Slashdot Mirror
How We Knew AL00667 Would Miss Earth
jefu writes "In January there seems to have been an incident in which it was thought that an object (asteroid) in space might have hit the earth within a couple of days of being spotted. It did miss, though. This story (from NASA/Ames) talks about the discovery of the object and the process that astronomers went through to determine if the asteroid was or was not a threat."
I'm glad they're so confident. I, for one, find the thought terrifying. :)
Too bad they already made the (17 versions of) the movie about this. It's a nice story.
Xbox reviews.. We think they're funny.
perhaps AL00667 creates MADMEN
Another article on Miss Earth
Have Linux installed at your place in Amsterdam, for cheap
that most people didn't hear about the asteroid until long after the near-miss was over. Seems to bring up the old argument of whether it'd be better to inform the public and try to do something about it or keep it under wraps and possibly die in blissful ignorance...
So many to choose, since it was an entire episode, but this one seems appropriate:
Sounds like the doomsday whistle! Ain't been blown for nigh onto three years.
Cheers,
IT
Power corrupts. PowerPoint corrupts absolutely.
Where is my MADMEN when i need one?
Note to self: get smarter troll to guard door.
Else we'd be meeting all the time travelers from the future
No problem! ... Bruce Willis will bust us out! ... Our super-geniuses will come up with a 5min to deadline plan and blast this bugger to pieces! ... It won't hit us anyway, because it did not hit us up to today.
Tell me Mr.Politician, what is more important: Survival of mankind or playing the powermonger game with your politician-buddys?
I say, if politicians (which are by the way trusted with OUR FATE!) behave like they do today they are gambling with the chance of survival for the entire human race. This should be considered a crime and prosecuted accordingly.
Meme of the day: I browse "Disable Sigs: Checked". So should you.
Onlooker1: It would mean the end of life as we know it ? ... but we don't really see a threat to the human species. .... not to mention rabid money hungry CEO types... along with a few cities as collateral damage.
Scientist: No, but it might burn up a few cities and destory 70% of the humans
Onlooker2: So I'd be dead ?
Scientist: But the people left alive will have an excellent chance of survival due to the systematic culling of slashdot trolls
Onlooker1: Why did you keep it under the wraps ?
Scientist: We were kinda hoping it would slag Sanford Wallace in location... and have the Pope claim it was divine intervention
Onlooker3: What about SCO ?
Scientist: Looks like the next one from Kuiper belt would do that clean
PS: maybe you should read "God's Debris" to be frightened by Slashdot.
Quidquid latine dictum sit, altum videtur
After buying a milion cans of baked beans, a zillion beer cans and 10 years worth of Playboy magazines (only for historical purposes, of course) they waited it out for a couple of days in an underground bunker.
Since they didn't felt any shake, it was proven that the meteorite had missed the Earth.
It was further proven that a zillion cans of beer barely lasts a couple of days and that having a million cans of baked beans is pretty useless when you forgot to bring a can-opener
One thing of note is that somehow, 10 years worth of Playboy magazines disapeared without a trace.
Most all missle defense proposals depend on punching a hole in an ICBM by heating it. For all their destructive potential, ICBMs are 90% thin skinned gas tank. You could take one out with a grenade, if you could somehow get it there.
The power required to destroy any rock big enough to survive atmospheric entry would be orders of magnitude greater.
"Faith: Belief without evidence in what is told by one who speaks without knowledge, of things without parallel." - A.B.
Short Warning Times
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Article Posted: February 19, 2004
By: David Morrison
For the story of AL00667, which briefly masqueraded as an asteroid that would hit the Earth within two days of its discovery, read on.
February 19, 2004 Short Warning Times
Following is information on the small asteroid known last January 13-14 as AL00667. A preliminary analysis of the discovery data for this object yielded a possible impact with Earth in less than 2 days time -- a situation not encountered previously in the Spaceguard Program. Although we knew at the time that such a prediction of imminent impact was improbable, a collision could not be ruled out. And if a possibility of an impact in 2 days existed, what should we do about notifying governments or the public? The story of this situation on January 13, 2004, is included as part of a paper by Clark Chapman (Southwest Research Institute) presented on February 22 at the Planetary Defense conference of the AIAA (American Institute of Aeronautics and Astronautics). Several paragraphs taken from this paper are reproduced below. Following these quotes from Chapman's paper are additional quotes from a letter Brian Marsden (Minor Planet Center) wrote to CCNet on 14 January on the same subject. Finally, there is a statement posted on the website of the IAU (International Astronomical Union) discussing what lessons we should draw from the story of AL00667, and how such a situation might be better handled in the future.
