the path, towards our handrail.

464
00:25:04,880 --> 00:25:08,360
OK. And, yeah, you ready for that?
Yeah, let's do it.

465
00:25:08,360 --> 00:25:09,920
I am going to make you go first. OK.

466
00:25:09,920 --> 00:25:12,040
Good plan. And if you vanish,
I am running.

467
00:25:12,040 --> 00:25:15,720
OK. But otherwise,
let's go for it. OK.

468
00:25:15,720 --> 00:25:18,320
This is proper off, I can confirm
we have left the path.

469
00:25:21,280 --> 00:25:24,440
Careful, some sort of springy bits
there. Yeah, got it.

470
00:25:28,480 --> 00:25:32,360
At this point I knew that we needed
to head south to get back.

471
00:25:32,360 --> 00:25:34,240
But inside the dense woods,

472
00:25:34,240 --> 00:25:37,720
it was harder and harder
to work out which way that was.

473
00:25:37,720 --> 00:25:39,880
And the clouds were not helping.

474
00:25:42,240 --> 00:25:46,360
A clearing. I am not making out any
constellations at the moment.

475
00:25:46,360 --> 00:25:50,680
But there is a little technique
we can use.

476
00:25:50,680 --> 00:25:54,520
If you see the odd star and you have
tuned into which way the clouds are

477
00:25:54,520 --> 00:25:57,720
moving... Right. ..then unless there
has been a massive weather change,

478
00:25:57,720 --> 00:26:01,120
that will stay consistent.
OK, so I can see a star there.

479
00:26:01,120 --> 00:26:04,640
And the clouds are going...overhead.
Exactly.

480
00:26:04,640 --> 00:26:07,280
The clouds are moving
from the west to east.

481
00:26:07,280 --> 00:26:10,320
Right, OK. So we can use the stars
there. Without them, it would

482
00:26:10,320 --> 00:26:12,600
actually be very hard at night to
get any feeling

483
00:26:12,600 --> 00:26:15,560
for what the clouds are doing.
Right. So that is giving us...

484
00:26:15,560 --> 00:26:19,200
That is one of the most ridiculous
sentences anyone has ever said on

485
00:26:19,200 --> 00:26:22,080
an astronomy programme! But I am
glad they are useful to you.

486
00:26:22,080 --> 00:26:24,440
Good, OK. So we have got some idea
of our bearings,

487
00:26:24,440 --> 00:26:27,320
it does not have to be exact, that
is the beauty of the handrail. Yeah.

488
00:26:27,320 --> 00:26:30,360
If we know west is out there,
somewhere... South must be that way.

489
00:26:30,360 --> 00:26:33,920
Yeah. Right. OK. So let's head
south. Let's do it, yeah.

490
00:26:40,320 --> 00:26:42,760
There's something up ahead.
Oh, careful.

491
00:26:42,760 --> 00:26:44,920
There's a branch here. Yeah.

492
00:26:44,920 --> 00:26:46,000
Got it.

493
00:26:48,880 --> 00:26:52,080
Is that the edge? It looks like
we're hitting something.

494
00:26:53,800 --> 00:26:56,280
Looks like a fence, doesn't it?
It does. You all right?

495
00:26:56,280 --> 00:26:58,680
Civilisation. Yeah, I'm good.
OK. Yeah, yeah, all right.

496
00:26:58,680 --> 00:27:02,360
This is the intrepid bit.
There we go.

497
00:27:02,360 --> 00:27:06,400
You got it? Watch yourself.
Yeah, it's barbed. Very good.

498
00:27:09,040 --> 00:27:12,920
And, finally, the edge of the woods.

499
00:27:12,920 --> 00:27:16,560
And here we are. We've broken out

500
00:27:16,560 --> 00:27:18,160
of our woods.

501
00:27:18,160 --> 00:27:21,280
And this is what you called our
handrail, this edge of the woods.

502
00:27:21,280 --> 00:27:25,600
Yeah. And we know it runs
west to east,

503
00:27:25,600 --> 00:27:28,560
and it's the handrail that's allowed
us to explore,

504
00:27:28,560 --> 00:27:30,640
to wander and not worry
about getting lost.

505
00:27:30,640 --> 00:27:32,160
It's great to be out here,

506
00:27:32,160 --> 00:27:34,880
and whether you're doing what you do
or looking at the stars,

507
00:27:34,880 --> 00:27:37,880
the more time you spend outside
at night, the more you see.

508
00:27:37,880 --> 00:27:41,200
Yeah, I love natural navigation
at night.

509
00:27:41,200 --> 00:27:43,000
You know, being outdoors at night,

510
00:27:43,000 --> 00:27:45,760
a small adventure becomes a really
big one. Well, shall we wander?

511
00:27:45,760 --> 00:27:47,320
Yeah. Let's do it.

512
00:27:49,880 --> 00:27:54,360
My walk reminded me of just how
incredible the night sky is,

513
00:27:54,360 --> 00:27:59,120
and how time passed just looking up
is always time well spent.

514
00:28:04,280 --> 00:28:07,280
That's it for this month. We hope
we've inspired you to get outside

515
00:28:07,280 --> 00:28:09,840
and look at the wonders
of the night sky.

516
00:28:09,840 --> 00:28:12,920
Join us in January when we'll be
back with answers to some of

517
00:28:12,920 --> 00:28:14,960
the biggest questions of all.

518
00:28:14,960 --> 00:28:18,840
And don't forget to look out for
my star guide on the website, too.

519
00:28:18,840 --> 00:28:21,320
In the meantime,
have a very Merry Christmas

520
00:28:21,320 --> 00:28:24,720
and get outside and get looking up.
Goodnight.