The Earth is a mysterious place. There is much going on around us every day that goes unexplained. For all our advanced technology and scientific understanding, there are events that occur, more or less, on a regular basis for which (as yet) we have no answers. Here is a list, in no particular order, of 10 of the most perplexing, documented phenomena that have baffled us for years—in some cases, decades and much longer.

In 1821, Tilloch's Philosophical Magazine carried an unusual item about a stone mason named David Virtue who made an astonishing discovery while working on a large chunk of rock that had come from about 22 feet below the surface. Upon breaking it open "he found a lizard embedded in the stone. It was coiled up in a round cavity of its own form, being an exact impression of the animal. It was about an inch and a quarter long, of a brownish yellow color, and had a round head, with bright sparkling projecting eyes. It was apparently dead, but after being about five minutes exposed to the air it showed signs of life. It soon ran about with much celerity."

There are numerous documented accounts of such findings, mostly involving frogs, toads or lizards. Most often the animals come out alive. And very often there is an imprint of their skin or shape on the cavity in which they are entombed. And this raises a number of interesting questions: How could the animal have gotten in there and survived? How did rock—which geology tells us takes hundreds if not thousands of years to form—take shape around the animal? How long could the animal have been in there?

"We were passing down this road, and there was a thunderstorm a coming up behind us. We smelled this animal as we come by. We came back to check on it and found it was mutilated. We examined it and its sexual organs was taken out. Its eyes were taken out, and its eyelashes were taken out. Well, there wasn't no predators. Couldn't have been killed by a predator cause all the surgical work was done by an expert..."

Rancher C.E. Potts, 1990

The report is typical for the phenomenon, which began to be documented in the early 1970s when reports came in from ranchers in Minnesota and Kansas. The mutilations were like nothing they had ever seen with their cattle; they seemed to have a surgical precision that ruled out predators (whose work ranchers were quite familiar with). The selectivity is also unusual: often only the eyes, tongue or sexual organs have been removed, and quite often there is an unexplained absence of blood from the scene. Theories to explain the mutilations include Satanic cults, aliens, government experiments (unmarked black helicopters are sometimes seen in the vicinity) and bizarre diseases. As yet, however, no conclusive answers have ever been found.

Unexplained Hums

Citizens in Britain and portions of the Southwestern U.S. have been complaining about a maddening hum that just won't go away. And researchers have been unable to pinpoint its source. Not everyone can hear the low-pitched hum and those who do say that it seems artificial in nature—and is driving them crazy. In 1977, a British newspaper received nearly 800 letters from people complaining of loss of sleep, irritability, deteriorating health, inability to read or study because of the incessant hum.

Most famous in the U.S. is the Taos Hum. There the annoyance was so acute for the "hearers" in Taos, New Mexico that they banded together in 1993 and petitioned Congress to investigate and help them find the source of the noise. No conclusive causes were discovered. One prevailing theory holds that the hum is created by a military communications system used to contact submarines.

In January 1984, ball lightning measuring about four 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.

Ball lightning is another natural phenomenon for which science has yet to come up with a full explanation. The problem for scientists is that the manifestation of the phenomenon is so rare that it is almost impossible to study. Attempts have been made to recreate it artificially in the laboratory, but an actual specimen of naturally occurring ball lightning has yet to be captured for study. This may be impossible since the phenomenon is fleeting - floating about for awhile and then fading away or exploding with a loud pop.

What makes ball lighting so fascinating and puzzling is its strange "behavior." Witnesses have said that it moves about as if with a kind of intelligence, following patterns on walls or furniture, and seeming to avoid obstacles. More mysterious still is its ability to pass through solid objects. Sometimes it leaves holes, as with the airliner above, but it has also been seen to pass through window glass and even walls without even leaving a mark.

This might be a phenomenon related to ball lightning... then again it might not be. No one really knows what the many "spooklights" reported around the world are caused by. And there are many. Most famous, perhaps, are the Marfa Lights seen for generations near Marfa in Western Texas. The lights appear almost nightly and can be seen at a distance from Highway 90. Yet when investigators try to approach the lights, nothing can be seen.

Other spooklights include: The Tri-State Spooklight near the borders of Oklahoma, Kansas and Missouri; the Brown Mountain Lights near Morganton, North Carolina; the Gurdon Light near Gurdon, Arkansas; the Cemetery Lights of Silver Cliff Colorado; the Hebron Light in Maryland; the Hornet Spook Light in Southwest Missouri; and the Peakland Spooklights in Britain.

There are many unproven theories, of course, including alien activity, mirages, ghosts (usually headless railroad workers), and ball lightning induced by tectonic stresses in rocks.

