meridian circle

例句：

1. 1. The meridian circle is the line that divides the earth into two equal halves.
   子午圈是地球被分为两个等分的界线。
2. 2. The sun's rays are reflected off the surface of the earth, creating a meridian circle around the planet.
   太阳的光线反射到地球表面，在地球周围形成了一个子午圈。
3. 3. The meridian circle is used to determine the time zones in different parts of the world.
   子午圈用于确定世界上不同地区的时区。