If you’re out in space, you would be able to navigate the galaxy with one simple navigational tool we’ve been using for centuries, a compass. 

By definition, a compass is a device that responds to magnetic fields providing cardinal directions used for geographic orientation . Since the core of the earth is made of molten, and compasses are made of metal, we’re easily able to identify north, south, east, and west because of Earth’s natural magnetic field. 

But did you know Saturn, Jupiter, stars, and even our galaxy have their own magnetic fields? If you are traveling through space, a simple compass can point you to the closest magnetic field, helping a space traveler navigate the galaxy. 

MICHELLE THALLER: How do you find your direction in space 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.

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.

NARRATOR: Get smarter, faster with videos from the world's biggest thinkers. And to learn even more from the world's biggest thinkers, get Big Think+ for your business.