Dear Longing,
Don't do anything. He hasn't asked you out on a real date or called you at home. For all you know, he's a bit of a flirt who likes to take attractive young women out to coffee. Perhaps he prefers to run to the bathroom afterwards and jerk off while fantasizing about the perfect push-button interface rather than risking his professional career by doing the nasty with you. So for now, you should just hang tight and direct your amorous feelings elsewhere.

But if he does ask you out for something more than some innocent flirting, it is OK to proceed to the next level, as long as you proceed with caution. Despite what your RA, your dean and even your parents will tell you, there is nothing wrong with a student dating her teacher. Until about 20 years ago, this was a completely acceptable way of meeting one's mate. Also, at Columbia there are only rules against May-December romances in the Science department (I guess they {really (put in italics)}don't want SEAS students to get laid). Gateway doesn't fall in this category, as it is truly more of an art than a science. All of that talk about him having power over you because he can grade your papers is complete bullshit. He, at the most, can fail you. This is unlikely to happen because if he did try to give you a bad grade, you could get someone else to grade it, which would not only improve your grade but would land him in hot water. You have the real power in this situation. With the market glutted with PHD's as tight as Al Gore's ass, one small complaint could ruin his chances of ever doing more than programming the auto-brew function at the capuccino machine at the local Starbucks.

Just recognize that you are probably at different stages of your life, so don't expect anything longterm to develop. And because many of his colleagues would disapprove, don't expect to become a big part of his life either. You two will probably end up going out to eat far away from campus to avoid detection. He will never be able to visit you in your dorm. Dates near his cold-water flat in Hoboken become more trouble than they're worth, even though meals at the famous Clam House are indeed delightful. While all of this secrecy will seem exciting at first, it could make you feel like he is ashamed of you after awhile.