Why Do the Seasons Change on Earth?为什么会有四季的变化？

Two things cause the seasons to change. First， the Earth moves around the Sun. Second， the Earth has a tilted axis of rotation.

The Earth spins around an axis. This imaginary line extends from the South Pole to the North Pole. The Earth’s axis is not vertical. It’s actually tilted at an angle of 23.5°. The planet is always tilted in the same direction as it moves around the Sun.

What does the Earth’s tilted axis have to do with seasons？ It means that different parts of the planet are tilted toward the Sun at different times of the year. It’s also why the seasons are different in different parts of the world.

Not all parts of the Earth have four distinct seasons. But they all experience seasonal variation. Closer to the North Pole and the South Pole， daylight and temperatures change with the seasons. Near the Equator， days are always about 12 hours long. But these areas usually have a wet season and a dry season.

引起季节变化的原因有两个：地球围绕太阳运动，地球的自转轴倾斜。

地球围绕着一条假想的从南极延伸到北极的地轴旋转。地轴不是垂直的，它的倾斜角度是23.5度。当地球绕太阳运行时，它总是朝着同一个方向倾斜。

地轴倾斜与季节有什么关系呢？这意味着地球上的不同地区在一年中的不同时间向太阳倾斜。这也是地球上不同地区季节不同的原因。

地球上的各个地区并非都四季分明，但都有季节变化。在靠近北极和南极的地方，日照和气温随着季节的变化而变化。在赤道附近，白昼时长多为12小时左右，但这些地区通常有雨季和旱季之分。

How Are Seasons Different in the Northern and Southern Hemispheres？

南北半球的季节有何不同？

Seasons happen at different times in different parts of the world. The tilt of the Earth doesn’t change as it rotates around the Sun. But the part of the planet that gets the most direct sunlight does change.

The Northern Hemisphere is tilted away from the Sun from September to February. That means the northern half of the planet doesn’t get as much light and heat from the Sun. This causes autumn and winter. During the same months， the Southern Hemisphere is tilted toward the Sun. That means the southern half of the planet gets spring and summer.

From March to August， the Northern Hemisphere is tilted toward the Sun. So that’s when the northern half of the Earth experiences spring and summer. During the same months， the Southern Hemisphere experiences autumn and winter.

在地球上不同的地区，其所在的季节也不同。地球绕太阳公转时，倾斜角度不会改变，但被阳光直射的区域会发生变化。

从 9 月到次年2月，北半球会偏离太阳。这意味着北半球不能从太阳那里获得太多的光和热，从而进入秋季和冬季。在相同的月份里，南半球向太阳倾斜，该半球便进入春季和夏季。

从3月到8月，北半球向太阳倾斜，进入春季和夏季。与此同时，南半球会进入秋季和冬季。

Do you know？

你知道吗？

It takes about 365.25 days for the Earth to orbit the Sun. We have leap years to make up for the extra ¼ day！

地球绕太阳一周大约需要365.25天。我们用闰年来弥补多出来的 1/4 天！

Word Bank

tilt v. & n. 倾斜；倾侧

axis n. 轴（旋转物体假想的中心线）

rotation n. 旋转；转动

extend v. 使达到；使延伸