ct axis?? Now that I am looking at spacetime diagrams that involve the speed of light, I am seeing the vertical axis as "ct". Since "c" is meters/second and "t" is seconds then wouldn't ct be ((meters/seconds)*seconds) and end up being METERS? Why would the time axis be in meters? I would think that I would want my time axis to be just in time (not ct), and simply to be told that the x to t scale is 299,792,458 meters for every second. In other words, every unit of the grid horizontally is 299,792,458 meters and every unit of the grid vertically is 1 second. This keeps the vertical axis as purely time and the horizontal axis as purely distance. So in summary: doesn't "ct" end up being a measure of distance, not time? And if so, why is it on the "time" axis? Thanks.