The gravitational pull on the moon is much less than on Earth, about 1/4 as strong. This means that a person's weight and jumping ability would be different - a person with an 8 inch vertical jump on Earth would be able to jump 48 inches on the moon. The document asks how high Lebron James, who has a 40 inch vertical on Earth, could jump on the moon according to this relationship between gravitational pull and jumping height.