Those who went into finance/economics, what did you find difficult in the beginning?

Learning in a Vacuum might be a Shock to you: you might wake up dead !

I built an N-body orbital simulator in Python and I’d like some honest feedback.

What’s causing these lines of light?

What forces in the universe are not a function of time?

how were they able to choose whether to detect the photons after they had passed through in John Archibald Wheeler's slit experiment?

Sugest me a book.