The end of the world is getting nearer and nearer, hurling towards us at over 25,000 miles an hour. The current assumption is there is a 10% chance per century of a dangerous, life destroying space object striking the earth.

Apophis is small by asteroid standards, perhaps 300 meters across, but it could hit with about 60,000 times the force of the Hiroshima bomb– enough to destroy an area the size of France.
Quotation from The Atlantic, The Sky is Falling by Gregg Easterbrook

If Apophis is a RETROGRADE rotator on the small, less-massive end of what is possible, the measurement uncertainty region will get pushed back such that the center of the distribution encounters the Earth’s orbit. This would result in an impact probability much higher than computed with the Standard Dynamical Model.
Quotation from U.S. National Aeronautics and Space Administration (NASA), Near Earth Object Program, Predicting Apophis’ Earth Encounters in 2029 and 2036.

The risk of collisional cascading is called Kessler’s Syndrome. When U.S. and Russian satellites collided in space this week, more than 600 bits of debris joined 18,000 other objects orbiting our planet. These artifacts, including rockets, satellites, bolts, screws, pieces of titanium and paint flecks, travel faster a bullet. They pose a danger to other space vehicles, including the International Space Station. Kessler’s Syndrome describes a situation where each collision causes more debris which causes more collisions, until it is unsafe for anything to orbit the earth.

Houston, We Have a Trash Problem (Wired Magazine)
Lottie Williams of Tulsa, Oklahoma reported that she was struck on the shoulder by space debris (Center for Orbital and Reentry Debris Studies)

Space isn’t remote at all. It’s only an hour’s drive away if your car could go straight upwards.
Quotation from Sir Fred Hoyle