Asteroids never cease to surprise us. We may never encounter a situation just like this again, but we are fairly sure to have other crises as the rate of discovery of NEAs continues to increase.
David Morrison
FROM CLARK CHAPMAN'S AIAA PAPER "NEO IMPACT SCENARIOS"
presented February 22, 2004
"Just last month (January 2004) perhaps the most surprising impact prediction ever came and went, this time out of the view of the round-the-clock news media. It illustrates how an impact prediction came very close to having major repercussions, even though -- with hindsight -- nothing was ever, in reality, threatening to impact. It is a story of success in that the impact prediction was nullified in record time, less than half-a-day, but the success was accomplished through a set of ad hoc, unofficial, and often unfunded activities and relationships, although assisted in major ways by the official infrastructure, such as it exists (the LINEAR Project, the IAU Minor Planet Center, and the NASA NEO Program Office).
"About 36 hours before President Bush's planned speech at NASA Headquarters on future American space policy, the Lincoln Near Earth Asteroid Research (LINEAR) observatories in New Mexico routinely recorded four images of a moving object. Half a day later, on Tuesday, January 13th, these data were sent (as part of the daily submission of data) to the Minor Planet Center in Cambridge, Massachusetts. Just before going to dinner, MPC research Tim Spahr ran the data through standard software to generate a nominal ephemeris for the new object. These are posted on the publicly accessible NEO Confirmation Page (NEOCP) so that amateur and professional asteroid astronomers around the world might be able to follow up on the LINEAR observations that night. It is through such follow-up astrometry that NEO orbits can be refined so that the object is not permanently lost. Spahr posted the ephemeris, based on LINEAR's four detections, on the NEOCP under the designation AL00667, along with ephemerides for several other recommended targets. Less than an hour later, a European amateur astronomer, Reiner Stoss, went to the NEOCP and noticed a curiosity: AL00667 was predicted to get 40 times brighter during just the next day, meaning that it was going to be six times closer to the Earth! He expressed his amazement on Yahoo's MPML (Minor Planet Mailing List) chatroom on the internet.
"Professional asteroid researcher Alan Harris happened to be monitoring the chatroom and noticed the strange
NASA Server hit by slashdot asteroid. They didn't see it coming...
cpghost at Cordula's Web.
In the past fifty years, we have started to gain the technological capability to detect potential collisions with asteroids.
That does not make such a collision more likely in the next fifty years -- or hundred and fifty, or fifteen hundred. Significant and successful collision are _rare_, much rarer than earthquakes, tornados, or even human-caused meteorological effects (as in weather systems, not meteors).
It doesn't matter if we can see "just how close we came". It matters that we know, empirically, that there are vastly more pressing concerns.
What I don't want to see is an orbital weapons platform deployed under false premises. If the pretenses are true, that's a different story. Just don't tell me its to shoot down asteroids!
--Dan
Um, the problem with that is the whole concept is to be dealing with targets launched from earth, at earth based targets.
Meaning they'd be pointing in the wrong direction.
try this link for more info http://www.hohmanntransfer.com/mn/0402/09.htm
That's about the size of the Tunguska object (probably a comet, since it exploded in mid-air and didn't leave a crater). Enough to make a mess of a big city or a pretty impressive tsunami, but not enough to wipe out mankind.
When I am king, you will be first against the wall.
what are requirements for such a rock to survive its way through atmosphere? I doubt that size is only thing that matters. material shoul'd be counted too.
/ss
I find the number 667 Highly suspicious..
Is number 666 ever issued? A lot of numberiung systems miss this one out, in order to keep the religeously insane from freaking. For instance the UK number plate authority stopped using it a few years ago after complaints from some quarters.
So my real question is: Would this have -actually- been AL00666?
Spooky...
"Oops, I always forget the purpose of competition is to divide people into winners and losers." - Hobbes
true. Composition matters a lot too. For a given size, a "stony" or primarily rock asteroid will burn quite a bit more than it's "iron", or mostly metal counterpart.
