Oh, it's certainly inevitable, but it's still very improbable in our lifetime. I'm quite impressed at how close that got, though.
How long do they think we have until this eventually happens?
Species killers are thought to be pretty rare, like million year timescales, but I don't know about the smaller ones.
What do you mean the smaller ones?
Smaller asteroids. They hit us more frequently than large ones. The one that killed the dinosaurs was thought to be about 10 miles in diameter. If one that was sized one mile or less struck the earth, I doubt that it would kill all of us.
Oh those smaller ones. Bit off topic but related: how big are the meteroites that cause those phenomenal meteror showers?
Technically, they are not meteorites unless they hit the ground, and it takes a fair sized chunk to do that. Most of what you see in meteor showers are no bigger than a grain of sand.
Near Miss could be bad for us
Like ST and others, I think it very unlikely that Earth will be hit by a asteroid large enough (actually it velocity at impact is more important as energy delivered is quadratic in this variable) to abolish human life. I have not tried to do the numbers, but suspect that if a major asteroid, especially one in the ecliptic and orbiting in same sense as Earth about the sun - longer gravitational impulse) were to change Earth's orbit, it could do mankind in with greater probability.
It would not kill us directly of course. If the Earth were given an orbit as eccentric as Mars has, I think Earth would be plunged into an ice age. (This BTW is central concept of my book Dark Visitor which has sub title "The coming ice age" - An undetected black body (black hole?) of mass 2.2 solar misses Earth by 12 times the distance to the sun - much larger cross section than an "Earth hit.")
Milder, moist winters with lots of heavy "spring snows" all winter long, that do not entirely melt the following summer can send one hemisphere quickly (a few years) into an ice age. The other Hemisphere is in summer, and its evaporating oceans, supply the moisture, but life there is rough also as torrential rains wash away whole cities and little sunlight reaches the ground because of continuous cloud cover (not good for most crops). More at www.DarkVisitor.com including how to read for free.
I just tried simulating that. A 2.2 solar-mass object passing through our solar system in the plane of the planets wreaks havoc on the outer solar system, adds a lot of eccentricity to Mars' orbit, but leave Mercury, Venus, and Earth virtually unchanged.
Depending on starting conditions, the outer planets can be stripped from the solar system, be forced into orbits that cross each other, or be forced into comet-like orbits. Mars can be forced into an Earth-crossing orbit which would ultimately affect Earth.
Trouble is, Bill_T, we have no information on which to base a prediction on the likelyhood of such an event (besides the zero data point: the fact that its never happened before).
Has anybody noticed that the "near miss" could intersect the orbits of geostationary satellites? Oops. Also in the linked article, there is a statement about the possibility that the near miss could put the asteroid into a resonance with Earth that could increase the chances of a future collision. It may be a good idea to plan a mission to give that rock a rocket ride into the sun.
At the very least, before it is done, the human race can expect to lose dozens of cities containing millions of people to 'natural space events'. Also, meteor events rarely arrive as a 'singlet' event, but rather as a 'storm' or 'shower', an entire planetary bombardment of hundreds to thousands of impacts containing several megatons of energy in each.
- planetary scientist Clark R. Chapman of the Southwest Research Institute
"The good news is that comets represent 1 percent of the danger," said Donald K. Yeomans, who manages NASA's Near-Earth Object Program at the Jet Propulsion Laboratory. "The bad news is that should we find one, there's not a lot we can do about it. . . . We detect them only nine months from impact."
This is basicly the ground line, if an extinction level asteroid were detected, all the human race could do, is celebrate its own extinction, like it was...2029.
Detecting an extinction level event nine months prior to impact, only means that there is only plenty of time to get a great seat and popcorn for a spectacular light show that would stop the ticker on the entire human race.
Maybe we need to boost a few empty rockets into space and fuel them up in orbit before stationing them at the Lagrange 4 and 5 points, just to have them ready for that 9-month warning. That might not be enough time to get the craft into a usable intercept path, but its a heck of a lot better than we have now.
For several reasons, I made the "dark visitor" approach from the north polar region, on trajectory nearly perpendicular to the ecliptic. One reason being that an approach nearly perpendicular to the ecliptic tends to produce little relative motion between the planets longer (while dark visitor is still far away) and thus is less disturbing and harder to detect longer.
I did not do your "in ecliptic" pass, but think you are surely correct.
I tend to agree, but suggest in book and more strongly at www.DarkVisitor.com that the perturbation of Neptune that lead to Pluto's discovery definitely was not caused by Pluto, as originally believed. (Pluto is smaller than the moon, and must have several Earth masses to have been responsible for the perturbation.) It could have been caused by a massive unobserved object (a "dark visitor") passing outside of the solar system. I am not claiming that it was, only that this could have been the cause of both the perturbation and Pluto's tilted orbit plane.
How can you say: "fact that its never happened before"?
I at least have some bases for suggesting that it may have happened in the 1920s. I also argue that if a stellar core black hole did cause the perturbation, then it is quite possible that it was one of a pair. - Most stars do form in pairs.
Furthermore, most of first few generations of stars (which formed and died before our sun was even born, back when the universe was much smaller) were much larger and both members of the pair quickly (in comparison with the sun's life time) died and left gravitionally bound black holes behind. Because there were several generations of these black-hole pairs forming stars, it is at least arguable that there may be more black-hole pairs than all the currently luminous stars. (See next paragraph for addition increase in their numbers.)
My postulated 2.2 solar mass dark visitor, is on more weak generally accepted grounds because it is so small. I think that the final collapse of an iron-core star that forms a black hole is far from the nice symmetric event treated by mathematicians. I think it is the source of much smaller iron masses that do not be become black holes. Even those which we call "iron meteorites when they hit Earth. If this is even partially correct, then a star of 20 to 50 solar masses might be able to also produce several small black holes, some of which escape from each other (in the "hypernova" implosion)and some of which decay into one by gravity radiation, but most are probably still gravitationally bound together at this stage of the universe.
It is all very complex, but I don't think it is necessarily false in any aspect as a possibility. Since I can at least point to the possibly that one passed less than 100 years ago, (Neptune's unexplained perturbation), I think your support for your statement that "it never has happened" is weaker than mine that only suggests that it cold have and we don't know how probable it is.
I am pretty sure that the number of expected Tunguska sized events [per unit time] has been upped in recent years. I know that at least one noted astronomer has made this statement in the sci/tech media.
One big concern here is, or at least some years ago was, that a meteor or comet strike could trigger an accidental nuclear war.
Yeah, that would really suck. I don't know enough about the topic to say anymore, but fortunately, at the moment, there's only a small fraction of the earth on which that would be a problem.
It happened in the 20s? AFAIK, the earth (or any other planet) didn't get flung out of its orbit in the 20s, like you're "predicting"...
Sorry, but your burden of proof is far more stringent than just the fact that we don't know what is perturbing Neptune's orbit. You're pulling things out of the air that you have no reasonable basis for. Besides that, you're wrong about your understanding of some things: like what's going on with Neptune's orbit. It wasn't changed in 1920 in any meaningful way - its just irregular (and as far as we know, always has been). For starters, it was known to not exactly fit predictions as early as 1905 and the irregularities continue today. And the irregularities are very small. They do not support the hypothesis that an object flew by and perturbed it in a single, isolated event.
Of course, a hit of that size [Tunguska] anywhere else would probably generate a 500 foot tele-tsunami. :yuck:
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