THUNDER AND LIGHTNING

Just listen to that thunder roll and reverberate in the canyon! Did you ever try to read a newspaper on a night when a real "side-winder" of an Arizona thunderstorm is in full sway? Yes, it can be done! Many of us who dare to brave the awe inspiring display of electricity and earth-shaking thunder by keeping our heads above the pillow (instead of under it!) can vouch for the midday brilliance of the "big" storms. But, to those who get a bit squeamish when old Mother Nature begins throwing her diamonds and sapphires around like a banshee need not bow their heads in shame because they are overawed by the unknown fury of the storm. So little is known about the marvels of Nature-the great outdoor laboratory is so limitless and conditions are so changeable. Even world-renowned scientists are still puzzled by the wonders of lightning. Many theories have been advanced, and almost as many have been cast aside. It seems that some phase or other did not fit certain evidence which has been found in the atmosphere. But there are a few theories on the origin and cause of lightning which are accepted by most scientists. Perhaps they might help us to understand, in a little way, the wonders in the sky and mayhaps dispell some of our fears, too!

This planet upon which we all experience our joys and sorrows bears a negative charge of electricity on its surface. (You don't suppose that is why we all have days when our answers are "No" to almost everything?) All levity aside though, the earth's surface does bear a negative charge of electricity.

Ah, now we have something to sink our mental teeth into! Electricity. Yes-but what is electricity? The answer is simple, but not too informative. Electricity is electricity, and it cannot be described or defined in terms of anything else. We will have to learn something about how electricity behaves and then try to define it by its actions.

If we take a fountain pen (the black, hard rubber-cased kind is best) and rub it vigorously on our coat sleeve we will find that small bits of paper, thread, or dry sawdust are attracted to it. Thus by rubbing the pen on our coat sleeve we have caused the material from which the pen is made to acquire a property wherein it is able to exert a force on other bodies with which it has no contact. By means of other experiments we learn that the same results are received whenever two unlike bodies are brought together (rubbed) and then separated. Moreover, both of the bodies rubbed together acquire this same power in exactly the same degree. We say that the bodies are electrified. The term "electricity" is derived from the Greek word for amber which is electron. Yes, the Greeks discovered this property when rubbing resin (amber) back about 200 B.С. Further experiments show that when two rubber or two glass rods are electrified they will repel each other. However, a glass and a rubber rod will attract one another. Thus we see that there are two types of electrification. Not only that, but we find that equal charges of both kinds of electricity are produced whenever two unlike substances are brought together and separated.

We are beginning to get into deep water with all of this talk of two kinds of charges. So, let's simplify the problem by calling one charge the positive and the other charge the negative one. This all seems very remote from lightning but when we investigate the charge on a closed conductor such as a metal ball or tin can we find that the charge is all located on the outside surface!

Imagine how important that simple statement becomes to so many of us. A closed surface such as a shell, gives us protection from lightning. For example, the inside of a sheetiron house would be perfectly safe in case of a lightning storm as long as we were insulated from the iron. Nearly complete protection is afforded by a modern steel frame building. Think of the Forest Service lookouts on the top of upthrust peaks in a wild thunderstorm! They receive their protection from lightning by being inside of their steel house or one that is protected by an umbrella of steel cables. Your rubber-tired auto is a sanctuary in a thunderstorm as long as you do not touch the metal parts.

Another discovery which held tremendous import was that an insulated egg-shaped metal shell had a much greater electrical charge on the small end than on any other section. Going one step, it was found that if the conductor had a sharp point, the charge became so heavy on it that the electricity leaked off rapidly. Here we have the principle which is used in the protection of buildings by lightning rods. The numerous sharp points result in a quiet discharge between the earth and the clouds and thus tend to prevent lightning strikes. Should a strike occur close to the rod, it would pass down it to earth, thus leaving the structure unharmed.

Now, let us go back to our statement that the planet Earth had a negative surface charge. But, we say, where is the "equal and opposite charge"-the positive charge? Well, through scientific research and theory it has been proven that many miles above the earth there are several layers of positively charged particles. These layers, which lie many miles above the earth's surface, are called the ionosphere.

Now the picture begins to take form. The earth's surface with a negative charge, and an envelope high above the surface called the ionosphere which has a positive charge.

H. W. AUSTIN, a resident of Douglas, has an interesting hobby-photographing the weather, or rather, manifestations of weather. Herein are produced some of his studies of storm skies and a lightning storm at night. Thunder storms in Arizona are bold and dramatic things to see -and to photograph!