Clouds are fluffy, benign masses of water vapor, right? Consider this: In an otherwise clear September sky near Agen, France in 1814, a small, white, spherical cloud appeared. It floated motionless for a while before beginning to spin and head quickly southward. Witnesses reported that deafening rumbling noises thundered from the cloud, and then it suddenly exploded in a shower of rocks and stones. The cloud then slowly faded away.

This is one case of extremely rare and highly unusual behavior from clouds. Other documented reports tell of clouds that move against the wind, clouds that rain insects or carry peculiar shadows. There is even a story of a man from Oyster Bay, Long Island who was attacked by a spitting cloud. It's difficult to come up with any kind of rational explanations for these weird tales.

One of the most recent examples of fish falling from the sky took place in the summer of 2000 in Ethiopia. A local newspaper reported: "The unusual rain of fish, which dropped in millions from the air—some dead and others still struggling—created panic among the mostly religious farmers." This is just one of the countless case studies of rains of fish, frogs, periwinkles—even alligators—that have been cataloged over the centuries, many by famed paranormal researcher Charles Fort (such rains of creatures have been, in fact, come to be known as "Fortean" activity).

Most often these rains of animals are attributed to severe storms, tornadoes, waterspouts, and related phenomena. Although the theory has not yet been proved, it holds that strong winds pick up the fish or frogs from bodies of water such as ponds, streams, and lakes, carry them aloft - sometimes for miles and miles - and then drop them over land.

The peculiar fact that challenges this theory is this: in most cases, the rains are of one kind of animal only. It rains one species of herring, for example, or a particular kind of frog. How can this be explained? Could a powerful gust of wind be so discriminating? If the storm scooped up water from a pond, wouldn't it rain all kinds of things one finds in a pond—frogs, toads, fish, weeds, sticks and probably beer cans?

I hesitate to include crop circles because I'm nearly convinced that they are all probably man-made. Yet, even though many groups of people have come forward to admit that they have designed and created the sometimes elaborate—and quite often beautiful—crop formations, there remains a die-hard faction of believers that insists that at least some crop circles are caused by some unexplained phenomenon.

Crop circles have been reported in nearly every country on Earth. In fact, according to Crop Circle Central, the only major countries that have never reported formations are China and South Africa. Plain round crop circles as we know them began to appear in abundance in the 1970s. But then in 1990, we began to see far more intricate and complex pictograms. Believers suggested they might be a form of communication from extraterrestrials—or from the Earth itself. Those who say they are not manmade point to several peculiarities found in the affected crops: woven stalks, cellular changes in the grain stalks, and strange phenomena experienced by researchers examining the circles, such as unexplained equipment failures, sounds, and other physical effects.

After 90 years, the explosive event at Tunguska, Siberia in 1908 remains one of the most puzzling natural disasters in recent history. On June 30 of that year, a blazing fireball descended from the sky and devastated an area about half the size of Rhode Island. Trees were felled for miles in a radial pattern, fires burned for weeks and the sound of its thunder could be heard at great distances. It's been estimated that its explosive force was equal to more than 2,000 Hiroshima-type atomic bombs.

What it was that fell on Tunguska that fateful day is still a mystery. Although for many years scientists thought it was probably a meteor that exploded over the Siberian wilderness, today's best guess is that it was probably a comet. The change, in theory, came about because no meteor fragments could be found at the scene. In fact, there was very little evidence of any kind to explain precisely what occurred that day. This lack of hard evidence led, as if often does, to wild speculations: a UFO with a nuclear reactor had crashed; a powerful electric weapon created by Nikola Tesla was intentionally or accidentally aimed at the area from somewhere across the globe.

In recent years, the Tunguska event has received renewed attention as we realize more clearly that the Earth is at risk at almost any time from a strike from outer space.

"Rods" are one of the most fascinating and intriguing Earth mysteries of recent times. Discovered accidentally by filmmaker Jose Escamilla in March of 1994, what he calls "rods" are strange flying things that can only be seen on slowed-down film and videotape, and sometimes captured in still photographs. Apparently, these things—whatever they are—move too quickly to be seen with the naked eye. Escamilla first noticed them in film footage he had taken in Midway, New Mexico, and he (along with others) have since filmed and taped them in several other locations.

According to Escamilla's own definition, rods are "cigar or cylindrical shaped objects that travel at high velocities barely visible with the naked eye. They appear to be alive as they move through the air like fish swim in the sea. They appear to have fins or appendages along the torso and the torsos bend as they travel." Escamilla has several film clips and stills of the creatures on his website.

The rods measure from just a few inches to several feet in length and there seem to be a few varieties with different kinds of appendages. They have been spotted and recorded in Mexico, Arizona, Indiana, California, South Dakota, Connecticut and even Sweden. Some have even been seen underwater. Are they some unknown species of animal? If so, why has no one ever seen these creatures at rest?