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Wobbleon

The Chandler Wobble Physics

\[T_{\text{Chandler}} \approx 433\ \text{days} \qquad T_{\text{rigid Earth}} \approx 305\ \text{days}\]
$29.99 USD
$29.99 USD
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Size guide S–5XL · inches

Wobbleon holds up a spinning globe, and its pole drifts in a small circle he cannot quite stop.

The Physics

Earth's rotation axis is not fixed to the crust; the pole wanders in a loop a few metres across. In 1891 S. C. Chandler found a component with a period of about 14 months, about 433 days. A rigid Earth of the same shape would wobble freely with a period of about 305 days; the elastic mantle, the fluid core and the oceans lengthen it.

The wobble damps, so something must keep exciting it. Richard Gross showed in 2000 that during 1985–1996 it was driven mainly by changes in ocean-bottom pressure, with the atmosphere second.

T_Chandler ≈ 433 days vs T_rigid ≈ 305 days

  • T_Chandler: observed free-wobble period
  • T_rigid: Euler period for a rigid Earth of the same shape

S. C. Chandler, Astronomical Journal 11, 59 (1891); Gross, Geophys. Res. Lett. 27, 2329 (2000).

Honest caveat: Gross's result covers 1985–1996; the balance of excitation in other periods is still studied. The wobble is not precession, and its size in metres varies.

On the shirt

Front: Wobbleon, the pixel-art character, with “THE CHANDLER WOBBLE”. Back: the wandering pole, the 433-day period, the rigid-Earth comparison, the ocean-pressure driver and Chandler's 1891 paper. Printed on a unisex tee.

Shipping calculated at checkout by destinationMade to order, ships in 2–5 business days

Details

Size & fitS–5XL

Unisex heavy cotton (Gildan 5000), classic fit.

SizeWidthLengthSleeve
S182815.1
M202916.5
L223018
XL243119.5
2XL263221
3XL283322.4
4XL303423.7
5XL323525

Pour l'échelle : la taille M mesure 20 in (50.80 cm) de large, soit environ 3.143 × 1034 longueurs de Planck (lP = 1.616255 × 10−35 m). Un mètre ruban est plus rapide.

Measurements in inches, ±1.5 in tolerance.

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Returns & replacements21 days

Every item is printed to order, so we can’t accept returns or exchanges for change of mind, or if you ordered the wrong size or colour.

Print defect, misprint, damage or the wrong item? We’ll send a free replacement, or a refund if you prefer. Report it within 21 days of delivery with a photo; no need to send it back.

Full refund & replacement policy

The physics

The Earth's rotation pole does not sit still. It wanders in a loop a few metres across, and I ride that wobble.

Seth Carlo Chandler found it in 1891 in careful records of latitude: a period of about 433 days. A perfectly rigid Earth would wobble with a period of about 305 days. Ours is longer because the Earth flexes: its mantle yields and its oceans slosh.

A wobble like this should die away within decades, so something must keep it going. Richard Gross showed in 2000 that, from 1985 to 1996, the main driver was changing pressure on the ocean floor, with the atmosphere helping. That covers one period of time; what drives it in other epochs, and why its size changes, is still being studied.

Equations

\[T_{\text{Chandler}} \approx 433\ \text{days} \qquad T_{\text{rigid Earth}} \approx 305\ \text{days}\]
SymbolMeaningUnit
\(T_{\text{Chandler}}\) observed period of the Chandler wobble (433.0 ± 1.1 d, Gross 2000) \(\mathrm{s}\)
\(T_{\text{rigid Earth}}\) free-wobble period a perfectly rigid Earth would have \(\mathrm{s}\)

Sources

  1. Chandler (1891) On the variation of latitude, I, Astron. J. 11, 59
  2. Gross (2000) The excitation of the Chandler wobble, Geophys. Res. Lett. 27, 2329

Field notes

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