Interesting that Cecil reprinted an old column about chances of being hit by a meteor. I just ran across this:
http://www.nytimes.com/2006/11/14/science/14WAVE.html?pagewanted=1&_r=2
This article is a couple of years old, I wonder what the upshot was.
ETA by Rico: Link To Column
There was a fairly hefty meteor strike (or ice comet) in Siberia 90 years ago; a Scientific American article described a series of meteor strikes in the Amazon in the 1930’s - where the incoming body broke up and probably had a line multiple impact sites in a sequence, like the Jupiter strike 5 or 10 years ago. There was apparently one in the south Indian ocean off South Africa recently, and something else interesting happened in the Indian Ocean about 20 years ago when everyone was wondering whether apartheid South Africa and/or Isreal were collaborating on a nuclear test.
So 2 to 4 strikes in 100 years, any of which could have fatal consequences in a built-up area. Maybe our odds aren’t that remote after all.
Also Cecil’s 1976 article implies we have little to no defence against huge meteorite collisions.
How about the state of things today?
We could of course send a group of undisciplined, but ultimately brave and honourable oil-well engineers, to save the earth entirely plausibly.
But failing that, do we have a missile defence system? Do we have any kind of plan for what we’d do, given, say, 2 weeks before a 10-mile wide object struck us?
No. No missile defense system (certainly not the Ground-Based Midcourse Defense System) could do more than a gnat’s sneeze to deflect a “10 mile wide object.” They’re designed to physically intercept an incoming vehicle or warhead bus and do enough damage to make this delicate device useless. Even using a large nuclear warhead you couldn’t create enough impulse transfer to deflect such a large meteor. Fortunately, something that size would be readily visible from quite a distance. The danger is somewhat smaller meteors that have low albedo and aren’t visible until they pass relatively close.
A space probe with a nuclear weapon that produced focused x-rays, which delivered their impulse to a large consumable plastic or metallic plug (to provide effective and moderated momentum transfer without shattering the meteor), used to deflect an incoming threat while several months out is the best bet. However, we don’t have anything like this, and keeping a vehicle capable of breaking Earth’s orbit at ready (i.e. within 30 days launch) is just currently beyond our capability. What would be smartest, if it weren’t illegal, would be to park a few of these systems in a high orbit where they could be deployed easily. However, this would require hardening and qualifying systems to operate in high orbit/interplanetary space longer than anything other than planetary probes have operated. It’s not inconceivable, but it would take money and effort to accomplish. However, this is one threat that few seem to be willing to devote the required capital to support.
Stranger
A buddy of mine is an astronomer working at NASA to study this problem. The challenges are to move something that big, that may or may not be solid (some asteroids are loose conglomerations of rocks, some have the consistency of cotton candy).
There is one idea to use a fairly large-massed vehicle (like building the Chrysler building in space with a propulsion system) and then using that to gravitationally pull the asteroid. Very complicated. Some lines of study could be in using bombs to see how these different composition objects take the blast. Do you make an explosion on the side to deflect away, or in line of path to slow down or speed up slightly? Can you move loose objects with a blast?
Figure out how to install a propulsion system on a solid asteroid then use that solid asteroid to affect the soft one?
Something I was wondering about - I hope the people dealing with tracking these things have took into account that if something was heading in our direction, every hour it takes to get to us, we will be at least another 30,000 miles further along in space.
Do these planetary bodies have homing devices on them?
They track them to see if their projected path intersects the Earth’s projected location in orbit when the object crosses the Earth’s orbit. Part of the tracking goal is to increase the number of sightings of identified objects so then can refine the projected paths to get better projections of what is likely to hit us v.s. what is just going to come close (and if a close passage affects the object’s future path so that it will come closer next time).
What about sending out a rocket with a gigantic net? Even if it only makes the smallest difference in the body’s trajectory before the net fails, it’d probably miss the earth.
So, how do we determine where we are within our own galaxy? Do we actually know for certain, or are we just extrapolating? [DEL]Do we only have to worry about objects within our own galaxy, or could meteors from another, travel across the void between galaxies and threaten us?[/DEL]
It seems to me that if galaxies are travelling at massive speeds, the chances of 2 of them occupying the same bit of universe at the same time, would be so unlikely as to be negligible, so what’s this business about the Milky Way and Andromeda being on a collision course?
Ignore the struck-out bit.
If you can break the incoming object soon enough, then it results in a few hundred smaller meteors spread over hundreds of miles.
The problem isn’t mile-wide asteroids. There really aren’t that many and we’ve noted the orbits of most of them. the problem is stuff a few hundred feet across or so; quite a lot more of them, harder to spot, and still capable of city-vaporizing damage.
The Tunskanga event in Siberia for example, was IIRC attributed to an iceball no more than 100 feet in diameter; yet flattened trees for dozens for miles around from the blast wave without having enough oomph to hit the ground and leave a crater.
Could a large object like this break through our atmosphere, miss the planet and exit the other side, or once it enters our atmosphere, is it going to land somewhere?
For the same reason atoms occasionally smash together unbidden. Mutual attraction, and relative distances that aren’t really all that large if you look at them in the proper scale.
