Mysterious explosion still haunts us

It was night in the Western Hemisphere and early morning on the eastern side of the planet. Suddenly, an enormous curtain of fire split the skies. It crossed from west to northeast, and then a big thunderstorm-like explosion was heard around the globe.
    This is not fiction. It really occurred 100 years ago, on June 30, 1908.  This event is known as either the Tunguska event or the Tunguska explosion. Tunguska is a remote region of Russia, located in central Siberia. Scientists puzzle over it even today.
    Perhaps other witnesses of this great event are still alive. My father, who died in 1982, witnessed it and told me in detail about what he referred to as "the big fireball story."
    My father was a 14-year-old boy at the time of the Tunguska explosion, and he said he was playing with other boys in the streets of his hometown in Nicaragua.
    The event probably occurred between 7 and 7:30 p.m. My father described it this way: "Suddenly, an intense light more brilliant than the sun covered the sky and the entire town. We became paralyzed when we saw, slowly rolling across the sky, an enormous fireball moving apparently from west to north.
    "All the townspeople exited from their homes and knelt on the ground, praying for God's forgiveness. They embraced each other in confused crying and moaning, also asking each other for forgiveness. People yelled that it was doomsday. The fireball also made a frightful noise, like a wildfire.
    "Maybe the fireball took two or three minutes to disappear. But a few minutes later, a tremendous explosion was heard whose echo remained vibrating in space with a noise like that of a big waterfall. The brilliance left by the fireball was diminishing but did not disappear for the rest of the night. That night, the whole town kept praying until the new day arrived. Really, it seemed like the end of the world."
    What my father witnessed was one of the most compelling and frightening event of modern times. The entire world witnessed or felt the effects of the object wrapped in fire, which was responsible for the devastation in Tunguska.     Scientists agree it was a massive explosion that occurred around 7:14 a.m. local solar time in Tunguska. They estimated the energy of the blast was about 30 megatons of TNT, or about 1,000 times as powerful as the bomb dropped on Hiroshima.
    What provoked so enormous an explosion? The scientific community still does not know, 100 years later. Scientists have formulated different hypotheses to try to explain the phenomenon. According to historical records, the first scientific expedition arrived at the scene of the devastation in 1921, 13 years after the event.
    Remember: There were no modern transportation or sophisticated communication systems at the time. It wasn't until 1927 that another expedition, conducted by Russian scientists, was able to find the great forest that had been destroyed. They found a vast area of more than 30 miles of scorched trees that, strangely, will standing upright with the bark stripped from their branches.
    Scientists also heard and recorded the frightening testimony of the natives. A Siberian peasant named Semnov told the scientists: "The sky lighted, and a fire appeared high and wide over the forest. It became larger, and the entire northern side was covered with fire. At that moment, I became so hot that I could not bear it, as if my shirt were on fire. Then I threw it down."
    Another witness, Chuchan, said: "The morning was sunny, and the sun was shining as usual, but suddenly there came a second sun. Then I felt one, two, three thunder strikes, and it was moving from east to north to west. A herd of more than 1,000 reindeer, along with other animals, was destroyed."
    The Russian newspaper Sibir published a story about the phenomenon on July 12, 1908: "In the Karelinski village, the fire body rolling on the sky appeared as a big pipe or a big cylinder. All villagers were stricken with panic and took to the streets. Women cried, thinking it was the end of the world."
    Five hypotheses concerning the explosion have been formulated, and four have been amply discussed, but none are convincing to the scientific community. the first one is that a four- to six-mile-wide meteorite exploded above the earth. The second one, stated by American astronomer Fred Whipple in 1930, suggested that it was a small comet, since bright nights were observed across Europe for several nights after the explosion.
    Albert Jackson and Michael Ryan, physicists at the University of Texas, theorized in 1973 that a small black hole passing through the earth's atmosphere caused the explosion. A black hole is a mass so dense that not even light can escape its gravity. In addition, Jackson and Ryan said, a large black hole could have absorbed the earth like an enormous space vacuum.
    Another hypothesis is that a chunk of antimatter falling through space was responsible for the explosion.
    The least credible explanation claimed that the explosion was the result of an exploding spaceship or even an alien weapon going off to save the earth from an imminent threat. Of course, this last claim is more a science-fiction story than a scientific theory.
    The great explosion has inspired books such as "The Fire Came By" by Thomas Atkins and John Baxter in 1976, and the 1998 television series "The Secret KGB UFO Files." What is not fiction is that scientists now believe the earth could be struck by a meteorite, an asteroid or even a comet. What they don't know is when.
    Before 1994, that was considered only a remote possibility with little basis in scientific fact. But that year, a comet hit Jupiter and wrapped it in fire — a stunning event that made the scientific community change its opinion and reflect on our planet's fate.
    Perhaps the most plausible theory of the Tunguska explosion — or "the big fireball," as my father called it — is that our planet was on the brink of the end 100 years ago.