Question

why is there a lesser warning for when a comet is going to hit earth than when an asteriod is going to hit earth?

Answer 1

Comets are smaller bodies and do not become visible until they are close enough to the sun to form a tail

Answer 2

yes that makes sense..so since the comet's tail moves in the opposite direction when nearing the sun, thats the only way NASA can detect its presence near earth...AND moreso, it seems like the comet doesnt dwell in the solar system, its as if its just passing by..

Answer 3

Astronomers can detect comets far out in the solar system, and work out their orbits, without seeing their tails. However, comets though are harder to prepare for, since many of them are on very long orbits, and new ones come into the solar system each year, so one could always surprise us with an impact course. Asteroids on the other hand orbit within the inner solar system, and so are easier to track and hence know their positions for many years into the future, and we know of no asteroid of significant size on an impact trajectory, though there are small concerns over the asteroid named Apophis which is due to make close approaches in 2029 and 2036, which has a very very small chance of impact in 2036 if it passes through a "gravitational Key hole" in 2029 http://en.wikipedia.org/wiki/99942_Apophis.

Answer 4

JONNYMCA YOU ARE RIGHT..I HAVE HEARD OF APOHIS...I BELEIVE ITS WHAT SCIENTISTS HAVE THEIR EYE ON NOW. ABOUT THREE BASEBALL FEILDS...MAN IF SUCH AN OBJECT HIT EARTH, THERE WUD BE DARKNESS AND DEVASTION 100 TIMES THE IMPACT OF THE ASTERIOD THAT DESTROYED THE DINOSOURS..WHAT A THOUGHT!!!!

Answer 5

Not true. The impact that killed the dinosaurs is thought to be between 10-15 kms in size. Apophis is less than 1 km in size its about (0.35-0.5 km in size) Since impact energy scales with mass, and mass scales with size (it scales with the radius cubed), then assuming impact speeds are equal, the K-T impact 65 million years ago would impact with about 10,000 times the energy of Apophis.

If Apophis does colide with us, then its impact energy will be in excess of 1000 times more than the 1908 Tunguska blast (based solely on size, since I dont know the respective velocities, and assuming equivalent densities). It wont be likely to destroy global civilisation, but it will be bad news for any country it hits, or if it impacts mid ocean. But it certainly wont be worse than the K-T impact.