The translation of What is a Thing? (GA 41; winter semester, 1935-36) is out of print. This is unfortunate for those interested in Heidegger and philosophy of science, because this lecture course was his lengthiest survey of science.

In this excerpt, he uses Newton's First Law and Galileo's experiment dropping balls from the tower of Pisa to question what science and maths can tell us about things themselves.

The Essence of the Mathematical Project
(Galileo's Experiment with Free Fall
For us, for the moment, the question concerns the application of the First Law, more precisely, the question in what sense the mathematical becomes decisive in it.

How about this law? It speaks of a body, corpusquod a viribus impressis non cogitur, a body which is left to itself. Where do we find it? There is no such body. There is also no experiment which could ever bring such a body to direct perception. But modern science, in contrast to the mere dialectical poetic conception of medieval Scholasticism and science, is supposed to be based upon experience. Instead, it has such a law at its apex. This law speaks of a thing that does not exist. It demands a fundamental representation of things which contradict the ordinary.

The mathematical is based on such a claim, i.e., the application of a determination of the thing, which is not experientally created out of the thing and yet lies at the base of every deteremination of the things, making them possible and making for room for them. Such a fundamental conception of things is neither arbitrary nor self-evident. Therefore, it required a long controversy to bring it into power. It required a change in the mode of approach to things along with the achievement of a new manner of thought. We can acuurately follow the history of this battle. Let us cite one example from it. In the Aristotelian view, bodies move according to their nature, the heavy ones downward, the light ones upward. When both fall, heavy ones fall faster than light ones, since the latter have the urge to move upward. It becomes a decisive insight of Galileo that all bodies fall equally fast, and that the difference in the time of fall only derive form the resistance of the air, not from the different inner natures of the bodies or from their own corresponding relation to their particular place. Galileo did his experiment at the leaning tower in the town of Pisa, where he was professor of mathematics, in order to prove his statement. In it bodies of different weights did not arrive at precisely the same time after having fallen from the tower, but the difference in time was slight. In spite of these differences and therefore really against the evidence of experience, Galileo upheld his proposition. The witnesses to this experiment, however, became really perplexed by the experiment and Galileo's upholding his view. They persisted the more obstinately in their former view. By reason of this experiment the opposition toward Galileo increased to such an extent that he had to give up his professorship and leave Pisa.

P. 88-90

Continued.  ¶ 7:58 AM