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Since the Moon has no atmosphere, is it possible to perform the Galileo's Leaning Tower of Pisa experiment on its surface? Has any astronaut performed anything similar?

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    $\begingroup$ Why wouldn't it be possible? The lack of atmosphere makes it easier. $\endgroup$ – Keith Thompson Sep 23 '13 at 19:11
  • $\begingroup$ It was most likely a though experiment. He (probably) did test it by rolling balls down an incline. He also did another thought experiment: tie the 2 balls together with a rope. Will the resulting "body" fall faster than either one, because it has more mass, or will the lighter ball hold back the heavier? That leads to a contradiction. $\endgroup$ – hdhondt Jul 31 at 23:33
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A very similar experiment was performed, dropping a feather and a hammer on the moon. They weren't tied together, as Galileo's experiment was done, but it is similar enough that it is worth mentioning.

enter image description here

From this YouTube Video

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    $\begingroup$ I wonder how the Moon landing conspiracy people explain away that video. $\endgroup$ – Schwern Dec 15 '14 at 23:54
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    $\begingroup$ @Schwern: It could have been done in a vacuum chamber. $\endgroup$ – Keith Thompson Dec 16 '14 at 0:10
  • $\begingroup$ @KeithThompson That solves one part (in an absurdly expensive way, but that doesn't seem to stop Moon hoaxers). How do you make things fall slower in a vacuum? $\endgroup$ – Schwern Dec 16 '14 at 2:32
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    $\begingroup$ @Schwern: Film it at high speed and play it back slowly. $\endgroup$ – Keith Thompson Dec 16 '14 at 2:34
  • $\begingroup$ @KeithThompson sigh So mundane! :) $\endgroup$ – Schwern Dec 16 '14 at 2:45
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Performing the experiment on the Moon would make it more accurate. The lack of atmosphere means there's no drag on the falling objects to interfere with the measurements.

Galileo was smart/lucky enough to pick two balls which would minimize the effect of then very poorly understood drag. There was a small discrepancy due to drag when the two landed, but Aristotle had stated things fall with a velocity proportional to their weight, so this discrepancy should have been huge. Had Galileo picked something else with more drag, the discrepancy might have been larger and the march of science might have been set back.

We have vacuum chambers on Earth to repeat the experiment. Feathers and bowling balls are used to underscore the point.

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  • $\begingroup$ "science might have been set back" -- or just not advanced at that time, since "Experimental confirmation of what Aristotle said 1800 years ago" might well not have been newsworthy. Then you wonder whether Galileo's insight here was unique, or whether someone else would have realised quite soon afterwards that Aristotle must be wrong, and done the better version of the experiment. $\endgroup$ – Steve Jessop Dec 16 '14 at 10:00
  • $\begingroup$ @SteveJessop It's actually a bit of a myth that Galileo originated this experiment or discovered the freefalling law. John Philoponus was clearly aware of the gist of things in the 6th century CE. Many thinkers in the 2000 years knew what the correct answer was. It's simply that Aristotle was held up as dogma that hindered wide discourse along the correct lines. $\endgroup$ – WetSavannaAnimal Dec 16 '14 at 12:56
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    $\begingroup$ I agree. Someone else had and someone else would repeat this experiment. The question is when someone famous enough would do it to get heard and contradict Aristotle. Probably pretty soon as a lot of people were in the business of working out ballistics to better batter down walls. Aristotle said a lot of trivially falsifiable stuff and wasn't big on experimentation. $\endgroup$ – Schwern Dec 16 '14 at 19:41

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