Breathe
By Edmée Pardo
I open my phone, tap the compass app and the task is done. If I look at the window it says I am 319 degrees northwest. If I turn 90 degrees, exactly the same place, and look at my computer screen, it says I'm 221 degrees southwest. How does the phone know! I look for an old-fashioned compass, a little acrylic ruler with two watery circles that my mom used to keep to put magnets on so I would know that the north side was toward my skin. It confirms the orientation, but not the degrees.
It is said that it was the Chinese, as with so many things in antiquity, who made the first compass around the first century. By rubbing a bar of magnet stone, called calamite, and placing it on water, they noticed that one end always pointed north and the other south. That north it pointed to is magnetic north, which, in case we didn't know, is not the same as geographic north.
Perhaps we could begin by understanding that the earth is a magnet and that at its center there are metals in constant motion that generate a giant magnetic field, which extends from the North Pole to the South Pole. This field is invisible, but it has lines of force that wrap around the planet, as if they were the invisible threads of a net. So far I understand well.
