Early mathematicians, right up to the Middle Ages, were convinced that whenever a body is moving there must be a force acting on it, i.e. a force a needed to ‘make it keep moving’.

We can see, now, that something is wrong with that hypothesis by considering for example, a puck skimming across the ice during an ice hockey match.

The puck is struck with a stick and sent moving ( i.e. a force start the motion but what happens next? The puck continues to move although there is nothing to push it once it has left the hockey stick.

There is just one example where motion exists without a force to cause it.

However, it was not until 1687 that, with the publication of  Newton’s Law of Motion, the old hypothesis was discarded and a completely new school of thought established.