Re: If Elvis Stojko found ice on the moon, could he do a

Stuart - what a great question, especially with the Olympics coming up. And, somehow the MadSci administrators know I was Canadian, so of course I know who Elvis is!

The answer to your question is - probably. The first problem with skating on the Moon is the Moon's lack of an atmosphere. This would mean that any ice on the surface would be be very cold. The cold and the lack of atmospheric pressure would make it impossible to skate `outside' on the surface of the Moon. Here's why:

When you skate, almost all of your weight is carried on the very small area of your skate blades. The force of your weight on the small area creates tremendous pressure. In regions of high pressure, water melts at lower temperatures, so the temperature of the ice beneath your is above the high-pressure freezing point and the ice turns to water. This makes a film of water between your blade and the ice, which allows you to slide along.

If you were on the surface of the moon, the temperature of the ice would be much lower than it is on a skating rink. The pressure exerted on the ice under your blades (which would be lower because of your lower weight) would not be high enough to make the melting temperature under the blades equal to the ice's temperature. The ice wouldn't melt and you wouldn't slide along. You can see this effect for yourself if you try skating outside on a really cold day.

So, no skating outside on the Moon. Let's pretend that there is an indoor (pressurized) ice rink somewhere on the Moon, though. Then the pressure and temperature problem goes away. Now could Elvis do his quint?

I found this very interesting website on the physics of skating jumps. From this, I think the important things in a jump are:

• vertical velocity (this plus gravity determine how long a skater is in the air)
• horizontal velocity (determines how far skater travels in air and, with body position, how fast skater rotates)

I would guess that Elvis' vertical velocity would probably be about the same on the Moon, because that should depend mostly on how much force he exerts with his leg muscles. His horizontal velocity would probably be a bit faster (the force of friction, which would slow him down, would be lower because he would weigh less). So Elvis would spend longer in the air because of the lower gravity, and he could rotate faster, so I think he could do a "quint".

As you can see, there is a lot of interesting physics in ice skating!