Asteroid

[PaulB]

Is it true that an asteroid almost hit the Earth a few years ago (just missed by a million km) and wasn't discovered until a couple of hours before it passed?

[sft42]

Oh yes indeedy and not just once several times...have a click here

http://www.abc.net.au/science/news/stories/s174370
.htm

and here http://www.cbc.ca/stories/2002/08/18/asteroid02081
8

and here http://news.bbc.co.uk/1/hi/sci/tech/3160352.stm

and lastly http://www.cnn.com/2002/TECH/space/03/19/asteroid.
blindside/

It happens quite regularly according to most website and if you google for "Near miss asteroid" you'll get loads of pages of info.

[PaulB]

Oh dear.... Thanks sft42 will have a look later and worry myself ;o)

[Phantaxus]

There was one that came from the direction of the sun and was not detected untill four hours after it passed. Also current theories say that there is a significant asteroid strike every 30-50 years (by significant they mean that it could wipe out a city).

[Phantaxus]

Just had a look at the CNN report and I think that was the one I was thinking of. So please read four days instead of four hours for my above post.

[PaulB]

Worrying.... isn't it.

[TommyC]

Nah... I'm not worried...!! Interesting that the "current theories" state the expected frequency of every (comparatively few) years, but that in actual fact, the entirety of recorded human history doesn't contain a single known "strike" (with the possible exception of the 1908 Tunguska explosion in Siberia, for which there is no definitve evidence as to cause...!! :o)

[Phantaxus]

TommyC: The Tunguska explosion is just the most well known It is not the only one. There is evidence for at least another two large impacts durring the 20th century. Im sure this was on Horizon or some similar program a few years back. From what I can remember they found evidence of a large impact in a middle eastern desert that was thought to have happened about the mid 1930's and another one in the south american rainforest was thought to have happened in the 1960's and another one in 2002. to quote from http://en.wikipedia.org/wiki/Near-Earth_asteroid "On June 6, 2002 an object with an estimated diameter of 10 meters collided with Earth. The collision occurred over the Mediterranean Sea, at approximately 34�N 21�E. The energy released was estimated (from infrasound measurements) to be 26 kilotons to TNT, comparable to a medium-size nuclear weapon. At that time India and Pakistan were at a heightened state of alert, ready to initiate a nuclear weapon war with each other. If this asteroid impact had hit in this area the results might have been catastrophic."

[Phantaxus]

Found a few maps to look at
http://www.unb.ca/passc/ImpactDatabase/index.html target=_blank>http://www.lpl.arizona.edu/SIC/impact_cratering/Wo
rld_Craters_Web/intromap.html
http://www.unb.ca/passc/ImpactDatabase/index.html