Gravity

Here is the sixty-fifth episode of Quantum Foam, Gravity. It is the force that attracts 2 bodies towards each other such as the earth pulling objects toward its center. It is important for keeping planets around the sun and is a fundamental interaction in the universe. The force of gravity extends infinitely although its strength diminishes with distance. The strength of gravity depends on the masses of the objects involved. Isaac Newton first described gravity as the force that governs the motion of celestial bodies. Einstein later described gravity as the curvature of space-time caused by mass. Gravity is the weakest known force in nature and thus plays no role in determining the inertial internal properties of every day matter. Einstein released his papers on gravity in 1905 and 1915. Gravity acts through the space and effects objects from one to another through the empty space. Newton's law of universal gravitation states that any 2 objects attract each other with a force directly proportional to the product of their masses and inversely proportional to the square of the distance between them. Johannes Kepler accepted the argument of Nicolaus Copernicus, which stated that the planets orbit the sun and not the earth. Using the improved measurements of Tycho Brahe, Kepler described the planetary orbits with simple geometric and arithmetic relations. He then proposed 3 laws of planetary motion. Galileo was the first to show by experiment that bodies fall with the same acceleration whatever their composition. This is the weak principle of equivalence.
Newton discovered the relationship between the motion of the moon and the motion of a body falling freely on earth. He assumed the existence of an attractive force between all massive bodies, one that that does not require bodily contact and that acts at a distance. He concluded that a force exerted by earth on the moon is needed to keep it in a circular motion about earth rather than moving in a straight line. He assumed the existence of an attractive force between all massive bodies that does not required bodily contact. In his theory, every least particle of matter attracts every other particle gravitationally. On that basis, he showed that the attraction of a finite body with spherical symmetry is the same as the whole mass at the center of the body. Thus, Newton could relate the 2 accelerations of the moon and that of a body falling freely on earth to a common interaction. He saw that the gravitational force between bodies must depend on the masses of the bodies. The weight of an object can be measured by the equal and opposite force necessary to prevent the downward acceleration. The moon has about 1 sixth the weight that is measured on the earth. The Apollo astronauts proved this as they were able to hop around on the moon pretty easily. A satellite going around the earth is in free fall. It is falling sideways at just the right speed. The gravity allows it to be in a state of free fall. Gravity is very important in describing these orbital devices.