Don Lincoln is a physics researcher who studies the laws of nature. He is the author of several books, including "The Large Hadron Collider: The Extraordinary Story of the Higgs Boson and Other Things that Will Blow Your Mind." Follow him on Facebook. The opinions expressed in this commentary are his.

(CNN) Chicken Little was right. In a very literal sense, the sky is falling. Not today and not tomorrow, but eventually. NASA has announced that on September 22, 2135 (which happens to be a Thursday, if you need to check your schedule), there is a small chance an asteroid a third of a mile across (named Bennu) will slam into the Earth with an impact energy equivalent to the currently deployed arsenal of US nuclear ballistic missiles.

Needless to say, if that happens, it will definitely be a bad day for everyone.

Don Lincoln

But, not to worry, NASA has a plan. In a theoretical exercise, a team of engineers devised a conceptual design of the Hypervelocity Asteroid Mitigation Mission for Emergency Response vehicle, or HAMMER. It is a hypothetical spacecraft that could either ram into Bennu or target it with a nuclear device, either of which it is hoped would deflect the asteroid away from Earth.

HAMMER is not an actual NASA program, but rather an investigation into the technical challenges that would arise in building such a device. The 1998 movies "Armageddon" and "Deep Impact" were dramatizations of broadly similar efforts.

While it is rather unlikely that Bennu will actually hit Earth, it is inevitable that eventually a similar one will. The probability of an impact is high for smaller rocks and decreases rapidly for larger asteroids.

Read More