Expert: Tom Whiting - 1/29/2008

Question
We all fear of falling meteoroids. So why don't we send up rockets that will follow these meteoroids that have chances to impact on earth, and attach to them and then fire the rockets so that the meteoroids will change course, even if it's just a slight variance?

Answer
Hi Abe....
Great suggestion, and I'm sure that NASA has already
considered doing this, along with high explosives,
nuclear bombs, and other orbit-altering devices.

Realize though, that right now, there is no good sized meteoroid currently on course to impact the earth. So, don't lose any sleep over it...it only happens, depending on the size, once every few thousand years, and we just took a hit back on June 30, 1908 in Siberia, the Tunguska Event (Google it). So the next is probably centuries away.

The key phrase to your suggestion is "attach to them"...(?)
These meteoroids don't come furnished with steel or cement
posts drilled down into their cores that you can attach
anything.  So we send a crew of engineers, cement
workers, and well drillers out to the asteroid ahead of time, costing trillions of dollars....to install deep well steel posts in the ground?  And most of these meteoroids are nothing more than flying gravel piles with no consistancy to them.  Then there's the time factor...how
much time before impact?? From discovery to impact, you
may not have that much time.

So there are other ways that are far less expensive, like
impacts or explosions...yes, even with nuclear weapons...
that are more economical in nature.  But even before that,
you have to be absolutely sure that there is going to
be an impact to begin with, otherwise all your work might
actually put you in more harm than before.  And right now,
with our technology, we don't as yet have a good handle on
that one.  In fact, we can only work in probabilities of
impact, rather than know for absolutely sure.
So when even the slightest doubt exists, it's best to do nothing according to the odds, because the odds are that any given meteoroid is just going to have a near-miss, as that is what almost always happens. Remember, real space
is 3 dimensional.

Don't lose any sleep over it because the Earth is a very
small, fast moving target, traveling at 18.5 miles per
second around the sun. So we move our own diameter (7960 miles) in space every 7 minutes.  So a potential impacting body has to not only be at the right distance from the sun, AND BE crossing either up or down thru the Ecliptic (our orbital plane)..it has to be ON TIME within that 7 minute period, otherwise it is a near miss.  All 3 factors have to occur at the same time, otherwise a near-miss occurs.

It would be equivalent to you in a light plane, the passenger side, hanging out the door with a .22 calibre
rifle, shooting a rabbit running across a field at top
speed, while your airplane pilot has you in a screaming
dive from 5000 feet down onto the field.  As he pulls out
of the dive at 500 feet, you have one shot, and only one shot at that running rabbit. How many rabbits do you think you'd hit? Oh, and you're only allowed to do this
maneuver once every 100 years! So it could be many many centuries before one would actually hit a rabbit under those circumstances, and then you'd probably only wound him, not kill him.  That's the equivalent of us taking
even a moderate (city killing) strike. And even when it
does eventually happen, there's a 70% chance it will hit
in the oceans, as 70% of our planet is water on the surface.
Hope all this helps,
Clear Skies,
Tom Whiting
Erie, PA