It takes 27.3 days for the moon to orbit the earth.
BUT it takes 29.5 days to go from new moon to new moon. Why?
It isn't really that strange. The answer makes sense.
The moon takes 27.3 days to complete an orbit of Earth. If nothing else moved, it would be 27.3 days from new moon to new moon.
However, the earth is also moving -- it's orbiting the sun. It takes an extra 2.2 days for the moon to be back in a position so that we see (or don't see) new moon again. Look at the diagram below:
More Strange but true...
Here's another interesting piece of information:
The moon also rotates on its axis. Its rotation is slower than Earth's (Earth completes one rotation in 24 hours). It takes 27.3 days for the moon to rotate once.
BUT, remember, it takes 27.3 days for the moon to orbit the earth.
27.3 days rotation and 27.3 days orbit.
What this means is that from Earth, we can only see one side of the moon (it's called the "near side" of the moon). We will never be able to see the other side of the moon unless we go on a spaceship and fly around to the other side -- or look at a photograph. Look to your right -- it is a photo of the far side of the moon, taken from the Galileo spacecraft on its way to Jupiter.
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The moon is grey and has plains (flat areas called "marias"), mountains (or "highlands"), valleys (or dips), and a lot of craters. Craters are holes, or dents, which were made when meteoroids hit the moon's surface. (Remember, the moon has no atmosphere to protect it from meteoroid collisions.)
COLD, COLD, COLD
The moon has no atmosphere, so when it's night and not facing the sun, it's very cold. When it's day and facing the sun, it's very hot.
Average daytime temperature: 107�C
Average nighttime temperature: -153�C
Maximum temperature: 123�C
Minimum temperature: -233�C
Think about...
Why does the moon's lack of atmosphere affect its temperature?
What else do you think might affect the temperature on the moon?
All photos of the moon courtesy of NASA -
National Space Science Data Center,
NASA Goddard Space Flight Center,
Greenbelt, MD 20771, USA
http://nssdc.gsfc.nasa.gov