Another thread got me thinking about this. If you are calling your service line, and a serve is hit right at you, how far "long" would the ball have to be before it was humanly possible to in fact see court between the ball and the line? I.e. you are really seeing court over the ball as it hits. A little simple trigonometry shows that if you are average height, standing up straight, and AT the baseline, the "shadow" of the ball hides 8.17 inches of court (from it's midpoint). So technically, are we calling serves that are long by 6 or 7 inches in? Or does our brain do a little calculation of "I know where the ball landed so it must in fact be long"?