The universe contains more stars than grains of sand on Earth, and it would take 100,000 years to cross at light speed. The Sun revolves around its axis in a month and around the galaxy in 26,000 years. Mercury orbits the Sun fastest, completing a revolution every 88 days. The Earth rotates at 1,600 km/hr and orbits the Sun at 100,000 km/hr. The universe is vast, with immense distances, times, and speeds.