Mercury’s Endless Sunset Explained #Space Mercury is the fastest planet around the Sun—but time moves strangely on its surface. 🌍☀️ Because Mercury rotates incredibly slowly, one full day-night cycle lasts 176 Earth days. In some locations, the Sun can actually set, rise again, and set once more, creating a rare double sunset. This surreal effect comes from Mercury’s unique 3:2 spin–orbit resonance, where the planet rotates three times for every two orbits around the Sun. At the boundary betwee