Is Prime Matter Energy?

Good thoughtful article.

Another interesting idea is 'potential energy'. If a boulder sits on a hill for 1 million years, because it's in a gravitational field, it has had a 'potential energy' compared to the bottom of the hill. Take away the field, you take away the PE. Usually the word 'potential' means 'capable of being but not yet in existence'. Similarly, the electric potential of two points in an electric field may be different ... and there's a 'potential difference' between them. (Confusing? No wonder the term was changed to voltage!)

Liked seeing that Feynmann quote for the first time: 'It is important to realize that in physics today, we have no knowledge of what energy is.' [In 4.1 of https://www.feynmanlectures.caltech.edu/I_04.html]