Hi
All,
A
couple inputs on the future-large-impact subject. Dirk Ross
opined:
>
NO GOVERNMENT in its right mind would give advance warning
even
> if scientists do detect the object in time.
Whether the "government" chose to provide advance warning or not,
nearly
everyone with a computer would know, and thus I feel confident that
most
governments WOULD make a formal statement, if only for fear of
being
accused of withholding information that could have saved
lives. How would
everyone with a computer know? Because there are a large
enough number
of
amateurs with good equipment that are perfectly capable of
making
asteroid measurements themselves and computing orbits, and they
are
not
the sort of people that would keep quiet about
it.
When a
suspected NEO is detected and its astrometric measurements
are
sent
to the Minor Planet Center, a preliminary orbit is computed and
quickly
made
publically available on the NEO Confirmation Page. This is to
facilitate
recovery of the object by other observers with
the goal of improving the
accuracy of the orbital solution. Naturally, the more measurements
you
have
from different locations, and the longer period of time those
measurements
span, the better the solution. If it turns out that impact is
only a few days to
a week
away, it won't take long to compute a fairly accurate time and
location
of
impact. This knowledge can definitely save lives, just as a tornado
or
hurricane warning can.
On the
subject of the aftermath of a large impact -- specifically the duration
of
"nuclear winter", Stan wrote:
> "In the
event of a large impact, we would need to build an enclosure
that
> protects food crops
from the environment, and provides an alternate source
> of energy to the crops. Rice isn't going to grow if the
sun is blacked out for
> 1000 years because of a comet
induced nuclear winter."
An
impact that doesn't kill everyone and everything within hours should
not
have
effects lasting anywhere near that long. Months to a few years, I
would
guess, depending on the size and velocity of the
impactor. It's a very difficult
thing to
estimate since the only contemporary, large energy releasing
events
we have to compare to are many orders of magnitude
smaller in energy.
Krakatoa's four
explosions on August 27, 1883, for
instance, are estimated
to have released the
energy equivalent of around
200 megatons of TNT.
They
gave us red
sunsets for more than a year
and lowered global temperatures as
much as 1.2
C.
The only modern events
that can provide some insight were the Shoemaker-
Levy 9 impacts on Jupiter. The 2- or 3-km diameter G-fragment hit
with the
energy of 6 billion megatons (30 million times
the energy of Krakatoa!) The
black spots from these
impacts are long gone, but perhaps
there are other
still measurable effects from these
impacts today.
(Anyone?)
--Rob
