Ask HN: How would you measure passion?

I started making myself this question one week ago. It actually sounds weird and I know it is the typical vague/philosophical question for what your friends stop talking to you, but I'd appreciate if any of you guys have a guess. Some research I've gone through suggests it is related to how you feel, how much time you spend thinking about it and what you're doing for it. I assume founding an startup is highly related to passion (at least for me) so...Do you agree with that? Do you have any other guess? Thank you so much guys ;-)