大象传媒

In the first of a new series of Frontiers, Peter Evans examines new insights into the earth's core - the most powerful dynamo imaginable that produces a giant magnetic field that keeps earth a living planet and protects us from deadly radiation sweeping through the solar system.

There's a region of our planet that no human has ever visited, yet what happens within and around it affects all of us- it's the earth's molten core 2000 miles beneath our feet. Here, a vast ocean of liquid iron generates an invisible magnetic force which not only makes our compasses point north, but creates a magnetic cocoon around our earth that protects us from deadly solar radiation.

This so called "geodynamo" generates a force which history has shown fluctuates wildly and over the course of evolution has undergone several reversals. Current observations show worrying signs that we're due for another of these flips.

If that's the case, scientists predict that during the shift, lethal radiation could reach the earth's surface with potentially disastrous consequences for the atmosphere, climate and life.But short of drilling to the centre of the earth, how can we gain better insights into the current and future behaviour of the geodynamo?

The alternative is, it seems, to make your own. Peter Evans meets the ambitious teams of experimentalists who are attempting to create magnetic dynamos in their labs - giant rotating spheres of molten metal with which they are attempting to unlock the mysteries of the well known but poorly understood phenomenon.

The experiments are huge technical challenges, but as research teams compete to produce the first significant results, the subtleties of the system are beginning to emerge.They offer insights into how magnetic fields grow and subside and what the future really holds for the protective force around our own planet.