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Hank tells us about NASA's Near-Earth Object Program, which tracks the paths of asteroids and categorizes them according to the likelihood that they will strike the Earth at some point in the future.

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Hank: You know what I'm really glad exists?  Like besides my family, and hot pockets, and They Might Be Giants? NASA'a Near-Earth Object Program

(0:08) Intro music

Hank: The NEO collects data from astronomers around the world who track nearby asteroids and calculates the asteroids' paths and ranks them by risk so we don't have to.  Threats are ranked from 0 to 10, 0 meaning don't bother worrying and 10 meaning don't bother getting out of bed.  

Hank: The highest rating ever assigned was 4, when asteroid 2004 MN4, aka Apophis, was given a 1.8% chance of hitting the earth in 2029.  But to show you how quickly things can change in the asteroid tracking business, once astronomers projected all of the other bodies that Apophis would interact with in its travels, the NEO realized that the probability of impact was more like 0.00074%.  So it's okay.  

Hank: So like almost all of the thousands of asteroids that NEO tracks, Apophis is now a 0.  And yeah, I said almost.  There's still 2007 VK184, it's about 130 meters across, plenty big for it to burn through our atmosphere and have enough left to wreak some serious havoc.  It's actually swinging by in 2014, but that's not the problem.  NEO says that when it returns on June 3rd, 2048, its chances are 1 in 1,820 that it's going to punch the Earth right in the face.  Still that's just a 0.055% chance.  

Hank: Then there's 2011 AG5.  It's slightly bigger, about 140 meters across and on February 5th, 2040, NEO figures the odds of a collision are 1 in 500, or a 0.2% chance.  The good news is that AG5 comes by every few years, so we've got a lot of opportunities to observe its path more and refine our predictions.  In fact when it comes by in 2023, we already know the exact path it has to take if it's going to hit us the next time around.  

Hank: Astrophysicists call this a keyhole.  It's the area through which the object would have to travel for the Earth's gravitational pull to sort of pull it into a collision course when it returns in 2040.  And in the case of AG5, the keyhole is only 360 kilometers wide, which seems kind of big but not when you're space.  AG5 finding its way through that narrow of a keyhole seems about as likely as bouncing a beer pong ball in New York and having it land in a solo cup in London, which is why both of these asteroids are still ranked at a lowly 1.  

Hank: But there is one asteroid of interest that's not on NEO's lists, only because its possible threat is centuries away.  Asteroid 1950 DA has been freaking people out for decades because it's more than a kilometer across, big enough to cause planet-wide, extinction event level destruction.  And it also has the highest impact probability so far.  As worst, 1 in 300 or 0.33%.  

Hank: Thing is, our rendezvous with 1950 DA won't happen until March 16th, 2880.  And by then, my descendents and your descendents and the descendents of They Might Be Giants will probably be enjoying hot pockets on colonies far away, so either way, it'll be okay.

Hank: Thank you for watching this episode of SciShow.  I'm so glad that I could help deliver you the good news that we're not all about to die as the result of an asteroid impact.  If you want to know more you should subscribe and if you have questions leave them in the comments below or contact us on facebook or twitter.  

*outro music*