{"product_id":"wobbleon-the-chandler-wobble-physics-t-shirt","title":"Wobbleon – The Chandler Wobble Physics T-Shirt","description":"\u003cp\u003eWobbleon holds up a spinning globe, and its pole drifts in a small circle he cannot quite stop.\u003c\/p\u003e\u003ch3\u003eThe Physics\u003c\/h3\u003e\u003cp\u003eEarth'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. Wilson and Vicente (1990), using 86 years of optical astrometry, estimated 433.0 ± 1.1 days with a quality factor Q ≈ 179; later estimates fall near 431 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.\u003c\/p\u003e\u003cp\u003eThe 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.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eT_Chandler ≈ 433 days   vs   T_rigid ≈ 305 days\u003c\/strong\u003e\u003c\/p\u003e\u003cul\u003e\n\u003cli\u003eT_Chandler: observed free-wobble period\u003c\/li\u003e\n\u003cli\u003eT_rigid: Euler period for a rigid Earth of the same shape\u003c\/li\u003e\n\u003c\/ul\u003e\u003cp\u003eS. C. Chandler, Astronomical Journal 11, 59 (1891); Gross, Geophys. Res. Lett. 27, 2329 (2000).\u003c\/p\u003e\u003cp\u003e\u003cem\u003eHonest caveat:\u003c\/em\u003e 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.\u003c\/p\u003e\u003ch3\u003eOn the shirt\u003c\/h3\u003e\u003cp\u003eFront: 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.\u003c\/p\u003e","brand":"Printify","offers":[{"title":"S \/ White","offer_id":50960518545511,"sku":"21414699644599269591","price":29.99,"currency_code":"USD","in_stock":true},{"title":"S \/ Black","offer_id":50960518578279,"sku":"10525920089088840661","price":29.99,"currency_code":"USD","in_stock":true},{"title":"M \/ White","offer_id":50960518611047,"sku":"32033802834506051582","price":29.99,"currency_code":"USD","in_stock":true},{"title":"M \/ Black","offer_id":50960518643815,"sku":"75712323106556682174","price":29.99,"currency_code":"USD","in_stock":true},{"title":"L \/ White","offer_id":50960518676583,"sku":"27190068823255940904","price":29.99,"currency_code":"USD","in_stock":true},{"title":"L \/ Black","offer_id":50960518709351,"sku":"72880505131063641326","price":29.99,"currency_code":"USD","in_stock":true},{"title":"XL \/ White","offer_id":50960518742119,"sku":"25222852125351422258","price":29.99,"currency_code":"USD","in_stock":true},{"title":"XL \/ Black","offer_id":50960518774887,"sku":"34898626260307423254","price":29.99,"currency_code":"USD","in_stock":true},{"title":"2XL \/ White","offer_id":50960518807655,"sku":"30214696836998328986","price":29.99,"currency_code":"USD","in_stock":true},{"title":"2XL \/ Black","offer_id":50960518840423,"sku":"26434791720225976061","price":29.99,"currency_code":"USD","in_stock":true},{"title":"3XL \/ White","offer_id":50960518873191,"sku":"37319403640764484309","price":29.99,"currency_code":"USD","in_stock":true},{"title":"3XL \/ Black","offer_id":50960518905959,"sku":"32743030515909235785","price":29.99,"currency_code":"USD","in_stock":true},{"title":"4XL \/ White","offer_id":50960518938727,"sku":"29372681900079865206","price":29.99,"currency_code":"USD","in_stock":true},{"title":"4XL \/ Black","offer_id":50960518971495,"sku":"23928258876576811903","price":29.99,"currency_code":"USD","in_stock":true},{"title":"5XL \/ White","offer_id":50960519004263,"sku":"16427800906463337542","price":29.99,"currency_code":"USD","in_stock":true},{"title":"5XL \/ Black","offer_id":50960519037031,"sku":"32074507430094045025","price":29.99,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0596\/8746\/9159\/files\/chandler-wobble_front_01_white.png?v=1793625738","url":"https:\/\/pixelatedphysics.com\/zh-hant\/products\/wobbleon-the-chandler-wobble-physics-t-shirt","provider":"Pixelated Physics","version":"1.0","type":"link"}