Credit: Getty images
Earth's solid inner core formed 550 million years ago and restored the planet's magnetic field
Approximately 1,800 miles beneath our feet, swirling liquid iron in the Earth's outer core generates the planet's protective magnetic field. The magnetic field is invisible but is vital for life on Earth's surface because it shields the planet from the solar wind—streams of radiation from the sun.
About 565 million years ago, however, the magnetic field's strength decreased, to a level of only 10% of the strength it has today. Then, mysteriously, the field bounced back, regaining its strength just before the explosion of multicellular life on Earth.
