1991 VG: Man-made Object or Alien Probe? - Article
James Nicoll + Jasmine
John Stepkowski <leg...@werple.mira.net.au> wrote:
snip
> Of Asteroids and Aliens
>
> By Dr Duncan Steel
>
> This article is a pre-emptive strike. In a scientific journal called
> _The Observatory_ will appear shortly a paper in which I make the
> suggestion that an object observed in the Earth's vicinity
> (astronomically-speaking) in late 1991 was perhaps an alien probe.
snip
> Another way of phrasing what I'm doing is this. Three possible
> origins for 1991 VG come to mind, and for each we can estimate a
> probability. One is that it is/was an asteroid; call that probability
> A. The second is that it was a man-made body returning to our
> vicinity, call that probability B. The third is that it was of alien
> origin, call that probability C. Those three probabilities sum to
> unity: A+B+C=1. In the presence of perfect information, one derives a
> value of one for one of them, and zero for the other two. But we
> don't have perfect information (as is the case in most scientific
> investigations), so we have to assess A, B. and C as best we can. So
> far I have found that A is small (it seems unlikely that it was an
> asteroid).
Surely that should be A+B+C+D, where D is 'other explanations
we haven't thought of yet'? Why not make C = 'The Ascended Body of the
Prophet Elija, in a holding pattern' and then the paper could be used
by certain people to support their view of the Old Testement?
> Next I attack B. 1991 VG had an orbit slightly bigger than that of
> the Earth, meaning that it _could_ (not _would_) come close to the
> Earth once every 16.75 years. That means that an approach early in
> 1975 was possible, and early-to-mid-1958 (although an approach in 1975
> could have altered the orbit by enough to make an approach perhaps in
> 1959 feasible).
Hmmm. 1958 - 17 = 1941. A tad early, but just how far did the
Germans get on the intercontinental version of the V2? There's a D,
a heretofore unsuspected ICBM launch by the Germans in the early to mid
1940s. I'm sure we can massage the numbers to say 'A is unlikely,
B is unlikely, C is unlikely, therefore the biggest chance is that
the Germans got off one attempt at an ICBM and it was *too* successful."
James Nicoll
--
I corrected Henry Spencer and all I got was this lousy .sigfile.
John Stepkowski
>From "the Skeptic" (ISSN 0726-9897) Vol 15, No. 1, pp. 8-9.
Published by: Australian Skeptics Inc.
PO Box A2324
Sydney South NSW 2000
Australia
====================================================
Of Asteroids and Aliens
By Dr Duncan Steel
This article is a pre-emptive strike. In a scientific journal called
_The Observatory_ will appear shortly a paper in which I make the
suggestion that an object observed in the Earth's vicinity
(astronomically-speaking) in late 1991 was perhaps an alien probe.
However, I do not _believe_ that it was such an (hypothetical)
object. To me, as a practising scientist, that makes good sense: if
you come to a certain conclusion then you should make that conclusion
clear, regardless of your personal beliefs (for which read 'biases').
When I looked into the data pertaining to this object, I found that a
case could be made for it being of unknown provenance (ie alien), so it
is good practice to say so. But I anticipate that various UFOlogists,
journalists and other yahoos will say that 'astronomer believes object
was an alien spacecraft,' when I don't; but it is a plausible
explanation. I just want to put on record somewhere that I _don't_
believe it to have been an alien object, and where better to do that
than in _the Skeptic_?
The facts are these. In early November 1991 a peculiar object was
spotted by Jim Scott, using the so-called Spacewatch telescope at Kitt
Peak in Arizona. That telescope is the first fitted with a CCD video
camera to be used for routine searching for asteroids and comets near
the Earth, and the team there have made many pioneering discoveries.
The object in question is called 1991 VG, which is an asteroidal
designation: 1991 tells you the year, 'V' means that it was found in
the first half-month of November (that being the 21st half month of
the year, V being the 22nd letter in the alphabet, and we don't use
'I' since it could be confused with a '1'), and 'G' means that it was
the seventh object classified in that half-month. So that's the
terminology.
