Slashdot Mirror
Study: Space Rock Impacts Not Random
sciencehabit writes When it comes to small space rocks blowing up in Earth's atmosphere, not all days are created equal. Scientists have found that, contrary to what they thought, such events are not random, and these explosions may occur more frequently on certain days. Rather than random occurrences, many large airbursts might result from collisions between Earth and streams of debris associated with small asteroids or comets. The new findings may help astronomers narrow their search for objects in orbits that threaten Earth, the researchers suggest.
http://en.wikipedia.org/wiki/M...
http://stardate.org/nightsky/m...
I knew you could
It's a bit worse than that. The Heisenberg uncertainty principle states that you are not allowed by the laws of physics to simultaneously know all the initial conditions with arbitrarily high precision.
It's even worse than that. Going by this quote, they're using it to mean even or homogeneous:
contrary to what they thought, such events are not random, and these explosions may occur more frequently on certain days.
You know, like if a coin comes up heads four times in a row that's "not random".
Actually, that's not a very good analogy. The main pattern that they noticed is clustering of events over long periods of time . It would be more like if you had a coin that was weighted in such a way that it only came up heads about 1 time out of a 100 or something. You flipped it once per day.
According to normal probability, if the only thing that's influencing the coin is just its weight that produces a 1 in 100 chance of heads, the pattern of heads should look relatively homogeneous over a long time span.
Instead, what they tended to find was a lot of clustering of events -- so it would be like going for hundreds of days and then suddenly getting heads on 2 or 3 days in a row, then going again for hundreds of days without any heads again.
In that case, it would be fair to say that there is something else influencing the distribution -- it's not just a "random" distribution you'd expect for a 1 in 100 chance of getting heads. Some other factor is leading to clustering.
Just from looking briefly at the article, it doesn't seem to me that they have a long-enough timespan or enough events to claim strong evidence for a pattern. They basically come up with a 2% stat that this pattern could occur by chance -- sure, that's better than the standard 95% confidence interval for exploratory studies, but there are various statistical features of their study that could be giving them a false-positive here. But it's enough that further study may be warranted.
To all the commenters claiming we've already known this for centuries... no, we haven't. There's no reason to presume a priori that large objects occur in "showers" like the smaller (ash particle to pea sized) objects that make up familiar meteor showers. And astrostatisticians are very unhappy with the quality of the statistics in this paper, and they are suggesting the null hypothesis can't be rejecting using better statistical tools: https://astrostatistics.wordpr...
"I'm so moist I'm sticking to the leather." -Kermit the Frog on The Late Late Show
Heisenberg's uncertainty principle is just an application of the Fourier uncertainty principle to the quantum position and momentum wavefunctions. Since those are a Fourier pair, the Fourier uncertainty principle applies. So it's not a matter of which interpretation you pick, it's about whether QM is correct. If the behavior of quanta is not wholly determined by their wavefunctions then QM is wrong, and Heisenberg's uncertainty principle might be violated, since the true functions for position and momentum may not be Fourier pairs. This is widely considered to be extremely unlikely. Also, if spacetime is quantized (there's a minimum possible distance and a minimum possible time, and all times/distances are integer multiples of these minima) then the wavefunctions wouldn't be continuous, so the uncertainty principles might not be applicable. Loop Quantum Gravity is one theory that posits this.
Not a sentence!
So, the same as with meteor showers. Not entire unexpected, i'd think.
Not entirely unexpected, but -- to be clear -- this study is NOT talking about normal meteors in meteor showers (which are presumed to be clustered since they are typically remnants of a comet).
Instead, this study is focusing on LARGER bodies (multi-kiloton impacts), most of which do not have a common origin like bits of a comet. Many scientists assume that they are random hunks of rock from the asteroid belt or some other collection that get perturbed from their normal orbit by interacting with Jupiter or something. Point being -- there's no actual reason why they should cluster together unless they originated from a body that fractured. From TFA:
The paths followed by these objects are strongly perturbed, and exhibit fast and chaotic nodal precession over time-scales of ~10 Myr (see e.g. Ito & Malhotra 2006). It is therefore not surprising that most studies assume that the angular elements, in particular the longitude of the ascending node, of the orbits of near-Earth objects (NEOs) are randomly and uniformly distributed in the range 0-2 pi. For many, this intrinsic chaoticity necessarily means that they are completely random, and that all the impacts must be interpreted as uncorrelated events distributed according to Poisson statistics.
In other words, many people -- who probably know much more about this than the average Slashdot poster -- have recognized there are many differences exhibited in the behavior of these big hunks of rock compared to meteor showers, and thus assume their origin is probably different. Which means there's no reason to assume the same sort of clustering.
This study seems to show clustering. If this study seems valid, the next thing is to explain WHY this sort of clustering happens with large bodies. The authors suggest it may have something to do with planetary perturbations. In any case, it's probably not the same mechanism as meteor showers.