Chandler wobble

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The Chandler wobble or Chandler variation of latitude is a small deviation in the

rotation relative to the solid earth,[1] which was discovered by and named after American astronomer Seth Carlo Chandler in 1891. It amounts to change of about 9 metres (30 ft) in the point at which the axis intersects the Earth's surface and has a period of 433 days.[2][3] This wobble, which is an astronomical nutation, combines with another wobble with a period of six years, so that the total polar motion
varies with a period of about 7 years.

The Chandler wobble is an example of the kind of motion that can occur for a freely rotating object that is not a sphere; this is called a free

precessions of the equinoxes
.

Predictions

The existence of Earth's free nutation was predicted by

superconducting gravimeter.[5]

Measurement

The

International Earth Rotation Service
(IERS).

The wobble's amplitude has varied since its discovery, reaching its largest size in 1910 and fluctuating noticeably from one decade to another. In 2009, Malkin & Miller's analysis of IERS Pole coordinates time series data from January 1946 to January 2009 showed three phase reversals of the wobble, in 1850, 1920, and 2005.[2]

Hypotheses

Since the Earth is not a rigid body, the Chandler wobble should die down with a time constant of about 68 years,

oceans, or crust (from earthquakes
), for a long time the actual source was unclear, since no available motions seemed to be coherent with what was driving the wobble.

An investigation was done in 2001 by Richard Gross at the Jet Propulsion Laboratory managed by the California Institute of Technology. He used angular momentum models of the atmosphere and the oceans in computer simulations to show that from 1985 to 1996, the Chandler wobble was excited by a combination of atmospheric and oceanic processes, with the dominant excitation mechanism being ocean‐bottom pressure fluctuations. Gross found that two-thirds of the "wobble" was caused by fluctuating pressure on the seabed, which, in turn, is caused by changes in the circulation of the oceans caused by variations in temperature, salinity, and wind. The remaining third is due to atmospheric pressure fluctuations.[6]

Chandler wobble of Mars

Using radio tracking observations of the Mars Odyssey, Mars Reconnaissance Orbiter and the Mars Global Surveyor spacecraft, the Chandler wobble of Mars has been detected. It is the first time it has been detected on a planetary body other than the Earth. The amplitude is 10 cm, the period is 206.9 ± 0.5 days and it is in a nearly circular counterclockwise direction as viewed from the North Pole.[7]

See also

References

  1. ^ e.g. Mueller, I.I. (1969). Spherical and Practical Astronomy as Applied to Geodesy. Frederick Ungar Publishing, NY, pp. 80.
  2. ^
    S2CID 17120582
    .
  3. ^ "Earth's Chandler Wobble Changed Dramatically in 2005". TechnologyReview.com. MIT Technology Review. 2009. Retrieved 23 January 2024.
  4. ^ Euler, Leonhard (1765). "Du mouvement de rotation des corps solides autour d'un axe variable". Mémoires de l'Académie Royale des Sciences et Belles Lettres. 14: 154–193.
  5. ^ See, e.g., Fig. 2.3. Virtanen, H. (2006). Studies of Earth Dynamics with the Superconducting Gravimeter (PDF) (Academic Dissertation at the University of Helsinki). Geodetiska Institutet. Archived from the original (PDF) on June 5, 2011. Retrieved September 21, 2009.
  6. ^
    doi:10.1029/2000gl011450
    .
  7. S2CID 225131576
    .

Further reading

External links
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