I don’t want to sort through the whole article. Quote the bit you mean.
If we couldn’t veer an asteroid off course, would it be slightly better to break it up? I know the mass would remain, but might it be preferable to be hit by many smaller rocks than one huge one?
Shoemaker-Levy-9 says not really, if the original asteroid is big enough: Jupiter got many hits instead of one, but every one of them would have done our planet.
If all asteroids are cows, we all get BSE or a new mutation of it. This is called pan-un-spermia.
So how much notice are we talking here? If it’s 15 km wide, do we see it coming for years? At what point does it become visible to the naked eye?
We do have the detection/prediction technology, right now. The problem isn’t developing new technology; it’s just deploying it on a large enough scale that it wouldn’t be a crapshoot to find something. It would be fairly cheap, even with current tech, to deploy a system that could find every extinction-sized potential impactor a century in advance. And if we find one, well, then we have a century’s advance warning to develop and deploy whatever deflection scheme we’re going for, which should be plenty of time.
But humans suck at understanding probability and expected value, so good luck getting the political will for even that modest expenditure.
As I said before, it could be any amount. We have telescopes that will see that centuries in advance, if they’re pointed at it. But for a rocky (as opposed to icy) object, the naked-eye visibility would come maybe a couple of minutes before impact.
It’s literally the second sentence, which the poster paraphrased. Correctly.
Our best hope that said doomsday asteroid or comet is detected years in advance; if it’s spotted weeks or a few months away from impact, there would be potentially widespread pandemonium.
When I was a kid it had rained a lot one year, maybe late spring, early summer. I was walking around the neighborhood and noticed a mud puddle that had lasted long enough for a frog to lay eggs in it and newly hatched tadpoles were swimming around. But things were rapidly drying up, and I felt bad to realize that these tadpoles swimming around blissfully unaware were not going to make it to adult frog hood because their puddle home was going to dry up soon.
When I got a little older it hit me— the entire human race are just tadpoles in a mud puddle.
SDI has one, not had decades of development. It pretty much withered after a few years. Why? Because two, the issue of sending a laser through atmosphere to hit a target has a fundamental scatter problem.
Currently the world’s most powerful laser is capable of output at 10 pentawatts. There seems to be no fundamental issue blocking this line of development. (If it can stay focused over distance.)
Yes the problem would likely be political issues, both in terms of even modest expenditures, and in terms of mutual trust that such a device in space would not be used as a weapon against each other.
The examples cited - sea turtles and crocodiles - start off as tiny hatchlings and grow to be huge; so survival of species that can grow larger does not imply specimens of the adults did. Articles I recall suggest nothing over about 5 lb (so, the “cat size” estimate) survived.
An impact by a meteor 10km diameter, able to leave a 112-mi crater, is somewhat destructive. If you scroll down to the “Effects of Impact” in the Wiki article, there are suggestions that global firestorms resulted; I assume massive earthquakes and huge tidal waves would be concurrent catastrophes, plus flash-frying much of exposed life. The article mentions the follow-on - acidification of the oceans and a global winter for several years due to aerosols, followed by a round of greenhouse-gas induced global warming. What the impact did not get, presumably climate and lack of food would help devastate.
For comparison - the notable meteor that hit Siberia maybe 10 years ago, captured on multiple video cameras, was estimated to be about 50 feet diameter; possibly ice since it did not appear to have reached the earth. Regardless, it lit up the sky and shattered windows and shook things for dozens of miles around. Most interesting was - we had no clue it was coming. You have to wonder what would happen with a rock that size? (And what is it about Siberia that makes it the favourite target of ET’s throwing rocks?)
I recall a Scientific American article discussing the odds of meteor impacts suggesting they were more common than we think; claimed a possible moderately large impact in the Amazon basin in the 1930’s was overlooked and not well documented since it was not accessible, and the world became too busy with WWII. There’s the event in the ocean off South Africa, which at the time (1970’s?) was suspected to be SA and Israel testing a nuclear weapon, which both have denied.
Another factor overlooked - getting to the threat. It takes a year to get to Mars, using an orbital transfer. Yet comets come and go in a year or less. Some killer coming in from the Oort cloud or such will give little time, even if we see it far out. Then we have to build the rockets (or assemble pieces). To make it to the threat in decent time, we need much bigger rockets than we use to send things to Mars, to get the velocity to intercept far enough out that a minor course change will matter. Then we have to be sure that our actions deflect in the right direction, with the associated risk that using something like nuclear impulse may shatter the threat instead. (Gravity is not too strong for a mass only 1km diameter) A 1km-diameter asteroid can make a lot of 5-storey fragments, and do we have enough additional rockets to then deflect a hundred or more of them?
