No, a Huge Asteroid Is Not "Set To Wipe Out Life On Earth In 2880" 123
An anonymous reader writes "Phil Plait wants you to know that asteroid 1950 DA is very, very unlikely to hit the Earth in 2880, despite what you may have read. He writes: "As it happens, 1950 DA is what's called a 'near-Earth asteroid', because its orbit sometimes brings it relatively close to Earth. I'll note that I mean close on a cosmic scale. Looking over the next few decades, a typical pass is tens of millions of kilometers away, with some as close as five million kilometers — which is still more than ten times farther away than the Moon! Still, that's in our neighborhood, which is one of the reasons this asteroid is studied so well. It gets close enough that we can get a decent look at it when it passes. Can it impact the Earth? Yes, kindof. Right now, the orbit of the asteroid doesn't bring it close enough to hit us. But there are forces acting on asteroids over time that subtly change their orbits; one of them is called the YORP effect, a weak force that arises due to the way the asteroid spins and radiates away heat. The infrared photons it emits when it's warm carry away a teeny tiny bit of momentum, and they act pretty much like an incredibly low-thrust rocket. Over many years, this can change both the rotation of the asteroid as well as the shape of its orbit."
Re:Photon pressure is a joke. (Score:5, Informative)
Especially when you compare it to the gravitational changes induces by each pass by the Earth/moon system and its pass of Mars and (more weakly) Jupiter.
Each one affects it FAR more than anything from photon pressure.
Yeah, TFS makes it sound like the YORP [wikipedia.org] effect is something significant, but if you read TFA (I know, i know...) you discover that the YORP thing seems to be there to point out: (1) there are lots of very small effects that make long-term predictions for orbits difficult, and (2) one needs to do a LOT of observations to be able to predict all of these factors, but (3) we HAVE an unusually large set of observations on this asteroid (including enough to predict things like YORP effect factors).
Hence, from TFA:
They accounted for a lot of small effects on the asteroid, including the YORP thrust, the gravity of the planets, the gravity of other asteroids, and so on. They found that the probability of an impact [nasa.gov] in 2880 is about 2.48 x 10^-4, which is about 1 in 4000.
I realize that lots of people out there are idiots, and everyone here thinks that they can immediately think of something obvious that no expert doing a study would ever consider... but, you know, sometimes the experts actually have thought of the obvious thing before you posted about it on Slashdot.
Re:Asteroids are a threat - let's deal with them (Score:5, Informative)
This asteroid is only around 1 km in diameter. An impact would be distinctly annoying, but civilization, and most people, should survive.
Re:Photon pressure is a joke. (Score:4, Informative)
"The Yarkovsky–O'Keefe–Radzievskii–Paddack effect, or YORP effect for short, is a second-order variation on the Yarkovsky effect that changes the rotation rate of a small body (such as an asteroid)."
http://en.wikipedia.org/wiki/Yorp
Re:Actually... (Score:5, Informative)
Suppose somebody built a nuclear power plant next door to you that had a 1 in 4000 chance of going critical on any one day. That's a median of 11 years, right?
Yeah, sure. But the thing here is that it's not a 1 in 4,000 chance of this asteroid hitting us every day; it's 1 in 4,000 that it'll hit us once. 800-odd years from now.
1 in 4,000 is a small enough chance to be a virtual certainty over a few hours for events happening once a second - does that mean anything at all to a 1 in 4,000 once-in-a-lifetime chance? No. And this event is not even a once-in-a-lifetime event; it's once-in-several-tens-of-lifetimes.
Or to put it another way: People suck at probability assessments.
Re:Actually... (Score:4, Informative)
Even a common place apendectomy has a mortality rate of about 2% last time I checked.
You must have checked it a VERY long time ago. It is true that the rate of complication is about 2-3%, but the MORTALITY rate (i.e. the number of people that die as a result of the surgery) is
estimated at one to two per 1,000,000 cases of appendicitis
(Source: http://www.surgeryencyclopedia... [surgeryencyclopedia.com])
Not 1 in 50 as a 2% mortality rate would indicate.