Most asteroids found are in the main belt between Mars and Jupiter,
but the name of the game for Spacewatch folk, and my own group at
the Anglo-Australian Observatory, is looking for asteroids on
eccentric Earth-crossing orbits (which could, at some time, hit our
planet). 1991 VG was on an Earth-crossing orbit, and was found very
nearby, astronomically speaking, about seven times as far away as the
Moon. The observations obtained by Scott soon showed that its orbit
was very similar to that of the Earth, having an orbital plane less
than half a degree inclined to our own, and a near-circular path. Its
brightness suggested that it was only 8 to 20 meters in size,
depending upon how much sunlight one assumes that it reflects. The
suggestion was therefore made that this was not an asteroid at all,
but actually a rocket booster which by chance had returned whence it
came. That idea was boosted by observations from the European
Southern Observatory in Chile, which showed that it appears to flash.
Such flashing is often seen in the case of artificial satellites going
overhead, with occasional glints occurring as they spin and some flat
metallic face catches the Sun.
So it appeared that 1991 VG was not an asteroid after all, but some
artificial object. Another thing counting against it being a natural
asteroid was its orbit: such a very Earth-like orbit would lead to
close approaches to the Earth every 50 years or so, with the
terrestrial gravity then causing the orbit to be changed (as was
actually observed). If it were a natural body, it would need to have
arrived in such an orbit within the past millennium or so, which is
unlikely. For example, one possible origin would be as ejecta from a
massive impact on the Moon, but those occur infrequently, and in any
case the flashing observed could not be explained in that way.
Another way of phrasing what I'm doing is this. Three possible
origins for 1991 VG come to mind, and for each we can estimate a
probability. One is that it is/was an asteroid; call that probability
A. The second is that it was a man-made body returning to our
vicinity, call that probability B. The third is that it was of alien
origin, call that probability C. Those three probabilities sum to
unity: A+B+C=1. In the presence of perfect information, one derives a
value of one for one of them, and zero for the other two. But we
don't have perfect information (as is the case in most scientific
investigations), so we have to assess A, B. and C as best we can. So
far I have found that A is small (it seems unlikely that it was an
asteroid).
Next I attack B. 1991 VG had an orbit slightly bigger than that of
the Earth, meaning that it _could_ (not _would_) come close to the
Earth once every 16.75 years. That means that an approach early in
1975 was possible, and early-to-mid-1958 (although an approach in 1975
could have altered the orbit by enough to make an approach perhaps in
1959 feasible). An inspection of the records of mankind's launches
into space showed that there were no candidates from 1975. In October
1974 the Russian Luna 23 was sent to the Moon, and hit it, so count
that one out. I thought that the upper stage from the American launch
of the German satellite Helios 1 in December 1974 was a possibility,
but then I learnt that it was put back into geocentric (rather than
heliocentric) orbit. From the earlier period there were no candidates
until late in 1958 (and of course the space age began only the year
before), but none of these could be made to fit the observations
unless some force acted upon them which was not known to have occurred
(like fuel left on board venting due to a leak, or perhaps solar
radiation pressure giving a push).
The consensus though, was that 1991 VG could not be linked with
surety with any launches in the late 1950s or the mid-1970s. Another
possibility was one of the Apollo upper stages used in the Moon
landings, which could be suggested to have hung around in orbit near
the Earth and Moon for a few years, and then escaped (unobserved) in
1975. Again, this would be hypothesising an event which is not known
to have occurred.
Even if one were to accept the possibility that 1991 VG was a
man-made rocket returning to our vicinity, one then might estimate the
probability that it would be spotted. Only the Spacewatch telescope
is capable of discovering such small, faint, moving objects (which is
why our knowledge of small asteroids has been revolutionised since
Spacewatch began operations in 1989). Using the amount of sky which
is covered by its scans, and the number of nights each year in which
observations are made, and so on, I estimated that there was about a
one-in-2,000 chance that any arbitrary object with the brightness of
1991 VG would be spotted, given that it came somewhere within the
geocentric distance occupied by 1991 VG when it was found (about 3.3
million kilometres). Passage within that distance, assuming that 1991
VG was not under control, occurs about once every 50 years. Thus if
1991 VG were a solitary, uncontrolled rocket body, one would expect
Spacewatch to spot it about once every 100,000 years. On that basis
one has to conclude that B (the probability of it being a man-made
object) is very small.
