My seven-year-old daughter and I are moving along a thin trail under a stretch of pious pine trees in a direction that is believed to be north. As I do not carry a compass – or a GPS device – my general northerly confidence is attributed to the position of the sun relative to the time of day.
I am not certain about moss growth patterns or freshwater flow or any other natural guideline. We are simply moving northward with whatever certainty resides in my head.
I have read that the earth’s magnetic fields are expected to reverse. Scientists say the magnetism at the north pole is weakening and that we are entering a transition period. This transition period will last a thousand years or so before the poles flip from “normal” to “reverse.”
[Quotation marks are supplied for anthropocentric illustration].
A compass reading in a reversed scenario will dutifully point south instead of north. While this is strange, it does not appear to be dangerous.
Reversals have happened hundreds of times over the course of the earth’s history, most recently 780,000 years ago. They are as common as ice ages. Paleomagnetists are quick to remind us of commonness in terms of geologic time, versus – again – our more anthropocentric and brief experience of time.
The sun goes through these reversals approximately every 11 years. So the experience is not unique to our planet.
Scientists do not understand how magnetic reversals happen – nor do they understand why they happen. They are also puzzled by the randomness of magnetic field reversals – in terms of frequency and of duration.
The trail we are on meanders eastward. It climbs toward a bluff where the brush is curiously thicker. I ask my daughter to point out the four corners of north, south, east, west. She does not appreciate the sudden cerebral vibe of our hike.
Scientists understand that magnetism is a force between electric currents and that magnetic fields are produced – in part – by the molten core of the earth. They do not know how the electric currents are produced.
Many animals – including birds, salmon, bacteria, sea turtles, butterflies, hamsters, and whales – have sensitivity to magnetic fields and use those fields to pilot them.
I think about this and contemplate a reversal and the potential for the extinctions of the many species that rely on magnetic fields for navigation.
There is no evidence in the geologic record linking extinctions to the many reversals that have occurred over time. Sea turtles – a species that has been around for 120 million years – stand as just one example of an animal that has survived these changes. This is a relief.
I mention the coming reversal to my daughter. We climb on for a minute before she suggests that Santa Claus will have to move. This is the impact.
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