Observatory on Instagram: "The terminator line is the moving edge on Earth where night meets day. As the Earth spins, this line shifts across the surface, creating a boundary between sunlight and darkness. What makes it fascinating is that sunrise and sunset both happen at the same time along different sides of this line. On one side, the sun is just rising above the horizon. On the opposite side, it is setting below it. This happens because Earth is round and rotates steadily, allowing light to