Expert: Tom Whiting - 12/21/2008

Question
QUESTION: Hi again I recieved an answer from  another expert who said the big stuff happens about 10.000 years and that if an asteroid were detected we could send rockets to change its course.
Is this reallistic? and what are the chances we would know about it ahead of time.mot7e

ANSWER: Hi Jane,
Yes, I saw that communication too, as we typically read each other's
answers. And of course, we all have sometimes slightly differing
opinions on subjects that are very subjective. Which this one is.

The fact remains that had Reagan's SDI program not been shot down
in Congress in the early 1980's....and I'm not talking about the particle laser or space-maser portion of that concept...we would have still been much farther along in an anti-missile rocket defense system today, than what we are. (From the intercept missile standpoint, not the 'starwars' standpoint)....And thus have a much better capability today, of confronting a known incoming. But I guess
this country would rather spend billions of dollars bailing-out/paying off....rich Bank Executives and Car Companies that screwed up, rather than build an effective missile/asteroid anti-missile system.  (Which would have employed thousands of American workers to build the system, but that's another story).
(When NASA launches a rocket into space, we don't send 'money' into
space; the money goes to pay American workers to design, BUILD and test, the equipment!)

That being said, in all honesty, no one really knows if or when the next major asteroid impact will be...we only know from 'recent'
(say the last 100 million years) past history what an average
frequency is.  The chances are about 85% of knowing about a potential
threat ahead of time...how far ahead of time is another question.
There is always that 15% chance that an incoming would be coming
at us from the solar angle, from the direction of the sun, in which
case the body strikes without warning. This was the case in 1908
with the Siberian Tunguska event...but even if we would have had an advanced warning of it, the deflecting missiles and nuclear weapons to intercept, did not exist back then.
Also, the time frame depends on what size of body is being debated.
Yes, Tunguska events can vary from 1000 to 10,000 years. But a major
6 mile wide body or larger, is in the tens of millions of years.
Tunguska was not considered a major extinction event.

But hey, there are threats all around us....a deadly new viral disease could spring up and with our modern transportation system,
spread around the world in a matter of days, annhilating
most of the population. Do you worry about that happening too?
(Read the book "Earth Abides" by Stewart). A supernova or GRB could explode nearby. A nuclear war (say India/Pakistan) could start....we can't live our lives worrying about each and every major disaster...at least, I can't.
Besides, if it happens, it happens, and you just do the best you
can to survive; that's all we can do. At least, as I said before,
at least we are doing something in tracking down every major
Earth-crossing body for a possible future warning. What else can
we do?  Since this is a major interest of yours, maybe you can offer
more suggestions of what more can we do.  At least the very rare
problem now has our attention, and give us credit that we are
at least doing something about it, no matter how rare the event is.
Clear Skies,
Tom Whiting
Erie, PA





---------- FOLLOW-UP ----------

QUESTION: Thank you for your answer. I just also wondered if nasa had tracked 90% of large neo's as I have read that this was something they said they would do in 1998.

Answer
I really don't know what the percentage is (does anyone really
know for sure?) but I know we just passed over logging and tracking 1000 NEA's this past month, see
http://www.spaceweather.com
at the bottom of the home page, 1010 I believe.

We can estimate that there are zero 100 mile or greater asteroids in our vicinity, maybe a couple from 10-100, and an unknown but small amount from 1-10 miles across.

To further ease your mind, remember all these bodies are at an
angle to the plane of the ecliptic, so to impact the Earth, they
have to not only be on target from left to right, but UP to DOWN
too, passing thru the plane of the ecliptic, otherwise they pass over or under the Earth.
FURTHERMORE, the Earth is moving at 18.5 miles per second around the sun, thus we move a distance of our own diameter every 432 seconds, or around 7.2 minutes.  SO, a potential body has to not only be
lined up left and right AND up and down, passing exactly thru the
plane of the ecliptic, IT also HAS be ON TIME, meeting all those
above requirements, within a 7.2 minute time span!!... otherwise....it's a near miss; ie..it passes ahead of us or behind us.
 
The Earth is a very fast moving, small target to hit, equivalent to you hanging out of the passenger door of a  Cessna 172 aircraft, steeply diving on a running rabbit in the rolling field below, at 140 miles per hour in the dive, you have one shot, and only one shot (with your 30-30 rifle) with the wind in your face (solar wind), at hitting that fast moving rabbit at a distance of 100 yards high (300 feet)as the pilot is beginning to pull out of the 140 mph dive.
(And no fair aiming the gun...you just have to point and shoot...
no 'sighting him in' using the gun sights...because that's what asteroids are doing; they aren't 'aiming' for us either; they are
just there!)  You can only point....and fire....once!
What are the chances of you hitting (let alone killing) the fleeing rabbit with only one shot out of your 30-30 rifle under those conditions? Pretty slim.  And you're only allowed to take that one shot every 100 or 1000 years. As you see, it would take many centuries to hit the rabbit, and the odds are you're only going to wound him (in the ear, foot, tail, etc) and not outright kill him.  We are in the exact same position as that long living rabbit, and the shooter is the 1 mile wide range of asteroids. So there is a
good analogy for you to think about.
Clear skies,
Tom Whiting
Erie, PA

PS That's why we who are in this field, don't lose any sleep over
....Hollywood induced, killer asteroids.