Earth's magnetic field

What makes this fascinating

• A shield from a molten sea — Churning liquid iron in Earth's core generates the field that deflects harmful solar radiation.

• The geodynamo — How exactly moving metal sustains the field is modeled, but not fully solved.

• It flips — The poles have reversed hundreds of times; the field is weakening now, and the next flip can't be predicted.

Frequently asked questions

What creates Earth's magnetic field?

A 'geodynamo': the churning of molten iron in Earth's outer core generates electric currents that produce the magnetic field shielding life from harmful solar and cosmic radiation.

Why does Earth's magnetic field flip?

The poles reverse irregularly over geological time, on average every few hundred thousand years. The flips are recorded in rocks, but exactly what triggers them isn't fully understood.

Is the magnetic field about to reverse?

The field has weakened in recent centuries and the poles wander, but scientists can't predict a reversal; if one began it would unfold over centuries to millennia, not overnight.

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