that doesn't involve a magnetic field,

out between the galaxies

where really there's no detectable magnetic field at all?

Everything is moving.

There's nothing to say this point is still

and this is the reference point we're gonna use

and everything moves according to that point.

We're moving around the sun

at about 66,000 miles an hour right now.

The sun is moving around the galaxy,

around the core of the galaxy,

at about half a million miles an hour.

We are actually falling gravitationally into the center

of a cluster of galaxies

at about a million and a half miles an hour.

And that's just when we say relative to what?

Relative to the sun.

Relative to this group of galaxies.

There is no absolute standard of reference in the universe.

(upbeat music)

Let's talk first about compasses,

and then maybe talk a bit more about the idea

of how we locate ourselves in space in general.

A compass is something that responds to a magnetic field.

So the reason a compass always points north

is that it's responding to the magnetic field of the earth.

Our planet has this wonderful core of molten metal.

That metal moves around inside the earth

and it generates a magnetic field that has two poles,

a north pole and a south pole.

So when you make a compass,

you make it out of something metal

that can respond to that magnetic field,

and it points to the magnetic pole of the earth,

which is very close to our North Pole.

So, a magnetic field directs compasses.

Obviously, if you go away from the earth,

far away from our planet,

it's no longer gonna able to feel our magnetic field.

So a compass will not point to the North Pole of the earth

if say, you're out by Saturn.

Saturn and Jupiter are separate planets

and they have magnetic fields of their own.

So certainly if you were actually close to Jupiter,

Jupiter has a magnetic field,

much stronger than the Earth's magnetic field,

your compass would definitely point

to the North Pole of Jupiter

if you were actually around Jupiter now.

But what if you get farther out?

What if you'd actually go farther from there?

Is there any magnetic field out in space itself?

Well, actually it turns out that there are,

that our galaxy does have a magnetic field

as a whole too.

This magnetic field might be hard to detect.

You might need a very, very sensitive compass,

but if say you had it,

you would actually see that our galaxy

does have sort of a magnetic north and south pole,

and that magnetic field permeates our whole galaxy.

So, with compasses, you could actually at least find out

where the north and south pole of another planet is,

the north and south pole of a star.

A star has a magnetic field too.

Even the north and south pole of a galaxy.

So, if you were trying to navigate with a compass in space,

just remember that compass is going to respond

to the strongest and closest magnetic field.

It will point north,

north to the pole of the planet.

North to the pole of star.

Even to the north and south magnetic poles of our galaxy.

But what you're reading is a magnetic field.

That's what a compass does.

And that's pretty much all I can tell you.

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