American and Canadian scientists have reported in the latest issue of Science that the magnetic field of our planet is at least 4 billion years old, up from the previous estimate of 3.45 billion years. An artist’s depiction of Earth’s magnetic field deflecting high-energy protons from the Sun around 4 billion years ago. Image credit: Michael Osadciw / University of Rochester. Earth’s magnetic field is generated in its liquid iron core, and this...
