Here are my top 10 unexplained mysteries of the world. Or at least, so some people claim. I'd like to offer some rational explanations for these so-called mysteries, including the direct evidence that debunks them.
He's big, he's hairy, and he's starred in his own TV show.
Bigfoot is world-famous for spooking the bejesus out of hikers and hunters in North America. Scientists consider Sasquatch to be the result of folklore, misidentification and a whole lot of hoaxes.
However, many people still believe these humanoid creatures exist around the world, just like the Yeti of the Himalayas.
One of the most famous unexplained mysteries in the world today, Bigfoot has been described as an ape-like creature, some 6-10 feet tall, weighing more than 500 pounds, and covered in dark brown or reddish hair. Witnesses give him large eyes, a heavy brow ridge and a crested head, much like a male gorilla. Footprints allegedly belonging to Bigfoot are 24 inches long.
Is Sasquatch really one of the great truly unexplained mysteries of the world? Somewhat disappointingly, the most famous footage of Bigfoot at Bluff Creek, California, was shot down by a man called Bob Heironimus. Years after the event, he claimed he wore an ape costume for the filming.
What's more, with so many Bigfoots (Bigfeet?) running around, we would have found much more physical evidence of them, such as fecal matter, hair, footprints, and even numerous corpses and skeletons. We have myriad such evidence for dinosaurs, and they preceded us by 65 million years.
Nevertheless, Bigfoot's cousin - the Yeti (aka the Abominable Snowman) - has a strong alleged presence in the Himalayan regions of Nepal and Tibet. Teams of scientists continue to seek out photo evidence which is also thin on the ground - yet many locals accept the reality of a breeding Yeti population as read.
In the 1960s, the earliest crop circles were primitive circular patterns of flattened crops, often created in mysterious circumstances overnight.
During the last 20 years, though, crop circles have evolved to be far more complex. They now form geometric shapes like the DNA double helix, or fractals like the nautilus shell. Whoever creates these mysterious patterns has become rapidly more advanced in just a period of a few decades. A bit like man.
The first crop circle, recorded in 1966, was discovered by an Australian sugar cane farmer who claimed to see a saucer-shaped spaceship rise up from a swamp before flying away. This was around the time that flying saucers became really popular in sci-fi literature, and ever since, our obsession with alien visitation has fuelled the frenzy.
As unexplained mysteries go, this one has been debunked numerous times. There is ample evidence to show how crop circles are a man-made hoax.
Further studies have dismissed claims that alien saucers have been leaving excessive nitrate deposits at crop circle locations. The trace deposits are explained by the nitrate-based fertilizers used by farmers to grow their crops.
Other paranormal fans claim that there is a mysterious energy left behind within crop circles and people go there to mentally make contact with an extra-terrestrial energy. What could create such a widespread psychological effect?
Science refers to this as The Placebo Effect - where the mind can produce powerful effects on the body simply because the person expects it to. Indeed, the mind is so powerful (and science fully accepts this) that it can sometimes heal the body just as well as medicine when that medicine is replaced by a sugar pill, even when the patient knows it's a fake.
The first reported UFO sighting happened in Texas in 1878, when a local farmer reported seeing a large, dark, circular flying object flying "at wonderful speed".
Another early sighting occurred in the UK in 1916, when a pilot reported seeing a row of lights that rose and disappeared into the sky.
As with crop circles, after UFOs were popularized by science fiction in the 1950s, the number of sightings went through the roof. Theories to explain the paranormal phenomena range from the good old Extraterrestrial Hypothesis (aliens from another planet) to the Interdimensional Hypothesis (aliens popping over from a parallel universe).
Although I do heartily believe that there is other intelligent life out there (and tons of it - the universe is so mind-bogglingly huge, perhaps even infinite) I don't believe aliens are visiting us, let alone in 1950s-style flying saucers.
This is supported by the fact that in photos and videos, many UFOs are debunked as being dust on the camera lens or simply all-out hoaxes (which is easy to do now with PhotoShop). Meanwhile, night-time alien abductions are attributed to the hallucinogenic effect of sleep paralysis.
Meanwhile, UFO conspiracy theories center around Area 51 in Nevada, about 90 miles north of Las Vegas. The site houses a large airbase that was selected in the 1950s for testing of a U-2 spy plane. It has since become America's testing ground for secret "black budget" aircraft before they go public.
In 1971, in the small Spanish village of Belmez, Maria Pereira claimed a human face spontaneously appeared on her cement kitchen floor. It wasn't long before she destroyed the floor and replaced it - and a new face promptly appeared.