Sorry, I have trouble imagining a laser having the impulse to deflect any significant sized rock. Plus, consider scale. Mars is 40 million miles away at its closest. let’s say we try deflecting the rock from that distance. We need a beam that will not spread significantly over 40,000,000 miles to hit a rock a fraction of a mile diameter (we hope, no more that that big). I’m not up on recent killer laser tech, but a divergence of less than 1 in 40M seems overly optimistic. Plus, how long can we hit the target with an earth-based laser? Once the target gets close to the horizon, atmosphere effects are going to be even worse. So we’d have to move the thing to orbit. As I recall, a key issue with anything in space is cooling - you have a device that generates massive amounts of heat - lasers are only a few percent efficient - and no nearby oceans or evaporation towers to cool it off, it’s all up to thermal radiation…
I think 50 years for the tech to defend ourselves is optimistic - unless we have 50 years warning.
Realistically, you’d need a bunker moderately earthquake proof, with several years’ supply of food and a subsistence farmer starter kit. be located well above sea level, on a stable tectonic plate, and hope the impact zone is far enough away. if we’re talking another CT killer, you’re probably screwed anyway. If it’s something less severe, then the biggest problem will be surviving the environmental effects and having the food and tools to start again. If it was localized, say took out anyone living in Europe but only produced a few horrific disasters on the rest of the world, the question would be whether we would miss them, and what the resulting impact would do to the rest. As we seem to see with recent problems in Texas and New Orleans, a major problem is not that something would kill life, but that many would survive without an external help to come and feed the survivors and repair the damage. Like those apocalyptic post-nuclear stories that were popular in the 1970’s, they dealt with what happens when a society loses external support structures and has to survive. Mostly, few can. What sort of homicidal social chaos will follow complete loss of the food supply chain? The modern mechanized farms can’t survive without the industrial society they rely on, and the industrial society can’t survive without mechanized agriculture. Then there’s a whole series of discussions on the loss of global communications, or modern financial institutions that rely on that.
i disagree with the starter population issue. The best example to point to is Easter Island. Presumption is a single canoe expedition, maybe one or two of the very large Polynesian canoes, maybe around 100 people - was sufficient to create a civilization with up to 15,000 inhabitants, whose collapse was driven by (likely) environmental problems, not genetics. Plus, they would have been at the far end of an expanding population so limited genetic diversity to begin with.
I’m not seeing how this responds to the post.
GIVEN an asteroid of a certain size say just large enough top likely be a civilization ending event if it hits the earth, blowing it up would create a wider spread of smaller objects, some fraction of which would have different trajectories that would miss the earth. Total mass hitting the earth would be less but I think the question even assumes that ALL the fragments would still hit, same total mass … then the question is if a hailstorm of smaller objects totalling mass X causes same, more, or less harm than a single object of mass X.
One aspect is that given each object loses some of its mass as it travels through the atmosphere to some degree correlated with surface area, the greater surface area of the hailstorm means less mass making land/ocean fall. For those with ocean fall more energy would be expended before hitting bottom. The damage would be at more surface layers but more broadly … would that increase of decrease the amount of climate changing water, dust, soot, and gasses released in aggregate?
Is there a GQ answer to that?
I suspect that the first object that we identify as a potential impactor would probably be quite a bit smaller than the Chixulub meteor. So we might have a chance to divert it, given capabilities a few decades or centuries in advance of today’s.
One disturbing possibility is that we might try to divert a potential impactor and fail to do so, but instead give it enough delta vee to change its impact point significantly. We might move the impact point towards a different city, nation or territory, and thereby become responsible for any damage caused. Splitting up a single impactor might result in a spread of impacts that causes more damage than a single hit. It might be better to leave well alone.
That was the initial question I was asking, is there a fundamental limit to creating a laser that can stay focused over great distances assuming space located with true vacuum between laser and target? I understand crudely that the larger the aperture the more focused it stays? Is there a limit?
I’m going to make the WAG (wild-assed guess) that turning half the planet into a superheated atmosphere with associated firestorms from a shotgun of impacts is probably not healthy for the other half of the planet either. But a multitude of fragments probably avoids the issue from the CT killer, that ejecta from the initial impact went suborbital and came down all over the globe, even well over the horizon.
