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For the following two nights the skies of Europe and Asia were unusually bright. The glare in the sky was compared to the atmospheric effects that followed the volcanic eruption at Krakatoa in In , Leonid Kulik, a geologist at the Mineralogical Museum of the Soviet Academy of Sciences, came across an old newspaper clipping about the explosion. He travelled to Kansk hoping to find a giant meteorite that the newspaper said was buried nearby, but on examination it was merely a natural rock that was wrongly attributed to the event.
Over the following years more eyewitness testimony was collected and it was anticipated that a huge crater and meteorite was likely to be found in the area. Kulik obtained funding for a proper expedition in ; he had to use horses and then sledges pulled by reindeer to traverse miles of frozen countryside. Using local guides he found a vast area of trees knocked down and uprooted as if dashed down by a giant hand.
Odd clumps of trees remained standing but they were stripped of bark and foliage. For example, an iron asteroid fragment perhaps m across hit Arizona about 20, years ago, leaving the kilometer-wide "Arizona Meteor Crater," which is open to visitors; and a km asteroid hit Earth 65 million years ago, ending the reign of dinosaurs. Brick-sized interplanetary stones fall from the sky in various locations every year. Several houses and a car have been hit in recent decades.
Tiny dust grains are even more common; they can be seen every night if you watch long enough; they are the bright streaks of light sometimes called "shooting stars. All of them move in elliptical orbits around the sun as prescribed by Kepler. Occasionally their orbits intersect those of planets, leading to a collision. Large enough bodies leave sizable craters on planets or satellites.
This explains why impact craters are present on surfaces of planets and moons throughout the solar system. If we continue to study asteroids and build more telescopes for detecting and tracking them, we will have better information about the frequency of such asteroid impact-explosions, and more chance to have warning about impending impacts.
Tunguska-sized explosions occur on Earth about once per century, and larger explosions the size of the largest H-bombs, occur about once per millennium. Many of these explode in the atmosphere and cause devastation over tens of kilometers, but don't leave long-lasting craters. Using these facts comment on whether meteorite explosions of this scale might plausibly have produced legends of wrathful or capricious celestial gods who could rain fire onto the Earth, as for example in the legend of the destruction of Sodom and Gomorrah by celestial fire.
Take into account that oral traditions, such as the associations of certain star patterns with constellations such as the Great Bear Ursa Major , can apparently be passed down for thousands of years.
Let's make use of what scientists call an "order of magnitude" estimate, or "back of the envelope calculation. Thus it seems plausible that in 12, years of oral tradition and about years of written records in some cultures, there may have been one ore more explosions considerably larger than the Tunguska event.
By the same logic, if Tunguska-scale events happen once per century, there could have been several just in the last several scattered around the populated land areas of the world in the last years. Thus, it seems at least plausible that large explosions of meteoritic objects were among the celestial events together with smaller meteorite impacts, auroras, hurricanes, storms, and floods that gave rise to belief in capricious god-like forces acting from the skies.
Compare the energy released by such an object with that of an atomic bomb sucs as those dropped on Japan in World War II. First, we have to know the energy liberated by an A-bomb. The Hiroshima bomb expended the energy of roughly ten thousand tons of TNT, or 18 "kilotons" in military parlance. One kiloton 1 KT is about 4. The Hiroshima bomb thus represented roughly 8 x 10 13 joules of energy. Now all we have to do is calculate the energy of the meteoroid.
The trick in using any equation like this is to be sure to use the correct units. To get the mass, we have to figure out the mass of a meter wide rock. Rock has a density of about kg per cubic meter, so we need to calculate the volume of the rock and multiply times this density.
Thus we have,. To be safe, let's imagine that half the kinetic energy is lost to noise, slowing, and fragmentation of the meteoroid before it explodes. That still leaves about 2 x 10 15 joules for the Tunguska explosion, compared to about 3 x 10 13 joules for the Hiroshima A-bomb. It was closer in effect to a very large H-bomb. Chyba, C. Thomas, and K. Zahnle Nature , p. Calculation of size of the bolide.
Gallant, Roy A. Boslough, who was not involved in the study, told Live Science in an email that if an object "skimmed through the atmosphere" and didn't blow up, the resulting shock wave would be significantly weaker than an explosion's blast wave. What's more, the pattern of felled trees at the site is radial — emanating from a single point of tremendous energy release, he said. That's something you'd expect to see after an explosion rather than a sonic boom, "even if it had been strong enough to blow trees over.
While the study authors didn't numerically calculate the impact of a shock wave that a "grazing" iron meteor of this size could produce, their estimates still suggest that such a wave would be powerful enough to flatten trees and damage the ground as the Tunguska event did, Pariev said in the email. The findings were published online in the March issue of the journal Monthly Notices of the Royal Astronomical Society. Originally published on Live Science. Mindy Weisberger is a Live Science senior writer covering a general beat that includes climate change, paleontology, weird animal behavior, and space.
Mindy holds an M. Her videos about dinosaurs, astrophysics, biodiversity and evolution appear in museums and science centers worldwide, earning awards such as the CINE Golden Eagle and the Communicator Award of Excellence.
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