More and more faces continued to appear on the floor of Maria Pereira's kitchen, attracting thousands of visitors every day. Some were male, some female, some large, and some small. In time, she discovered that the house, built around 1830, apparently stood above a graveyard used by the Romans, Spanish Muslims and then Medieval Christians.
But did Maria Pereira just paint the faces herself?
If so, she never benefited financially from all the attention. She lived a simple life in that same house and eventually died in 2004.
Paranormal fans suggest that the faces were manifested on the floor by telekinesis. This notion was based on the absurdly unscientific claim that the expressions on their faces used to change with the mood of Maria Pereira.
Finally, modern technology has saved the day for this unexplained mystery.
Many now believe that the paintings were actually created by Maria's mischievous son, Diego Pereira, who dedicated years to spooking his long suffering mother.
This one falls directly under my personal remit.
Out of body experiences, often cited as a literal "exiting" of the physical body in soul or ethereal form, aka astral projection, is superbly explained by a certain type of lucid dream. I've experienced many vivid OBEs myself while practicing lucid dreaming techniques and the process has even been replicated under laboratory conditions.
So, is this proof of the spirit? The afterlife? Alternate dimensions?
Not quite. As lucid dreamers know, we are entirely capable of creating a perfect replica of the real world inside our dreaming minds. When we are dreaming consciously, this can even look, sound and feel as vivid as waking life. This is the great appeal of lucid dreaming.
The instinctive interpretation is that we have projected out-of-body but this fallacy is overcome when you recreate the experience for yourself in the context of a lucid dream. Indeed, many famous out of body explorers use identical techniques to go out-of-body as we lucid dreamers use to enter the dreamworld.
Out of body explorers have long tried to prove the validity of their experience by trying to obtain data from faraway locations. Unfortunately nothing truly definitive has been recorded under verifiable conditions.
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As unexplained mysteries go, the Pyramids of Giza in Egypt really are something special. We still don't really know how the Egyptians built the largest pyramid of all, known as the Great Pyramid of Cheops (or Khufu), some 5,000 years ago. Remember, this was even before the invention of the wheel.
The Pyramid of Cheops is the size of a 40-storey building and covers an area big enough to fit 10 football fields in it. More than 2 million stone blocks were used to make the pyramid, each weighing 2-5 tons and cut from a distant limestone quarry on the other side of the Nile. Experts reckon it took 400,000 men some 20 years to complete.
Engineering feats aside, I'd like to examine the unexplained mystery of Pyramid Power. In the 1940s, a French hardware dealer spotted some mummified animals exactly one-third up the height of the Pyramid of Cheops. The remarkable thing was they showed no signs of decomposition. He deduced that the pyramid shape was responsible for preserving them.
Later, a Czech radio engineer claimed to conduct an experiment in which he placed a brand new razor blade inside a 1:1,000 scale model of Cheops. He aligned his pyramid on a north-south axis exactly like the real thing. After getting 50 shaves from the razor, he was forced to conclude that it was only getting sharper from being inside the pyramid. It took him 10 years to obtain a patent for this device, which he claims still has no scientific explanation today.
But is it a genuine unexplained mystery - or an embellishment of the truth, an anecdotal claim that can't be replicated?
If Pyramid Power did create a real, observable effect, it would be certainly have been commercialized (but never was).
According to many New Age believers, the 2012 prophecy states that the world as we know it will end on December 21, 2012. This is not a new phenomena; as landmark dates draw near, end-of-the-world theories creep out of the woodwork with astonishing popularity. People love this Armageddon stuff.
And yet, we're still here.
I don't consider 2012 to be one of the true unexplained mysteries... far from it. Yet many people are really into this one. So let's look at the idea more closely.
The theory is based on the idea that when the ancient Mayans plotted our position in the Milky Way, they created a special astrological calendar. And on the Winter Solstice (in the Northern hemisphere) in 2012, the Earth would pass into a new astrological phase and something dramatic would happen. Many people have interpreted that as the world ending.
Unfortunately for Mayan fans, there is no real-life evidence to support the idea that the alignment of planets in relation to distant star constellations viewed from our Earthly perspective has anything to do with day-to-day changes in your personal life. It's about as scientifically reliable as reading your horoscope. (Don't get me started.)
While your life may come to an abrupt end any day without warning, there is very little you can do about it. One thing is for sure: our society, like all civilizations before us, is doomed to postulate over end-of-the-world mysteries with gusto.
Stonehenge is one of the greatest unexplained mysteries of the world. It's certainly no hoax (estimated to be more than 5,000 years old) and is probably the most important prehistoric monument in the whole of Britain.