Should also add that the Wiki article mentions that sulphur compounds and other crustal debris had chemical effects on the environment (acidification and aerosols creating global winter, for example) that a large number of smaller impacts might not.
The real question would be - is it worthwhile? How much specific impulse could a system like that impart? Current tech for downing missiles simply hopes to inflict severe mechanical failure on the missile, not to completely vaporize and certainly not to just drive it off course. It would have to be a powerful laser to boil off enough of the target to create a jet effect of the material boiling off. Plus, is the target spinning? I presume launching a bunch or a flock of impulse engines (rockets or ion engines) to attempt to push the target off course is more productive, especially if you could simply continuously resupply them with more fuel given enough time.
I cannot do the math myself but again the source cited said that 10 kW lasers could be worthwhile to alter the course of a 100 meter wide asteroid if identified 30 years before impact. We apparently are needing over 6 orders of magnitude more power than that, space based. The current 10 PW laser is 13 orders of magnitude larger. You’d need such space-based (with enough power and cooling), able to maintain focus on its target, and at the smallest possible beam divergence. A reach but not beyond imagining.
Another key issue in space is actio = reactio. If the laser is powerful enough to move an asteroid with a mass of trillions of kilogramms, where and how fast will the laser move?
It doesn’t matter what size animal survived right after the impact. The size of any animal 1 year out, 10 years out, 100 years out matters a lot. We can’t tell if a crocodilian slightly bigger than a housecat managed to survive the initial period but even larger ones may have survived as eggs. Who knows what dinosaurs of what size were still wandering around some remote part of the world trying to survive for how long, they were all gone before long save for the ones that became modern birds.
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ICBMs are kept on standby because of the perceived deterrence value. (Whether they actually provide the level of assumed deterrence isa debate for another thread; I’m just establishing this in terms of the conventional justification.) In order to prevent a large potential impactor we would need to have many months of lead time, both to get the redirect system into position to intercept the object and because of the limited amount of impulse that could conceivably be applied to it means that we’d need to make a trajectory alteration as far out as possible. Now, obviously having a system capable of launching and deploying an asteroid redirect system would be prudent, but it isn’t as if you’d need to launch it at a moment’s notice; in fact, you’d probably want to run extensive and peer-reviewed studies on the best way to apply impulse to redirect it to prevent future hazards and contingencies for breakup scenarios.
No, absolutely not, although most large asteroids are a consolidation of smaller bodies and preventing them from breaking up is a significant challenge. Although breaking it up into smaller pieces means that more or all of it will “burn up” (vaporize) in the atmosphere, that atmosphere is still a crucial part of our planet and delivering that much energy will still do tremendous damage even if no solid parts of it reach the surface. Furthermore, breaking it up means dozens or hundreds of individual pieces that would then have to be tracked and moved separately rather than redirecting one large mass, and if in a periodic orbit could repeatedly intercept the Earth. The only reason I could see for wanting to do this is if the singular object is too large to shift, but that doesn’t fundamentally change the total impulse requirements, so it remains a problem noentheless.
Here is a concept I have promoted for using nuclear weapons to generate a mediated impulse to redirect a hazardous object without breaking it up. This is obviously not trivial, and the potential for weaponizing this, particularly if it were kept on some kind of standby status, is evident, but it would make sense to develop this capability or something like it as a hedge against a future threat.
Although the SDI program only lasted for a few years, the research and development of very high throughput lasers has gone on for decades without producing something capable of actually destroying an ICBM from hundreds of miles away. And while there is the thermal blooming problem of firing through an atmosphere, inherent divergence and other issues with laser throughput are actually the more problematic issues with making such a system workable.
The laser system cited in the press release you linked to is the centerpiece of a large research facility which is developed for doing nuclear physics research. It is a pulsed laser in no way a system that could ever be developed for shooting large rocks in space for extended periods of time, with pulse durations measured in the hundreds of femtoseconds. Although we may some day be capable of building very high power throughput lasers capable of continuous operation sufficient to disintegrate or provide impulse to very large objects millions of miles away in space as portrayed in science fiction and specious asteroid redirect proposals, that is very far away from current capabilities in directed energy science. I believe @CalMeacham actually works in this field and can provide specific expertise to this proposal but I think he’ll agree that it is not feasible within the foreseeable future, and the fundamental energy requirements to do so would be prohibitive in any case.
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