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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...
I find the number 667 Highly suspicious..
Is number 666 ever issued? A lot of numberiung systems miss this one out, in order to keep the religeously insane from freaking. For instance the UK number plate authority stopped using it a few years ago after complaints from some quarters.
So my real question is: Would this have -actually- been AL00666?
Spooky...
"Oops, I always forget the purpose of competition is to divide people into winners and losers." - Hobbes
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.
"We probably could have had something in place to shoot such a threat down if we had fully funded the Star Wars MDS project, but sadly geopolitics killed that project."
Doubtful. Weapons for bringing down delicate ICBMs -- even if they had surprised everyone and actually worked -- would be useless against a mountain of rock and ice moving at kilometers per second.
It would be like flicking peas at the Exxon Valdez.
To deal with large objects on a collision course we first need a few decades of warning. Given time, a little nudge can make a big difference. For a rock kilometers in diameter, even thermonuclear explosions count as nudges. If we only have a few months of warning; we're well and truly screwed.
Iz
that most people didn't hear about the asteroid until long after the near-miss was over. Seems to bring up the old argument of whether it'd be better to inform the public and try to do something about it or keep it under wraps and possibly die in blissful ignorance...
Using utilitarian calculations, you can actually compute whether or not the expected consequences of informing are preferable to the expected consequences of secrecy. It would go something like:
Inform if EU(i) > EU(s)
where
EU(i) = p(h) * (1 - p(prev)) * U(knowing)
EU(s) = (1 - p(h)) * U(nondisr)
where
EU(i), EU(s) are the expected utility functions of informing and keeping secret, respectively
p(h) is the probability of a hit
p(prev) is the probability that a hit could be prevented if known to the public
U(knowing) is the value people would place on knowing in advance if they were going to be dead tomorrow
U(nondisr) is the value people would place on the avoided distruption of a global panic (the economic + emotional "costs" saved)
Thus, whether to inform depends on:
- How certain are you that the asteroid will hit?
- How big do you think the disruption will be if word of potential impact spreads?
- Is there anything you can do, given that it is going to hit?
I think the first one is really important. It has repeatedly been shown in research that people do not react rationally to probabilistic information. Thus, telling the public that "there is a chance that an asteroid could hit us", even when qualified by a quantification of the probability to the best of our knowledge, could actually lead to a greater mis-assessment of the risk than if nothing were said of it.
This is, of course, not a question of probabilistic and utilitarian calculations. There is a "right to information" aspect to it, as well. A good formulation would be "where is the borderline between 'creating unneccesary panic' and 'respecting people's right to know'". I would say that if the expert is worried to the point of personally taking significant action based on the information, such as buying emergency supplies etc., then he should inform the general public.
Only the older American missiles which used their outer wall as the skin of the fuel tank. It saved on weight and gave them formidable acceleration. The Soviets always used separate tanks and a thick steel skin - largely because they never worked out how to build precision skins. Both of which gave their missiles a massive strength.
Both countries now use solid fuelled boosters which are much tougher.
And as for a grenade - why bother - you can use a wrench.
Best wishes,
Mike.
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.
Depends on what the object's properties are, the local geology, etc. In many cases, most of the energy from an impact will "splash" back upwards, with relatively little lateral damage. An air burst spreads the carnage much more widely.
As an example, many military weapons, including the original 2 atom bombs, detonate shortly before impact.
"Faith: Belief without evidence in what is told by one who speaks without knowledge, of things without parallel." - A.B.
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-
What's heavier a ton of feathers or a ton of lead?
Would depend on how one measures and verifies the mass or weight of the material. Let's make the reasonable assumption that we're weighing both at room conditions (760 torr, 295 K) using a beam balance. The point is that feathers displace a lot more air than lead. This means that when we add enough feathers or lead to measure 1 kg, the mass of feathers is slightly more than that of lead (due to compensating for buoyancy in air etc). This applies even to a beam balance because the masses we use on the other pan are far smaller and denser than feathers.
Hence, "one kg" of feathers (as measured) has a real mass of about 1.01 kg, while "one kg" lead has a real mass of about 1.000091 kg. This difference is about 9.91 grams per kg measured, which adds up to 9.91 kg per metric ton measured.
Hence, "one metric ton" of feathers has 9.91 kg more matter in it than "one metric ton" of lead.
If you really want to answer that question satisfactorily, you must find measure out the masses AND verify the masses in a perfect vacuum.
Time flies like an arrow. Fruit flies like a banana.
I just can't get out of my mind that ludicrous ending where the aging Sen.Jellison dramatically gets up and sends his minions to "give our children the lightning!" Their idea of good government did not appeal much to me either.
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>