Also, stony asteroids tend to explode if/when they reach the lower atmosphere. Comets, which are primarily ice and stone, are very unlikely (but not impossible - see tunguska) to survive entry.
Any of these are much stronger than an ICBM, of course.
"Faith: Belief without evidence in what is told by one who speaks without knowledge, of things without parallel." - A.B.
Nah they just have been hit by an asteroid, and you will be crushed by the waves in some minutes. =)
Don't you know it is now both immoral and criminal to think beyond the next quarterly report?
"We probably could have had something in place to shoot such a threat down if we had fully funded the Star Wars MDS project, but sadly geopolitics killed that project."
Doubtful. Weapons for bringing down delicate ICBMs -- even if they had surprised everyone and actually worked -- would be useless against a mountain of rock and ice moving at kilometers per second.
It would be like flicking peas at the Exxon Valdez.
To deal with large objects on a collision course we first need a few decades of warning. Given time, a little nudge can make a big difference. For a rock kilometers in diameter, even thermonuclear explosions count as nudges. If we only have a few months of warning; we're well and truly screwed.
Iz
you wouldn't want to destroy such a beast. several pieces of rock flying towards earth are after all even more dangerous than one big stone -- even if the big rock would be way bigger than the small ones :-)
:-)
what you would want to do is attaching some kind of nuclear device to it, which melts away pieces of its surface and with the gas and pressure created it slowly pushes the meteor (or comet) in another direction.
it would be like pushing a huge ship away with your hands, whilte it is just floating in the water: probably slow, but it would definitely work. there's no (relevant) opposing force in space
Exciting !!
And maybe my neighbours underground bunker would have finally proven to be useful for things other than coding marathons...
This would also be one hell sure way to get rid of windoze once and for all... only something as distributed as open-source software can survive such a catastrophy... wouldnt it be amazing if entire source code of windows was lost. wow !
Now compare that to the linux source present on millions(?) of computers all over the world. Reminds me of the phoenix...
tisk tisk..
(warning: seriousness levels dangerously low)
[all generalizations are untrue except this one]
So instead of one huge target you could in principle land on, you'd get a swarm of smaller but still deadly rocks that would rain devastation on Earth?
No, the only permanent solution to the extinction level event problem is to get some of us off this goddamn planet.
The owls are not what they seem
Here's an animation of the object. The link to the yahoo egroup discussion is also worth looking at. The discussion morphs from everyone thinking it's a joke post to realizing that the asteroid exists. It's an interesting log of people coping with uncertainty.
Slashdotters can continue to sleep comfortably with the knowledge that TCP/IP is designed to withstand such an event; lets just hope there's a backup of the /. backend in case its server(s) get struck, shorted by the tsunami, or looted by the local villagers.
I'm waiting for the follow up article: "The Slashdotting that hit without warning."
see tunguska??
Tunguska was Tesla, MAN! wake up and smell the ozone
they never found not one drop of evidence of foreign matter in soilcores from all the expeditions back there since. It was Tesla testing his death ray, i'm convinced
... Much like the server with the article, the Asteroid was slashdotted causing it to malfunction and miss the earth.
Use your head, can't you, use your head,
You're on earth, there's no cure for that - S. Beckett
Only the older American missiles which used their outer wall as the skin of the fuel tank. It saved on weight and gave them formidable acceleration. The Soviets always used separate tanks and a thick steel skin - largely because they never worked out how to build precision skins. Both of which gave their missiles a massive strength.
Both countries now use solid fuelled boosters which are much tougher.
And as for a grenade - why bother - you can use a wrench.
Best wishes,
Mike.
The news told me everything was good and everybody was happy, so I really don't see your point :)
The current best missle defense, the AirBorne Laser (think 747 with a bad attitude) carries a massive chemical laser that takes a couple of seconds to destroy missles. It's mostly designed for theatre of war (intracontinental) missles, and is still in the testing phases.
How would an electron gun produce any significant kinetic change in the rock? Alternately, you could boil off part of the asteroid and "jet" is to the side, but the energy this would require, if it's only a few days out, would be enormous. you'd need to hit it years out to have any hope of significantly changing it's trajectory.
