The
Moon travels around the Earth. It takes 28 days to go around this orbit.
The Earth moves around
the Sun, it takes 365 days (one year) to go all the way around. As the
Earth moves around the sun it is spinning. It takes 24 hours (one Day)
to spin around on its axis ( the axis is just an imaginary line that goes
through the middle of the Earth from the North pole to the South pole,
take a look at a spinning globe in your classroom if you're not sure.)
This shows what the Earth looks like from near the Sun.The part of the
Earth that is facing the Sun is lit up, it is daytime here, but the other
half of the world is facing away from the Sun so it is in darkness. As
the Earth turns on its axis different parts turn to face the Sun and this
is why we get day and night. If you were standing on the Earth (and you
probably are!) you would see a very different picture. From here it looks
as if the Sun is moving accross the sky, rising in the East and 12 hours
later setting in the West.
As the sun appears to move across the sky it means that the shadows also
move. The shadows appear long in the morning and evening, but at midday
they are very short.
The Moon.
T
The Moon appears to move across the night sky just as the Sun does during
the day. But as well as moving across the sky the moon appears to change
its shape from one night to the next. It seems to start as a thin crescent
then get fatter and fatter until, after a couple of weeks, it is a full
circle. Then it gets thinner and thinner until it becomes a crescent
shape and eventually seems to disappear altogether !
The Moon appears to change shape because only the part of the moon facing
the Sun is lit up. As the moon moves around the Earth we can see more or
less of the bright half. This animation shows what happens. The half of
the Moon that is not lit up by the sun is in total darkness and we cannot
see it at all.
It takes about one month (28 days) for the Moon to orbit the Earth so the
changing face of the Moon repeats itself every 28 days.