Was it Galileo or Newton who first proposed the concept of inertia?
Galileo first proposed concept of inertia.Inertia is the resistance of any physical object to any change in its state of motion.it includes changes to its speed, direction, or state of rest. It is the tendency of objects to keep moving in a straight line at constant velocity. Galileo in 1632 went on to conclude the inertia, it is impossible to tell the difference between a moving object and a stationary one without some outside reference to compare it against. Isaac newton modified and codified as the first laws of motion in 1687.Unless we don't apply any external force on an object it will maintain a constant velocity. He defined "inertia" to mean the cause of the phenomenon, rather than the phenomenon itself. The actual term “inertia”was first introduced by “johannes kepler”in his Epitome Astronomiae copernicanae published in three parts from 1617-1621. Kepler defined inertia only in terms of a resistance to movement.