Even IF we had a point defense mechanism... unless we vaporize the rock, or reduce it to very small (inches) pieces, we'll have just created an intergalactic shotgun...
"Faith: Belief without evidence in what is told by one who speaks without knowledge, of things without parallel." - A.B.
If it's got an impact velocity of 30,000 meters per second (not out of the question), it wouldn't be in the atmosphere for any more than a second or two. Even if it does "blow apart", the heat transfer into the atmosphere isn't going to be insignificant.
>what are requirements for such a rock to survive its way through atmosphere
High density and low total surface area
Actually that could be a really bad idea, the majority of asteroids threatening Earth are probably not solid bodies - more like aggregations of rubble. A blast could smash such bodies to rubble (all of which would still be heading our way). Many bodies have a composition similar to foam - very fragile with lots of pores and spaces filled with volatiles. When hit by a blast, a small amount is vaporised, the remainder just soaks up the explosion - and keeps on coming.
There are several proposals for deflecting asteroids - either attaching a mass driver to produce a small, almost constant thrust. Alternatively a huge solar mirror could be put on to a trjectory close to the asteroid. It would focus the light of the Sun on to one point on the asteroid - vaporising material into space and creating a thrust.
Sadly both approaches need us to have plenty of warning. The accelerations produced are so small (in the orders of cms^2) that you need plenty of time to get a sizeable deflection.
Such an observation system could be put in place for a tiny fraction of the cost of Star Wars or NMD and wouldn't cause any international uproar. Sadly it doesn't produce nice fat Pentagon contracts.
There's quite a nice summary of the various technologies here.
Beat wishes,
Mike.
We were lucky this time, but it is clear that we need to do something about such threats. Here is what I propose:
We build a nondescript isosceles triangular spaceship, controlled by one man with a joystick. Left and right rotate the ship, up thrusts the ship forward, and down, well, down depends upon your configuration. Optionally, it could throw the ship through hyperspace to some other random point in space, or else it could put deflector shields up around the ship.
In addition to the joystick, the ship's pilot should have access to a red button (it must be red). Pressing the button should cause balls of energy to shoot out of the front of the ship, capable of breaking apart large asteroids, and destroying small ones. Pressing the button should also make a "PCHOW!" sound.
It is our clearest and best long-term option.
Mod me down as flaimbait or whatever, but I personally think we need a global cataclysm. We don't need something that kills off the entire human population, but we certainly need something to cleanse our planet. We need something to take our collective heads out of our asses and come together as one people and work together for the common good.
do you really think a global cataclysm would make people work together for the common good more than they do today? Or is it more likely that resources would become greatly limited so humans would be more likely to kill each other for their own good? While human life is still a struggle for resources, I doubt the red cross was around in the caveman days, helping the guy who got clubbed on the head and had his dinner stolen.
An asteriod 2" in size would be a significant impact if it hit you on the head! However, they can't watch EVERYTHING. They have to draw the line somewhere. 1km seems to be the size needed to possibly wipe out all life on Earth. Yes, 1/2km would do a lot of damage and kill a lot of the population of Earth, but some would still survive the initial impact. I would assume once all the 1km NEOs are charted by 2008 that they would move on to the smaller ones. Also, as shown by this article, they found a 30m and now know its orbit. It's not like they are just throwing out the data for objects smaller than 1km if they happen to find them. Such small objects, however, are not the focus of the search.
Let's just get this straight: according to the article, the initial data were of low precision, they implied a very large uncertainty in the asteroid's trajectory. (In the event, it wasn't even a near-miss -- it was millions of km off, several times the moon's distance.)
The large uncertainty meant that at any one moment before the conceivable (but very unlikely) arrival of the body at or anywhere near the earth, there was a very large area of uncertainty, in which the asteroid's actual point of arrival would be one tiny and uncertain spot, and the possible trajectories leading to earth would be represented by another tiny blob (tiny relative to the whole area of uncertainty), most probably located very far away from the spot containing the real asteroid.
Calculations on real computers often represent an area of uncertainty like this by a nominal position that is very roughly at the centre of the area of uncertainty, accompanied by a measure of the size of the area of uncertainty.
The fact that one can physically read from the printed result and see that nominal position separately from its accompanying measure of uncertainty, because of the way the figures are presented on screen or paper, that does not give the nominal position any reality.
