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:
“Another danger is imminent: A contested result. And we have no such means for its decision as ought to be provided by law. This must be attended to hereafter.... If a contest comes now it may lead to a conflict of arms. I can only try to do my duty to my countrymen in that case. I shall let no personal ambition turn me from the path of duty. Bloodshed and civil war must be averted if possible. If forced to fight, I have no fears from lack of courage or firmness.”
—Rutherford Birchard Hayes (1822–1893)
“Reporters for tabloid newspapers beat a path to the park entrance each summer when the national convention of nudists is held, but the cult’s requirement that visitors disrobe is an obstacle to complete coverage of nudist news. Local residents interested in the nudist movement but as yet unwilling to affiliate make observations from rowboats in Great Egg Harbor River.”
—For the State of New Jersey, U.S. public relief program (1935-1943)
“In two or three hundred years life on earth will be unimaginably beautiful, astounding. Man needs such a life and if it hasn’t yet appeared, he should begin to anticipate it, wait for it, dream about it, prepare for it. To achieve this, he has to see and know more than did his grandfather and father.”
—Anton Pavlovich Chekhov (1860–1904)
“Sad men made angels of the sun, and of
The moon they made their own attendant ghosts,
Which led them back to angels, after death.”
—Wallace Stevens (1879–1955)
“The sun shines bright in the old Kentucky home;
‘Tis summer, the darkeys are gay;
The corn-top’s ripe, and the meadow’s in the bloom,”
—Stephen Collins Foster (1826–1884)