Chandler wobble

The Chandler wobble is a small variation in Earth's axis of rotation, discovered by American astronomer Seth Carlo Chandler in 1891. It amounts to 0.7 arcseconds over a period of 435 days. In other words, Earth's poles move in an irregular circle of 3 to 15 metres in diameter, in an oscillation.

The wobble's diameter has varied since discovery, reaching its most extreme range recorded to date in 1910. The cause is unknown: barring any external force, the wobble should have eventually subsided. Originally it was believed that the wobble was caused by weather fluctuations from season to season causing shifts in atmospheric mass distribution, or possible geophysical movement beneath Earth's crust. On 18 July 2000, however, the Jet Propulsion Laboratory announced that "the principal cause of the Chandler wobble is fluctuating pressure on the bottom of the ocean, caused by temperature and salinity changes and wind-driven changes in the circulation of the oceans."

The Chandler wobble is a factor considered by satellite navigation systems (especially military systems). It is also theorised as the cause of major tectonic activity, including earthquakes, volcanism, El Niño, and global warming phenomenon.

During the first hour of the national radio broadcast of Coast to Coast AM on January 28, 2006, Lloyd Stewart Carpenter reported that the Chandler wobble has stopped (i.e., its amplitude has reduced to zero) -- which could be a harbinger of a catastrophic pole shift. This is however completely unfounded speculation as the actual recorded data shows no indication that the wobble has stopped, or shows any signs of stopping. If it did stop for any length of time this would be of great interest in gaining a better understanding the causes, but would not cause any catastrophic changes in the overall rotation axis of the planet.

The Truth of the matter.

The Chandler wobble has changed, simply take a look at the US Navy data for the past 2 years. It clearly shows the wobble has diminished as of mid-late 2005.

link to the graph on US Navy website - http://maia.usno.navy.mil/yplot2.gif & http://maia.usno.navy.mil/xplot2.gif Historical data can be seen here - http://maia.usno.navy.mil/yplot1.gif & http://maia.usno.navy.mil/xplot1.gif

References

• Carter, B, and M.S, Carter, 2003, "Latitude, How American Astronomers Solved the Mystery of Variation", Naval Institute Press, Annapolis.
• Lambeck, K., 1980, The Earth's Variable Rotation: Geophysical Causes and Consequences, Cambridge University Press, London.
• Munk W. H. and MacDonald, G. J. F., 1960, The Rotation of the Earth, Cambridge University Press, London.

External links

• IERS International Earth Rotation Service (IERS) incorporating the Earth Orientation Paramaters (EOP) and International Celestial Reference System (ICRS) groups
• The United States Naval Observatory
• Jet Propulsion Laboratory press release announcing cause of the Chandler wobble
• Mystery of wobbly Earth solved