So you think global warming is a big problem? What could happen if a 25-million-ton chunk of rock slammed into Earth? When something similar happened 65 million years ago, the dinosaurs and other forms of life were wiped out.

"A collision with an object of this size traveling at an estimated 30,000 to 40,000 mile per hour would be catastrophic," according to NASA researcher and New York City College of Technology (City Tech) Associate Professor of Physics Gregory L. Matloff. His recommendation? "Either destroy the object or alter its trajectory."

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