https://phys.org/news/2018-06-dark.html > Around 1600, Galileo Galilei's experiments brought him to the conclusion that in the gravitational field of the Earth all bodies, independent of their mass and composition feel the same acceleration. Isaac Newton performed pendulum experiments with different materials in order to verify the so-called universality of free fall and reached a precision of 1:1000. More recently, the satellite experiment MICROSCOPE managed to confirm the universality of free fall in the gravitational field of the Earth with a precision of 1:100 trillion. > These kind of experiments, however, could only test the universality of free fall towards ordinary matter, like the Earth itself whose composition is dominated by iron (32 percent), oxygen (30 percent), silicon (15 percent) and magnesium (14 percent). On large scales, however, ordinary matter seems to be only a small fraction of matter and energy in the universe.