By Dr. Robert Thorson

Each Thanksgiving I find something to be thankful for that most people miss. This year, my gratitude is for a new discovery about our beautiful blue planet.

For the past few days, I’ve been reading Florence William’s new book about the medicinal value of nature. For her, “The Nature Fix” (the title of her book) comes from the sensory experience of being surrounded by living nature. For me, the fix also comes from linking that experience to something deeper and grander.

But before moving on, let’s pause to consider the bad behavior of one species: Homo sapiens. Congressional millionaires are cutting taxes for corporate billionaires. Women have reached a tipping point on sexual harassment, exposing unhealed wounds. Fellow Americans in hurricaneravaged Texas, Florida and Puerto Rico are becoming depressed by the crawling pace of reconstruction. An America-first mentality is undermining our global credibility, especially with respect to the environment.

My litany isn’t meant to bum you out. It’s to let you know that I live in the same world you do, rather than some intellectual fantasy.

Does the deep molten core of our planet have weather? Can periodic sloshes of liquid iron influence the lives of human beings living 2,000 miles above?

The answer is yes. Earth is far more than a spherical patch of real estate in the neighborhood of our solar system. From top to bottom, it’s a colossal system within which we have become an important part.

Geophysicists have long known that the spin of the earth isn’t perfectly constant, but periodically slows down by a millisecond or two. One regular and well known oscillation is about three decades long, and coincides with a slight tweak in the earth’s magnetic field. The current explanation for this coincidence is that the mass of fluid iron within the outer core “sloshes” back and forth on a regular time scale.

The recent good news was published last August in Geophysical Research Letters and presented last October at the annual meeting of the Geological Society of America in Seattle. Geophysicists Roger Bilham and Rebecca Bendick showed us that the frequency of destructive earthquakes (greater than magnitude 7) during the last century rises and falls with the same regular 32-year period as that of day-length variations. Significantly, peak earthquake activity coincides with peak slowdowns.

Here’s the hypothesis. Changes in the behavior of the liquid outer core are felt by the solid lower mantle, causing a slight change in the rate of spin. Over the next few years, this slight difference propagates slowly upward through the soft mantle to reach the earth’s brittle crust, where earthquakes happen. Because earth’s surface spins at about 1,000 miles per hour, slight changes in angular momentum create enough differential stress to trigger earthquakes.

The last rotation-rate slowdown began four years ago and will peak next year. In consequence, Earth can expect about 20 large earthquakes, instead of the normal 15.

Why is this good news? Because information is power. If correct, the hypothesis will allow us to make long-range forecasts for seismic seasons analogous to those we make for hurricane seasons.

Though these seismic predictions will not be specific to location, date and magnitude, prior knowledge regarding statistical frequency, peak timing and potential destructiveness may be helpful, if only for knowing when the worst is over.

It’s also good news because these geophysicists are illustrating how science works. For the millionth time, one small footstep in scientific progress is being put to a clear test. If peak earthquake activity fails to coincide with peak slowdown, then this elegant hypothesis will be gently laid to rest with no hard feelings, and they will move on in search of other explanations.

That’s why I’m so thankful for science. It provides a path to knowledge that is distinct from tradition, mysticism and faith, and far more likely to give us the certainty we crave without taking any of the wonder away.

This year, I’m especially thankful for the whole of planet Earth, on which the thin veil of organic life depends, on which all of humanity depends.