Moons of our Solar System

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# 2.3 Falling objects on the Moon

The force of gravity determines how long an object will take to fall to the ground. In the absence of air resistance, all objects will accelerate towards the ground at a rate denoted by g, which is measured in metres per second squared (m s−2).

On Earth, g = 9.8 m s−2 but on the Moon g is only 1.6 m s−2. Hence an object dropped from a given height will take longer to fall to the surface on the Moon than it would on the Earth.

This experiment on the Moon was a recreation of a legendary experiment performed by Galileo in 1589. He is supposed to have dropped two balls of different masses off the Leaning Tower of Pisa and demonstrated that they hit the ground at the same time because they were both subject to acceleration due to gravity, which is independent of mass. If you tried this experiment on Earth with say a hammer and feather, the hammer would hit the ground first because the feather would be slowed down more by air resistance. However, when the experiment was done on the Moon, the feather and the hammer both hit the ground at the same time because, in the absence of air resistance, all objects do in fact accelerate towards the ground at the same rate. As the Moon has virtually no atmosphere, there is virtually no air resistance. The lack of atmosphere is also responsible for the extreme temperatures on the Moon, whereas the atmosphere of the Earth acts like a blanket trapping heat. When the Sun sets on the Moon, the temperature drops very rapidly to −153 °C.

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#### Transcript

COMMANDER DAVID SCOTT
Well, in my left hand, I have a feather. In my right hand, a hammer. But I guess one of the reasons we got here today, was because of a gentleman named Galileo, a long time ago, who made a rather significant discovery about falling objects in gravity fields. And we thought that where would be a better place to confirm his findings than on the moon. So we thought we’d try it here for you.
And the feather happens to be, appropriately, a falcon feather, for our Falcon. I’ll drop the two of them here and, hopefully, they’ll hit the ground at the same time.
MISSION CONTROL
COMMANDER DAVID SCOTT
That proves that Mr. Galileo was correct in his findings.
MISSION CONTROL
Superb!
End transcript

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