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.

How Stuff Works explains the Giant Impactor or Ejected Ring hypothesis: When the large object that was around the size of Mars hit the Earth, it threw debris into space from the Earth's mantle region and overlying crust. After the impact, the object of impact itself melted; and, it merged with the interior of the Earth. The hot debris merged to create the moon.

This hypothesis explains certain things, such as: why the moon has rocks that have a composition similar to the Earth's mantle, why the moon has no iron core, and, why moon rocks look as if they have been baked, although they have no volatile compounds. Computer simulations demonstrate that this hypothesis is possible.

Throughout the years there have been other theories to suggest why there is a moon. Some believe that the moon was made through fission and the Earth moved so rapidly on its axis that a large part of it during the molten stage spun off and formed the moon. Another theory is that the moon and Earth just happened to form at the same time. However, both of these theories have been proven wrong over time.

Learn More

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.

    Full Answer >
    Filed Under:
  • 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.

    Full Answer >
    Filed Under:
  • Q:

    What are the phases of the moon?

    A:

    The phases of the moon are: new moon, waxing crescent, first quarter, waxing gibbous, full, waning gibbous, third quarter and waning crescent. After the waning-crescent phase the moon returns to the new-moon phase and the cycle starts again. The complete cycle takes a little over 29 days.

    Full Answer >
    Filed Under:
  • Q:

    Why does the moon appear bright?

    A:

    The moon appears bright because the side visible on Earth reflects the light from the sun. As the moon and the Earth move around their respective orbits, different portions of the moon are visible to people on Earth, depending on the angle at which the light hits the moon and reflects back to Earth. The moon reflects back about 12 percent of the light from the sun that hits it.

    Full Answer >
    Filed Under:

Explore