Tuesday, July 14, 2009

New Insights Into Lightning

ATMOSPHERIC COMPOSITION AND LIGHTNING

The mechanisms behind lightning are still a mystery and I gave it some thought. Conventional wisdom is that currents of air brushing past each other as updrafts occur under towering cumulonimbus clouds and downdrafts adjacent to the cloud cause static electricity.

The problem with this scenario is that any physics class experiment to produce static electricity shows that it must be two different materials that are rubbed together to create static electricity. Static electricity can only be created by two different materials because when there is friction between the two materials, the one with the strongest hold on the electrons in it's outer electron shells will knock electrons out of the material with the weakest hold on the electrons in it's outer electron shells. The one with the weaker hold will become positively-charged and the other negatively-charged.

So, I ask how the static electricity that results in lightning can be caused by friction between air currents when in is two of the same material? Static electricity cannot be produced unless there is a significant difference in the hold the two materials have on the electrons in the outer electron shells of it's atoms.

The conclusion that I arrived at is that most of air actually is two different materials, about 78% of dry air is nitrogen and about 21% is oxygen. Both exist as diatomic molecules in the air. The two are next to each other in the periodic table of the elements. Nitrogen has an atomic number of 7, meaning that an uncharged nitrogen atom has 7 protons and electrons. Oxygen has an atomic number of 8. Nitrogen has 5 electrons in it's outer shell and oxygen has 6. This causes them to have different holds on electrons in the outer electron shells of atoms.

This means that the static electricity that causes lightning can be caused by friction between oxygen and nitrogen. This has got to be the basis of lightning. It exists only because there are two different major components of the atmosphere. If the atmosphere were all oxygen or all nitrogen, there would be no lightning and if it were half oxygen and half nitrogen, there would be more lightning than there is now. I cannot find that this has been documented anywhere.

We could actually describe lightning as a form of physical oxidation, as opposed to the chemical oxidation in burning and digestion. The opposing updrafts and downdrafts in the air occur under ordinary cumulus clouds as well but the friction produced there is not enough to dislodge the electrons to produce lightning. The atmospheres of other planets also must have at least two component gases to produce lightning, it can be detected on Venus and especially Jupiter.

THE DURATION OF THUNDER

It is known that static electricity can only come about when two different materials are rubbed together so that the material which has the stronger hold on the electrons in it's atoms' outer orbitals knock electrons out of the other material. My conclusion was that lightning is dependent upon the fact that most of air is composed of two different gases, nitrogen and oxygen.

Lightning is a vast electrical spark between two areas of potential voltage difference. Namely, an area that has acquired a positive charge and an adjacent area that has acquired a negative charge. Lightning strikes between a cloud and the ground or between two clouds. There is actually no such thing as "sheet lightning", which appears as a bolt of lightning illuminates the side of a cloud.

Anyone that has been in an electrical storm knows that there is a time gap between the flash of the lightning and the rumble of the resulting thunder. This is simply because light travels so much faster than sound. The exact speed of sound varies with altitude, temperature and humidity but generally, sound travels a kilometer in about three seconds or a mile in about five seconds while light is essentially instantaneous for our purposes here.

During a recent electrical storm, I noticed something that I have never seen referred to before. Here is a question to ponder: If the speed of the lightning bolt is essentially instantaneous from our perspective, then why does the rumble of the resulting thunder last for several seconds?

The length of the rumble of thunder relative to the speed of the lightning bolt cannot be due to cyclic expansion and contraction of the air in a shock wave because if that were the case, the sound of thunder would start loud and then get progressively quieter and that is usually not the case. There must be another reason for the long length of the sound of the thunder resulting from the nearly instantaneous flash of the lightning bolt.

My conclusion is that the reason the length of the rumble is so long is that it results not from the duration of the lightning bolt but from it's length.

When a lightning bolt strikes nearby, the shock wave in the air that we hear as thunder propagates outward. The shock wave from the part of the bolt closest to the ground, and thus closest to us, is what we hear first. Then, as the seconds go by, we hear the shock wave from those parts of the lightning bolt furthest from us, in other words closest to the cloud.

The length of the rumble that the listener will hear is proportional to the length of the bolt, as it creates thunder, divided by the distance from the observer to the bolt. This means that the closer the lightning strike, the longer the length of the thunder rumble is likely to be.

Another conclusion that I came to while listening to the thunder is that the reason the volume of the rumble is uneven, louder-quieter-louder, is that the path of fork lightning tends to be jagged and is rarely a straight line. This is because a current of electricity will follow the path of least resistance to it's destination.

The shock wave produced by the bolt when it is most nearly perpendicular to the observer will be the loudest and when it is at an angle, will be less loud. Another factor is that the thunder echoes off the ground.

Put simply, sound travels at a finite speed so we hear the thunder from the closest point of the bolt first and it's furthest point last. This explains why the bolt of lightning is close to instantaneous but the resulting rumble of thunder lasts several seconds.

No comments:

Post a Comment