20190407-Rotation and Revolution

2019.04.07 Rotation and Revolution自转与公转   Let’s look at the Earth’s movement. First, the Earth is always moving around the Sun. The Sun is the center of the Solar System. The Earth and all other planets orbit it. We call this the Earth’s Revolution. It takes about 365 days. We call this time “one year”. Other planets have longer or shorter years. 我们来看一下地球的运动。首先，地球总是绕着太阳运动。太阳是太阳系的中心。地球和其他几个行星沿轨道围绕太阳运行。我们称之为地球的公转。地球公转（一圈）花费大约365天。我们称这段时间为一年。其他行星的公转时间有长有短。   The Earth also spins around. It rotates. We call this the Earth’s Rotation. Have you ever watched a top spin around? The Earth does the same thing. The Earth’s Rotation is very important to us. Days and nights happen because of the Earth’s rotation. It takes 24 hours for the Earth to rotate once. We call this one day. 地球同时还在旋转。它会自转。我们称之为地球的自转。你见过陀螺旋转吗？地球做的就是同一运动。地球的自转对我们来说非常重要。昼夜更替就是源于地球的自转。地球自转一圈需要花费24小时。我们称之为一天。   We say the Earth rotates on its axis. The axis is not straight up and down. The Earth tilts a little as it spins. It’s the reason we have seasons. The top of the Earth is called the Northern Hemisphere. The lower half is called the Southern Hemisphere. Sometimes the northern hemisphere is tilted toward the Sun and sometimes it is tilted away from the Sun. 我们说地球绕其轴自转。地轴不是直上直下的。地球在旋转的时候有点倾斜。这是我们能够拥有不同季节的原因。地球的上面部分被称作北半球。下半部分被称作南半球。有时候北半球朝向太阳倾斜，有时候它会背离太阳的方向倾斜。   In January, the northern hemisphere is tilted away from the Sun, so it doesn’t get much of the Sun’s light. The southern hemisphere gets more sunlight. So the southern hemisphere has summer while the northern hemisphere has winter. 一月份，北半球背离太阳倾斜。所以北半球接受不到太多日照。而南半球会接受到更多的日照。所以南半球是夏天，而北半球是冬天。