Superconductivity has been observed with transition temperatures as high as 138 K (−135 °C) [1]. I doubt the Earth's surface is getting any colder or that we'll

Superconductivity has been observed with transition temperatures as high as 138 K (−135 °C) [1]. I doubt the Earth's surface is getting any colder or that we'll discover much colder surface temperatures. We've gone from requiring 4K for superconductivity to 138K in a century. Even if we don't find room-temperature superconductors, going from 138K to 180K means it could be possible to have superconductors in natural environment for short periods of time. As the range is raised to 200K - 220K, we could have outdoors superconductors in the far North. If we don't have to cool them manually, is there a limit to how large we can make them? Mini train-track sized maybe? Come to Alaska and ride the levitating train! Someday... 1. http://en.wikipedia.org/wiki/High-temperature_superconductivity http://en.wikipedia.org/wiki/High-temperature_superconductiv...