PLEASE NOTE:
*
CAMBRIDGE-CONFERENCE DEBATES, 21 April 1998
-------------------------------------------
This is my first attempt to use the University's newly installed
Microsoft Exchange e-mail programme for the CCNet (that's also
why I've
re-subscribed all 250 list members). I have been told that this
programme is more reliable than the old one which failed quite
frequently. Please be so kind and let me know should you
experience
problems with this or any future mailings. I only hope this is
going to
work. Let's see ....
Benny
=============================================
(1) "DEEP IMPACT" ACTOR TELLS IT ALL
Clark Whelton <cwhelton@mindspring.com>
(2) SPACEGUARD IS ABOUT REDUCING THE CURRENT UNCERTAINTY
Oliver Morton <abq72@pop.dial.pipex.com>
(3) PROBABILITY STATISTICS MAKE ME FEEL LIKE I'VE BEEN KICKED BY
A MULE
Bob Kobres <bkobres@uga.edu>
============================
(1) "DEEP IMPACT" ACTOR TELLS IT ALL
From Clark Whelton <cwhelton@mindspring.com>
Several scenes from "Deep Impact" were shot in
Washington Square Park
in New York City, which happens to be directly adjacent to my
apartment. I wandered outside to see what all the fuss was about
and
was immediately asked to participate in the filming of a scene in
which
panic-stricken New Yorkers abandon their cars and taxis on Fifth
Avenue
in a desperate effort to escape a giant wave that's sweeping over
the
city. When the director shouted "Action!" I took off
through the park
at top speed, while wind machines created a whirlwind of dust and
paper
around us. After several takes, the director shouted,
"People, please!
No smiling! A huge wave is about to drown you! Look
scared!" Everyone
giggled. "And remember," he continued, "this could
happen tomorrow!"
The giggling stopped. We all looked at each other, then up Fifth
Avenue
to make sure a wave wasn't already on the way.
"Action!" This time we
got it right.
=========================
(2) SPACEGUARD IS ABOUT REDUCING THE CURRENT UNCERTAINTY
From Oliver Morton <abq72@pop.dial.pipex.com>
At 18:01 +0100 17/4/98, Mark Bailey wrote:
>The public, after all, are quite used to
>astronomers disagreeing whether there is, or is not, life on
Mars;
>whether the Universe is open or closed; whether for example
the latter
>emerged from a `pea'; and whether the dark matter is mostly
`hot' or
>`cold'. Astronomers disagree about many things --- which is
the sign of a
>healthy and vital area of science.
which was spot on. He also wrote:
>A subliminal message has therefore got across, to the effect
>that Spaceguard is likely to be a waste of time, since in all
probability
>it will merely `certify' the present NEA population as
benign. Of course,
>writing somewhat imprecisely, the probability of a large
asteroid hitting
>the Earth within the next 100 years is either zero or unity;
the
>situation is not affected by whether or not we mount a
Spaceguard Survey,
>or even whether we eventually discover all the present
population of
>Earth-crossing objects or NEOs (including cometary
asteroids).
There is indeed a presentational problem here. My preferred
approach is to
be clear that the issue is the risk due to unknown NEOs. At the
moment, the
risk of death due to an unknown NEO is, say, one in 20,000 over a
lifetime.
That is large enough to worry about. The purpose of a
spaceguard-like
survey is to reduce that risk from unknown NEOs to something more
like one
in 100,000 or further. At that point it seems to fall below the
threshold
for reasonable policy making. It is this change in the assessment
of the
risk which is worth paying money for: we are paying in order to
stop
worrying.
On top of this, there is also a very small chance that such a
survey will
increase the risk from known NEOs, currently zero. At that
point we live
in a different world and change our actions accordingly. However,
we would
still have reduced the risk from unknown NEOs.
This is why talking about spaceguard as insurance is not quite
right;
spaceguard is about reducing the uncertainty in a specific risk
calculation.
This may strike some of you as sophistry -- it does me, sometimes
-- but I
think it is in fact somewhat clarifying. Policy makers are used
to the
notion of paying to reduce uncertainty.
Oliver
==============================
(3) PROBABILITY STATISTICS MAKE ME FEEL LIKE I'VE BEEN KICKED BY
A MULE
From Bob Kobres <bkobres@uga.edu>
I must say; these Poisson statistics Duncan keeps bringing up
sure seem
tied to some old half-ass observations. Makes me feel like I’ve
been
kicked in the head by a mule(* see below).
That’s the problem with using probability statistics to
convey impact
risk to people — the numbers carry almost no data useful to
the casual
consumer of information on this subject. I’ve used the term
‘statistically overdue’ from time to time just to
effect a feeling of
contemporary danger, however I generally emphasize the fact that
these
numbers actually tell us nothing about when to expect the next
impact
because they would be the same even as a PHO entered our
atmosphere.
My preference is to express the situation like this:
If we do not develop a defense system there is a 100% chance that
Earth
will sustain an environmentally disruptive impact in the future.
If we
do effect a defense system and prove its utility by nudging a few
examples (safe ones first—not PHOs for a while) we will have
a better
than 99% likelihood of being able to prevent all dangerous
objects
from harming our environment. Plus, there is the added benefit of
our
more rapidly developing an industrial infrastructure in space
than we
would be apt to in the absence of such a threat. This enhanced
space
development factor alone can be expected to rapidly reduce some
of our
own recent negative impact on Earth’s environment by
affording the
opportunity of moving harmful industrial activities out of the
biosphere.
Though I can but hope that a 99+% effectiveness is achievable, I’m
damn certain that the first assessment of risk is correct!
Persevering stubbornly.
bobk
*) Recherches sur la Probabilité des Jugements by French
mathematician
Siméon Denis Poisson, 67, establishes rules of probability based
on the
incidence of death from mule kicks in the French army.