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How does the phenomena of "seasons" occur. Why would it be summer inMaryland when it is winter in the southern hemisphere?Does the moon have seasons?

Seasons are caused by the 23.5 degree tilt of the Earth's axis. This axis always points in the same direction, so that the North Pole always points towards the star, Polaris. Think of the Earth as a spinning top, tipped over to one side. It remains tipped in the same direction as it travels around the Sun. This means that sometimes the northern half of the Earth is pointing towards the Sun, and sometimes it is pointing away.

When the northern half of the Earth is pointing towards the Sun, the northern hemisphere of the Earth gets more direct sunlight and we call this season "summer" for the north. At this same time, the southern half of the Earth is pointed away from the Sun, so people in the southern hemisphere get less direct sunlight and we call this "winter" for the south. So, because of the tilt of the Earth's axis, the seasons in the south are the opposite of those in the north.

Suppose the Earth's axis were not tilted; in other words, suppose the Earth was straight up and down relative to it's orbit around the Sun. Then everybody would have the same season all year round: an eternal spring! No more summer and winter! The Moon is tipped over about 1 degree. Because the Moon has such a slight tilt, each spot on the Moon has the same "season" all year.

Even if the Moon had seasons, they would differ from seasons on the Earth. The Moon has no atmosphere. Hence, many of the weather phenomena which we associate with seasons (wind, rain, and snow, for example) cannot occur on the Moon.


Submitted by Joan (Massachusetts, USA)
Submitted by Alex (Maryland, USA)
(October 22, 1997)



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