Movements of the Earth
and it turns majestically
|Updated June 01, 2013
The Earth moves in an orbit around the Sun at an average speed of 107 218.8 km/h (between 29.291 km/s 30.287 km/s). In the solar system, planets have orbits that are all roughly in the same plane. This orbital plane called the ecliptic. At the same time the Earth rotates on itself about an axis at speed (at the equator) 1 674.364 km/h, this axis is oriented toward the north celestial pole. The inclination of the axis of a planet is the angle between the axis of rotation of the planet and perpendicular to its orbital plane. This inclination is called obliquity 23.4388°, but it varies in a cycle of 41,000 years, between 24.5° and 22.1°. It was shown by Jacques Laskar, French astronomer, the moon stabilizes the value of the obliquity of about 23°, thus preventing it to vary chaotically. The slow change in direction of the axis of rotation of the Earth is called the precession of the equinoxes. This angle of about 23° is the succession of seasons. The tidal forces of the Moon and the Sun disrupt the movement of precession and causes the Earth's axis oscillation, like a spinning top. This movement leads to moving the orientation of the North Pole among the stars, over time, we change our polestar. Currently, the star nearest the north celestial pole, the gap is only 1°, α Ursae Minoris is called North Star (Polaris).
A complete cycle of precession takes 25,765 years, called great Platonic year. Add to this the attraction of the Moon which disrupts the precession slightly by adding small oscillations whose period is 18.6 years. This effect is called nutation. In addition, the tidal effects of the Moon on the Earth's slowing rotation and the Moon moving away from Earth at a rate of about 38 mm/year, producing a longer day than 23 microseconds land per year. Over several million years, these small changes produce significant changes.
Image: The Earth moves like a top around its orbit. The end of the axis describes a circle slowly in a horizontal plane, towards the north celestial pole, the motion of precession. All movements of the Earth are irregular and vary continuously in time, the measurement of a microphone exceptional variation of a local event on Earth, like an earthquake, is virtually impossible.
The day would have shortened by 1.26 μs!
On December 26, 2004 at 00 h 58 min 53 s UTC (7:58 to Jakarta and Bangkok) took place off the Indonesian island of Sumatra earthquake of magnitude 9.1 to 9.3. At the time, Richard Gross, a geophysicist at NASA's Jet Propulsion Laboratory in California, had indicated that the length of days may have less than 3 microseconds, but the measurements on the rotation of the Earth did not detect anything. The powerful 8.8 magnitude earthquake that struck Chile on the Saturday, February 27, 2010, near Conception, over 300 km from the capital Santiago, may have had effects on the axis of rotation of the Earth, according scientists at the Jet Propulsion Laboratory (JPL) of NASA. According to preliminary calculations, derived from a computer simulation, the earthquake of 27 February 2010 could have resulted in a shift of 8 inches from the axis of rotation of the Earth and that should cause a shortening of the days of 1.26 microsecond. A major earthquake can disrupt slight rotation of the Earth. In fact, when a plate of Earth's crust collapses during an earthquake, the earth's circumference narrows slightly. This movement of mass towards the center of the Earth can cause an acceleration of the Earth's rotation around its axis, like an ice skater speeds up its rotation by closing the arms.
Phenomenon is not surprising astrophysicist Alfred Vidal-Madjar. "It is a law of physics, says he. Each time a body changes shape, its rotational speed changes."
Image: The earthquake in Chile, was caused by a piece of the Earth's crust that has plunged sharply towards the center of the Earth.
Wonderful journey of man
The planet Earth is a miraculous blue dot, an oasis of life amidst the vastness of a Universe without end.
Supercluster, Virgo Supercluster and Hydra Centaur fall themselves to another major city clusters of galaxies known as the Great Attractor.
Image: Image taken by Apollo 8, first mission to be carried men beyond earth's orbit between 21 December 1968 and December 27, 1968.