Since we know that A+B+C=1, and we have derived small values for A
and B, that implies that C must be substantial. It is on that basis
that I suggested, very tentatively, that it is a candidate as an alien
spacecraft. In fact my bias says that it was a man-made body, but a
scientific analysis indicates that this would require a fluke to
have occurred. That is, _a priori_ its discovery was unlikely; but _a
posteriori_ things are as they are, not as we might believe them to
be.
There is also another piece of evidence that supports the 'alien
probe' interpretation. Although 1991 VG was first spotted when it was
3.3 million kilometres from the Earth, it actually passed just 485,000
kilometres from our planet. If it were an uncontrolled object
(either an asteroid or a fluke returning man-made rocket body) then
passage within that 3.3 million kilometres would occur at a random
distance. Only about one in 40 would come within 485,000 kilometres.
That argues for it indeed having been under control: an alien probe
coming to take a look at us, but keeping a distance away at which they
thought they were safe from detection (well beyond the grasp of
military radars). One might object that the same sort of statistics
would apply for an alien craft as outlined above for man-made craft
(one discovery per 100,000 years), but that would be in error: if this
were an alien craft under control then it could buzz repeatedly past
the Earth, but under free flight (as observed) whilst within the grasp
of our telescopes.
OK, one last time, I don't believe that 1991 VG was an alien object,
but the simple analysis above does lead to the conclusion that it is a
decent candidate for consideration. Most of us have heard about the
Search for Extra-Terrestrial Intelligence (SETI), which seems to be
the only science with nothing to study (just pulling their tails). A
sub-division of that is SETA, or Search for Extra-Terrestrial
Artifacts. All I'm suggesting is that the SETA people might at least
have something to argue about. And some Skeptics might like to put in
their two cents worth too.
==========================
*E-O-F*
*-------------------------------*
|...............................|
|.. leg...@werple.mira.net.au ..|
|...............................|
*-------------------------------*
Tom Kalafut x34853
> In article <3jslln$5...@werple03.mira.net.au>,
> John Stepkowski <leg...@werple.mira.net.au> wrote:
>
> snip
>
> > Of Asteroids and Aliens
> >
> > By Dr Duncan Steel
> >
> snip
>
> > Another way of phrasing what I'm doing is this. Three possible
> > origins for 1991 VG come to mind, and for each we can estimate a
> > probability. One is that it is/was an asteroid; call that probability
> > A. The second is that it was a man-made body returning to our
> > vicinity, call that probability B. The third is that it was of alien
> > origin, call that probability C. Those three probabilities sum to
> > unity: A+B+C=1. In the presence of perfect information, one derives a
> > value of one for one of them, and zero for the other two. But we
> > don't have perfect information (as is the case in most scientific
> > investigations), so we have to assess A, B. and C as best we can. So
> > far I have found that A is small (it seems unlikely that it was an
> > asteroid).
>
> Surely that should be A+B+C+D, where D is 'other explanations
> we haven't thought of yet'? Why not make C = 'The Ascended Body of the
> Prophet Elija, in a holding pattern' and then the paper could be used
> by certain people to support their view of the Old Testement?
Or E = 'other explanations' and D = 'It's just astronomical propaganda
with some ulterior motive.'
>
> > Next I attack B. 1991 VG had an orbit slightly bigger than that of
> > the Earth, meaning that it _could_ (not _would_) come close to the
> > Earth once every 16.75 years. That means that an approach early in
> > 1975 was possible, and early-to-mid-1958 (although an approach in 1975
> > could have altered the orbit by enough to make an approach perhaps in
> > 1959 feasible).
>
> Hmmm. 1958 - 17 = 1941. A tad early, but just how far did the
> Germans get on the intercontinental version of the V2? There's a D,
> a heretofore unsuspected ICBM launch by the Germans in the early to mid
> 1940s. I'm sure we can massage the numbers to say 'A is unlikely,
> B is unlikely, C is unlikely, therefore the biggest chance is that
> the Germans got off one attempt at an ICBM and it was *too* successful."
