temporaneità

You can’t leave the mind of an engineer alone more than five minutes without getting back and finding some kind of (strange or silly, you have a choice as usual) questions.

Today I left it alone for that time and when I got back I found it was wondering what a machine is.

Well, Wikipedia says a machine is a “device that transmits or modifies energy” and it lists the inclined plane as a kind of “Simple machine”. In my opinion a stone pushed in order to slide down a hill is not a machine (it’s not even a device); everything can be used to transmit or modify energy but we don’t think about it as a machine.

I need a better answer.