It's long been known that people aren't very good at aligning their fears and emotions, and resulting behavior, with statistics. For example, the chance of dying in a car is much greater than in an airplane, but many more fear to fly than to ride. Even people who are numerate are prone to this quirk of human nature (e.g., the great science fiction author and chemistry PhD Isaac Asimov had a severe fear of flying, and always traveled by train). On the other hand, people vastly overestimate their chances of winning the lottery, at least from a rational expected-value perspective.

I've occasionally talked about the dangers of asteroids in this weblog, and in fact featured it in my Fox News column last week. I've seen quite a bit of skepticism on the issue, some of which may be justified, but it often appears to me to be driven as much by the non-rational parts of us as the rational, even when coming from scientists.

When coming from politicians, of course, it's even worse. A couple of weeks ago, an Australian cabinet minister ridiculed people who were concerned about asteroids, and refused to allot the paltry sum of a million dollars in order to look for them in the Southern Hemisphere, one of our current major blind spots. There are many sky surveys being done above the equator, but very few below.

It actually reminds me of the controversy of a couple of decades ago, when Luis Alvarez at Berkely first put forward his theory of dinosaur extinction being caused by an extraterrestrial impact. While it's become fairly well accepted today, many aren't aware, or have forgotten, that there was a tremendous amount of resistance to it when it was first propounded. And that resistance seemed to go beyond rational scientific argument--it seemed almost religious in its fervor.

Viewing this as a college student, who was interested in and familiar with space, I found nothing exceptional about the theory at all, but it was clear to me that much of the scientific community had a deep emotional investment in not believing that our planet could be so dramatically affected by an event beyond our atmosphere.

I'm not sure why exactly, but one might speculate that, to a planetary scientist used to thinking in terms of geological and biological processes forming and reforming the earth and its inhabitants, invoking forces extraterrestrial perhaps had the feel to it of the supernatural--a blow literally from the heavens, and one from a source with which they were (not being astronomers or extraplanetary scientists) unfamiliar and unknowledgable. It may have almost seemed like a creationist theory of evolution.

More practically, to accept such a concept might imply that their chosen field was much broader than their traditional education, and that much of what they had been taught was wrong. It was probably a natural resistance to a major scientific paradigm shift.

Fortunately, unlike actual creationist theories, it was testable, and evidence for it has been found, and now, after a quarter of a century, it's now taught as the prevailing theory.

Anyway, there's an interesting article on this subject in Space.com today, that has some interesting statistics on the subject (though I can't vouch for them). Anyone whose interest has been piqued by my previous comments on the subject will find it at least as interesting as mine.

Basically, the thesis is that we base our fears not on analysis, but on what's familiar. Prior to September 11, few took the terrorist threat seriously--now concern about it is very high and it can command huge numbers of societal resources. Hopefully, it won't take an asteroid strike to get similar motivation to map and deter potential cosmic threats, but judging by human nature, it may.

Excellent!

Excellent!

Interesting article. The following quote jumped out at me;
"For each nearby asteroid that is spotted, several pass entirely unnoticed, some closer to us than the Moon, scientists say. One researcher estimates that each year, 25 asteroids roughly as large as 2002 EM7 whiz by at even closer distances."
This seems speculative to me. Is there any evidence of the asteroids we are missing? Perhaps based on the orbits of distant rocks that might be thought to come close over time (say, with a period of 50-100k years?) I don't want to be dismissive of the problem (although I have been in the past), but this doesn't seem to be supported by the text of the essay. The relative risk calculation seems a bit farfetched to me also. Is there any evidence of people dying as a result of an asteroid or meteor impact? For example, an ancient hominid tribe in a region impacted 50-100k years ago? Just some stuff to think about from a lifelong (well, not that long a life!) skeptic.

The statistics in the space.com article just don't make any sense. If a person's lifetime risk of dying by asteroid are the same as dying by plane crash why is it that we do have *lots* of examples, very sad ones, of people dying by plane crash and yet I can't think of a single incident of someone dying by asteroid in my lifetime? The 1:20,000 risk seems ludicrous. As, frankly, does the 1:20 risk of the destruction of a city or small state.

God knows we need to find and catalogue all of the NEOs and try and figure out what to do if one is coming for us, but this article seems no more realistic than the assessment the general public has on the subject and the psychological arguments seem weak at best. They really need to rethink this one if there is to be any hope of getting the general public behind this.

