Surprisingly many scientists deny the existence of this anomaly but this is illogical, in light of so many eyewitness accounts.  And equally amazing is there are no accepted theories about it’s origin or purpose, natural or otherwise.  There is not much the fertile fictional mind can’t come up with a speculation for, even an illogical one, for which it is famous.  It is rare by any standards and does not linger long enough for any kind of examination.

Visual sightings are often accompanied by sound, odor, and other natural and unnatural phenomenon.  Most are accompanied by a loud humming.  Sometimes ball lightnings are reported to emit a hissing sound. Many observers report a distinctive odor accompanying ball lightning. The odor is usually described as sharp and repugnant, resembling ozone, burning sulphur, or nitric oxide.

Many eyewitness accounts describe its movement as having the characteristics of an intelligence guiding it.  It often enters structures through windows or doors though it seems to have no difficulty passing through solid walls.  It travels down hallways and up and down stairs, and other lines of logical access and egress within structures.  It pauses at objects and living things as though observing them.  It has been described as similar to remote reconnaissance drones portrayed in science fiction movies. 

A diameter of 6-18 inches is the most common size, although reports range from ½ inch up to 50 feet in width.  They are luminous and spherical in shape and come in a rainbow of colors, often changing color many times during a single event.  They do not seem to do a great deal of harm although in their exits they sometimes explode which can cause damage. They have even been sighted in aircraft flying in clear skies and on marine vessels without a cloud in sight. 

Another oddity is that witnesses do not often detect heat and electricity even though ball lightning has been known to boil water. However, accounts of ball lightning, which burned barns and melted wires do exist. Ball lightnings have also been observed to hang in mid-air far above the ground and have been observed falling from a cloud towards the ground.

Ball lightning and St. Elmo's fire are sometimes confused. St. Elmo's fire is a corona discharge from a pointed conducting object in a strong electric field. Like ball lightning, St. Elmo's fire may assume a spherical shape. Unlike ball lightning, St. Elmo's fire must remain attached to a conductor, although it may exhibit some motion along the conductor. Further, St. Elmo's fire can have a lifetime much greater than the lifetime of the usual ball lightning. 

Ball lightnings decay in one of two modes, either silently or explosively. The explosive decay takes place rapidly and is accompanied by a loud noise. The silent decay can take place either rapidly or slowly. After the ball has decayed, it is sometimes reported that a mist or residue remains. Occasionally a ball lightning has been observed to break up into two or more smaller ball lightnings.

Though the reported sightings are rare a few are available.

1886
Venezuela. During the night of the twenty-fourth of October last, which was rainy and tempestuous, a family of nine persons, sleeping in a hut, a few leagues from Maracaibo, was awakened by a loud humming noise and a vivid, dazzling light, which brilliantly illuminated the interior of the house.  The occupants, completely terror stricken, and believing, as they relate, that the end of the world had come, threw themselves on their knees and commenced to pray, but their devotions were almost immediately interrupted by violent vomiting, and extensive swellings commenced to appear in the upper part of their bodies, this being particularly noticeable about the face and lips. It is to be noted that the brilliant light was not accompanied by a sensation of heat, although there was a smoky appearance and a peculiar smell. The next morning the swellings had subsided, leaving upon the face and body large black blotches.  No special pain was felt until the ninth day, when the skin peeled off, and these blotches were transformed into virulent raw sores. The hair of the head fell off upon the side, which happened to be underneath when the phenomenon occurred, the same side of the body being, in all nine cases, the more seriously injured.  The remarkable part of the occurrence is that the house was uninjured, all the doors and windows being closed at the time.  No trace of lightning could afterward be observed in any part of the building, and all the sufferers unite in saying that there was no detonation, but only the loud humming already mentioned.  Another curious attendant circumstance is that the trees around the house showed no signs of injury until the ninth day, when they suddenly withered, almost simultaneously with the development of the sores upon the bodies of the occupants of the house.  This is perhaps a mere coincidence, but it is remarkable that the same susceptibility to electrical effects, with the same lapse of time, should be observed in both animal and vegetable organisms.  I have visited the sufferers, who are now in one of the hospitals of this city; and although their appearance is truly horrible, yet it is hoped that in no case will the injuries prove fatal.

