Hi, This is my first post, so hello everyone! I just have a quick question about the k-calculus, and am using the 2nd diagram on http://www.geocities.com/ResearchTriangle/System/8956/Bondi/intro.htm as a reference since it is the same one as in the book i am reading from. In the diagram kT seems to be measured along B, but as time is measured along the y-axis, how on earth can kT represent time - surely kT must be some sort of time/distance unit. Surely kT would be the vertical distance between O and 'the top of the kT bit of B' if you know what i mean? X0) Thanks in advance, James.