June 18 – Making Sparks

Today’s Factismal: The first modern battery was built in order to investigate frog’s legs.

If you’ve studied the history of science, then you know that nothing drives the discovery of new things like an argument between two scientists. Cope fought with Marsh and the result was an (almost literal) explosion of new dinosaur discoveries (including some that weren’t). Hawking fought with Presskill and the result was a deeper understanding of how black holes work (and a new encyclopedia for Presskill). Newton fought with Leibnitz and the result was a new type of math that would describe the universe and plague college freshmen forever after. And, around 1780, Galvani fought with Volta and the result was the discovery of how nerves work and how to create electricity.

As with most feuds, it started over something small but interesting. While Galvani was working with frog’s legs, trying to tease out the secret of the nerves, his assistant touched a frog’s leg with a scalpel – and it twitched! If your pork chop dinner jumped up and did the tango, you wouldn’t have been half as astonished as the two scientists were. They quickly tried an assortment of things to replicate the result and discovered that it only worked when the metal scalpel touched the frog’s leg; feathers, wooden sticks, and quill pens had no effect. Galvani declared that he had discovered “animal electricity” and sent the details out to the world.

Volta, who was a sometime colleague of Galvani’s, wasn’t convinced. He replicated the experiment and was able to make twitching frog’s legs of his own, but he didn’t think that the secret was in the animal; he thought that it was in the scalpel. If the electricity were in the animal (as Galvani supposed), then just about anything would have made it twitch. But if the electricity were being created by the metals, then only being touched by a metal thing would make it twitch. And in a series of experiments stretching over several months, that’s exactly what Volta proved: it was the two metals that made the electricity.

Look, ma! I made a battery!

Look, Ma! I made a battery!

But then Volta went one step further and made the world’s first modern wet cell battery. He kept the two metals but substituted paper soaked in salt water for the frog’s legs (the paper stacked better). By alternating layers of metal and slipping paper between the metal, Volta was able to generate a steady electric current. The modern lead-acid battery (found in most cars) was born.

If you’d like to build a “Voltaic pile” of your own, all you’ll need is five nickels, five pennies, some paper towels, a plate, and a bowl of salt water. First cut small circles out of the paper, just slightly smaller than a penny. Next, put a nickel down on the plate. Dip a paper circle into the salt water and then place it on top of the nickel. Top it with a penny, then dip another paper circle into the salt water and put it on top of the penny. Continue stacking the coins and paper until you’ve got a tower ten coins high. Your battery is now done! To see if it is working, you can try connecting it to a LED or ammeter with a pair of wires or simply touch the ends of the wires to your tongue; the bitter taste you get is caused by the flow of electricity across your tongue.

And the coolest thing about making that Voltaic pile is that it means you’ve made something on The National Day of Making. For more making ideas, go to:

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