It happened that the nominal position first calculated in the case of AL00667 would have been (if of zero error) a trajectory heading for earth. But it wasn't of zero error, nor even close.
The whole scare looks like an artifact of the way in which uncertain results involving a continuum are presented using discrete digits.
-wb-
If anarchy is ever declared...
...ask under what authority the "declaration" was made.
taken! (by Davidleeroth) Thanks Bingo Foo!
For a great novel about asteroid armageddon and the resulting collapse of society, read "Lucifer's Hammer" by Larry Niven and Jerry Pournelle. It's slow for the first half, but man, once that asteroid hits, it's sweet, sweet chaos.
But that assumes an absolutely perfect, dead-on impact trajectory taking the most direct path from space to surface, and hitting at a ninety-degree angle. Most space debris will fall into the atmosphere at an angle, which will drastically increase the amount of time it's exposed to atmospheric friction.
Why do you think shooting stars seem to streak a long way across the sky?
Please be advised that we are raising the Asteroid alert to code orange--high from yellow--elevated. This is due to intelligence that there may be big rocks nearby planning on heading in our general direction. Please be on the alert and double-check your umbrellas.
Yeah, if L00667 had hit Washington DC, the rest of the world would point and snicker that America got a smackdown. The rest of the US would point and snicker as well because there would be no Congress left to appropriate eighty ba-zillion dollars to rebuild itself.
But would anyone really, fundamentally change their ways?You were 80% angel, 10% demon. The rest was hard to explain. - Over The Rhine
"Math in a song is good."-Linford
If it was AL00666 the doomsdayers would've been going nuts about how this is the event that will wipe out all of humanity.
;)
AL00667 reminds me of that "neighbour of the beast" joke
smile, it makes everyone else wonder what you're up to
What's heavier a ton of feathers or a ton of lead?
Would depend on how one measures and verifies the mass or weight of the material. Let's make the reasonable assumption that we're weighing both at room conditions (760 torr, 295 K) using a beam balance. The point is that feathers displace a lot more air than lead. This means that when we add enough feathers or lead to measure 1 kg, the mass of feathers is slightly more than that of lead (due to compensating for buoyancy in air etc). This applies even to a beam balance because the masses we use on the other pan are far smaller and denser than feathers.
Hence, "one kg" of feathers (as measured) has a real mass of about 1.01 kg, while "one kg" lead has a real mass of about 1.000091 kg. This difference is about 9.91 grams per kg measured, which adds up to 9.91 kg per metric ton measured.
Hence, "one metric ton" of feathers has 9.91 kg more matter in it than "one metric ton" of lead.
If you really want to answer that question satisfactorily, you must find measure out the masses AND verify the masses in a perfect vacuum.
Time flies like an arrow. Fruit flies like a banana.
I looked this info up during an earlier discussion of planet killing asteroids. Sorry, I don't have the references handy. My recollection was that it didn't matter what the composition was if it were only a little bigger than the estimated size of the Tunguska rock... IIRC if an asteroid were about 100 meters in diameter, it would be sure to strike the surface and dig a crater.
From the lack of a crater the Tunguska rock was seen as one of the more fragile kinds. But, in terms of killing a city, the mass and velocity of the rock is what matters most, not its composition. Nickel-Iron rocks are thought to be more robust, and able to survive to hit the surface, and dig a crater, even if they are smaller than Tunguska.
I also came across the very interesting suggestion that the Tunguska event may not have been extraterrestrial at all. Tunguska is an area with huge natural gas deposits. The other suggestion was that seismic activity allowed a jet of Natural gas to jet out, that its fumes had been accumulating for days, until lightning set it off. This theory explained some aspects of the Tunguska event that the asteroid theory didn't.
Don't know about where you are but around here the Walmarts sell guns and ammo. And there are already a good 30 to 40 employees already inside. Good luck taking over the place.
So in the event of a meteroid strike, I for one will welcome our new Walmart line level employee overlords... As opposed to the Walmart corporate type overlords we have now.
Everybody knows that if you want to stop a killer asteroid, all you have to do is change the gravitational constant of the universe for a few seconds. Trivial, really... Ow, my back!
