Astronauts appear to be bouncing on the moon because the force of gravity is weaker on the moon.
On planets such as Earth and natural satellites such as the moon, gravity causes objects are pulled towards the center of the planet/natural satellite.
On the moon, this force is weaker than on the Earth. Indeed, the gravity of Earth is equivalent to 9,807 m/s, while the gravity on the moon is 1,62 m/s.
This causes objects are still pulled towards the center of the moon but they are pulled with a much weaker force. Therefore, when people walk on the moon they seem to bounce.
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