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 10th November 2008, 01:43 PM #29 Thabiguy Muse   Join Date: Feb 2007 Posts: 804 Originally Posted by ponderingturtle If you can go faster than the wind in its own dirrection why do you need a wind? You need the wind, because the wind means that the ground is moving with respect to the air. When you're moving at the same speed as the air, you can use the moving ground to propel yourself against the air - even in the opposite direction. If there was no wind, then if you were at rest with respect to the air, you would also be at rest with respect to the ground and you could use nothing to move. Originally Posted by ponderingturtle It is also like using wind power on a still day, as once you start moving you will be going against a wind, and you can use that for your power right? No, it is not like that at all. Do you know how a sail can sail against the wind? Well, in this case it's switched: instead of moving air to push you, you would have to use the moving ground to push you, and instead of water to push against, you would have to use the air to push against. It's perfectly possible to construct a vehicle that will move faster than the wind - in a zig-zag pattern, but still in the direction of the wind. Identically to a sail moving against the water in the opposite direction of the wind, the vehicle will move against the air in the opposite direction of the ground movement - i.e. faster than the wind (only by a small amount though). As an exercise, look up the sailing technique and figure out how the land vehicle would have to be constructed to utilize an analogous technique. So the question is not whether it's possible, the question is whether this device could do it. And I have to admit, this is difficult for me to determine. I have considered several simple models, but no conclusion yet.