Despite what Hollywood tells us, stopping an asteroid from creating an extinction-level event by blowing it up may not work.

In a simulation, material smashed away from an asteroid following a collision is attracted back to the object by its gravity.CreditBy Charles El Mir/johns Hopkins University
Faced with the prospect of a sizable asteroid heading toward Earth and causing doomsday, humanity has come up with various responses.

Hollywood may reckon that the best way to destroy an errant space rock is with nuclear weapons. This is rarely the preferred option of experts, but using some sort of spacecraft system to smash an asteroid into small, harmless pieces is seen as a real-world possibility. A new study, looking at a gigantic space rock-on-space rock clash, hints at how utterly ineffective this type of asteroid assassination attempt may be.