Question. What keeps an object moving with constant speed in a straight line? Is some kind of an agent or force required to accomplish this?
Experience seems to teach that the answer to this question is YES. E.g., a car moving on a straight level highway with constant speed does require a working engine to maintain this speed.
The idea that a force is required to maintain the speed of an object moving in a straight line was held by the Greek philosopher Aristotle, 384 BC - 322 BC, and was widely accepted until the 16th century AD when the Italian physicist, astronomer, and mathematician Galileo Galilei, 1564 -1642, proposed a contrary point of view.
Galileo's point of view, as subsequently modified by Newton, has become the accepted view by physicists until the present time. However, this view is not 'natural' or 'intuitive' even today, because a view similar to Aristotle's is what is commonly held by people who have not studied Newtonian mechanics. To understand physics as it is practised today one needs to learn to take off the Aristotelean glasses and see things in a new perspective.
Contents of the following pages