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Aristotle was Right about Falling Bodies

It is common to hear people say that modern science has proven Aristotle wrong because Aristotle thought that “heavier” objects would always fall a greater speeds than “lighter” objects and this is now known to be false.

Of course, whenever we hear modern scientists, who have never studied the works of Aristotle at any point in their education, dismissing Aristotle as a careless simpleton, we should be prepared to dismiss the scientists as pretenders.

The truth is that Aristotle was perfectly aware that, in a vacuum, objects of different weights would move at the same speed. He said so himself in the Physics, almost 2,000 years before Galileo was born:

“If air is twice as easy to cleave as water, the passage through air will be twice as swift, and the time taken in covering a given distance half as long in air as in water. According to this universal principle, then, the velocity will in every case be greater in proportion to the unsubstantiality and diminished power of impeding and easier cleavability of the medium…Where there is nothing to cleave, all bodies will move at the same velocity.”

Aristotle, Physics Book IV, Ch. 8

Aristotle, however, said that this was impossible.

But, don’t modern scientists demonstrate that, in a vacuum, a hammer and feather do, in fact, fall at the same velocity?

Was Aristotle, therefore, wrong?

Rather than allow ourselves to be persuaded at this point that Aristotle was wrong and modern science right, we should ask, “Why did Aristotle say that this was impossible?”

The answer is that Aristotle was not using electrical laboratory equipment to produce artificial “vacuums” inside vacuum chambers. He was speaking of bodies moving in the natural world.

“Vacancy…is nowhere to be discovered in the cosmos. For air is substantial, though it does not appear so…for touch is the test of existence for the tangible. From all this it is clear that there is no such thing as a self-existing void.”

Aristotle’s argument that there was no such thing as a “void” or “vacuum” in nature was the reason for his assertion that the falling of two bodies of different weight at the same velocity in a vacuum is impossible. This, after all, is a book on natural philosophy, that is, the science of mobile bodies in the natural world.

Some may object and say, “But space is a vacuum!”, since they were likely taught this in a school Science course.

This, however, is not held to be true by modern science.

“Space is not empty. It is filled with tenuous (and in some places not so tenuous) plasma. This plasma is much like our atmosphere.”

NASA Source

The truth is that there is no vacuum in nature because, as Aristotle argued “nature hates a vaccum” (horror vacui). Consequently, there is no place in nature where objects of different weights fall at the same velocity.



  1. Mackey Mackey April 11, 2024

    This was a helpful article. It seems like even in the best “vacuum” there would still be some matter present. How could a place contain nothing? Space is described as a near perfect vacuum, yet it still contains plasma. So, even in these experiments where the hammer and the feather are dropped in an artificial vacuum, perhaps it is the case that if the objects were allowed to fall for long enough we would still see the hammer moving at a greater velocity; it would just take a very very long distance or hyper precise tools to detect the difference. Thus, Aristotle was right, and right in all cases.

    • William C. Michael, O.P. William C. Michael, O.P. Post author | April 13, 2024

      Space is not a vacuum…It contains planets, stars, comets, meteors, etc. The idea that nature is composed of (1) atoms and (2) void is the ancient Epicurean philosophy, which is why scientists even think of it. They are Epicurean materialists.

  2. Roy Roy April 12, 2024

    Even considering artificial vacuums, none are true vacuums. An artificial vacuum is made by exploiting a difference in air pressure. It moves air out of chamber 1 into chamber 2 by reducing the pressure in chamber 2. But there is always always some air in both chambers. So again Aristotle was right.
    “Now there is no ratio in which the void is exceeded by body, as there is no ratio of 0 to a number. For if 4 exceeds 3 by 1, and 2 by more than 1, and 1 by still more than it exceeds 2, still there is no ratio by which it exceeds 0; for that which exceeds must be divisible into the excess + that which is exceeded, so that will be what it exceeds 0 by + 0. For this reason, too, a line does not exceed a point unless it is composed of points!” – Physics Book IV, Part 8

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