Thank you all for the replies, and for helping me feel that I'm on the right track. I just recently read about the concept of rotating the space-time coordinate system to geometrically account for relative motion, which sounds like what you mean, pervect, by the space-like component of time. I...
After I posted this, I realized, of course, that the beam would always appear horizontal since it consists of many photons at different points along their paths, each taking a different path since the source is always moving up. So nix the straw.
But it still remains that the outside observer...
I found this nice book on Google
http://tinyurl.com/yh2y2zb
that does a great job explaining relativity, however, even though the conclusions make perfect sense to me so far, I'm stuck on a conceptual issue when reading over the classic thought experiments that makes me feel like I'm still...