For me, it was notes, calculations, and having access to the necessary information for making the two.

I might be sitting on the train, looking out the window, zoning out, and suddenly I start thinking about the melting point of tungsten. I begin to wonder how much power an arc furnace would draw while melting tungsten, and could you keep one running with just solar power. How many panels would you need at this location? I have so many questions, and most of them involve calculations.

You can imagine how glad I am that I don’t need to carry a calculator and a bunch of books with me.