PLEASE NOTE:


*

From: Christopher Bassford <cbassfrd@mnsinc.com>
To: Benny J Peiser <B.J.PEISER@livjm.ac.uk>,
cambridge-conference <cambridge-conference@livjm.ac.uk>
Subject: Re: Louis Frank's triumph
Date sent: Fri, 30 May 1997 12:56:24 -0400

Your point, then, I take it, is that we should therefore elect Newt
Gingrich as President?

Chris Bassford

----------
> From: Benny J Peiser <B.J.PEISER@livjm.ac.uk>
> To: cambridge-conference@livjm.ac.uk
> Subject: Louis Frank's triumph
> Date: Friday, May 30, 1997 8:43 AM
>
> from Robert Matthews [The Sunday Telegraph] <rajm@compuserve.com>:
>
> LOUIS FRANK'S TRIUMPH
>
> Before the early 19th Century, anyone agreeing with the claims of
> farmers to have seen stones falling out of the sky was regarded as
> barking mad/fraudulent/ignorant. They turned out to be right.
>
> Before the early 1990s, anyone agreeing with the claims of Alvarez
> et al that the KT extinction was due to a bolide impact was
> regarded as barking mad/fraudulent/ignorant. They turned out to be
> right.
>
> Before May 28th 1997, anyone agreeing with Louis Frank that
> 100tonne comets were constantly dumping water into our atmosphere
> was regarded as barking mad/fraudulent/ignorant. He has turned out
> to be right.
>
> Hmmm....is there a pattern here ?
>
> Robert
>



*

Date sent: Fri, 30 May 1997 08:43:28 -0400 (EDT)
From: Benny J Peiser <B.J.PEISER@livjm.ac.uk>
Subject: Louis Frank's triumph
To: cambridge-conference@livjm.ac.uk
Priority: NORMAL

from Robert Matthews [The Sunday Telegraph] <rajm@compuserve.com>:

LOUIS FRANK'S TRIUMPH

Before the early 19th Century, anyone agreeing with the claims of
farmers to have seen stones falling out of the sky was regarded as
barking mad/fraudulent/ignorant. They turned out to be right.

Before the early 1990s, anyone agreeing with the claims of Alvarez
et al that the KT extinction was due to a bolide impact was
regarded as barking mad/fraudulent/ignorant. They turned out to be
right.

Before May 28th 1997, anyone agreeing with Louis Frank that
100tonne comets were constantly dumping water into our atmosphere
was regarded as barking mad/fraudulent/ignorant. He has turned out
to be right.

Hmmm....is there a pattern here ?

Robert



*

Date sent: Fri, 30 May 1997 08:33:15 -0400 (EDT)
From: Benny J Peiser <B.J.PEISER@livjm.ac.uk>
Subject: WHAT ABOUT DARK SUN-CROSSING OBJECTS?
To: cambridge-conference@livjm.ac.uk
Priority: NORMAL

from: Duncan Steel [SPACEGUARD AUSTRALIA] <dis@a011.aone.net.au>:


A FEW COMMENTS ON THE STORY ABOUT ICY MINI-COMETS IN THE
VERY-NEAR-EARTH ENVIRONMENT: WHAT ABOUT DARK SUN-CROSSING OBJECTS?

A few years back I was considering the "anomalous observations" of
dark objects crossing the face of the Sun as observed by
ground-based observers. A relatively recent example is "Manchester
Mystery Object" (O'Sullivan, Jordan & Bailey, Sky & Telescope, 70,
196, 1985). There have been many such observations recorded
historically, as catalogued by W.R. Corliss (Mysterious Universe: A
Handbook of Astronomical Anomalies, The Sourcebook Project, Glen
Arm, MD, 1979; and The Sun and Solar System Debris, ditto, 1986).
For example, anonymous notes in MNRAS, 30, 135-138, 1870 & Nature,
120, 201, 1927; and F. Hopman, JBAA, 8, 127-131, 1898, and W.H.
Steavenson, JBAA, 31, 107-108, 1920. If one asks regular visual
observers of the Sun whether they see such things, then the answer
tends to be "Yes, of course, but not very often." For example, for
many years Tom Cragg would draw sunspots using his own telescope
sat at the base of the Anglo-Australian Telescope building during
his lunch-hour; I asked him about this topic, and he replied that
over some decades he'd seen such dark, moving spots several times
(I forget how many), and that he had written records somewhere of
two or three.