Don't you remember when Battlestar Gallactica found earth, "the 13th
colony", in the 1940's and they helped thwart the development of a German
missile. That's why the ICBM was *too* successful - Apollo and Starbuck
saved the day ;-) .
But seriously folks, if this 1991 VG is that important, has the Hubble
space teleeeescope been considered? I know I'd like to view it using el
Hubble!
Not an astronomer but a stargazer,
Tom Kalafut,
Another lowly worker bee at the Pentagon.
M.T.S., Datanamics Computer Corp.
kal...@pentagon-emh6.army.mil
----
"That's not a cat license. It's a dog license with the word 'dog'
scratched out and the word 'cat' written in in crayon."
- Monty Python, 'Eric the Half Bee' skit
David Tonhofer
>
> >From "the Skeptic" (ISSN 0726-9897) Vol 15, No. 1, pp. 8-9.
> Of Asteroids and Aliens
> By Dr Duncan Steel
>
> This article is a pre-emptive strike. In a scientific journal called
> _The Observatory_ will appear shortly a paper in which I make the
> suggestion that an object observed in the Earth's vicinity
> (astronomically-speaking) in late 1991 was perhaps an alien probe.
[...]
> The facts are these. In early November 1991 a peculiar object was
> spotted by Jim Scott, using the so-called Spacewatch telescope at Kitt
> Peak in Arizona. That telescope is the first fitted with a CCD video
> camera to be used for routine searching for asteroids and comets near
> the Earth, and the team there have made many pioneering discoveries.
[...]
> Another way of phrasing what I'm doing is this. Three possible
> origins for 1991 VG come to mind, and for each we can estimate a
> probability. One is that it is/was an asteroid; call that probability
> A. The second is that it was a man-made body returning to our
> vicinity, call that probability B. The third is that it was of alien
> origin, call that probability C. Those three probabilities sum to
> unity: A+B+C=1.
[...uh..oh..I see something coming...]
> ...so we have to assess A, B. and C as best we can. So
> far I have found that A is small (it seems unlikely that it was an
> asteroid).
[...]
> On that basis one has to conclude that B (the probability of it being a
> man-made object) is very small.
[...]
> Since we know that A+B+C=1, and we have derived small values for A
> and B, that implies that C must be substantial.
[...Here the reader is suddenly shocked into "active modus" and lurches
to the next shelf to get the book "Probabilistic reasoning in expert
systems" by E.Neapolitain...which isn't there at the moment, so he
tries to remember what it was about and carefully places his finger
on the keyboard typing "F"...]
Sorry, but you are making a mistake here. You cannot just estimate P(A) and
P(B), demand that P(A)+P(B)+P(C)=1 and conclude that P(C)>>0, because
P(C) is NOT P(alien artifact) at all. What you SHOULD do is the following:
Use CONDITIONAL PROBABILITIES and BAYES' RULE (BAYEZ RULZ, OK?)
------------------------- -----------
Let's make a ballpark estimate for the "A PRIORI PROBABILITIES" (they are
called "a priori" because they are the probabilities that you would use
if you just heard that an object had passed earth, without having any
additional information).
P(Asteroid) = 0.8 Probability that object = asteroid
P(Human artifact) = 0.1999 Probability that object = manmade
P(Alien artifact) = 0.0001 Probability that object = alien
------
1.0000
Note that these actually sum to unity, as they should. Note also that the
value above includes the historical launch dates (thus reducing
P(Human artifact)). The problem is that we have no way to really estimate
these values, as we cannot collect statistics about how many of the objects
seen by Spacewatch are asteroids or human artifacts or alien artifacts (the
latter case having never been observed, of course). However, just for the sake
of the argument, let's admit the above values. NOW:
We make the observation O (using Spacewatch). We now conclude:
P(O | Asteroid) = 0.1
P(O | Human artifact) = 0.8
P(O | Alien artifact) = 0.8
The first value is the "probability that the observation O could have been made
knowing that (under the assumption that) the object was an asteroid". Let's
say that it is rare to have such an observation, let's set it to 0.1.
