The weather changed right on schedule. Wednesday’s ocean of gloom had drained away by Thursday. The first day of astronomical winter was unreasonably warm, dawning with a clear sky etched horizon to horizon in vapor trails. It looked like an air-route map in the back of an inflight magazine.
We will emerge from the solar recession rather slowly — not until Jan. 25 will we have a full 10 hours of sunlight in Washington. Winter is not our best season. This part of the world has too much sleet, freezing rain, “wintry mix.” But there will be fine days, too, when frozen ground greets legitimate snow. It is a striking season visually, with the landscape starker, the architecture more vivid. The vegetation vanishes and the surface reveals its secrets, the old chimneys and foundations. The clear night sky explodes in big, young, blue stars.
The Earth is a giant clock moving through space. The spring inside was wound up billions of years ago. The planet spins, and simultaneously falls around a star. It is an old star, stuck in its ways, fortuitously dull, and residing in a galactic cul-de-sac where not much happens. That’s a desirable location in a universe where things explode, collide, collapse into black holes, etc.
The galaxy itself moves, as does the whole galactic neighborhood – everything going somewhere. The entire universe is expanding. Change is a cosmic imperative. The clock can’t stop.
The problem with the Earth-clock is that it’s analog, not digital. This is a conundrum for an increasingly technological, wired civilization. Time can be measured very precisely with atomic clocks. A second is defined internationally as 9,192,631,770 oscillations of a cesium atom. Whereas the Earth, spinning its way through space, seems kind of old-fashioned and Pontiac-like by comparison.
And it is wobblier than you think. Listen to Brian Luzum, astronomer at the U.S. Naval Observatory and head of the Earth Orientation Department.
“There are five components that we measure,” he says. “There are two polar-motion components, there is one earth-rotation component, and then there are two precession-nutation components.”
Precession mutation?
“Nutation. ‘N.’ Nancy.”
If there were a long, straight rod through the axis of the Earth, from the Antarctic to the Arctic, it wouldn’t stick out at the geographically designated North Pole, but from a spot hundreds of yards away. That spot would wander over time. As it moved, we’d notice that the earth is wobbling on its axis the way a spinning top wobbles.
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