(new age music)
-  Now that
we're talking galaxies,
it's time to introduce a new scale model.
Our next challenge is pretty simple:
if we could fit our
galaxy on a smartphone,
and Andromeda on a tablet,
how far apart would they be?
- So these are our galaxies.
- This is the Milky Way, and this is
our closest galaxy, Andromeda.
- (Voiceover) The Milky Way is
100,000 lightyears side to side.
With that information,
I want my volunteers to work out
the distance between the two galaxies.
- So, our Milky Way is 100,000
light years wide. And Andromeda
is 2.5 million light years away.
So in this scale, comparing this to this,
how far away is this galaxy?
- So this is 100,000 light years across,
and there's ten times that in a million,
and so that's 2.5
million light years away.
So that would make
- [American Woman] Twenty five of those
- Twenty-five of these.
Should we measure it?
One, two, three...
twenty-five!
- That's it?
- That's it!
And that's our nearest galaxy.
-  The Milky Way and Andromeda
are just the start.
They are surrounded by dozens
of galaxies in the local
galactic neighborhood.
And it doesn't stop there.