The second value is the "probability that the observation O could have been
made knowing that (under the assumption that) the object was a human artifact".
Pretty good match, we set it to 0.8 (why not?).
The second value is the "probability that the observation O could have been
made knowing that (under the assumption that) the object was an alien
artifact". If we assume that alien artifacts are similar to human ones, we
have to set this value to 0.8, too.
Note that these three value do NOT sum to unity; they don't need to as the
conditions are different on all three of them.
Now for the MEAT: The A POSTERIORI PROBABILITIES, i.e. the probabilities
P(Asteroid | O)
P(Alien artifact | O)
P(Human artifact | O)
can now be calculated. These probabilities express our belief that the
object was a [Asteroid | human artifact | alien artifact] GIVEN THAT
we have made observation O.
Bayes' rule: P(X|Y) = P(Y|X)*P(X)/P(Y)
..and this has to be true for our three values, thus:
P(Asteroid | O) = P(O | Asteroid) * P(Asteroid) / P(O)
P(Alien artifact | O) = P(O | Alien artifact) * P(Alien artifact) / P(O)
P(Human artifact | O) = P(O | Human artifact) * P(Human artifact) / P(O)
Ewwwhh...but we don't KNOW P(O) you may now scream. Don't worry: We demand
that
P(Asteroid | O) + P(Alien artifact | O) + P(Human artifact | O) = 1
as these probabilities partition the probability space under which O is
true. Thus P(O) is just a normating factor "a", and we can leave it out...
Let's calculate, by plugging in values
P(Asteroid | O) * a = 0.1 * 0.8 = 0.08
P(Human artifact | O) * a = 0.8 * 0.1999 = 0.15992
P(Alien artifact | O) * a = 0.8 * 0.0001 = 0.00008
-------
0.24 ---> a = 4.166
Thus
P(Asteroid | O) = 0.3333
P(Human artifact | O) = 0.6663
P(Alien artifact | O) = 0.0003 <--- Deception!
------
1.0000
So, even the unusual observation "O" did not make up for the low value
P(alien artifact) in a really significant amount...
-- David
Next time, we will take potshots at Abian and explain to him that something
that moves through time, where movement is defined as Delta(t)/dt, must
really be something with twisted physical properties.
Ben Weiner
> Of Asteroids and Aliens
> By Dr Duncan Steel
[much deleted]
> ... I estimated that there was about a
> one-in-2,000 chance that any arbitrary object with the brightness of
> 1991 VG would be spotted, given that it came somewhere within the
> geocentric distance occupied by 1991 VG when it was found (about 3.3
> million kilometres). Passage within that distance, assuming that 1991
> VG was not under control, occurs about once every 50 years. Thus if
> 1991 VG were a solitary, uncontrolled rocket body, one would expect
> Spacewatch to spot it about once every 100,000 years. On that basis
> one has to conclude that B (the probability of it being a man-made
> object) is very small.
> Since we know that A+B+C=1, and we have derived small values for A
> and B, that implies that C must be substantial. It is on that basis
> that I suggested, very tentatively, that it is a candidate as an alien
> spacecraft. In fact my bias says that it was a man-made body, but a
> scientific analysis indicates that this would require a fluke to
> have occurred. That is, _a priori_ its discovery was unlikely; but _a
> posteriori_ things are as they are, not as we might believe them to
> be. ...
Well now. Clearly the probability that Spacewatch would detect any
random alien artifact passing close to the Earth is also small -
something like 1 in 2000 given your numbers. Thus unless one believes
that alien probes are passing the Earth at a rate on the order of
a thousand per year or so, the probability C (prob. of alien origin
for 1991 VG) must also be very small - larger than B by a factor of 50
perhaps (that's the 1 approach every 50 years), but still much less than
one. This leaves us in somewhat of a quandary, as Dr. Steel has shown
that A, B, and C are all very small yet A+B+C=1. Had the article
included a detailed calculation of C, as it did for A and B, this
difficulty would be more apparent.
