Q #3-Aristotle and The Pig’s Bladder


Aristotle and The Pig's Bladder2-3-7-Aristoteles-Schweinenluft

Aristoteles lived about 100 years before Archimedes. He brought the observing of natural phenomenon and thinking about it logically to a first brilliant highlight.

Regarding their insights he and his combatants remain restricted. They never reached the abstraction of an Archimedes which for example led to the principles of upthrust. Nevertheless did Aristoteles also examine the properties of air.

He weighted a bladder of a pig, at first filled with air, then empty. Why could he never find a difference in weight between both measurements?

  1. a) There were no scales available, accurate enough for that tiny difference.
  2. b) He would have definitely been able to measure the additional weight of the air filling, but it was balanced by the yet unknown upthrust of the full bladder within air.
  3. c) Aristoteles just did a thought experiment. Real measurements and experiments had been nearly heretical at that time.


The answer is: b) As Aristoteles didn’t know anything of upthrust in liquids and gases, he could not see, that the weight of the filled-in air was exactly balanced by this upthrust which effects the bladder within the ambient atmosphere.

to a)  Aristoteles already knew pretty accurate beam balances. After all a completely filled pig bladder of 30 cm diameter contains 20 g of air.

to c)  It is right, that the ancient Greek scientist did not execute real planned experiments. Thought experiments as Zeno‘s paradoxon of Achilles’footrace with the tortoise were approved to gain news insights (see also above Movement – What is that?). Still, simply measuring something like the air was a common thing even at that time.