Explore different phases of the Moon over the course of a month.
The Moon is Earth’s constant companion, so much so that the same side of the moon always faces us (that is called tidal locking). It orbits Earth approximately every four weeks (27.322 days, to be exact), during which we see the Moon in different phases depending on the Moon’s orientation with respect to us and the Sun. The Moon doesn’t shine on its own, it only reflects the Sun’s light to us. Astronauts have traveled to the Moon in one of humankind's greatest technological achievements. They collected 4 billion year old rocks that tell us about the early formation of Earth and the Solar System.
This image from 1991 shows Earth's Moon, with its dark basaltic mare, clearly visible in great detail. Our Moon is Earth's only natural satellite, unlike several other planets in our solar system. For example, gas giant Jupiter has more than 70 known moons. Credit: Lick Observatory/ESA/Hubble