A big full moon called a supermoon showed up on Aug 19. It’s the first of four this year. People often use “supermoon” as a name for a big full moon, but it is not a scientific term (科学术语). It happens (发生) when a full moon and Earth get super close (接近的). This makes the moon look bigger in the sky. It happens about three or four times a year. If the sky is clear, you can see a supermoon from anywhere.