What astronomical event provoked the search of Near Earth Objects?

Answer 1

Even as late as the America Revolution in the late 1700's, the idea of meteors was not widely accepted. Thomas Jefferson wrote that he would rather believe that a Yankee scientist would lie, than that rocks could fall from the heavens.

But over the past 200 years, we have come to accept the idea that rocks DO fall from the skies, and we all know that falling rocks HURT. So perhaps, if a falling rock was big enough, it might cause a lot of damage?

As late as the 1970s, scientists did not believe that meteoric impacts could pose an existential threat to humanity; that is, could threaten the very EXISTENCE of the human race. But Luis Alvarez hypothesized that a massive enough body, impacting the Earth at orbital velocities, could radically re-shape the Earth. And then he discovered sufficient evidence that 65 million years ago, such an event HAS HAPPENED. And now most people believe that the dinosaurs went extinct because an asteroid about 6 miles in diameter impacted what is now the Gulf of Mexico just off the Yucatan Peninsula.

And if it could happen once, it could happen AGAIN. In 4 billion years, it WILL happen again.

And if if..... WHEN it does, life on Earth will die. Unless we can prevent it.

So scientists over the past 15 years or so have started watching for large objects that might have a potential to someday collide with the Earth. We haven't found one yet - but we've found several that have come fairly close. In early October, 2009, an asteroid a half-mile long passed closer to the Earth than the orbit of the Moon, and in 2029 the asteroid Apophis will come closer to the Earth than a communications satellite.

There are some other dismal thoughts floating around. Many great scientists have wondered, "Where are the other intelligent races in the universe?" and "What if all the other intelligent races in the universe were destroyed!?!?" and "Are we NEXT!?!?" What if the average intelligent race in the universe is destroyed by a cosmic impact?

And so scientists have started watching the skies for objects that might pose a hazard. The odds of such an impact are very low - but the potential damage of such an impact are terribly high. So we are right to start preparing.