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Zapping Fish

Zapping Fish Photo Credit: By Ian Boggs from Astoria, US (Lightning on the Columbia River) [CC-BY-SA-2.0], via Wikimedia Commons

Spring rains will soon be falling, and warm temperatures will bring the return of thunderstorms. A caller to our 1-800-WHY-ISIT line notes that while most people know enough to leave the water during a lightning storm, most fish continue swimming recklessly. His question is: Why don't they all get zapped?


Transcript

Does lightning fry fish? I'm Bob Hirshon and this is Science Update.
Today's question comes from Matthew Dabney of Longmont, Colorado.

Matt:
"Why is it that we're directed to get out of water during a lightning storm to avoid electrocution? Do fish get electrocuted when the lightning strikes a lake?"

We asked Don MacGorman, a physicist at the National Severe Storms Laboratory in Norman, Oklahoma. He says that as long as the fish are underwater, they're probably okay.

Don:
"Basically lightning stays more on the surface of the water rather than penetrating it. That's because water is a reasonably good conductor, and a good conductor keeps most of the current on the surface."

So, when lightning hits the water, the current zips across the surface in all directions. And if you're swimming anywhere in the vicinity, it'll probably hit you. But below the surface, most of the electricity is instantly neutralized. So the fish are generally spared.

Of course, if the fish happen to be surfacing, they're at risk just like you are. And Dr. MacGorman adds that some electricity does penetrate the water, right at the strike point.

Don:
"So fish under a lightning strike can be killed, if it's close enough to the surface. But it has to be much closer than you do on the surface of the water."

If you've got a striking science question, call us at 1-800-WHY-ISIT. If we us it on the show, you'll get a free Science Update mug. For the American Association for the Advancement of Science, I'm Bob Hirshon.


Making Sense of the Research

People are often both frightened and thrilled by the lightning storms that appear in the summer sky. And we are all advised to get out of the water if we are ever caught outside during a lightning storm.

The key to understanding why it is important to get out of the water during an electrical storm is to know about the forces of nature and electric currents and conductors. You should understand that different kinds of material respond differently to electric forces. In conducting materials, such as water, electric charges flow more easily than through insulators, such as glass.

Now try to answer the following questions:

  1. How is it that fish can avoid being electrocuted when lightning strikes water?
  2. Is water a conductor or an insulator?
  3. What happens to the electric current when lightning hits water?
  4. What happens to the electric current from a lightning strike below the surface of the water?
  5. Does any of the electricity penetrate the surface of the water?
  6. Under what circumstance might the fish be killed?

For Educators

As a follow up to this Science Update, take part in an interactive feature called Lightning: The Shocking Story, presented by National Geographic.

For information on Ben Franklin and his experiments with electricity, go to Point...of Inventionfrom the Franklin Institute.

To get a better understanding about electricity, you can try What is Electricity?
at the Energy Quest website.

Another good source for information about electricity and electric safety is Frankenstein’s Lightning Laboratory, part of the Atom's Family site hosted by the Miami Museum of Science.


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