Hi!
I love this question, because it set me off looking for *proof* of
something I already knew - that worms and bugs underground that aren't
killed immediately by the heat right at the strike (lightning can
reach up to 50,000 degrees F!) come up out of the ground so they don't
suffocate.
Now ask me how I know.
I'm a Midwestern girl, brought up near Lake Erie, and I like to fish.
Every Lake Erie angler knows that the best way to catch worms is to go
out after lightning has struck nearby and snatch them up. And when
it's not storming? Stick a thick metal rod into the ground and
connect a car battery to it. Brings the squirmy little things right
up.
But how to prove this to your satisfaction? Nobody really seems to
worry about the poor little worms! Instead, the school kids ask about
why fish don't turn into Filet O' Fish after every storm:
Science NetLinks - Zapping Fish
[ http://www.sciencenetlinks.com/sci_update.cfm?DocID=54 ]
Water is a pretty effective conductor of electricity - when lightning
hits a good conductor, the charge is kept near the surface and damages
very little.
Not so for a bad conductor - the charge will either scatter and skim
the surface, or ram right through and destroy it.
Quality Power Systems' Lightning Facts Sheet describes it this way:
"What is the difference between a good conductor and a bad conductor,
in relation to the flow of lightning currents?
The major difference in these conductor types is the way they
withstand a hit from lightning or the flow of lightning currents
through the objects in question. Good conductors, such as metal
objects, suffer little damage as a result of a lightning current
flowing through it. Bad conductors, such as wood, are more likely to
suffer serious damage from the flow of lightning currents. The
following examples will help in understanding these differences.
While a heating element glows red hot, the wires joined to it remain
cool. This is due to the fact that the wires are much better
conductors than the heating element itself.
If lightning happens to hit a bad conductor, like wood, it will either
skip over the surface or flow through the wood causing major
destruction and possibly exploding the wood. This explains why some
trees are destroyed by lightning and others do not appear to be harmed
at all."
QPS Lightning Facts
[ http://www.qpsys.com/Fun%20Stuff/tech03.htm ]
So what about the ground? Good conductor or bad?
Bad. Lightning seeks the ground because of a buildup of a negative
charge in the lower portion of a storm cloud and a positive charge on
the ground. Opposites attract, and in the case of cloud to ground
lightning strikes, it's a spectacular and explosive attraction - as
the charge on the ground builds, it sends the first stroke upwards
(called a "stepped leader stroke") in search of the negative charge.
As it reaches upwards, the negative charge finds the positive, and
follows the path right back to the ground. The energy discharges, and
spreads up to 50 feet from the strike point, occasionally setting
grass on fire, and heating up everything in the vicinity.
There's a nifty explanation of cloud-to-ground lightning strikes here:
Storm Encyclopedia
[ http://www.weather.com/encyclopedia/thunder/light.html ]
I know, I know. What about the worms?
They're very little, and because of their very small surface area, the
charge generally misses them. It's the same principle as balancing on
the balls of your feet if you find yourself in a strike zone -
minimizing contact with the ground also minimizes your chances of
getting struck:
"Lightning has approximately a 50 foot search radius on the ground in
the area that the strike will occur. If you are smaller than anything
else in this radius the strike should miss you."
Lightning Strike!
[ http://www.seaox.com/lz/lz19-a.html ]
Lightning usually goes for the tallest thing in the area, so it's
generally trees, stumps, or even rocks that get hit, minimizing the
amount of energy released into the ground - thus making the worms and
bugs the smallest things in the strike zone and leaving them
relatively unscathed.
The strike *does* heat the ground up, though - remember, lightning
bolts can get up to 50,000 degrees! When that much energy is released
into the ground, things get hot. The creatures cannot respirate, so
they come to the surface...and end up in the bait bucket.
I have another source for my lightning facts. One of my favorite
places to go, ever, is the COSI hands on science center. I'm
especially fond of the Power Zone, which explain all aspects of
electricity, including lightning:
COSI- Power Zone
[ http://www.cositoledo.org/v_learningworlds_powerzone.htm ]
...and Forces of Nature, which includes a great lightning
demonstration involving firing up a Tesla coil, enclosed in a Faraday
cage. Observers sit right beneath the Faraday cage to watch!
COSI - Forces of Nature (In the WaterWorks)
[ http://www.cositoledo.org/v_learningworlds_waterworks.htm ]
The little kids have asked a dozen times over what happens to the
worms when lightning strikes, and the reply is always the same: "They
come up for air."
For explanations of how lightning works and what is and is not a good
conductor, to help explain what happens to the worms, I searched on
the following terms:
"lightning strikes" ground
"lightning strikes" what happens
"lightning strikes" worms
I hope this answers your question! It was great fun to research for
you!
missy-ga |
Clarification of Answer by
missy-ga
on
26 May 2002 08:32 PDT
Hi Ray!
You might think that all - or even most!- of them would end up crispy.
But they don't. The lightning bolt itself is only about a
half-dollar size in diameter (I know, it sounds odd to refer to
something that powerful as "only"), and doesn't really penetrate that
far. Remember, it's the positive charge on the surface of the groud
reaching up to seek out a negative charge in the storm - when the
opposites meet, the energy is discharged, and they don't exactly meet
on the ground. The Earth, being not so hot as a conductor, stops the
electricity fairly quickly. (Think "grounding", "grounded" and "ground
wires" in relation to household appliances - it's the same concept.)
Rather than allow the flow of the electricity, the ground just gets
hot, which drives our little pals up to the surface (not a long trip,
earthworms live only a couple feet below ground).
Remember, too, that lighting gives us a 50 foot "blast radius". As
the released energy (heat) spreads, it begins to dissipate. So
Charlie Earthworm and his pals living directly at the strike point are
likely going to be vaporized (like the fish in the article noted
above), but the further out they are, the less likely they are to be
hurt (again, like the fish in the article). And again, they're very
little - lightning seeks out the big stuff, like you and your golfing
buddies. You're an easier path to the ground than the worms are.
Even if *you* got struck, you'd stand a good chance of surviving -
though lightning is more dangerous for people than it is for worms,
eighty percent of people struck by lightning survive.
So says the National Lightning Safety Institute here:
[ http://www.lightningsafety.com/nlsi_pls/lstrike.html ]
...but I really wouldn't recommend you test this out!! If you get
stuck in a storm, make like a bug - crouch on the balls of your feet
to minimize ground contact, and curl up tightly!
And Ray? Thanks for your very kind comment. I actually was educated
as a teacher (Secondary German!), but these days, I stay home with my
sons and endure the thorough humiliation of being whomped at Trivial
Pursuit by the ten year-old.
Best wishes, and don't go golfing in the rain!
missy-ga
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