Although the Moon completes one orbit of Earth with respect to the stars about every 27.3 days,
the Moon revolves around Earth once with respect to the sun in about 29.5 days
following a slightly elliptical path at an average distance of 384,000 km.
The Moon's gravitational force is nine times less than the Earth's,
which means that you would weigh nine times less on the Moon.
The Moon is a dead world with no atmosphere. The sky is always dark, and you can see the stars and Sun at the same time.
Keep reading and learn more about Moon's phases, surface and exploration.
When you look up at the night sky, does the moon always appear the same? Have you noticed how the shape appears to change?
We can see only the half of the Moon that is lit by the Sun.
Since the Moon orbits the Earth we see this bright hemisphere from different perspectives.
The shape looks different from one day to the next because we see different parts of the moon's sunlit surface as it moves around the Earth.
This means that over the course of about a month, or to be more precise, in exactly 29.5 days, the Moon goes through the following main phases:
- New Moon is when the moon isn't at all visible in the sky because the sun is shining on what has falsely been
termed the "dark side of the moon."
Obviously it isn't always dark; it is just the side of the moon that we can't see from Earth.
During a New Moon the stars appear to shine more intensely, making it the best time to view the stars!
- First Quarter is when half of the waxing or growing moon is visible because the Sun is shining only on half
of the hemisphere that is visible from Earth.
- Full Moon is when the moon appears to be a complete circle because the Sun is shining directly on the entire visible hemisphere.
- Last Quarter is when the waning or shrinking moon is a semicircle because the Sun shines on the other half of the visible hemisphere.
Have you ever noticed the dark areas on the moon? Depending on your imagination these areas may have resembled a face,
a rabbit or something other interesting object.
These areas are called maria
, which in Latin means seas in Latin, because early astronomers thought they were large bodies of water.
These areas do not contain water, but appear darker because they are deeper and covered with dark basalt rocks from ancient lava flows.
Since the Moon cooled down long time ago, it is now geologically dead and all volcanic activity has stopped.
Most of the surface rocks are between 3 and 4.6 billion years old.
Most of the craters were form long time ago, yet the surface continues to be bombarded by meteoroids
forming more impact craters
and a layer of rubble and debris, called regolith.
Since the Moon is so close to the Earth, it is the most studied celestial body. The most exciting of all studies were the astronauts' visits.
Since 1969 twenty American astronauts have flown to the Moon. Some of them studied the Moon's surface and brought back samples of moon rock and dust.
Among the long list of space flights, perhaps the most interesting was the Soviet Luna 3
, which first photographed the Moon's far side.
The satellites Clementine
in 1996 and Lunar Prospector
in 1998 registered evidence of ice at the poles.
The Lunar Reconnaissance Orbiter (LRO)
, the first mission of NASA's Robotic Lunar Exploration Program,
and its companion craft the Lunar Crater Observation and Sensing Satellite
, known as LCROSS were launched in 2009.
LRO is involved in mapping the moon's surface and collecting data to be used for determining potential future landing sites.
LCROSS's main priority has been searching for water and ice.
Russia and the USA are not the only countries exploring the Moon;
China has recently announced plans to put astronauts on the Moon as part of their fledgling space program.
Is the Moon made out of cheese? Nope, and there are not any cows jumping over it, either. It's actually made out of rock.
Scientists now think that the Moon was formed from the collision of a Mars-sized object with the Earth.
This impact hit the Earth with such force that it scattered bits of Earth rock into space.
This scattered matter stuck together and formed the Moon. This explains why the Moon is less dense than the Earth:
when rocks and metals were thrown into space from Earth, the heavier metal objects fell back to Earth,
while the lighter rocks stayed in orbit long enough to stick together forming our Moon.
This is why the Moon is composed of less metal than the Earth.