Yes, but here is my point: those rocks did not come from outside our solar system. They came from within our solar system.
Our being hit by "debris" from outside our solar system isn't a realistic risk. The materials of interstellar space are so diffuse, and our planet is so small compared to the space involved, that the statistics show a collision, even on geologic timescales is just not going to happen. This is why I say you might not understand the scales involved. Space is so incredibly huge, and there's so little matter in it, that this just isn't a concern.
Now, if you want to say that our sun will be passing through a region in which there are more stars, and one of those passing nearby and might give a gravitational nudge to things in our own Oort cloud and that's a risk, you might have something.
Except that the nearby stars are well charted, and their velocities relative to us are known. None of them are on a path that's going to be an issue in the next few tens of thousands of years, as I understand it.
Yes. And all those rocks are within our solar system. None are "extrasolar".
I will say once more, just to be 100% clear. Getting hit by something is a notable risk. Getting hit by an object from outside our solar system is not a notable risk. You've got the right general idea, but you're attributing a danger from the wrong place.
I'm sorry if I seem to be harping on this. I'm a physicist by training, and when I see policy-influencing misinformation, I feel a bit obliged to correct it.
Yes, but objects moving at relativistic speed are few and far between. More rare than even non-relativistic objects. While it makes good theater, it is not a realistic risk.
If you want death from outside our solar system, worry about gamma ray bursts.
Hey, I'm not going to dispute your expertise. My training is in stats, business, and psychology.....not physics. I'm no expert.
The articles I'd read about our solar system's position, and objects from outside our solar system being a possible threat wasn't really talking about calculating risk for anybody in the near future. I think they were more hitting on theoretical risks down the road. Of course, what things will be like in 90,000 years, or 900,000 years is beyond anyone's ability to predict, when the weathermen can't even get the weather right two days in the future
A really basic statement is that pretty much any prediction, and most prognosticators are right 50% of the time. And wrong 50% of the time.
I'm not sure if astronomers or physicists are able to reliably determine where something that his us 65 million or 200 million years ago came from. Can they know *for sure* that a particular rock, that long ago, didn't come from outside the solar system? I frankly don't know.
Regardless, I think we're in general agreement that knowing where these rocks are, and if they're on collision courses is pretty important. They don't have to be outside our solar system to be a threat. There are enough of them within our solar system, on various orbits. Now, maybe I'm wrong, but I would think that the civilization ending rocks over 1 mile in size are the "big daddies" of space rocks, and likely the lowest quantity. Then, the ones that are between 140 and 1000m in size are much more common. And then rocks smaller than 140 meters are even more common than that. Does that statement agree with your training?
When they identify these rocks, particularly the large ones, which I think they've identified most of, have they been able to definitely determine that none of them are on courses likely to intersect with us? Or simply that they're not likely to intercept us in the next 500 years, but in 1200 years, or 11000 years, they might come really close?
I think that the fact that the smaller rocks can still inflict enough damage to wipe out a relatively large country is still a problem. Of course, the *probability* of it happening is likely not high. But because the funding isn't there, we just don't know. Could you imagine the chaos if a space object 400m in size hit a city in North America? It's not like it would turn Canada, the U.S. or Mexico into a giant crater. But the blast wave and everything would likely kill everything in a pretty wide radius, throw up a lot of debris to cut off sunlight etc. It's not like it would have to cut off sunlight for years. Even if it did it for several weeks to a month or two, what kind of plant life or crops would survive in the immediate area? If the degree of sunlight reduction is similar to that caused in the vicinity of volcanic eruptions, it would be utter chaos. I saw video of an eruption from several years back, and at noon it was pitch black. There was no visibility. My city got hit by the ice storm back in 98, and there was chaos at times. People breaking into places, generators being stolen. Driving down the streets at night was eerie...no power for days, or weeks in some areas, complete blackness. And that was just at night. Imagine that lasting 24/7?
In any case, Earth itself has far more ocean than land, so even if the planet did get hit again, it's far more likely to hit an ocean somewhere rather than a city. Again, just talking statistically.
In any case, we're talking very small chances. I mean it doesn't mean we should ignore the threat....but we shouldn't we wandering around ducking either, because it's unlikely to happen in any of our lifetimes.
Because of how big the universe is, and the sheer enormity of the technological and financial requirements posted by the idea of colonizing another planet, even in our own solar system, I think we're talking about relatively slow, long-term developments. If we do decide to go ahead with colonization (of Mars for example), even if we know it's theoretically possible, we may not be able to practically do it for hundreds of years. I want to draw a line in the sand to establish what I'm thinking of when I saw colonization. I'm not talking about sending a craft to Mars and planting a flag there. I'm talking about an actual, livable environment....not just a remote science station where a select few scientists are sent to do research. I'm meaning a living, semi-permanent community where people are living, working, and even having babies etc. Maybe not entirely self-sustaining....but growing. Is it likely such an environment could exist in a bunch of bubbles? Longterm? You'd need to have scientists, engineers, doctors.....and all the support people that help them do their jobs...nothing we've done as a species so far compares, with respect to putting people into such a hostile environment, longterm...in relatively large numbers.
So I figure it'll take awhile. And if it takes awhile, then the numbers and risks associated with having all of our population on one planet start to look a little more risky. I'm not saying it's a problem in 2010. But what about 2817? Or 3689, or 7982 AD? Or even further out? I use those years, because the mind can still kind of conceive of that span of time. Of course, given how much human civilization has changed between 1500 BC and 2010 AD, it's hard to imagine where we'll be at in 7982 AD. Or 21,385 AD. Or 91,998 AD. It boggles the mind. And cosmically speaking those are mere seconds......though I'm sure if humanity is still around at that point, our descendants would be pretty much unrecognizable to us at that point....maybe not from a physical evolution standpoint. But from a civilization standpoint.
Of course, the range of our scientific knowledge is constantly expanding, and we tend to find new ways to both push the boundaries of what we know, and find solutions to things that we once thought were hard and fast limitations. Maybe researchers 900 years from now will look back at Eistein's theories as advanced for the time, but quaint by the science we have 900 years from now. Maybe at that point, we'll have technology that can get us to another start in days or weeks. Who knows? I think it would be fascinating to *know* and experience those kinds of things, to stand on the shore of a planet orbiting another star......but I don't know if it'll happen. I'd like to know about if there's life out there. Given the size of the universe, it would seem kind of a waste if we were the only planet with life. Statistically, it's unlikely. But in any case, we're so immersed in our own worldview, with knowledge of how life works here that life on another planet could be completely unrecognizable to us.
Anyways, a really good book I read last year was "Risk: The Science and Politics of Fear" by Dan Gardner. It talks about a few of these things (meteor strikes etc.), and, in line with your comment about policy-based misinformation, I think you'd find lots of interesting tidbits. By no means does the author advocate the end of the world. Most of the book, he talks about how people spend so much time worrying about things that have statistically insignificant chances of occurring, because of how bad they are, and then blithely carry on behaviour that *is* statistically likely to cause them significant harm. And how governments and corporations play on those fears. But the idea of the book isn't to blame governments or corporations for playing on fears either. The author points out the simple fact that governments and corporations are themselves made of people, who are human as are all of us. They hear about things that could have major negative effects, and worry about them as well. And as a consequence, they try to implement policies or sell products to mediate those fears. A big point he makes is how often bad policy decisions are made as a result of a misunderstanding of the true likelihood of something being a problem. Anyways, I found it a very interesting read.
Banshee