Myria

Myria--

I can't be sure about this, but my first thought is, should an asteroid hit, so many people would die at once that the odds, er, even out, so to speak.

That's why I said I don't vouch for the statistics. It's pretty hard to get them right in a popular article, because the terminology can get arcane. We don't really know how that calculation is done, or what assumptions go into it.

But while I'm not defending the numbers per se, in comparing plane crashes to asteroid hits, you can't just say "I haven't seen it happen." It's like auto deaths versus aircraft deaths. One case has lots of accidents, with small numbers of people killed, while the other is a small number of accidents, each one of which kills lots of people. The odds could in theory come out the same (though aircraft are actually much safer), but you might go a long time without seeing any in the case of the airplane, whereas auto accidents occur every day.

Similarly, an asteroid hit might occur only once every few decades, but it would kill thousands or millions of people when it did. So right up until the second it happens, you'll think that it's unlikely to happen, or never happens. That's exactly the kind of thinking being described in the article.

As to Paul's question, as I said in my column last week, if Tonguska had been populated, it would have killed many people. For much of the history of mankind, the earth has been too sparsely populated for it to be likely that an errant asteroid would kill large numbers of people. That's no longer the case in the modern world.

Rand,
Although your point about the sparse human population is quite valid, it doesn't invalidate the criticism of the risk assessment. Human beings have been spread across the globe for about 30k years, I think (Jared Diamond's book Guns Germs and Steel has lots of this documentation, but I don't have it at hand). Given that 70% of the world is covered in ocean, a huge tsunami is the most likely visible impact of a distant impact, to an observing primitive man (or woman). Do you know of any attempts to correlate disaster reports from archeaological sites with known impacts? I am really curious if any substantial effort is being made to use these figures to make "post-dictions" about where and when impacts may have occured, and then look for physical evidence. Perhaps this is too much to ask of you, but you did bring it up...:)

Short answer is no, I'm not aware of that. Which is not to say that it doesn't exist.

But consider the possibility that many of the Biblical disasters might have been, literally, disasters (i.e., "bad stars"). For instance, a hit in the ocean, in addition to a tsunami, would presumably throw up a lot of steam into the atmosphere from the energy of the strike. That would later fall out as rain.

Over forty days and nights? Perhaps...

One of the reasons for the initial resistance to the asteroid strike theory was that it seized the popular imagination so quickly. I remember reading Sunday newspaper science features about it very shortly after Prof. Alvarez proposed it. It is indeed an immediately appealing idea.

I'm no scientist, but from what I glean from the popularized science publications, the AST is no longer considered the sole agent of dinosaur extinction. Dinosaurs seem to have been on their way out for some time before, due to those massive lava flows in the India subcontinent, and the breakup of the world's landmass into the present continents, with the attendent climate changes. An asteroid strike might have been the last straw, this argument goes, but it wasn't the only cause.
An interesting book to read is Charles Officer's _The great dinosaur extinction controversy_. He lambastes Alvarez for going to the newspapers so quickly. He also suggests that there's a snob factor at work: In the hierarchy of scientists, the opinion of a physicist like Alvarez carries more weight than that of a load of grubby, rock-hound paleontologists. He also finds fault with the AST's main proof, the shocked quartz crystals in the Chicxulub crater. Who knows, maybe there'll be another twist in the tale someday...

I certainly agree that a major asteroid hit is in a class by itself as far as natural disasters go. A big enough one and it could very well be hasta lasagna, humans. Not desirable, and at least in theory we can do something about it - if nothing else, get our eggs out of one basket. I'm definitely not arguing that we shouldn't be looking into this or spending money on trying to come up with a solution.

However, those numbers still look screwy to me. Yes, one might go a long time without seeing an airplane crash, but you do have some data to go on. All you've got with asteroid hits is a bunch of holes in the ground and those holes would tend to indicate that major asteroid hits are pretty infrequent, to put it mildly. It's not a matter of "every few decades", to the best of my knowledge there has never been anyone killed or a city wiped out in my lifetime and I'm a bit over halfway to having been here four decades. As best I can determine - and I'm sure you're far more knowledgeable on this than I - hits that might take out a city happen every few hundred years at absolute most - and there's an awful lot of land, let alone ocean, for them to hit without effecting anyone. TEOTWAWKI type hits only come every few million years. I just don't see any possible way to get from that to saying that my lifetime risk of going belly-up due to an asteroid is 1:20,000 or that there is a 1:20 risk of a major city or state being taken out every fifty years. If the risk was that high, we should have some hard data to go on. We don't.

