In order to know why what you're learning is important, contextual history is paramount. What, for example, sparked the invention of the stirling engine, or the beginning of the industrial revolution? What problems had to be solved? Why did X engineer come to Y conclusion etc. and did human affairs at that time had an impact on such invention?
Knowing the history around a scientific principle will help you to learn the principle itself, because you will step into the shoes of the people involved and look at it from their viewpoint. A good 50/50 balance is required.