Path of Earth and Moon Around Sun
When viewed from the north celestial pole, i.e. from the star Polaris, the Moon orbits the Earth counterclockwise, the Earth orbits the Sun counterclockwise, and the Moon and Earth rotate on their own axes counterclockwise.
The right-hand rule can be used to indicate the direction of the angular velocity. If the thumb of the right hand points to the north celestial pole, its fingers curl in the direction that the Moon orbits the Earth, the Earth orbits the Sun, and the direction the Moon and Earth rotate on their own axes.
In representations of the Solar System, it is common to draw the trajectory of the Earth from the point of view of the Sun, and the trajectory of the Moon from the point of view of the Earth. This could give the impression that the Moon circles around the Earth in such a way that sometimes it goes backwards when viewed from the Sun's perspective. Since the orbital velocity of the Moon about the Earth (1 km/s) is small compared to the orbital velocity of the Earth about the Sun (30 km/s), this never occurs. There are no rearward loops in the Moon's solar orbit.
Considering the Earth–Moon system as a binary planet, their mutual centre of gravity is within the Earth, about 4624 km from its centre or 72.6% of its radius. This centre of gravity remains in-line towards the Moon as the Earth completes its diurnal rotation. It is this mutual centre of gravity that defines the path of the Earth–Moon system in solar orbit. Consequently the Earth's centre veers inside and outside the orbital path during each synodic month as the Moon moves in the opposite direction.
Unlike most other moons in the Solar System, the trajectory of the Moon is very similar to that of its planet. The Sun's gravitational pull on the Moon is over twice as great as the Earth's pull on the Moon; consequently, the Moon's trajectory is always convex (as seen when looking inward at the entire Moon/Earth/Sun system from a great distance off), and is nowhere concave (from the perspective just mentioned) or looped. If the gravitational attraction of the Sun could be "turned off" while maintaining the Earth–Moon gravitational attraction, the Moon would continue to orbit the Earth once every sidereal month.
Read more about this topic: Orbit Of The Moon
Famous quotes containing the words path of, path, earth, moon and/or sun:
“If you are ambitious of climbing up to the difficult, and in a manner inaccessible, summit of the Temple of Fame, your surest way is to leave on one hand the narrow path of Poetry, and follow the narrower track of Knight-Errantry, which in a trice may raise you to an imperial throne.”
—Miguel De Cervantes (1547–1616)
“I notice well that one stray step from the habitual path leads irresistibly into a new direction. Life moves forward, it never reverses its course.”
—Franz Grillparzer (1791–1872)
“Night is a curious child, wandering
Between earth and sky, creeping
In windows and doors, daubing
The entire neighborhood
With purple paint.”
—Frank Marshall Davis (b. 1905)
“The moon is my mother. She is not sweet like Mary.
Her blue garments unloose small bats and owls.”
—Sylvia Plath (1932–1963)
“Perchance not he but Nature ailed,
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It was not ripe yet to sustain
A genius of so fine a strain,
Who gazed upon the sun and moon
As if he came unto his own,
And, pregnant with his grander thought,
Brought the old order into doubt.”
—Ralph Waldo Emerson (1803–1882)