Slashdot Mirror
Tunguska-Sized Asteroids Impacts Not So Common
JoeGee writes "MSNBC.com is reporting that a new study aided by data from U.S. Military satellites is causing scientists to revise the frequency of Tunguska-like impacts downward. Military satellites used to detect rocket launches and/or nuclear flashes are also good at monitoring the frequency of flashes in the atmosphere caused by ten meter to one meter sized objects burning up in our atmosphere. The study has concluded that Earth encounters much less interplanetary debris than was previously thought, and Tunguska-scale events only occur on average of once every millenium."
This information is only as good as the time period we've been collecting it for. Meteor frequency is quite variable, therefore one decade's (or less) observation may not be of much value.
this is a good thing:
"Peiser said the study was valuable in another way because it helped show the U.S. military can detect the difference between a nuclear explosion and a meteor that sets off a flash similar to it -- a capability he said could help governments avoid mistaking a meteor blast for a nuclear weapon.
It would probably be good to have this capability to keep some guy with a key in a silo from pushing the panic button and obliterating us all....
--"The revolution will be simulcast..."--
So if I read the article right, what they're saying is that because only X meteors of a given size hit Earth in a given period, only Y meteors of a much bigger size will hit Earth in a much longer period? How do they know that Y has any relation at all to X?
The correlation between ignorance of statistics and using "correlation is not causation" as an argument is close to 1.
Sure your right about telling the difference between a nuke and a rock. But isn't it kinda obvious when the flash is over the ocean that Bush thinks it's time the those islamic militant dolphins where taught a lesson. Or someone could be blasting open the NorthWest passage with H-bombs so that oil in the North Atlantic could flow free to our Japanese and Soviet comrades?
I can tell you why Tunguska-sized asteroid impacts aren't so common: the fact that Tunguska was probably cause by a comet. Go figure.
We now have confirmed reports from an informed Orange County minister that Ethel is still an active communist.
The ability to distinguish between a terrestrially originated nuclear blast in inner space (requires rocket/launched satellite), and an extraterrestrial meteor encounter has been around for quite a while now. NORAD follows the rocket stuff, but more importantly, the spectral signatures of the two are not nearly the same, and are easily distinguishsable.
http://www.nature.com/nsu/021118/021118-7.html
D*mn this new keyboard. Here is the Nature Abstract on the this subject
Don't you read Spider Robinson? Tunguska wasn't caused by an asteroid, it was caused by Nikola Tesla's death ray device!
If you believe everything you read, you'd better not read. - Japanese proverb
The rate of objects entering the atmosphere in the 10 years observation period is representative of the average rate of the 1000 years period of the conclusion
The rate is constant (no asteroids or comets storms like the Leonids shooting stars storm we just observed)
The sampling (300 meteors) is statistically significant
The extrapolation/interpolation to bigger size meteors is valid.
This is definitely not a sig.
...scientists found out that mass extinction of entire species (say, dinosaurs) may only happen about once in a hundred million years or so.
Come on, if it was any different, there would be records of unexplained explosions all over history books, not to mention that at least some of the holes would still be visible.
The Tunguska explosion devastated an area the size of England in the grimmest and most frostbitten lands of Siberia -- if one occurs every 1000 years, then it could absolutely devastate civilization and make the destruction of 9/11 seem absolutely trivial. If it had hit Europe or an ocean instead of killing a few Siberian eskimos, we would have been set back a century.
Too bad there is no chance we'll ever develop a system to intercept asteroids should we ever have to within our lifetimes.
Proponents of this theory describe how near the very center of the explosion the trees were unburnt. They say that the gas squirted out from the underground deposit under such high pressure, over a number of days, that an ice dome formed around the hole -- just like your can of canned air gets cold. This ice protected the most central trees.
The explosion is said to be right over a natural gas field. The region of Siberia has huge natural gas reserves .