I loved Sonic the Hedgehog as a kid mostly because I could simply point myself in a single direction, mash the spin button and then watch as he flitted from one side of the screen to the other at breakneck speed. Whilst the physics of that particular game aren’t rooted in reality some of the principles were namely the forces of momentum, inertia and, most importantly centripetal force. That last one is the force responsible for keeping objects pinned down when going through loop the loops although you usually only see it in action on roller coasters or special stunt vehicles. I honestly didn’t think it’d be possible for a human to accomplish what our speedy blue friend did but it seems that, like many other things, I was wrong.http://www.youtube.com/watch?v=OTcdutIcEJ4
I was surprised to learn that the required speed to get around the loop safely was so low, well within the reach of anyone with a modicum of fitness. The real key here though is the technique as the way we humans generate force is vastly different to that of more traditional vehicles that can accomplish this feat. You see the force we generate isn’t in line with the surface we’re on, it’s at something of a 45 degree angle, which means that as you get to the higher parts of the loop you’ll actually be pushing yourself off it with your face heading directly towards the floor.
This becomes evident when you see the initial trial runs where he has to flip himself over at the peak of the loop. In the final, successful run you can see that when his foot hits the peak he doesn’t actually use that to generate any force. Instead he’s doing something like an upside down split kick with one foot travelling from one side of the loop to the other. It’s incredibly impressive to say the least and just goes to show that given enough practice, persistence and good old fashioned science the impossible can be achieved.