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. Sky and Telescope , June, Description of a modern journey to the site, with photographs. Krinov, E. Description of the site and interviews with witnesses. All Rights Reserved.
Skip to main content. Login Register. You are here Home. What do we know about the explosion? Hartmann Witnesses in the town of Kirensk and nearby towns at the same distance recollected the fireball flashing across the sky in the following terms: "A ball of fire Hartmann The Russians collected a number of accounts from eyewitnesses at the trading station, which was probably the closest permanent habitation. These included: "I was sitting on the porch of the house at the trading station, looking north.
Hartmann Because the object exploded up in the atmosphere, instead of hitting the ground, it left no crater. They related: "Early in the morning when everyone was asleep in the tent, it was blown up in the air along with its occupants. Hartmann Some minutes after the explosion, distant observers reported a column of smoke on the horizon.
What was the explosion? If asteroids hit Earth, why don't we see more such explosions? Question 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. Answer: Let's make use of what scientists call an "order of magnitude" estimate, or "back of the envelope calculation. Answer: Here again we can make a simple "order of magnitude" calculation.
For further information: Chyba, C. A man is sitting on the front porch of a trading post at Vanavara in Siberia. Little does he know, in a few moments, he will be hurled from his chair and the heat will be so intense he will feel as though his shirt is on fire. Today, June 30, , is the th anniversary of that ferocious impact near the Podkamennaya Tunguska River in remote Siberia--and after years, scientists are still talking about it. Above: Trees felled by the Tunguska explosion.
Credit: the Leonid Kulik Expedition. While the impact occurred in '08, the first scientific expedition to the area would have to wait for 19 years. In , Leonid Kulik, the chief curator for the meteorite collection of the St. Petersburg museum led an expedition to Tunguska. But the harsh conditions of the Siberian outback thwarted his team's attempt to reach the area of the blast.
In , a new expedition, again lead by Kulik, reached its goal. While testimonials may have at first been difficult to obtain, there was plenty of evidence lying around. Eight hundred square miles of remote forest had been ripped asunder. So icy meteorites do not last long. Indeed, Khrennikov and colleagues calculate that an icy body large enough to cause such a large explosion would have traveled no more than miles kilometers through the atmosphere before vaporizing completely.
That suggests the Tunguska meteorite could not have been made of ice. Instead, Khrennikov and colleagues say a different scenario fits the facts. They say the explosion must have been caused by an iron meteorite about the size of a football stadium.
This must have passed through the upper atmosphere, heated rapidly, and then passed out into the Solar System again. The shock wave from this trajectory was what flattened trees. The shock wave would have caused an explosion of about the right magnitude, and any vaporized iron would have condensed into dust that would be indistinguishable on the ground.
Crucially, this scenario would not have left any visible asteroid remnants. If Khrennikov and colleagues are correct, then Earth had a lucky near-miss that morning. A direct impact with a foot-wide meter-wide asteroid would have devastated Siberia, leaving a crater 2 miles 3 kilometers wide.
It would also have had catastrophic effects on the biosphere, perhaps ending modern civilization. In the event, the Tunguska impact is thought to have killed perhaps three people because the region is so remote. It could clearly have been much worse. Ref: Krennikov et al. Receive news, sky-event information, observing tips, and more from Astronomy's weekly email newsletter.
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