Well, at least gravity hasn’t been disproved today. The defunct Upper Atmosphere Research Satellite is expected to return to earth on Friday, and NASA says the debris could spread across 500-miles. Problem is, no one knows exactly where it’s going to land.

As of 9:30 p.m. EDT Sept. 22, 2011, the orbit of UARS was 110 mi by 115 mi (175 km by 185 km). Re-entry is possible sometime during the afternoon or early evening of Sept. 23, Eastern Daylight Time. The satellite will not be passing over North America during that time period. It is still too early to predict the time and location of re-entry with any more certainty, but predictions will become more refined in the next 24 hours.

A few things expected to survive the burn-up include four steel flywheel rims, a 350-pound aluminum structure, and four titanium fuel tanks. Depending on the shape and size of the junk, their speed of impact will be between 55mph and 240mph.

[Via NASA]