The Earth spins on its axis every 24 hours, creating days and nights. It takes the Earth one year to orbit the Sun. A year is 365.25 days, requiring a leap year every four years. The Moon orbits the Earth every 29.5 days, creating lunar months. It phases are caused by the changing portion illuminated by the Sun. Eclipses occur when the Moon passes between the Earth and Sun or into the Earth's shadow. The Earth's tilted axis causes seasons, with summer in the northern hemisphere when its tilted toward the Sun. Planets reflect sunlight but do not make their own light, while the Sun is a star that gives off heat and light, like other stars seen in the night sky.