Perpetual Skislope
the hollow room writes: "How about skiing on a never ending slope? A story at New Scientist suggests that some fool is going to try to build one of these. Built like a huge tilted record player, it can spin at up to 30 km/h.
Any takers?"
I learned how to ski as a kid riding a huge conveyor belt made out of a big rug in the bottom of a sporting goods store. It doesn't sound like much, but it was fun as a kid. The coolest part was that you could turn it on and off with a garage door opener type gadget. I always wanted to turn it up really fast and see how much speed I could get up tucking, but my ski instructor wouldn't let me. Now that I look back, tucking really wouldn't matter. There's no wind resistence to worry about when you aren't actually moving.
The problem I'm seeing here is pretty major. If you take a 3000m ski run and compress it into a 300m run, there's still going to be 3000m worth of "snow damage" per skier/run, but it will be compressed into 300m of distance. So the snow is going to be 10 times as chopped up in any one place. And real ski resorts have multiple runs that reduces the traffic on any one run... to even begin to pay for this thing it's going to have to be packed.
If you think about it, there are natural perpetual slopes: Standing waves (wakes?) on rivers.
I even found a very cool video (8MB) demonstrating riversurfing on the Eisbach in Munich.
If you've never operated an LP phonograph -- the skating force is due to the differential friction on opposite sides of the needle on a phonograph, and tends to draw the needle inward toward the center of the record. It's large enough to cause a needle to skip, bump bump bump, right over the grooves unless a counteracting force is applied. Low-end turntables used springs to pull the needle outward and combat the skating force; high-end turntables used little weights with little mechanical linkages that were designed to match the changes in the skating force with radius.
You can see skating force in action at the bottom of a teacup if there are a few tea leaves floating around down there at the bottom. The tea leaves (after they're waterlogged) sink, so spinning the tea in the teacup "ought" to make them fly outward in the local gravity field. But in fact, tea leaves at the bottom of the cup tend to pile up in the center (when you spin the tea). Counter-intuitive and mysterious, until you realize that the leaves are also dragging on the bottom of the cup and therefore are subject to the skating force.