In 1600, William Gilbert published a paper detailing how Earth behaves as a giant magnet. That may seem like a long time ago, but in geologic time, it's nothing. It has taken hundreds of years to understand how Earth's magnetic field works. However, now that we do, scientists are trying to find hints from Earth's history that might reveal the future of this ever-changing invisible field all around us. Specifically, archaeologists are studying the handles of ancient pottery. But before I can explain it, we have to get to know how the field affects us. Scientists believe Earth's magnetic field is generated by the spinning of the Earth's core. Our planet's magnetic field is super important as it blocks harmful rays emanating out of the Sun from hitting us on the ground, destroying the possibility of life as we know it. No big deal, right? It's always around us and it strengthens and weakens over time. Sometimes, it even flips. If the magnetic field were to flip, the magnetic north pole would become the south, and suddenly all magnetic compasses in the world would be backwards. Everything else would be fine, though. It's not like it would turn off and turn back on. NASA knows a magnetic field flip happens about every two to three hundred thousand years. We know the magnetic field has flipped because there is evidence in the geologic record. Scientists poked lava from the mid-Atlantic ridge where two tectonic plates meet. The ridge is spreading, giving easy access to very old cooled lava flows. Minerals embedded in the lava are sensitive to Earth's magnetic field as the lava cools. So by collecting samples of that lava, called cores, and analyzing the rock, it reveals a record of Earth's magnetic field over hundreds of thousands of years. This shows that...