Detection.

==**There are many ways to detect these things like satellites that go up to 38000KM in altitude they use infrared sensors scan the earths disc every 10 seconds, which is very fast, it aslo makes shore we are safe. Also there is a space guard in Arizona USA where they use telescopes up to 2.5m long this telescope is quite slow David Morrison(mathmatician) predicts that it would take 25 years for it to see 90% of the worlds asteroids. Dection of Asteroid,Meteorites and Comets is very expensive a deticated centre would coast around $50million and a additional $10million per year to run the telescopes.**==

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