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How We Knew AL00667 Would Miss Earth
jefu writes "In January there seems to have been an incident in which it was thought that an object (asteroid) in space might have hit the earth within a couple of days of being spotted. It did miss, though. This story (from NASA/Ames) talks about the discovery of the object and the process that astronomers went through to determine if the asteroid was or was not a threat."
It seems like you are suggesting that this new technological ability to detect NEO's and possible impacts as being similar to the "Boy who cried wolf" fable.
The problem is, as we all know, the wolf finally did arrive one day...
true. Composition matters a lot too. For a given size, a "stony" or primarily rock asteroid will burn quite a bit more than it's "iron", or mostly metal counterpart.
Also, stony asteroids tend to explode if/when they reach the lower atmosphere. Comets, which are primarily ice and stone, are very unlikely (but not impossible - see tunguska) to survive entry.
Any of these are much stronger than an ICBM, of course.
"Faith: Belief without evidence in what is told by one who speaks without knowledge, of things without parallel." - A.B.
Think of it as an early-warning system. Someone who lives his or her life in the fear of getting tainted by a number from a fairy tale should not be let anywhere near positions of power.
The owls are not what they seem
An asteriod 2" in size would be a significant impact if it hit you on the head! However, they can't watch EVERYTHING. They have to draw the line somewhere. 1km seems to be the size needed to possibly wipe out all life on Earth. Yes, 1/2km would do a lot of damage and kill a lot of the population of Earth, but some would still survive the initial impact. I would assume once all the 1km NEOs are charted by 2008 that they would move on to the smaller ones. Also, as shown by this article, they found a 30m and now know its orbit. It's not like they are just throwing out the data for objects smaller than 1km if they happen to find them. Such small objects, however, are not the focus of the search.
Let's just get this straight: according to the article, the initial data were of low precision, they implied a very large uncertainty in the asteroid's trajectory. (In the event, it wasn't even a near-miss -- it was millions of km off, several times the moon's distance.)
The large uncertainty meant that at any one moment before the conceivable (but very unlikely) arrival of the body at or anywhere near the earth, there was a very large area of uncertainty, in which the asteroid's actual point of arrival would be one tiny and uncertain spot, and the possible trajectories leading to earth would be represented by another tiny blob (tiny relative to the whole area of uncertainty), most probably located very far away from the spot containing the real asteroid.
Calculations on real computers often represent an area of uncertainty like this by a nominal position that is very roughly at the centre of the area of uncertainty, accompanied by a measure of the size of the area of uncertainty.
The fact that one can physically read from the printed result and see that nominal position separately from its accompanying measure of uncertainty, because of the way the figures are presented on screen or paper, that does not give the nominal position any reality.
It happened that the nominal position first calculated in the case of AL00667 would have been (if of zero error) a trajectory heading for earth. But it wasn't of zero error, nor even close.
The whole scare looks like an artifact of the way in which uncertain results involving a continuum are presented using discrete digits.
-wb-
I'd like to see a movie based on Lucifer's Hammer. It's more about life after the comet hits than the struggle for bruce willis to blow it up.
The days of the digital watch are numbered.
It seems to me that over the last few years I have heard a LOT of reports of asteroid near-misses - much more so than in the 80's or 90's. Unfortunately, I think it's going to take an asteroid/comet impact, over a population center, before the humans "in power" even begin to "get it."
Recent movies aside, the thought of a HUGE rock (or solid chunk of iron) falling from the sky, is so completely beyond the experience of most humans, as to be practically ludicrous.
"I would sooner believe that two Yankee professors lied, than that stones fell from the sky." - Thomas Jefferson (supposedly)
--==>>BobT>