Aftermath of the earthquake: Shorter days Incredibly, the magnitude 9.0 earthquake that struck off Sumatra on Sunday morning caused a vertical displacement of so much material that the rotation period of the Earth has been permanently altered. By a tiny but measurable amount, the Earth is now rotating more quickly on its axis, and the 24-hour day is now one ten-thousandth second shorter.That's the result of calculations based on preliminary data made by Oak Park astronomer Dr. Leslie M. Golden. It's analogous to the increase in rotational speed that a twirling ice skater experiences when he or she draws in their arms. It is estimated that during the Sumatran quake, a block of material roughly 600 miles in length and 100 miles in width fell 30 feet closer to the Earth's axis of rotation. The planet has responded by rotating more rapidly, albeit ever so slightly, and our 24-hour days are now one ten-thousandth second shorter. [ Source: Tom Skilling, WGN-TV chief meteorologist, Dec. 28, 2004. Chicago Tribune. ]  ¶ 12/28/2004 11:13:00 AM