Why is the moon not a planet?
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Q:

Why is the moon not a planet?

A:

Quick Answer

The moon is not a planet because, by definition, a planet is a "spherical ball of rock or gas that orbits a star," according to About.com. While the moon is a spherical ball of rock, it orbits the Earth and not the sun.

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Full Answer

The moon is the Earth's only natural satellite and the clearest object in the night sky. It is 240,250 miles away from the surface of the Earth and the closest celestial object. The rugged lunar terrain is responsible for the dark and light spots, observable from Earth.

The Giant Impactor hypothesis, proposed after the lunar visits of 12 Americans, posits that during Earth's formation, a large object approximately the size of Mars impacted Earth at an angle, throwing debris from its mantle and overlying crust to create the moon. The theory teaches that the impactor then melted and joined the cooling core of the Earth to increase its gravitational attraction for the newly forming moon.

The reclassification of Pluto as a dwarf planet in 2006 leaves eight planets in the sun's solar system. Several of these planets, in addition to Earth, also have moons, with Jupiter and Saturn both having more than 60 moons that orbit them.

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Related Questions

  • Q:

    Why is the moon important?

    A:

    Most people know that the moon's gravitational influence has an effect on the tides on Earth, but some scientists also believe that the presence of the moon played an important role in making Earth habitable to begin with. The interplay between the Earth and the moon mirrors events that occurred throughout the early solar system, as a Mars-sized object may have hit the Earth, sending some of the mantle into orbit that soon cooled into the moon. Over time, the relationship between the Earth and the moon may well have assisted the advent of life.

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  • Q:

    How big is the moon?

    A:

    Earth's sole natural satellite, the moon, has a circumference of 6,783.5 miles around its equator. Its surface area is 14,647,439.75 square miles, which is approximately 0.07 times that of the Earth.

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  • Q:

    Why do we have a moon?

    A:

    No concrete evidence explains why there is a moon. The best hypothesis presented is the Giant Impactor hypothesis: It suggests that around 4.45 billion years ago, while the Earth was still forming, a large object hit the Earth at an angle.

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  • Q:

    How old is the moon?

    A:

    The scientific consensus is that the Earth's moon formed four and half billion years ago. About 100 million years after the formation of the solar system, another small planet is likely to have collided with the Earth, resulting in the formation of the Moon.

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