In their cases, the equatorial bulges
are so great that their orbs look clearly elliptical rather than circular.
The equatorial bulge
adds some 21 kilometres to the distance to the centre of the Earth compared to that at the poles.
Newton had suggested that, on the basis of his gravitational theory, the Earth ought to be an oblate spheroid and have an equatorial bulge
, because it was rotating (see 1687, Universal Gravitation).
In the case of Earth, the attractions of the Sun and Moon on our planet's equatorial bulge
try to tilt up the axis to make it perpendicular to the plane of the ecliptic.
Its perigee (the point of its closest approach to the Earth) moved somewhat with each revolution, in part because of the gravitational pull of the Earth's equatorial bulge
16 SCIENCE, Coffey and his colleagues applied their visualization technique to a simplified set of equations that included deviations caused only by the Earth's equatorial bulge
The Sun and Moon tug on the equatorial bulge
of the tipped Earth and try to pull it toward the ecliptic plane.
A: Situated in the Western Cordillera of central Ecuador, the 6,31 O-metre summit of the extinct Chimborazo volcano is not only the country's highest mountain but due to the equatorial bulge
is the farthest point from the centre of the Earth
Scientists have found that the spectrum for a perfectly spherical earth is split by the planet's equatorial bulge
from the earth's rotation, the uneven distribution of continents and oceans and structures in the mantle.
Gravitational torques from the Sun and Moon on the Earth's equatorial bulge
make our planet's axis precess about the orbital plane with a period of 26,000 years.
Meanwhile, a group of researchers led by Thomas Herring at Harvard University has used VLBI data to measure a different kind of motion of the spin axis, one that changes relative to the rest of space and is driven by the sun's and moon's gravitational fields acting on the earth's equatorial bulge
In exactly the same manner, the spinning Earth slowly precesses because of the force that the tidal gravitational tugs of the Moon and Sun apply to the Earth's slight equatorial bulge
- which is tilted with respect to the ecliptic.