I just can't get out of my mind that ludicrous ending where the aging Sen.Jellison dramatically gets up and sends his minions to "give our children the lightning!" Their idea of good government did not appeal much to me either.
... before its nearest approach. I remember last year, when an object near-misses Earth (I think it was bigger than our 667 friend). It was really close, in fact at that time, it was the one which was closer, about 120000 km (which didn't hit our planet). I don't remember the code, but that fact (the short distance of the fly-by) will help at finding out.
The problem: It was spotted TWO DAYS AFTER the nearest approach. Some scopes are needed in the southern hemisphere.
It seems to me that over the last few years I have heard a LOT of reports of asteroid near-misses - much more so than in the 80's or 90's. Unfortunately, I think it's going to take an asteroid/comet impact, over a population center, before the humans "in power" even begin to "get it."
Recent movies aside, the thought of a HUGE rock (or solid chunk of iron) falling from the sky, is so completely beyond the experience of most humans, as to be practically ludicrous.
"I would sooner believe that two Yankee professors lied, than that stones fell from the sky." - Thomas Jefferson (supposedly)
--==>>BobT>
Given a value of 6378.137 km for the Earth's radius, one would have to divert the asteroid 637,813,700 seconds, or about 20 years and 3 months, before the anticipated impact. Of course, under this scenario, the asteroid would brush Ecuador a little close for my taste, so I would recommend diverting the asteroid at least a few seconds earlier... This does not account for the earth's orbit or the continued trajectory of the asteroid. We would get pretty pissed at those scientists back in the 80's who diverted the asteroid so it wouldn't hit in 2004, only to have it hit in 2006 or whenever. On the other hand, the Reaganite politicians who arranged the diversion in the first place would be patting themselves on the back for making sure the asteroid wouldn't screw up GWB's reelection plans.
"Den som vover mister Fodfaeste et Oieblik; den som ikke vover mister Livet." -Soren Kierkegaard
So instead of one huge target you could in principle land on, you'd get a swarm of smaller but still deadly rocks that would rain devastation on Earth?
I've always wondered about this. If I have a chunk of rock 1 km in diameter hurtling toward the earth, wouldn't it be better to break it up into small chunks so it would be more likely to burn up in the atmosphere? Even though the mass is the same, the surface area presented to the atmosphere would be greatly increased, which would be much more efficient at ablating away mass and slowing down the incoming pieces (transferring energy to the atmosphere instead of into making a crater).
Where's the trade-off point between distributed death from all the smaller chunks and increased burnup in the atmosphere?
Tiller's Rule: Never use a word in written form that you've only heard and never read. You will end up looking foolish.
From: Alan W Harris Date: Tue Jan 13, 2004 7:24 pm Subject: "Turn out the lights"
Brian Marsden has substituted a different orbit that fits the observations within allowed uncertainties. There has been no added or re-worked astrometry, just a little push of the solution off the covariance minimum. On the one hand, this demonstrates that the limited observations so far are not sufficient to predict an impact with high probability. On the other hand, nothing has happened to invalidate the previous solution or reduce the probability that it is right. I'm reminded of an old pilot's story of how to do a forced landing at night in a populated area. The advice is that in order to avoid plowing into population on the ground, find a large dark area with no lights. If you're lucky it will be a field of some sort and you can do a dead-stick landing. As you approach, turn on your landing lights and see what's there. If you like what you see, go ahead and land. If you don't, turn off your lights.
I pretty much slept through thermodynamics, but I can't imagine that all that extra heat being transfered to the atmospehere is a good thing.
Jack Valenti and Orrin Hatch will be first up against the wall when the revolution comes.
GEODSS first came up in 1982. It consisted of four sites (three today, budget cuts) worldwide, each with three 1-meter telescopes. The whole system is computer-run and reports to NORAD automatically. This was the beginning of automated astronomy.
The telescopes scan the whole sky every night, subtract out everything in the star catalog, and report unknown objects. New satellites and space junk are found this way. Even dark objects that occult stars are noted. There's also a more elaborate USAF site on Maui with even bigger computer-controlled telescopes.
Some of the sites have lasers (Maui definitely does) and can illuminate their targets using one telescope while looking at it with another. This allows time-of-flight ranging, photography of dark objects, and determining whether a satellite has cameras. But illumination is only useful for near earth satellites; it doesn't help with asteroid search.
