On Thu, Oct 28, 2010 at 2:44 PM, Olin Lathrop w= rote: > Oli Glaser wrote: >>> 2 - You still rely on knowing parameters of the train, which in this >>> case is the spacing between wheels. >> >> Of course, but I thought that part was rther obvious.. :-) > > But yet you suggested a method with this obvious drawback. > >> Note the "something like" in my post - it depends a lot on what >> information is available, and the situation (which I am mostly in the >> dark about) >> For instance, if all trains are a standard length, then it could be as >> simple as timing the duration of the noise. > > Why go to great lengths to concoct a system that might sortof work if > everything is right and only Standard Trains pass by, when much simpler a= nd > reliable methods are readily available? Exactly, everyone knows that as the train approaches the speed of light, a clock on board the train will appear to run more slowly. So you just need to add a clock to the train and observe carefully. Regards, Mark markrages@gmail --=20 Mark Rages, Engineer Midwest Telecine LLC markrages@midwesttelecine.com --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .