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Schoolboy Corrects NASA's Math On Killer Asteroid
spiracle writes "A German schoolboy, Nico Marquardt, has revised NASA's figures for the chances that the Apophis asteroid will hit earth. Apparently if the asteroid hits a satellite in 2029, its path could be diverted enough to cause it to collide with Earth on the next orbit, in 2036. NASA had calculated the chances as 1 in 45,000 but the 13-year-old, in his science project, made it 1 in 450. NASA agreed." Update: 04/16 16:47 GMT by Z : This is not entirely accurate, it turns out — more details.
NASA previously estimated the chance "Apophis" the asteroid would strike earth in 2027 was 1 in 45,000. But a german schoolboy, Nico Marquardt, pointed out that NASA overlooked the probability the asteroid would strike one of the 40,000 sattelites orbiting Earth and enter a new solar orbit intersecting Earth in 2036. A german newspaper reports that NASA now concurs the chance this will happen is about 1 in 450. If the 200 billion tonne ball of iridium and iron stikes the planet then it's literally light's out for earth: 800 foot tidal waves followed by an indefinite period of dust cloud covered darkness, not to mention metal vapor in the atmosphere. The original Slashdot discussion was in 2007 when the odds were better. At that time it was known that there was a small risk of a gravitational slingshot dropping it into the 2036 collisional orbit, however, to do so the asteroid had to pass through an improbable 400 meter wide strike zone to be properly deflected, as described in 2006 in Popular Science from 2006. Today's announcement of the new finding is here and here.
Some drink at the fountain of knowledge. Others just gargle.
By the way, it passes by the earth in 2027 on friday the 13th. If it hit's it will hit in the pacific ocean. So California may get wet. The energy content is said to be 26,000 Hiroshimas which is not that much but recent calculation suggest is more than enough to darken the earth.
Some drink at the fountain of knowledge. Others just gargle.
He didn't really correct NASA. He only extended their prediction: NASA predicted, correctly, that the asteroid had a 1 in 45,000 chance of hitting the earth in 2029. Nico pointed out, also correctly, apparently, that if the asteroid missed the earth but hit a satellite in 2029, then it would have a 1 in 450 chance of hitting the earth in 2036.
Knowing how Earth moves in space, they simply had to look up which part of our planet would be facing the asteroid when it comes back.
This is within the distance of Earth's geosynchronous satellites. However, because Apophis will pass interior to the positions of these satellites at closest approach, in a plane inclined at 40 degrees to the Earth's equator and passing outside the equatorial geosynchronous zone when crossing the equatorial plane, it does not threaten the satellites in that heavily populated region. So what is being claimed here is not so implausible. It is going to pass within the geosynconous orbit distance.
Some drink at the fountain of knowledge. Others just gargle.
Here is the original article, in German, from the German newspaper. It looks like a professor helped him (Professor Spahn from Potsdam University). Bild is semi-infamous in Europe for sensationalizing stories but at least we know that the boy is real if nothing else...
NASA and Marquardt agree thatYes, actually, that's the easy part. We know very precisely when and from what direction it will be coming, the question is will it go left, right, or straight down the middle? (Metaphorically speaking... I don't know the details, for all I know we're above and to the left of the center track.)
Once you know when and what direction, you know which hemisphere. Once you account for projection distortion, that puts the odds as pretty good it lands in an area well less than half of the Earth's surface. Something the size of, say, the Atlantic Ocean.
Collisions in space are actually quite predictable. The asteroid is huge and fast, so the entire satellite gets obliterated -- no random debris falling off, because odds are that the satellite is either entirely within the path or entirely outside it. Supersonic (relative to speed of sound in asteroid / satellite, not something irrelevant like Earth's atmosphere) collisions are basically completely inelastic (details more complex, but reasonably well understood).
Satellites don't vary in mass all that much. The big ones are a few tons to a few tens of tons, once you ignore the ISS. The little ones don't matter, so you ignore them.
Telescope observations can most definitely produce the many nines of precision needed for this work. It goes something like this: on day one, it's within this error bar. On day two, within that error bar. On day a few thousand, this other error bar. Individually, the error bar is large, but as they spread out, the path through every one of them gets rather precisely defined. Imagine positioning a set of 1 meter wide gates across the US -- sure, you can't measure the position of the bowling ball you rolled through them to better than 1 meter at any one point, but by the time it's gone through *all* of them, you have sub-ppm accuracy on its exact angle. Extend the scale a bit and you get the precision needed.
Calling the pocket is the easy part: if it hits, then the piece of the Earth pointed in that direction will be the Atlantic. Sure, it might strike a glancing blow and hit at the edge, but thanks to foreshortening the odds are against that.
They didn't forget about them. There is almost no chance a satellite will be struck. If you read the original FA, you'd see that a) the asteroid will pass inside the orbit of them, b) it will pass at a 40 degree angle to them, and c) when the satellite does reach the distance the satellites orbit at, it'll be well beyond the region the satellites are in.
The kid calculated the odds of the asteroid hitting the earth IF the asteroid hit a satellite JUST PERFECTLY. The odds of the asteroid hitting a satellite, much less just right for that to occur, are remote at best. This is just media hype to increase ratings.
Thinking about the problem for a second, I can see how you can make some rough calculations. Generally any GEO, HEO, etc. type orbit will be fairly slow, especially compared to the hyperbolic orbit that the asteroid will be entering at (in the Earth's reference). Thus based on the range of velocities and masses you could predict a range of possible perturbations to the orbit.
Though I don't have any numbers to back it up right now, a small perturbation in the velocity can propagate forward to be a very large error after 7 years. Thats why we have so much trouble predicting whether or not it will hit us; a 10 meter error in its position or a 1 m/s error in velocity measurements translates into multiple Earth radii over a few years. So combine the small change in velocity from an impact with the gravitational slingshot from the 2029 close approach, and it may be enough to shift the keyhole.
Of course I think the article is misleading, it may be more like there's a 1/450 chance of some kind of impact that will have an unknown effect on the orbit but may shift it into an impact trajectory, or something like that. At any rate, there are still other unknowns such as the effect of solar wind that can vary the trajectory dramatically too.
Note of course that I could be completely wrong, although I do plan to attempt some simulations now, since one of my advisors classes is working on a related project.
No need to translate it to make it hilarious:
a) The source "newspaper" is Germany's biggest tabloid - with as much knowledge on astrophysics as a kindergarten kid
b) No 13 year old German kid says "stuerben"
First of all, the competition is "Jugend forscht", which is the largest science competition in Germany. It consists of three stages: first there is a regional competition with winners advancing to the state finals. The winners of the state finals then advance to the federal finals, which is the last round. Roughly speaking, in every round one winner (or winning team) is chosen by a jury in each discipline (mathematics, physics, chemistry, ...).
It seems that the kid won the regional competition, but failed to advance in the state finals.
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Sorry to burst the balloon, but apart from the one German article that was picked up by AFP, there's no source for this story. And NASA and the ESA deny ever saying that the schoolboy was right. It seems that the schoolboy's sums were wrong, and NASA's original workings are right. More info: http://www.theregister.co.uk/2008/04/16/esa_german_schoolboy_apophis_denial/ I'd file this under 'web hoax' or 'lazy journalists pick up on anything sensational'
Just in case anyone still believes we'll all be killed by an asteroid in 2029 or 2036, here's an article from El Reg, claiming that the boy got it all wrong.
I guess we'll have to live with the miniscule 1 in 45,000 chance.
link to article:
http://www.theregister.co.uk/2008/04/16/esa_german_schoolboy_apophis_denial/
"In April 2008 it was reported that 13 year-old Nico Marquardt from Potsdam, Germany had recalculated the odds as part of a science competition, and found the risk had been underestimated. Taking into account the possibility of the asteroid colliding with one or more of the estimated 40,000 artificial satellites orbiting the earth, possibly causing a shift in its orbit, increases the probability of a collision with [5] earth on its next fly-by in 2036 to 1 in 450. NASA was reported as confirming these results with the ESA[6], yet they have since apparently denied these claims, and on April 15, 2008 it was reported Nico Marquardt's calculations were incorrect." -- Wikipedia http://en.wikipedia.org/wiki/99942_Apophis/
"This is within the distance of Earth's geosynchronous satellites. However, because Apophis will pass interior to the positions of these satellites at closest approach, in a plane inclined at 40 degrees to the Earth's equator and passing outside the equatorial geosynchronous zone when crossing the equatorial plane, it does not threaten the satellites in that heavily populated region. " From here.
The force is strong with this one.
Nasa Watch has picked up the story. Turns out to be completely made up. Details here: Apophis risk not increasedYes it is all a hoax.
NASA denies this report: http://www.nasa.gov/home/hqnews/2008/apr/HQ_08103_student_asteroid_calculations.html#maincontent
The story apparently originates with german newspaper Bild. Bild is very poplar but also notorious for getting even the most basic facts wrong. There is a German blog ( www.bildblog.de ) which highlights out the quite peculiar world view of Bild reporters.
To name just the latest "highlight" cited in bildblog: "the sun takes 365 days to circle around the earth"
Nope. The kid didn't do his homework. While the asteroid may pass around 38,000 km from earth at the closest point, it will pass the equatorial ecliptic at around 51,000 km, too far away to collide with any geosynchronous satellites. Also to be noted: According to NASA, the kid did not contact anyone there to obtain any data. The kid's bright and engaged and had a heck of an idea for a science fair project, but his lesser-educated, sensation-mongering elders jumped the gun and made him look like a fool.