Space & Innovation

5 Unexplained Earth Mysteries

We look at some of the strangest mysteries of the recent past and some of mysteries that remain.

Odd Noises

There are several well-known mysterious sounds in the world. The most famous is New Mexico's Taos Hum, but another mysterious hum has plagued residents in Windsor, Ontario, since 2011. Not everyone hears it, and even those who do don't all describe it in the same way. Some say it's like a running refrigerator or an idling big truck. For years residents heard it -- and complained about it -- but local police couldn't help and no one was sure of its origin.

Several investigations were conducted including by the Canadian government. Finally in May a study confirmed for the first time that the hum is real (and not, for example, an auditory illusion), and conclusively identified the source of the sound: Michigan's Zug Island, across the Detroit River, the site of heavy manufacturing including a U.S. Steel plant. Though it's clear that the hum is mechanical in nature and coming from the island, scientists haven't been able to locate a specific building or piece of heavy machinery that's causing it. Though the infernal Windsor Hum remains, nearby residents can sleep a little easier knowing it's not all in their heads.

Missing Jet

On March 8, 2014, Malaysia Airlines Flight 370 veered off course after it left Kuala Lumpur and soon vanished. It seems impossible that with modern technology, the cooperation of several countries, and tens of millions spent on search costs, the plane would simply vanish, never to be found. Dozens of planes, submersibles and ships searched in vain for the Boeing 777, but not a trace has been found. Hopes for finding the flight mostly depended on locating the airplane's "black box," equipped with an electronic pinger that sends out a regular sound signature.

Unfortunately, the batteries died after three months, and early pings detected by the U.S. Navy were later determined to be false alarms that wasted precious time. The search for the missing plane was plagued by problems from the beginning, with erroneous information sending teams from one search area to another and another. To this day many questions remain: Were the pilots on a suicide mission, and if so, why? Did a mechanical failure cause the plane to go down? The search continues and though it's likely that this mystery will be solved one day, it may take months or years longer.

Strange Bolts

Ball lightning, according to the American Meteorological Society's Dr. Walter Lyons in his "The Handy Weather Answer Book," is "one of nature's most mysterious phenomena. Usually seen during violent thunderstorms, the spheres of glowing light are typically the size of bowling balls or basketballs. They can last from a few seconds to many minutes. The spheres can simply vanish into thin air, but can also pass through window glass and screens, leaving burn marks behind.... They usually do not cause much damage and can even seem playful."

A research team saw and recorded a ball lighting strike in northwest China in July 2012: "They were able to record a spectrum and high-speed video footage of the ball. The recorded glow was about 5 meters across -- the actual size of the ball was much smaller... The researchers found that the spectrum contained several emission lines from silicon, iron, and calcium."

This suggests that the lightning may be created by some unknown interaction with the soil, and though the research offers some tantalizing clues about the origin and nature of ball lightning, the phenomenon remains elusive and largely unexplained.

New World Mystery

Christopher Columbus wasn't the first European to set foot in the New World. The Vikings preceded him. And in 2013, we learned of the arrival of a mysterious group of European settlers to the "steps to the Americas" 300 to 500 years before the Vikings arrived in the New World.

Scientists had previously thought the Vikings were the first arrivals to the Faroes in the ninth century. Discovered at an archaeological site of Á Sondum on the island of Sandoy, researchers found evidence of human settlement in patches of burnt peat ash.

Although investigators have yet to discover clear evidence of the group's identity, possibilities include religious hermits from Ireland, late-Iron Age colonists from Scotland or pre-Viking explorers from Scandinavia.

Photo: Durham University

Undersea Mystery

A giant circular stone structure was discovered in the Sea of Galilee following a sonar survey, and archaeologists have no idea what it is or who put it there.

Weighing an estimated 60,000 tons, the cone-shaped structure is made of an "unhewn basalt cobbles and boulders." Aside from its proportions -- 32 feet (10 meters) high with a diameter of 230 feet (70 meters) -- little else is known about the structure. Researcher Yitzhak Paz, of the Israel Antiquities Authority and Ben-Gurion University, has suggested it could be more than 4,000 years old, citing other megalithic phenomena near the site.

Photo: Shmuel Marco