Re: Asteroid, invisible

[Gary Turner <turner@MORNINGSIDE.EDU>]

> When it passed
> closest to the Earth - just 1.5 times the distance to the Moon - it was
> too close to the Sun to be visible. Asteroids approaching from this
> blind spot cannot be seen by astronomers.

That sounds like a long way - its 375 000 miles.

However, think about that in terms of time.  The Earth moves at a speed of
about 70 000 miles per hour, so it missed by a little over 5 hours.  Floats
around for 3 or 4 billion years and misses by 5 hours.  Thats like driving
a half hour to a meeting and being late by ~10 nanoseconds.

[Of course, this is assuming the very unlikely event that it passed through
the orbital plane at closest approach.  It probably passed through the
orbital plane elsewhere, but its still a useful analogy when someone says -
 "but that's so far away"]

You could use the same analogy to show that the Tunguska event would have
hit Eastern Russia or Europe if it had been just 4 minutes later.