Asteroid search is a spare-time activity of one of the GEODSS sites. They continue their real job for the USAF, looking for anything near the Earth that shouldn't be there.
The GEODSS hardware was updated in 1999, with better sensors, new computers (the 20 racks of PDP-11 hardware had to go), better positioning accuracy, and some infrared capability for working around cloud cover. The original main optics remain in use.
Your tax dollars at work.
and the process that astronomers went through to determine if the asteroid was or was not a threat.
Scientist: Heads or tails?
in girum imus nocte et consumimur igni
>>Right then, do the maths, and work out a ballistic trajectory that will get a missile more than 5500km, without leaving the atmosphere.
a tmospheric_structure.html
Rather than maths, lets look at facts.
from this page: http://www.d-n-i.net/fcs/comments/c439.htm
(look for section 4)
" A typical ICBM gets about 500 to 1000 miles above the ground at the highest point of its trajectory."
Now, lets see what I said, an ICBM doesn't have to go out the _atmosphere_...
From this page: http://daac.gsfc.nasa.gov/CAMPAIGN_DOCS/ATM_CHEM/
" The exosphere is the outermost region of the Earth's atmosphere. Within the exosphere, atoms follow ballistic trajectories and rarely undergo collisions because the density of atoms in this region is so low. The exosphere begins at approximately 500 km and extends outward until it transitions with interplanetary space (at roughly 10,000 km)."
[Just incase you need to know:
1000 miles = 1609.344km;
10,000km = 6213.712 miles (3dp for both)]
The exosphere, which is part of Earth's _atmosphere_ extends HIGHER than an ICBM's launch max height. So therefore, I can conclude that my original statment was correct.
If you feel like doing the maths, by all means, do so, but you are going to have to show me that the ICBM leaves the exosphere (yes, part of our atmosphere).
NeoThermic
Use my link above, or to view my server, NeoThermic.com
In January there seems to have been an incident in which it was thought that an object (asteroid) in space might have hit the earth within a couple of days of being spotted. It did miss, though.
No way -- it really missed? I thought I was dead.
Slashdot: facts for hermits, stuff that's obvious.
Moderator hint: a comment is neither "Flamebait" nor "Troll" if it is true.
Sorry,
you are confusing mass with weight.
Your "beambalance" thingie says a lot about weight, and air pressure.
You might be correct about in which way the ballance would tip here on earth.
This has nothing to do with mass.
</nitpicker>
pAnkRat
--
"A bunsenburner.
What is a bunsen?
And why would one like to burn it?"
(Rincewind in the Discworld adventure)
we need an "-1 Plain wrong" moderation option!
but I can't imagine that all that extra heat being transfered to the atmospehere is a good thing.
This is rather easily estimated.
We can assume most (~95%) of the atmosphere lies in the first 14 kilometers (it's actually 18 km at the equator and 8 km at the poles). Assume Earth is a sphere of radius 6371 km. This gives a total atmospheric volume of 7.16e18 m^3. Assume a conservative average density of 0.8 kg/m^3; the mass is therefore 5.74e18 kg. If that seems overly heavy, consider that the Earth weighs about 5.98e24 kg, or about 1 million times more.
Assume the molecular mass of air is 29.2, and we get 1.96e20 moles. Assume its specific heat is (7/2)R == 29.1 J/K-mol, and we get the heat capacity of the entire atmosphere to be 5.71e21 J/K.
Hiroshima was a 5-kiloton blast, from 35 kg of Uranium. That is, 35 kg U directly converted to energy is like 5000 tons of conventional TNT-like high explosive. Hiroshima translates into 3.15e18 J, which would raise the global temperature by 0.0005 K.
Assume that life will be threatened if the atmospheric temperature rises by more than 2K. Raising the atmospheric temperature by 2K requires 1.14e22 J, which corresponds to 3622 Hiroshima bombs.
The question of whether a given asteroid is 3600 times as powerful as the Hiroshima bomb is left as an exercise to the (astrophysicist / nuclear physicist) reader.
Speaking as an engineer, I'd say that we're probably heating up the atmosphere far quicker all by ourselves, so we probably don't need to worry about asteroids.
Time flies like an arrow. Fruit flies like a banana.