There is certainly a risk, it's far from zero, and the magnitude of the consequences should a TEOTWAWKI hit come to pass are so incredibly high that we cannot ignore it, but we also have to be realistic about it too. Granted that statistical risk can be a tricky thing to present in an easy to digest manner, but this article just seems too over the top on too many levels to be of much use.

IMHO and all that...

Myria

- Asteroid catastrophe is possible, but so is a tsunami on the populous E. coast of the U.S., big earthquake in the Midwest, etc. Odds of events of this type are probably small and certainly unclear.

- Asteroid alarmism seems to dovetail with the funding interests of NASA, astronomers, space scientists -- for more orbiting telescopes, space stations, etc. (How better to make the funding case, in the post-Cold War world, than to stir the imagination with notions of enormous waves and worldwide dust clouds?)

- Money spent on asteroid protection, with uncertain benefits, can't be spent on other public-health concerns (diabetes, heart disease, 3rd-world infectious diseases, etc.) where it would certainly save lives.

- So it may make sense to allocate a couple of million bucks of public money to evaluate the asteroid threat. But to argue, as some people do, that a kind of precautionary principle applies, where the possibility -- however small or uncertain -- of catastrophe warrants a hugely expensive program to develop protective measures, is as irresponsible in this area as it is WRT global warming. A couple of modest research grants to competing technical think-tanks (i.e., not to individuals or institutions who would benefit from asteroid-related programs) might go a long way to providing useful estimates of the magnitude of the risk.

There is a difference between asteroids, and the other catastrophes that you mention. Asteroid impacts are preventable, if we choose to expend the resources. We don't have even a basic understanding of the science necessary to predict techtonic events, let alone prevent them.

Isn't it more a matter of accurately comparing costs and benefits than one of science and technology? People could be taxed heavily for choosing to live along the coasts or in potential earthquake zones, or even forbidden to live in such areas. The central question relating to these hypothetical examples, which is also valid WRT asteroid defense, is whether a particular tradeoff is worth making when other uses of the same resources might save more lives. Until there exists a better understanding than "it could happen" of asteroid-impact probability, these tradeoffs will remain incalculable and it will be difficult to defend the spending of public money on asteroid defense vs. other public projects (national defense, safer roads, cancer research, etc.) that have better-known costs and benefits.

This is why I think it makes sense to spend a modest amount of public funds to analyze the risks before we even consider doing anything else. (We might even decide, based on such research, that it would be most cost-effective to wait until technology improves before we design defenses. A similar argument has been made about global warming.) In any event such research should, as I suggested in my initial post, be conducted to the extent possible by researchers and institutions who don't stand to benefit from asteroid-defense programs. In this regard it may also make sense to evaluate other mega-threats of the earthquake and tsunami variety, to get a sense of the relative benefits to be gained from each unit of public spending in a variety of risk areas.

"This is why I think it makes sense to spend a modest amount of public funds to analyze the risks before we even consider doing anything else."

I've never proposed otherwise. The problem is, we aren't even doing that.

I'll shortly (like tonight or tomorrow) be posting some stuff over on Arcturus recycled from some goodies I sent to Brink Lindsey when he incautiously expressed a desire to find out more about this topic. The gist of it is that Tunguska-class (and smaller) events are far more common than dinosaur-killers and could interact most unpleasantly with human civilization and politics.

Terrific discussion here, as always. I think I'm going to have to permalink to this site.

Reading the above comments, I am heartened by the rationality of the respondents and am optimistic about the future of our species. However, it is not just the individual risk that concerns me -- I know that I am much more likely to die in an automobile accident than I am in an asteroid impact -- but it is primarily the species risk that concerns me. I want my kids, great grandkids, and my loveably hairless, six-fingered great * 50000 grandkids to be hurling insults at the universe and wreaking havoc in planetary biologic systems long after I am recycled.

Species survival is SEPERATELY important. It is why any comparison of risk/rewards should rationally include risk reductions against potential man-made species threats, such as biowar, cobalt-salted nukes, weaponized self-replicating machines, and the like (In decreasing order of risk). Planet-wide efforts to improve the odds of survival of our species is worth at least .001% of the global economic product, and should be worth many times what is currently spent in just one country to improve the odss of survival of non-human species.

Dave in Alaska