Then there are meetings, and various other demands on my time. I answer e-mails like this one. Almost none I'd say. You have to work hard to be successful in the academic world. But I try not to work at weekends.
Astrophysics is the most interesting thing there is.
No other reason is relevant. Certainly I could make much more money doing other things. But I love what I do, and can't imagine being fulfilled doing anything else. Being involved in some of the most interesting research questions that I can think of. You have to be good at physics and mathematics, and these days computing as well.