Thousands of miles beneath our feet, a giant nuclear reactor seems to be at work deep within Earth's core, and preliminary research suggests it may be the mysterious power source behind the planet's magnetic field and thermal energy, upon which all life on the planet depends for its survival...

A ball of uranium 5 miles in diameter could be the generator of Earth's magnetic field. It's hard to prove (!) but makes a lot of sense.

Because "a nuclear reactor can decrease power output -- and even shut itself down -- and come back to life again", it could explain why our magnetic poles flip regularly.