1921
Bavaria.  A nine-year-old girl and her uncle were in the first floor of a building during a severe morning thunderstorm. Ball lightning appeared on the left side of the windowsill. The ball fell to the floor where it jumped up and down once or twice, then started to roll slowly toward the observers across the wooden floor, leaving no marks. It was translucent, and the rapidly changing colors showed spots of light green, crimson, light blue, and pale yellow. It then rolled toward the tile stove, crept up the iron parts, leaving a deep groove about the width and depth of a thumb. Then it exploded in an air vent.

1936
England.  In a letter to the editor of the London Daily Mail, a reader described an unusual incident in which a ball lightning caused a tub of water to boil.  During a thunderstorm I saw a large, red-hot ball come down from the sky. It struck our house, cut the telephone wire, burnt the window frame, and then buried itself in a tub of water, which was underneath. The water boiled for some minutes afterwards, but when it was cool enough for me to search I could find nothing in it."

1977
A Coast Guard officer reported this sighting.  “The ball lightning phenomenon was very large and estimated to be about the size of a bus. It was a brilliant yellow-green transparent ball with a fuzzy outline. Intense light was emitted for about three seconds before flickering out. Severe static was heard on the radio. The object slowly rotated around a horizontal axis and seemed to bounce off projections on the ground.”

1984
England. In the summer, two men hitch hiking in the Derbyshire Peak district saw a very strange sight, which has been difficult to pigeonhole. The morning was bright, clear. It was 11am when one of the two caught sight of a shining ball of light moving down the slope from nether moor. He thought at first it was a piece of plastic, but was puzzled when it did not seem to get caught in barbed wire on top of a stone wall, but seemed to pass right through it.  He pointed this out to his colleague. Sheep were also undisturbed as it drifted across their pasture; then it passed through another fence and ascended to the top of some trees, where it hovered for a few seconds before proceeding along a road, having changed its direction of travel from north-south to east-west. It finally began to climb fast into the sky and was lost in the clouds.

In January, ball lightning measuring about 4 inches in diameter entered a Russian passenger aircraft and, according to the Russian news release, “flew above the heads of the stunned passengers. In the tail section of the airliner, it divided into two glowing crescents which then joined together again and left the plane almost noiselessly.” The ball lightning left two holes in the plane.

Glenn R. Frazier relates at incident at his grandfather’s cottage in upstate Pennsylvania. “I was sitting on a screened porch. I remember a brilliant flash of lightning and a large clap of thunder. Seconds later, my mother screamed. My grandfather and I turned to look in through the doorway and saw what looked like a ball of electricity coming down the hallway from the back door. It was about the size of a basketball and had an off-yellow kind of haze. It sounded like a large stream of water coming through a faucet. When it got to the kitchen area, it flickered and flashed a little brighter, and then was gone. They were glowing with a blue-green light that was about as bright as a  50-watt bulb and translucent as a balloon. They moved side by side, the larger one leading.”

“While on vacation on a small farm in Tennessee,” writes Bill Melfi, “I saw two balls of light, one about three feet and the other about four feet in diameter. They were glowing with a blue-green light that was about as bright as a 50-watt bulb and translucent as a balloon. They moved side by side, the larger one leading. The movement was quick and somewhat zigzag. I chased after it with a stick in hand, but they were faster than me. They didn’t break up, just disappeared in the woods.”

Kim LeVeque of Ann Arbor, Mich. tells this incredible story: “I first saw the ball lightning when it came out the front of the stereo. There was an explosion, smoke, and debris, and a large orange ball. It went into the front of the television set and exited through the wall behind the TV. With the explosion, cupboard doors flew open and were torn from the hinges, glass jars broke, the refrigerator door blew open and eggs cracked inside.”