...that's when Asteroid 1950 A has a 1-in-300 chance of hitting earth.

http://www.telegraph.co.uk/news/worldnews/northamerica/usa/11037247/Huge-asteroid-set-to-wipe-out-life-on-Earth-in-2880.html

I thought I remembered the orbit had been recalculated based on more detailed data, so I looked it up. Turns out the latest guestimate by the boffins is about one in 4000. Or so says Wiki.

The Telegraph is not to be regarded as a trusted source. Might as well watch Hannity on Fox.

Thank you. My bad. Appropriately red-faced now.

NASA also gives a good explanation of the true odds:

http://neo.jpl.nasa.gov/1950da/

The relative effect of error source and certain known and unknown dynamics on the nominal along-track position intersecting the Earth are shown below, normalized in units of numerical integration noise. This expands on Table 3 of the published paper.

  Parameter                                       Relative Along-track Effect  ----------------------------------------------- -----------------------------------  Solar particle wind                                    0.001  Galilean satellites                                   -0.333  Galactic tide                                         -0.833  Numerical integration error (128-bit vs. 64-bit)      -1.000      (9900 km, 12 min)  Solar mass loss                                       +1.333  Poynting-Robertson drag                               -2.333  Solar oblateness                                [   +4.08, +1.75]  Sun-barycenter relativistic shift                    +81.0        (inc. in nominal)  61 most perturbing "other" asteroids                -144  Planetary mass uncertainty                      [ +132,  -156]  Solar radiation pressure                           -1092  Yarkovsky effect                                [+1152, -6924]

Numbers in brackets indicate a range of possible values due to poorly known physical parameters. These factors together reduce prediction window extent from 2880 to 2860 (-20 years, or -2.3%)

______

Thanks to NASA's good explanation (tip of the hat to AS), my understanding of the matter is ever so much clearer now.

Thanks to NASA's good explanation (tip of the hat to AS), my understanding of the matter is ever so much clearer now.

One would have thought you knew better than to stray beyond the first paragraph of papers such as these.