Powers &8^]
That depends on how much speed and mass it has. No doubt there is some combination of those that would result in the scenario you describe, but the window is very small (due to how ridiculously thin our atmosphere is).
Powers &8^]
But there isn’t a mutual attraction is there? I thought most of an atom consisted of empty space and how often do it’s individual components usually collide?
Don’t they have to build massive machines to achieve that?
Oh, and what is the ‘proper scale’ then?
ivan astikov said:
Yes, the astronomers studying this are well aware that Earth is not stationary.
bup said:
How big is that net? What is it made of? What is the material strength? How heavy is it? I think without nanotube fibers, you’re not going to make a net with the right combination of strength vs weight. Then you’re still moving and deploying a hell of a lot of mass in order to spread out a net big enough. Plus, how tight is the weave on that net? What size rocks from the loose conglomeration can squeeze through the openings?
Yeah, it’s an idea, but one that requires extensive study, not a whimsical guess.
ivan astikov said:
Dude, there are pictures of galaxies that have crossed paths and are in the process of merging. This isn’t theoretical. Two objects aimed at the same location that have gravitational attraction are going to hit each other. For certain definitions of hit. It’s not like the stars themselves will be colliding. Rather, they will just be closer to other stars for a while, and get perturbed by the mutual gravity.
ivan astikov said:
Atoms collide without the protons and electrons hitting each other. This is because atoms have repulsive forces at play. When you whack your hand on a table, that sound you hear is the atoms of your hand colliding with the atoms of the table.
Galaxies do have mutual attraction - gravity.
The PBS series Nova actually showed such an event. The meteor in question hit our atmosphere, and you could see it as it went through, then left. I think this might be the video, but not 100% sure: http://www.youtube.com/watch?v=qth8i2GH6OE.
You Google meteor on Youtube, and you get a lot of fake stuff.
A) Why on earth would the fact that galaxies move quickly make it less likely that they would collide? That doesn’t make sense at all.
B) The universe is much more crowded with galaxies than galaxies with stars.
“Leaves, like the things of man, you
With your fresh thoughts care for, can you?”
[ul]Hopkins, Gerard Manley. “Spring and Fall: To a Young Child.”
Poems of Gerard Manley Hopkins Now First
Published. 1918. Ed. Robert Bridges. Prod. Lewis Jones. 26
Aug. 2007. Project Gutenberg. 22403. 5 Nov. 2009
<http://www.gutenberg.org/cache/epub/22403/pg22403.html.utf8>.[/ul]
Whenever I am tempted morbidly to fixate upon unlikely catastrophes, I,
as most do, find comfort comparing odds of the worst coming true with
those of more probable catastrophes. For example, the odds of
dying from West Nile Virus were about 1:6 million against in 2002.
[ul]Aguilar, Verónica. “West Nile Virus Case Found in Medford.”
Tufts Daily [Medford, MA.] 9 Sept. 2002. 5 Nov. 2009
<http://www.tuftsdaily.com/2.5541/west-nile-virus-case-found-in-medford-1.605117>.[/ul]
OTOH, the odds of being struck by lightning were twice as good;
nevertheless, I did empty and burn the whiskey barrels I used to keep
water lilies for fear of what the neighbors would think, inflamed by
sensational reports on TV, of my culturing mosquitoes on the premises.
I was disgruntled with myself for ducking any possible confrontation
over such unscientific mass hysteria. Woody-Allen-like, I have had
second thoughts, though – to justify my cravenness, I suppose: What,
really, are the odds of being wiped out in a mass extinction? I mean –
it isn’t like it’s never happened, but you have to figure that, when it
does happen, everybody buys it. Thus the numerator of the odds
ratio is the population of the earth – about 6 billion. The odds of
dying are still about 1:1, of course. Strangely, if it were determined
that mass extinction were imminent, then you would have to figure that
those born since Moses had a no-better-than-even chance of dying from
other causes.
[ul]Mikkelson, Barbara, and David P. Mikkelson. “Living Outnumber
Dead.” 21 July 2007. Snopes. 5 Nov. 2009
<http://www.snopes.com/science/stats/dead.asp>.[/ul]
One is forced to reconsider obscure risks. How about the possibility
of a large extraterrestrial impact event – a comet like the one that
did in the dinosaurs? These things happen every so often. The odds of
such occurring next year are 1:100 million against.
[ul]Choi, Charles Q. “Could Earth Be Hit, Like Jupiter Just Was?”
Space.com. 28 July 2009. 5 Nov. 2009
http://www.space.com/scienceastronomy/090728-asteroid-threat.html>.[/ul]
However, our species has been pushing its luck for at least 40 thousand
years, and one tenth of the people ever born are still alive, so the
odds of being a human being AND being wiped out by mass extinction are
really about 1:25 thousand against – maybe almost a hundred times
BETTER than being struck by lightning. Add in the possibilities of
climate change, pollution, pandemics, nuclear and biological holocausts,
crop failure, alien invasion and catastrophes not foreseen or imagined,
and you have plenty to worry about more or less legitimately.