The question is: what are they? I considered the question a few
years back (for example encouraging Australian amateurs, at their
biennial convention in 1992, to consider making automated video
recordings of solar disk images, later playing them back at speed
to search visually for dark objects passing across the disk). My
idea was that this might be a way to look for near-Earth asteroids
passing close by the Earth. However, when one does the sums (for
angular sizes detectable, hence ranges, hence expected detection
rates) this does not seem feasible/productive: to be detectable in
this way 1 km asteroids need to be closer than about 100,000 km,
and (thank goodness) that does not happen very often; and the Sun
covers only a small part of the sky. (On the other hand there are
advantages of looking for obscurations by low-albedo objects).

One could think about the fragmented mini-comet concept in the same
way, though. The dark solar-transiting objects are observed to
have straight-line motion & take 5-60 seconds or so to cross a
chord of the solar disk. Let us assume that these are indeed
objects in the vicinity of the Earth (at 1,000 - 25,000 km
according to the Frank model/observations), and that their relative
velocity (to the Earth) is just 10 km/sec. For a typical
observation time of 10 seconds crossing the Sun, the observed path
length is 100 km. The solar disk is about 1/120th of a radian
wide, but few pass across the centre, so let's take 1/200th radian
as being the observed path length. This renders a range of about
20,000 km, which is within the limits of the Frank concept. Note
that in my hypothesis here, one would expect most of the fragmented
mini-comets to be seen by solar observers at ranges towards the
upper limits of the Frank range, because (amongst other possible
effects) they are more likely to occur then within the cone defined
by the observer and the solar rim. Since I do not have experience
in viewing such dark sun-transiting spots, I don't know how large
they really are, but (i) From what I've heard and read, 0.5-1% of
the solar diameter seems about right (say 5-10 arcsec); (ii) One
would expect it to be rather larger than the astronomical seeing
due to (a) Heat turbulence; (b) The need to see a small dark
obscuration against a bright background. 10 arcsec is close to
1/20,000th of a radian, so that one arrives at a size of the dark
object of around 1 km at a range of 20,000 km. Now, for reasons
given above I don't think that these dark objects are large solid
lumps of that size (i.e., asteroids/comets) at that range, but it
does seem feasible that they could be Frank's fragmented
mini-comets: co-moving clouds of dust gradually dispersing.

Is there any other evidence which supports this idea? One source
is spacecraft impact measurements of micron-sized dust grains, in
particular those made using HEOS-2, which was in a large,
highly-eccentric geocentric orbit. The dust impacts were found to
come in bursts (dust swarms) as HEOS-2 was near perigee, and not
elsewhere. The suggested interpretation - which has not been taken
up by others, but is still current (I asked Eberhard Gruen about it
a couple of years back) - is that these are produced by large
bodies (the suggested mass was around a ton) which
electrostatically burst as they enter the Earth's Van Allen Belts.
The obscuration (dark sun-crossing object) would be due to the
recently-produced dust cloud from such an object breaking up as
described by Fechtig's group (Fechtig, p.370ff in Comets, ed.
Wilkening, U of Arizona Press, 1982; Fechtig et al., Planet. Space
Sci., 27, 511-531, 1979). I would then be thinking that the
Fechtig et al. HEOS-2 data (dust swarms) are due to passage through
such a cloud when it had been dispersed over a size of a few
hundred km (i.e., large enough to make passage through a swarm
likely; they only observed 15 swarms) but before it is totally
dispersed. I also note that there are other satellite impact
experiments which have delivered data which could be interpreted as
supporting this concept (e.g., Fred Singer's experiment on LDEF),
but the problem is that most dust detection experiments in Earth
orbit have been (i) Inert exposure devices with no time resolution;
and (ii) Performed in LEO, whereas the phenomenon in question is
occurring higher up (HEOS-2 had perigee near 5000 km).

