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* Moon Facts * Surface Features * The Moon's Appearance * Exploring the Moon * What is the Moon? * How did the Moon get there? * How does the Moon stay up in the sky? * How far away is the Moon? * How do we know how far away the Moon is? * How big is the moon? * How fast does the Moon travel around Earth? * What is the temperature on the Moon? * How much would I weigh on the Moon? * How long is a day on the Moon? * How old is the Moon? * Why is there no air on the Moon? * Is there any water on the Moon? * Is there any sound on the Moon? * Why doesn't our Moon have a name? * Why is the Moon covered with craters? * What is the largest crater on the Moon? * What are the dark patches on the Moon? * Are there mountains on the Moon? * What is the far side of the Moon like? * Who is the man in the Moon? * Why don't we see the other side of the Moon? * How does the Moon shine? * Why is the Moon gray? * Why does the Moon change its shape? * How does a lunar eclipse happen? * When was the first picture of the Moon taken? * When were telescopes first used to study the Moon? * How long does it take to get to the Moon? * When did the first spacecraft land on the Moon? * Who were the first people to land on the Moon? * How many astronauts have walked on the Moon? * Which astronauts walked on the Moon? * When was the last time people visited the Moon? * Where did the astronauts land on the Moon? * When were lunar rovers used on the Moon? * How fast and far could the lunar rover travel? * How many Moon rocks were brought back to Earth? * When will people go back to the Moon? * Can you see more stars from the Moon? The revolution of the Moon around the Earth makes the Moon appear as if it is changing shape in the sky. This is caused by the different angles from which we see the bright part of the Moon's surface. These are called "phases" of the Moon. Of course, the Moon doesn't generate any light itself; it just reflects the light of the Sun. The Moon passes through four major shapes during a cycle that repeats itself every 29.5 days.  (1) New Moon - When the Moon is roughly in the same direction as the Sun, its illuminated half is facing away from the Earth, and therefore the part that faces us is all dark: we have the new moon. When in this phase, the Moon and the Sun rise and set at about the same time. (2) Waxing Crescent Moon - As the Moon moves around the Earth, we get to see more and more of the illuminated half, and we say the Moon is waxing. At first we get a sliver of it, which grows as days go by. This phase is called the crescent moon. (3) Quarter Moon - A week after the new moon, when the Moon has completed about a quarter of its turn around the Earth, we can see half of the illuminated part; that is, a quarter of the Moon. This is the first quarter phase. (4) Waxing Gibbous Moon - During the next week, we keep seeing more and more of the illuminated part of the Moon, and it is now called waxing gibbous (gibbous means "humped"). (5) Full Moon - Two weeks after the new moon, the moon is now halfway through its revolution, and now the illuminated half coincides with the one facing the Earth, so that we can see a full disk: we have a full moon. As mentioned above, at this time the Moon rises at the time the Sun sets, and it sets when the Sun rises. If the Moon happens to align exactly with the Earth and Sun, then we get a lunar eclipse. (6) Waning Gibbous Moon - From now on, until it becomes new again, the illuminated part of the Moon that we can see decreases, and we say it's waning. The first week after full, it is called waning gibbous. (7) Last Quarter Moon - Three weeks after new, we again can see half of the illuminated part. This is usually called last quarter. (8) Waning Crescent Moon - Finally, during the fourth week, the Moon is reduced to a thin sliver from us, sometimes called waning crescent. A while after four weeks (29.5 days, more precisely) the illuminated half of the Moon again faces away from us, and we come back to the beginning of the cycle: a new moon. Sometimes, when the Moon is almost new, it is possible to dimly see its darkened disk. The light from the Sun cannot reach this part of the Moon directly; but at this time the Earth (as viewed from the Moon) is at its full and very bright, and what we see is light reflected from the Earth, that then bounces back at us from the Moon. It's a long trip for this light: from the Sun to the Earth, to the Moon, and back to the Earth. |