Only 10% of meteors more than 150 yards wide -- dubbed "potential city killers" by Holdren -- have been detected, meaning more than 10, 000 are out there without our knowledge, he said.
In its journey through space, Earth is bombarded by a hailstorm of comets, meteors and asteroids.
By comparison, meteors of the type that hit Russia originate at the earliest reaches of time in the disk of gas and dust that swirled around the early sun.
However, the detection efforts have been less successful for smaller meteors still capable of causing major loss of life and damage, such as the one over Russia.
Early research involved a colleague lying in a deckchair in the night-time open air with a piece of string to measure the meteors, while he observed electromagnetic signals on a cathode-ray tube in a nearby hut.
Meteors are a prime example of a worry-inducing event: vividly imaginable, highly publicized, novel, undetectable in advance, uncontrollable, potentially catastrophic, involuntary.
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Stargazers under this kind of night sky might see 30 or more meteors per hour.
Using NASA's WISE infrared satellite, astronomers estimate there are about 5, 000 known meteors that can impact the Earth with sizes of about 100 feet or larger -- that is, larger than the Chelyabinsk meteor.
Scientists have charted about 500 meteors near the Earth's orbit and estimate that 100 of those are potentially dangerous.
In the far distant past, immense meteorites meteors that slam into Earth likely contributed to the demise of the dinosaurs.
Though meteors from Halley's Comet can be seen at this time of year, he said it did not come from the comet.
At least two meteors broke up and collided into a zinc factory in the city outskirts, part of its concrete wall in shambles.
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