Imagine a scenario where you are in a cave and you need light. You have all seen the plastic crank-lights that put out dim light for a few seconds.
What if a very creative caver could make a much bigger one with heavy-duty gears that required a great deal of energy to pull a cord that turned the charging pulley ? The idea is to put a sack of rocks at the end of the cord and drop the sack. I doubt you could make a head-lamp do this, but you could install such a device deep in a cave in a big room, for a variety of reasons. The light would shine down on a particular spot for up to 30 minutes. See articles on gravity powered light. http://images.bwbx.io/cms/2013-03-14/tech_innovator1213__01__630x420.jpg http://www.youtube.com/watch?v=4kQxh5N9jvM The trick would be to find a cave that is dark and that has rocks in it, and has a ceiling to hang the light, all at the same time. David Locklear
