When the sun is moving backward in the sky, you may notice that it looks gigantic. Don’t worry, it’s not sun poisoning affecting your judgment. Because of Mercury’s closeness to the sun, the sun does appear larger in the sky than it does from Earth. The planet’s highly elliptical orbit enhances this effect, and the sun will seem to grow and shrink throughout the year. At Mercury’s closest approach, 29 million miles—known as perihelion—the sun looks three times as big as it does on Earth. During aphelion, when Mercury is at its farthest point, 43 million miles from the sun, it only looks about twice as big.