When you can not only observe phenomena but can measure them, in a system of units that is agreed in every country in the world by every colour and creed of human, that is progress. When you can extend your measurements from everyday objects down to the very atoms from which we are all made and up to the furthest reaches of the observable universe, that is progress. The results of observation and measurement form almost timeless records. For example, the science books of 200 years ago are full of descriptions, facts and figures that are as valid now as they were when they were made. Understanding, though, is often connected more closely with the general culture and values of a particular epoch.
Understanding involves synthesis and interpretation.
We each generate our own understanding. A few people of extraordinary talent manage that synthesis better than the rest of us. They generate new perceptions and produce 'the laws of physics'. One such was the true genius James Clerk Maxwell , who was Professor at Aberdeen about 140 years ago. He taught at Marischal College, and he lived in rented accommodation at 129 Union Street.