[ExI] (NASA.gov) NASA to chronicle close Earth flyby of asteroid (fwd)

Anders Sandberg anders at aleph.se
Sat Feb 16 16:26:54 UTC 2013

On 16/02/2013 15:59, Tomasz Rola wrote:
> I read about incoming NEOs in a kind of systematic manner, out of 
> curiosity, and it's not unusual to have predictions about 25m objects 
> coming in a month or so. The 2012DA14 is said to have 65m and I knew 
> about it since few months (and it had been first observed year ago). 
> So I guess it is not unthinkable to have a warning about 15m impactor 
> coming in a week. 

Yes, it is not uncommon for the astronomy community to find really small 
NEOs and figure out their orbits. 2004 FU162 is just six meters, 2010 
AL30 and 2011 MD are about ten meters. But most are found during their 
close pass, not far ahead of time - the small ones we know weeks ahead 
are coming are typically those who did a past pass. So we will no doubt 
get plenty of warnings about known rocks, but that doesn't preclude 
getting even more suprise appearances. Actually scanning for all 25 m 
objects would be a tough undertaking, requiring some seriously good 

> I mean, it is cool to say something like "bah, a kilometer-wide 
> impactor we could bother about but mere 20m is peanuts to us, it's 
> only umpteen statistical deaths per year". But I think limits should 
> be pushed a little further.
Cost effectiveness matters. One billion spent on traffic safety will 
save far more lives than one billion spent on anti-terrorism measures, 
yet save far fewer lives than if it were used for anti-parasite 
therapies in sub-Saharan Africa. Pushing one of the less effective uses 
requires at least an argument for why it is morally imperative to do it, 
even if it is not better at saving lives.

On 16/02/2013 14:08, The Avantguardian wrote:
> What do you estimate the probability of such a meteor strike on the 
> same day as a close flyby by an "unrelated" NEO is Anders?

Impactors like the Russian one happens about once a century or so, so 
the daily probability is 1 in 36524. Smaller ones like the Sudanese 
happens about yearly, so there the daily probability is 1 in 365 or so.

The probability of a predicted NEO close encounter can be guessed from 
http://neo.jpl.nasa.gov/ca/ - I see 80 encounters over the next 79 days, 
so one encounter per day seems plausible (and in the future this will of 
course go up). So the chance of yesterday was 1 in 36524 - unusual, but 
there are plenty of different ways coincidences can come about.

Anders Sandberg,
Future of Humanity Institute
Philosophy Faculty of Oxford University

More information about the extropy-chat mailing list