For 540 million years, the ebb and flow in the strength of Earth's magnetic field has correlated with fluctuations in atmospheric oxygen, according to a newly released analysis by NASA scientists. The research suggests that processes deep inside the Earth might influence habitability on the planet’s surface. Earth’s magnetic field arises from the flow of material in the planet’s molten interior, which acts like a giant electromagnet. The flow isn’t perfectly stable, and this causes the field to ...