When you visit Stonehenge, you'll find yourself driving for miles through rolling hills and countryside until, suddenly, you catch sight of this bizarre structure. There's an eerie feel to the area around Stonehenge, and for thousands of years it has soon silently, giving away few clues as to the meaning of its existence.
Excavations have revealed that Stonehenge was built in four stages:
Without a time machine to go back and ask, we may never know...
The Loch Ness Monster is claimed to be a prehistoric creature that inhabits the Loch Ness in the Scottish Highlands. As lake monsters go, Scotland has tales of a fair few, with Nessie gaining the most popularity of all on the back of anecdotal evidence.
Nessie first hit the headlines in 1933 when a story was published in the Inverness Courier. The report quoted a Londoner who had visited a few weeks earlier as seeing: "a most extraordinary form of animal... the nearest approach to a dragon or pre-historic animal that I have ever seen in my life."
After that, more sightings were reported and this unexplained phenomena hit international headlines. That same year, one motorcyclist claimed to nearly hit Nessie late one night as it lumbered across the road and slid back into the loch. Soon, apparent photos of the Loch Ness Monster were published.
In 1960, an aeronautical engineer filmed a hump crossing the water in Loch Ness in a powerful wake unlike that of a boat.
Years later, digital enhancement of the footage revealed what seemed to be the rear body, flippers, and two more humps of a plesiosaur-like body. The technician said: "Before I saw the film, I thought the Loch Ness Monster was a load of rubbish. Having done the enhancement, I'm not so sure."
There's no doubt that the story of Nessie has drawn huge tourist interest to the famed Loch Ness. But should it be considered one of the genuine unexplained mysteries of the world? While some people believe the monster is a living plesiosaur, New Scientist points out that such a creature could not physically lift its head up out of the water like the photos and anecdotes suggest.
The Bermuda Triangle is held responsible for the disappearance of countless airplanes and boats in the ocean between Florida, San Juan, and Bermuda. This area is one of the most heavily sailed shipping lanes in the world, with vessels crossing through daily for ports in the Americas, Europe and the Caribbean Islands.
So why do people think there are unexplained mysteries going on in this vast triangle of ocean?
Over the years, there have been a huge number of disappearances that happened in mysterious circumstances, supposedly falling beyond the possibilities of human error, equipment failure or natural disasters. Paranormal fans talk of a suspension of the laws of physics.
For instance, the first unexplained event occurred in the 1950s when the story of Flight 19 came to light, detailing a group of five US Navy bombers on a training mission. The flight leader was reported to have said: "We are entering white water, nothing seems right. We don't know where we are, the water is green, no white." It was also claimed that Navy officials said the planes "flew off to Mars".
So, do multiple airplane and boat disappearances over a patch of ocean count as unexplained mysteries? Skeptics say no.
Instead, they point out that such incidents have been greatly embellished, and that ships have sunk in many places.
Phew. Now we can all go vacation in the Caribbean in peace...
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For centuries, Tibetan Buddhists have been working on waking up in their dreams, so that they can "wake up" at the moment of their death. They also believe that whatever cultural assumptions you have during life will become true upon death. Can lucid dreaming prepare us for the dying process? What might happen at the actual moment of death? Why are we scared of death and how might bodiless lucid experiences help to reduce our fear? In this interview, Dr Clare Johnson and Dr Keith Hearne dive into the lucid void, Tibetan Buddhism, and lucid dreaming as an emotional and spiritual preparation for death.
Does this face look familiar? It should. This is the result of image averaging - a technique in which multiple headshots are averaged out into a single face. In this case, our composite guy was generated by psychology student and photography enthusiast, Bill Lytton. Lytton averaged out 32 attractive male celebrity faces. To avoid personal bias, he referred to Maxim's Hot 100 and other opinion polls. He also averaged out a bunch of unattractive male faces for comparison.
It's a myth that you could exhaust yourself having a great big run in a lucid dream. After all, your real muscles are paralyzed during sleep. Your body isn't really running or burning up energy. So why would you feel depleted? So, in terms of physical energy depletion, there's really no logic to this argument. But what about dreams being mentally or emotionally tiring? The best way to test this is to survey lucid dreamers themselves. Go ahead, take our poll. My intuitive response is no - and that's based on my 17 years of personal experience. Lucid dreams aren't tiring for me at all.
Experts agree that everyone is capable of having lucid dreams. Dreaming itself is a normal function of the mind. We all dream every night, even if we don't remember. And we all achieve conscious awareness while awake every single day. So what does it mean to combine these states? Why, the amazing ability to have conscious - or lucid - dreams. Sounds simple, doesn't it? So why do I keep hearing from people who say they can't achieve their first lucid dream?