What is lightning?
• a gigantic electrostatic discharge between
the cloud and the ground, between clouds,
or within a cloud
• the same kind of electricity that can shock you
when you touch a doorknob (static electricity)
• results from buildup and discharge of
electrical energy between positively and
negatively charged areas.
Lightning strikes
somewhere on
Earth 100 times
every second!
Each year
lightning strikes
the USA 20 million
times!
Most cloud to ground lightning – central Florida
Almost no lightning – Pacific Northwest
How Does Lightning Work?
1. Wind creates friction in an
ice cloud that creates
“static electricity.” The
bottom of a cloud
becomes negatively
charged. Since opposites
attract, positive charges
collect on the ground and
other surfaces under the
cloud.
How Does Lightning Work?
2. A stepped leader —a
negative electrical
charge made of zigzagging segments, or
steps—comes
partway down from
the cloud. The steps
are invisible. Each
step is about 150 feet
long.
How Does Lightning Work?
3. When the stepped
leader gets within 150
feet of a positive
charge, a streamer (a
surge of positive
electricity) rises to
meet it. The leader
and the streamer
make a channel.
How Does Lightning Work?
4. An electrical current from an object on the
ground surges upward through the
channel. It touches off a bright display
called a return stroke.
In this 5 minute
time exposure
photo, lightning
strikes Tucson, AZ.
Each flash
contains 1 billion
volts of electricity,
enough to light a
100 watt bulb for 3
months.
Results of Lightning
• A lightning flash happens in ½ a second. In that instant,
the lightning flash superheats the surrounding air to
50,000 ºF, five times hotter than the surface of the sun!
• The rapid heating and cooling of air near the lightning
channel causes a shock wave that results in thunder.
– Thunder - the booming sound produced by rapidly expanding
and vibrating air along the path of the lightning.
• Sound travels more slowly than light, so we see the
lightning before we hear the thunder.
Ball lightning occurs
after a ground flash.
The ball is usually red,
orange, or yellow, and
can be as small as a
grapefruit or as big as
a pumpkin. The ball
hovers or darts briefly,
fizzles out and ends
with a loud
BANG!
Cloud lightning never strikes Earth.
Spider lightning flashes crawl across the sky for
up to 90 miles.
Benjamin Franklin
• In 1752 the famous scientist and
statesman conducted an experiment to
find out if lightning was electricity. During a
thunderstorm in Philadelphia, PA, Franklin
and his son William flew a homemade kite
with a wire attached to it. Franklin
expected lightning to strike the wire, then
flow down the kite string to a key tied near
the end.
Benjamin Franklin
• The kite entered a rain cloud. Franklin
touched his knuckle to the key. Zap! An
electric spark! The experiment had
worked. The lightning behaved like
electricity. Franklin had been lucky. If the
lightning strike had been stronger, he
could have been hurt or killed.
• The church tower of many European cities,
usually the highest structure, was the building
most often hit by lightning. The buildings burned.
Parishioners were told NOT to go to the church
to seek shelter during a storm.
• Lightning starts many fires in the western US
and Alaska.
• After his experiments, Franklin invented lightning
rods to protect buildings.
An early form of
lightning protector
shows how the
electricity is sent
to the ground
where it
dissipates.
More modern lightning rods
use guide wires to send the
electrical charge safely into
the ground.
Parents “ground” their
children. Get it?
Lightning Safety FUN FACT
The Empire State Building
in New York City is struck
on average more than 100
times per year. The
building is actually
designed to simulate a
giant lightning rod in order
to help protect the other
buildings in the
surrounding area.
Where and when are you most
likely to be struck?
• Florida has twice as many lightning
casualties as any other state.
• Most lightning casualties occur between
noon and 4 p.m. Sunday has 24% more
deaths than other days, followed by
Wednesday. Lightning reports reach their
peak in July.
Who is most likely to be struck?
• Men are struck by lightning 4 times more often
than women. Males account for 84% of lightning
fatalities and 82% of injuries.
• Only 10-20 percent of lightning victims are
immediately struck dead.
• Many doctors do not fully understand how to
treat the injuries of the other 80% - 90% of
lightning victims who survive a strike.
• The pathology of lightning, or keraunopathy, is
known only to a few specialists.
What are the results of being struck by lightning?
• Many lightning victims had been walking in
an open field or swimming before they
were struck. Other lightning victims had
been holding metal objects such as golf
clubs, fishing rods, hay forks, or umbrellas.
• They suffer from paralysis, memory loss,
burns, loss of sight or hearing and other
neurological problems.
Where is it?
• Count the seconds between a flash of
lightning and the next clap of thunder.
• Divide by 5 to determine the distance to
the lightning in miles.
• By the time you hear thunder, you are
already within striking distance!
How far away is it?
• You see lightning and begin counting.
• You count to 10.
• How far away is the storm?
– 10 divided by 5
– equals 2 miles
Thunder
• Lightning emits a broadband pulse of radio
waves that our ears cannot detect.
• Picked up by specialized equipment, lightning
sounds like bacon frying or the crackling of a
campfire.
• Scientists call the sounds tweeks, whistlers and
sferics.
• Sometimes lightning bolts escape the
ionosphere and travel along Earth’s magnetic
field!
Lightning Safety
• Severe damage can be done by lightning and
certain safety procedures should be followed.
Lightning Safety
• Get into a large building or enclosed vehicle.
• Stay off corded phones, computers and other
electrical equipment.
• Stay away from water in pools, tubs, showers,
and plumbing.
• Install surge suppressors and ground fault
protectors to keep appliances safe.
• Wait 30 minutes after the last strike before going
out.
Lightning Safety
• If you cannot get to a sturdy building…
– Find a low spot away from trees, fences, and poles.
– If you are in the woods, take shelter under the shorter
trees.
• If you feel your skin tingle or your hair stand on end,
squat low to the ground on the balls of your feet. Make
yourself the smallest target possible, and minimize your
contact with the ground.
When
thunder
roars, go
indoors!
Fulgurite
• Sometimes when lightning strikes sand, the
sand is superheated. It melts and then fuses
together to form a fulgurite. These take the form
of tubes, sometimes more than half inch in
diameter, that look like lightning bolts.
• Rock Fulgurites are formed when lightning
strikes the surface of a rock, melting and fusing
the rock.
• The melting point of Si02 is 2950 oF.
Fulgurite
True Lightning Stories
• A watermelon on a kitchen table in
Arkansas blew up during a thunderstorm
in 1987. A clap of thunder caused it to
vibrate so fast that it exploded!
• A field of potatoes was struck by lightning.
The potatoes were cooked by the strike.
After being dug up, they were eaten like
baked potatoes!
Lightning Joke
• Teacher: Why is it said that lightning
never strikes the same place twice?
• Student: Because after it’s struck once,
the same place isn’t there anymore!