Is it true that once an object is in its natural resting place it cannot move by itself?

Answer 1

This is one of the axioms of the Aristotle's physics, introduced by the great Greek philosopher in the IV century before Christ (about 2400 years ago). The role of this postulate was to justify the observed motion of bodies by defining their natural resting place starting from the metaphysical idea of the body nature.

The most important consequence of this principle is that, while a body is in its resting place, an external force is needed to move it.

Modern science, that was born with the work of Galileo, Newton and several other scientists in XV century after Christ (2000 years after Aristotle and about 400 years ago) completely cancelled metaphysical assumptions, starting from mathematics and pure phenomena observation.

The fact that it was possible to observe a wider variety of phenomena with respect to the Aristotle's age allowed scientists, and in particular Isaac newton, to understand that the force is not needed to move a body, but to accelerate it. The fact that in normal experience bodies subject to no apparent force tend to stop (to come to their natural rest situation following Aristotle) is due to the fact that an forces in fact exist, the air and attrition resistance, that decelerate the body up to its stop.

No such resistance exists in space, where planets move, so that justification of the planet motion with the Aristotle's principle is not possible. As a matter of fact planets according to Aristotle, should decelerate up to a stop, while this does not happen.

Thus we can say that nature phenomena are not correctly interpreted by the Aristotle's postulate and at present is has to be abandoned in favor of a scientific approach to nature analysis.