Magnetism

5/27/07 – 6/2/07
by C. Zaitz

The earth is cooling. It had to. When it formed some 4.6 billion years ago, it was way too hot for any life to form. In fact, it’s taken a lot of time to cool enough for rhinos and beavers and gazelles to be able to roam freely without burning their hooves and paws and giant feet. Much of earth’s history has been spent cooling and changing into the planet we know and love. Unfortunately, earth doesn’t know and love us. It keeps changing, whether or not the life forms occupying its surface can survive it or not. It cares not whether its atmosphere grows thick or thin, whether its waters are pure, or if its movements will disrupt the parasites on its edge.

We know that huge volcanic eruptions and earthquakes can cause widespread destruction. They are caused by the movement of the plates of crust and mantle. Deeper within the earth lies the mechanism for creating an invisible shield, a barrier against the killing radiation from the sun. The earth has a fairly strong magnetic field, created and maintained by the movements of its liquid metallic outer core. The field extends out into space like a giant protective web. We have learned about the nature of our magnetic field from looking at the bottom of the ocean at the mid-Atlantic ridge. As magma flows out from the crack between two separating tectonic plates, little bits of magnetic material align in the direction of earth’s magnetic field. It hardens and the magnetic record is solidified. We can read the ocean floor like a book, and it’s telling us that over time the magnetic field of the earth changes. Sometimes it is aligned as it is now, but other times it’s completely switched. The north magnetic pole is sometimes in the southern hemisphere! What’s nerve-wracking is that while it’s switching, it can weaken and be non-existent for awhile. Our mid-Atlantic story book is telling us that it may be time for another switch. Or even more harrowing, as the earth cools and the outer core solidifies, the magnetic field may disappear forever.

Though we don’t often notice the effects of the magnetic field in our daily lives, it does provide an invisible barrier from the harsher radiation from the sun. We’re all familiar with the northern lights, which are caused by high energy solar radiation interacting with our atmosphere, spiraling in along the magnetic field lines near the poles. But what we’re not aware of is the daily bombardment of high energy particles from the sun that are deflected away from us. Without our magnetic field, we would be exposed to much more radiation than we’re used to, and it could be very harmful to all life forms on earth.

Between earth’s mantle and the cold, stark emptiness of outer space, lie the layers of geology that hold our history. Creatures have come and gone in the 3 billion year history of life on earth. It started with single celled organisms and has proliferated in the multifarious beings of today. But the creatures that were around 100 million years ago are not necessarily the ones we see now. Life has changed, often in big sweeping changes caused by the earth itself. Our magnetic field may be an important part of the plot of how life on earth changes, and we may be in store for the next chapter in the book. I hope it has a happy ending!

Until next week, my friends, enjoy the view.