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Back to the Future



It being near October 25th and having nothing else to do (with the obvious exception of last week's calculus homework), I found myself re-watching the Back to the Future trilogy. While the verity of the physics in these movies regarding time travel are questionable at best, I was more concerned with another facet of the film. In the second movie, there is a scene in which Marty McFly steals a hoverboard from a defenseless child in 2015 to escape Griff Tannen and his gang of futuristic toughs. McFly seems to be getting away despite having never set foot on a hoverboard in his life when all of a sudden he travels over a pond in the town square and the hoverboard ceases to go forward. One of Griff's goons proceeds to explain that "hoverboards don't work on water." This left me asking why. It appears that the hoverboard can travel over land without any significant propulsion, but the instant it encounters water it stops. However, the hoverboard does not immediately sink and leave McFly underwater; instead it hovers above the water. It would seem that if hoverboards don't work over water, the first thing to stop working would be the hovering part. Finally, I realized that like their ancient counterparts, skateboards, hoverboards rely on their rider's momentum to move forward. When Marty goes out over the water, air resistance slows him down to a stop, and there is no way for him to propel himself. Assuming the hoverboard operates using superconductors and magnets like many of the prototypes in development today, this would still allow it to hover above the water but not travel forward unless hooked up to some external propulsion system. But the question still remains: when will we get the flying cars and $50 Pepsis that Hollywood promised us?   

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Great question... although I'm a bit concerned about some of our drivers (banana) adding a 3rd dimension of travel to worry about in their cars.  

Edited by FizziksGuy
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