Is gravity a cosmic fluid? Part 1: The weight of history By Marcelo Fontinele "What goes up, must come down." Since we were children, we have heard this phrase that simply expresses one of nature's most fundamental phenomena: gravity. However, behind this apparent obviousness lies one of the deepest mysteries of the universe. Throughout the history of science, we have tried to decipher its nature: Is it a force? A curvature? Or perhaps something even more fundamental, like a fluid that permeates the cosmos? In this first part, we revisit the visions of two geniuses: Isaac Newton and Albert Einstein. Understanding them is essential to taking the next step toward a new interpretation. Newton: Gravity as a Universal Force of Attraction Isaac Newton, in his work Philosophiæ Naturalis Principia Mathematica (1687), postulated the Law of Universal Gravitation , formulated as: $$F = G \cdot \frac{m_1 m_...