What Wiped Out The Dinosaurs?

Nearly all of us now know--or think we know--how the dinosaurs perished: some 65 million years ago, a giant asteroid or comet struck the earth, spewing huge amounts of dust and debris into the air. That dust, according to a widely accepted theory first proposed by Nobel laureate Luis Alvarez, was circulated by the winds and enshrouded the earth for months, blocking sunlight and causing temperatures to plummet. As a result, the dinosaurs, and 70% of all other terrestrial species, were wiped out.

But this scenario was rudely challenged last week by Kevin Pope, a former NASA scientist. Reviewing recent studies...

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