Robin Brabham, age 14, of Sumter,, S. C., for the question :
Does sheet lightning strike?
When the thunder peals and the ragged lightning flashes across the sky, sensible people know that there may be trouble. The lightning may strike a tree or a wooden building with searing destruction. Boats on the water may also be struck and every year hundreds of forest fires are started by lightning. Do not shelter under a tree and make sure that buildings have proper lightning rods to conduct any possible flash safely to the ground.
The flashing lightning which goes along with the thunder is no different from the flat sheet lightning which glances silently across the sky. The sheet lightning, however, is further away. If it is going to strike, it will strike some place over the horizon. You do not have to shelter or take precautions to protect yourself when the lightning is the silent, hazy kind which lights up the distant sky.
Lightning, fierce anal blinding, is no more than the discharge of energy between electrically charged particles. These particles are the tiny electrons which orbit the atoms. The heart of a storm cloud is a. seething warfare of turbulent air currents where icy crystals, raindrops and perhaps hailstones are tossed to and fro. In the turbulence, electrons are brushed from atoms, leaving the atoms with a positive charge of electricity. Other parts of the cloud gain a negative electrical charge. Normally, the ground too has a negative electrical charge.
Pressure builds up with the differences in positive and negative electrical charges. At a certain point, the energy is released as a flash or flashes of searing lightning.
The flash may be between two parts of the storm cloud or between the cloud and the ground. The flashes which rip groundward are the ones that can strike sand set fires.
The thunder follows the path of the lightning, though the lightning reaches our eyes before the thunder reaches our ears. This is because light travels s o much faster than sound. Light, which brings the news of the flash to our eyes, travels at about 186,000 miles a second. The sound which brings news of the thunder pokes along at about one mile in five seconds. Moreover, the sound fades as it travels.
When a storm is way over the horizon, we cannot see the actual path of the flash. We see only its reflection in the clouds above it. This is sheet lightning. A storm at this distance is many miles away and no immediate danger to us, though our friends over the hill may be struck. At this distance, the sound of the thunder is all worn out long before it reaches us, which is why sheet lightning is silent.