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In Which I Gibber

04/03/09

I have been reading the BBC.

 

Very Big Rock

Very Big Rock

For those of you who, like me, somehow missed this: a piece of rock between twenty and fifty metres across zinged by us on Monday, close enough to ruffle our hair and scare the cat. We found out about it three days before (and when I say ‘we’ I mean Siding Spring Observatory in Australia) which is just about enough time to move to Switzerland and hide, but not much else.

I have already mentioned that I’m not a fan of letting a giant space rock destroy my garden and shower molten tungsten into my stamp collection.

What I had not realised was that a modest rock – say, between twenty and fifty metres across – hitting solidly, would release the same amount of energy as one thousand Hiroshima bombs. Or that the Tunguska Blast was produced by a rock in this range.

 

Tunguska, from Kuliks 1927 Expedition

Tunguska, from Kulik's 1927 Expedition

Holy cow.

I have, despite me preference for not being flattened from space, been a bit scathing about MPs asking questions about Near Earth Objects and their detection in the House of Commons. I feel somewhat sheepish about that now. This is another of those Zero-Infinity Risks (well, all right, technically it’s not, but in human terms it kinda is) where the probability is low but the risk is exceptional. Ask away, ladies and gents, and by all means let’s find ‘em early.

One Comment to “In Which I Gibber”

  • gary gibson said on March 5th, 2009:

    When people talk about low probabilities in terms of collisions with asteroids, they’re talking about ones big enough to wipe out the entire human race, which isn’t an event likely to occur more than once in a very long while, a ‘while’ being once or twice every billion years or so.

    A Tunguska event has a much, much higher probability; maybe once every hundred years or so, I seem to recall. It doesn’t wipe out civilisation, but it could certainly flatten a city. The chances of a city being wiped out, however, are still fairly low, but it’s certainly not impossible: Wikipedia makes the point that, ‘Although the Tunguska event is believed to be the largest impact event on land in Earth’s recent history, impacts of similar size in remote ocean areas would have gone unnoticed before the advent of global satellite monitoring in the 1960s and 1970s.’

    It’s also my understanding that we’re somewhat overdue to get hit by a Tunguska rock, statistically speaking (every century or so, as I said). When scientists talk about setting up a network to spot and destroy asteroids, we’re not talking about something out of Deep Impact; something about the right size to destroy New York or trigger a limited nuclear war is much, much more likely. That we need to worry about.

    Dang, think I should turn this into a post on my blog.

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