Arthur C. Clarke wrote that "any sufficiently advanced technology is indistinguishable from magic," but he was wrong. It's easy to tell the difference -- technology works. For example, "remote-viewing" mentalists claim they can see events far away, yet they fail every test. In fact, remote viewing is simple: It’s called TV.
Another example that recently circulated online was a fake video of someone charging his iPhone by jamming the end of a USB cable into an onion. How do I know it was fake? First, you need contacts made of two different metals, and second, you can't get enough voltage out of a single vegetable. What makes the ruse so disappointing is that it is possible to charge an iPhone this way, if you do it right.
A regulation vegetable battery, made by sticking strips of zinc and copper into a potato, generates about half a volt. The electricity comes from the oxidation of zinc; the vegetable is just an electrolyte (conductive barrier), and the copper completes the circuit. Stacking alternating layers of vegetable, zinc and copper is like wiring batteries in series, each set adding its voltage to the total.
After some 10 volts' worth of teary-eyed onion peeling, I decided to switch to apples, using a fruit corer to cut out the apple rods and a cheese slicer to cut them into disks. Pennies with the copper plating sanded off on one side made a handy source of copper and zinc layers in one.
About 150 of these, arranged into six parallel batteries of 25 apple/zinc/copper layers each, yielded enough power to charge an iPhone, but only for about a second. (Much larger zinc plates and whole slices of apple would have provided more power for longer.) Around 200 of the layers went into one three-foot-long apple battery, delivering much higher voltage. I was able to create a visible, and potentially fatal, spark with this battery. Yes, in the right configuration, you can electrocute yourself with an apple.
Achtung! This experiment could damage your iPhone if done improperly.
Five amazing, clean technologies that will set us free, in this month's energy-focused issue. Also: how to build a better bomb detector, the robotic toys that are raising your children, a human catapult, the world's smallest arcade, and much more.