Magnetic Fields

From the BBC comes the news that paleomagneticists have discovered newly sensitive techniques to examine remnant magnetism in ancient rock (above, the Barberton greenstone belt in Africa), pushing back the oldest known evidence of the young Earth's magnetic field, to 3.45 billion years ago.

The Barberton samples indicate the nascent field was considerably weaker than today's protective shield.

Whereas the modern boundary between our planet's magnetosphere and the solar wind might be located ordinarily at about 10 Earth radii, the ancient boundary would have been much closer - perhaps three to five Earth radii, said Professor Tarduno.

To me, though, the earth has always held a certain magnetism...