There are two simple experiments which one could suggest to bolster
the above hypothesis:

(i) Observations of dark objects crossing the Sun might show the
spot enlarging & diffusing, and occasionally they should appear
suddenly on the face of the Sun (i.e., eruption beginning; one
might expect this to take less time than the Sun-crossing time of
~10 sec because the dust grains only need to spread by about 1 km);

(ii) Two observing sites separated by about 10 km should show
significant parallax effects (range 20,000 km gives parallax of 2
arcmin cf. solar diameter 31 arcmin).

How often would one detect such a dark spot? Using figures given
above, a 100 km path length defines a circle of area equivalent to
0.000002 (2E-6) of a hemisphere of radius equal to the Earth's
radius plus 20,000 km. If the whole-Earth rate is 5 to 30 per
minute (as per Frank's hypothesis) then if one watched the solar
disk for an hour there is about a one in 1000 chance of detecting
such a dark sun-crossing object, if indeed these are dust clouds
produced by the disruption of Frank's mini-comets. To me that
sounds plausible: one has to watch the Sun for a long time to stand
a reasonable chance of spotting one, so that such observations
would be infrequent.

The question could of course be asked whether professional solar
patrols detect such events; when I made enquiries along these lines
a few years back the consensus was that if such short-lived, small,
dark spots were crossing the solar disk, then most likely the data
acquisition employed would mitigate against their detection. That
is, likely they would not have been noted - but this is a question
for experts in the solar patrol field. I am reminded of the
comments by Hermann Bondi (QJRAS, 443-450, 1970) in which he
made a plea for what he called "short-time constant astronomy",
emphasizing that astronomical research was moving towards long
integration times and therefore perhaps missing phenomena which
have short durations. This may be a good example.

Why are these putative dust clouds crossing the Sun not seen also
at lower altitudes by solar observers? Answers could be (a) They
have larger angular speeds therefore not noted, and less frequent;
(b) The cloud is more widely dispersed by the time it gets below
~5000 km, so that the dark spot effect no longer occurs. The dark
UV spots reported by Frank et al. from earlier satellite data
(looking down) were 40-60 km sizes, putatively due to water vapour
dispersed from the fragmented mini-comet; it would be expected that
the vapour would spread wider and faster than the dust.

Another question is that of the total mass influx. If these
mini-comets have masses of around 10 tonnes and a flux as claimed,
then the total influx to the near-Earth environment, averaged over
a year, is about three orders of magnitude higher than the standard
_meteoroid_and_dust_ influx measurements from space exposure
experiments (Love & Brownlee, Science, 262, 550, 1993),
micrometeorite collections in ice packs (Maurette et al., Nature,
328, 699, 1987) and radar meteor measurements (Thomas et al., J.
Atmos. Terr. Phys., 50, 703, 1988). These methods sample the flux
in LEO (around 600 km for LDEF), onto the Earth's surface, and into
the atmosphere, respectively. As aforementioned, few spacecraft
impact detectors have been operated above LEO (see notes on HEOS-2
above) . If Frank's mini-comets are disrupting much higher up, and
they are mostly water and other volatiles, and only a small
fraction of the mass is comprised of dust and heavy organics
reaching LEO and lower, then the various measurements _may_ be
reconciled.

Supporting evidence for the general picture comes from my own radar
meteor observations (in collaboration with Graham Elford and
others) over the past several years: we see many meteoroids
ablating at 100-140 km (previously undetected) and so far as we can
work out, these can only be made of heavy organics. Previous radars
were detecting only the lower-altitude (refractory, asteroidal)
3-4% of all incoming meteoroids in the microgram-milligram range
(where the majority of the mass of the 40 kton/yr influx occurs).
For example, Steel & Elford, J Atmos Terr Phys, 53, 409-417, 1991;
plus Taylor et al., Adv Space Res, in press; and the Thomas et al.
paper cited above.

There are, of course, many remaining objections to the hypothesis
which could be mentioned. For example, why are these disrupting
mini-comets not seen by the many amateur astronomers who search for
(large "proper") comets in the few hours before morning, and after
evening, twilight? Should they not be visible, given the ease of
satellite visibility out to similar ranges (note that Frank assumes
a very low albedo for the mini-comets, but the question remains).

All very interesting stuff.

Duncan Steel



CCCMENU CCC for 1997

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