Remember that like charges repel and unlike charges attract one another. The air between the earth's surface and the ionosphere acts as a great insulator which tends to keep these two attracting charges apart. If the electrical charge at any point on the earth increased or if some phenomena took place in the air which brought about a great increase in electricity over a relatively small area, the air (which is an insulator) could not keep these opposite charges apart. When the potential between charged parts of a thundercloud or between the cloud and ground becomes great, an electric discharge which forms a long, brilliant, tenuous and often a crooked spark occurs. This spark is what we call lightning.

How does this charge build up in the clouds? One theory explains the charge in clouds by maintaining that water droplets falling through the air have a positive charge on their lower side (remember that unlike charges attract one another), and negative charges on the top side of the droplet. Tremendous rising air currents in those billowy clouds we all have seen during the birth of a thunderstorm, tear these little water droplets apart, the larger portions of the droplet (with the positive charges) congregate in the lower portions of the thundercloud while the smaller fragments with their negative charges are carried to the middle portions of the cloud. After several hours of "raindrop tearing apart" the thundercloud has developed quite a charge of electricity. The stage is set Flash!!! And we are off to another one of those glorious shows that shake the very foundations of our homes. Repeated discharges finally neutralize the air in which the thunderstorm is imbedded and with a final quiet little rumble the storm is over.

The sound of thunder is caused largely, if not entirely, by a sudden increase of pressure along the path of a lightning stroke. Hence, thunder is harmless. The rumbling produced, sometimes interspersed with tremendous bumping sounds, is one of the chief characteristics of thunder. This is due to the source of the sound being long and irregular with different parts of it at different distances from the listener. The bumping sound is probably due to differing conditions of reflection, or to several successive strokes of lightning. Ordinarily thunder cannot be heard much farther than fifteen miles from the lightning flash. Thunderstorms are relatively rare during the winter but are common in summer. All areas of the earth have thunderstorms at one time or another. Tampa, Florida, has an annual average of 94 days with thunderstorms while Santa Fe, New Mexico, is second in the United States with an average of 73 days. Arizona sees its greatest number of thunderstorms in the mountain country along the New Mexico border with the White Mountain area averaging between 50 and 60 days each year with thunderstorms.

They are more common in sections where moist air currents from the ocean sweep inland over hot land surfaces. You will recall that tremendous rising air currents are needed to first form clouds, and then to furnish the mechanism of breaking up raindrops to form tremendous electrical charges in the clouds. These ascending air currents are furnished by energy received from the hot sun. The earth must be very warm, or layers of air close to the surface must be heated before enough energy is available to "trip off" the billowy clouds that gather unto themselves until forks of lightning lick out to break the peaceful but ominous calm that holds sway before the storm. The heat energy is absentduring winter storms. Only on rare occasions does cold, fast driving south-bound air from polar regions, lift warmer air with enough force and sustained power to furnish the necessary mechanism for a winter thunderstorm.

But we must remember that it is summer in the southern hemisphere when our half of the earth has winter. Hence, thunderstorms are under way someplace on the earth every day. There is about $200,000,000 worth of electricity floating around the world daily, and that's only counting it at the low rate of one cent per kilowatt hour! There are, over the earth as a whole, some 44,000 flashes of lightning per day. Some fellow with a lot of time on his hands has computed the energy in one lightning flash. If the streak is one-half mile long, the energy used up is the equivalent of about 2500 horsepower continuously for twenty-four hours. Some lightning flashes are as much as five miles in length, carry a billion volts, and last about one-thousandth of a second. Arizona is blessed with summer thunderstorms during July and August. Normally the first moist air from the Gulf of Mexico (yes-all the way from the waters off shore from Vera Cruz in old Mexico), arrives in southeastern Arizona between the first and fifth of July. Slowly, but implacably this moist air, attended by thunderstorms, spreads over Cochise and Santa Cruz counties, up toward the high country in Greenlee, Gila and Apache and finally into Coconino and Yavapai counties. The splendid panorama of majestic clouds and thunderheads marches from old Mexico into Arizonamighty mountain ranges such as the Chiricahua, Huachuca, Pinal and White Mountains help to "trigger off" the ascending air currents that cause old Thor to dance with glee. Then the Mogollon Rim country, like a giant hand, scoops up a mighty portion of the moist air and cools itself in the heaven-sent rains that accompany the crash and boom of forked lightning. Thus, in a veritable blaze of glory, end the long, dusty, dry months of May and June in our beloved land. Once again the streams run, and the ever-fertile land blooms in response to the symphonies in the sky that have passed overhead. The National Bureau of Standards in their code for protection against lightning mention the following points as a guide to personal conduct when a thunderstorm occurs:

Be careful folks, when a thunderstorm is in progress-but enjoy it also! It is one of Nature's greatest shows.