Newton’s First Law of Motion - if an object is at rest, it takes un-
balanced forces to make it move. Conversely, if an object is moving
it takes an unbalanced force to make it change it’s direction or speed.
Newton was the first to see that such apparently diverse phenomena as a satellite moving near the Earth's surface and the planets orbiting the Sun operate by the same principle: Force equals mass multiplied by acceleration, or F=ma.