Yeah, I read it, and I don't buy it. The whole conservation of momentum thing is true, but as far as it applies to a baserunner, it would only work if said baserunner was being propelled by something other than his stride, something independent of his legs' ability to maintain consistent motion. What your bit fails to address is that the center of mass will slow down as you prepare to dive because the act of rotating the body forward impedes the legs ability to maintain stride, resulting in deceleration. Try running 100 meters. Then run 100 meters, but bend forward for even just a couple of steps during. I'll bet you get a slower time. For someone who plays a lot, running through the bag at full stride is not difficult, because he /she would have have gotten it down through repetition. Now if you had to use time to alter your stride so that it hits the bag right, that would be a factor. But I doubt most players on most plays have to do that. Once you position your body to dive, you have stopped running. Maybe if the base was at chest-waist level, reaching out would allow you to touch it sooner. But you have to break stride to begin to dive forward, and that results in deceleration. Not because of the position of the body relative to the ground, but because it simply gets in the way of running. Granted this only takes a fraction of a second, but that is enough, IMO. Perhaps is there were some way to instantaneously launch into a dive without transitional deceleration, it would work, but obviously that is impossible. This has nothing to do with friction or the ground. I know what your argument is, and while it is great in theory, I just don't think it holds up in practical application because there are variables involved that aren't taken into account, and are hard to quantify. If you get out of the box well and hit the right stride, I don't think there is any way diving gets you to the bag more quickly than flat out sprinting. It really seems not only counterintuitive, but illogical. That is may argument for against the theory. The argument against the practice is easy. It's horrible on your body, and even if there were a time advantage, it would be so minuscule that it wouldn't nearly be worth it. And as far as the flat earth thing goes, I don't think there is anything wrong with implying old convention and perception (sliding into first is faster = earth is flat) is now amusingly out of place in a more enlightened time. The analogy may have been hyperbolic, but it made sense. That is unless you were implying that your theory was ahead of it's time, and you = Galileo, which would make it an issue of perspective.