The most popular theory regarding lunar formation is that a Mars-sized planetoid slammed into the Earth and flung molten debris into orbit around 40 million years after the solar system was created, according to scientists at the National Aeronautics and Space Administration (NASA). This is called the giant impact theory.Continue Reading
Debris from the collision was bound together by gravity, and these ejected particles coalesced to form the moon. Initially, both the Earth and moon spun very fast on their axes, but they have since slowed down. The giant impact hypothesis explains why the moon is made of lighter elements without a heavy core. This mathematical model also explains why the moon's orbit became tidally locked with the same face towards the Earth at all times.
There are two other theories regarding how the Earth's moon formed. One is that the moon was created at the same time as the Earth because particles were coming together during the solar system's formation. If this is true, then scientists believe the moon would be much denser.
Another theory of lunar formation involves the Earth's gravity capturing a moon passing by the planet. This is how Mars got its two moons. Scientists think that if this how the moon came into Earth's orbit, the celestial body wouldn't be spherical nor would the moon line up with the Earth's ecliptic orbit.Learn more about Our Moon
Sunlight reflects off the moon's surface, and it is seen at different angles from the Earth as the moon moves in orbit around the planet. These changes are known as lunar phases, which occur in a cycle that repeats every 29.5 days.Full Answer >
The moon completes one orbit around Earth with respect to the distant stars every 27.5 days. This constitutes a sidereal month. In contrast, the lunar cycle of 29.5 days is called a synodic month. It takes the moon an additional 2 days to begin a new lunar cycle because Earth is not stationary in space, but instead moves as it orbits the Sun.Full Answer >
The moon completes one full rotation about its axis in the same time it takes Earth to complete a full revolution, resulting in one side always turning to face the parent planet in sync with its orbit. This phenomenon is known as tidal locking.Full Answer >
The moon orbits the Earth at approximately 2,288 miles per hour and completes one full orbit every 27.322 days. Additionally, the moon takes approximately 27 days to complete one full rotation on its own axis, called its rotational period, which closely matches its orbit around Earth.Full Answer >