As I've mentioned previously, I contribute to the ABC (Australian Braoadcasting Corporation) Science Forum. Click here to enter the forum. Occasionaly, my two interests (science and trains) cross fertilise. Check this question out, click here to see the thread, and should you wish to reply to it, just click "reply". No need to register, just use the "guest" login. It is both a fun and serious forum, where there is no such thing as a silly question. (BTW, they are having software probs with that forum, only to do with replies. Sometimes you need to reply "more than once" to get it through).