The problem is that calculating the probability of something which is
known to have happened - a posteriori probability - is not very
meaningful. The misapplication of a posteriori probability, particularly
to calculate the unlikeliness of an observed event (here that Spacewatch
should happen to find a rocket booster - or that Halton Arp should find
three quasars in a line, or any number of less glamorous occurrences),
is a persistent problem in astronomy, by the way, nothing unusual but still
to be avoided. I see that Bill Lawson has made a similar and perhaps
better phrased version of this argument.
Henry Spencer
>The problem is that calculating the probability of something which is
>known to have happened - a posteriori probability - is not very
Or to put it in simpler terms, for those whose eyes glaze over when the
probabilities start being calculated: *coincidences* *happen*.
Just because the odds of an event are, say, 1 in 2,000, that doesn't mean
it won't happen. Improbable events happen every day.
People like the particle physicists, who live with this sort of problem
routinely, tend to set rather stiff standards. The Fermilab group which
seems to have found the top quark didn't formally claim the discovery
until the odds that their results were coincidence reached 1 in 2,000,000.
Dismissing possibilities whose odds are merely 1 in 2,000 is simply wrong.
--
There is a difference between | Henry Spencer
cynicism and skepticism. | he...@zoo.toronto.edu
Lars Blomberg, Alfven Laboratory, Stockholm
[...]
> Another way of phrasing what I'm doing is this. Three possible
> origins for 1991 VG come to mind, and for each we can estimate a
> probability. One is that it is/was an asteroid; call that probability
> A. The second is that it was a man-made body returning to our
> vicinity, call that probability B. The third is that it was of alien
> origin, call that probability C. Those three probabilities sum to
> unity: A+B+C=1.
This is true provided that the phenomena whose probabilities are A, B,
and C are mutually exclusive and collectively exhaustive. I would say,
that in this case you have: A+B+C+D=1, where D is the probability of any
possibility not covered by A, B or C.
[...]
> Since we know that A+B+C=1, and we have derived small values for A
> and B, that implies that C must be substantial.
No, it implies that C+D is substantial. Unless you can prove that also D
is small, your conclusion is not valid.
LGB
Russell Stewart
Anderson(aran...@kosepc01.delcoelect.com) said...
>
>John Stepkowski <leg...@werple.mira.net.au> wrote:
>>[Of Asteroids and Aliens]
>
>In <3jtvfs$o...@falcon.ccs.uwo.ca>,
>jdni...@engrg.uwo.ca (James Nicoll + Jasmine) writes:
>> Surely that should be A+B+C+D, where D is 'other explanations
>
>Another "D" candidate:
>When was that underground nuclear bomb test that blew the metal
>cover off the hole in the ground? There was some speculation that
>the cover exceeded escape velocity, and a remote chance that it
>might have survived the blast and entered a solar orbit.
Hey, I never thought of that! It would fit the profile, wouldn't
it?
That would be kind of an event, actually -- rediscovering the first
man-made object launched into space (albeit accidentally).
--
/~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~/|
/_____________________________________________________________/ |
| Russell Stewart | Albuquerque | What? | |
| dia...@rt66.com | New Mexico | Is it my hair? | /
|__________________|___________________|______________________|/
"After you've heard two eyewitness accounts of a motor accident,
you begin to worry about history." - J. McNab
Marcus Lindroos INF
Hmmm...at first glance, the Luna 23 upper stage appears to be the most likely
candidate. It was launched almost exactly 17 years earlier. If it didn't
impact on the Moon, a very small delta-V of 0.1km/s (360km/h) would be
enough to enter a heliocentric orbit from the initial Earth-Moon transfer
orbit.
---
You are probably correct about the lack of good candidates launched in
1958/59... I believe Luna 1/2 used a faster trajectory than its successors.
L1 entered a 150x200 million km orbit around the Sun, compared with ~150x160
million km(?) for 1991 VB.
---
Please post the orbital parameters and visual magnitude as well!!
MARCU$
William Sommerwerck
>>>[Of Asteroids and Aliens]
>>Another "D" candidate:
>>When was that underground nuclear bomb test that blew the
metal
>>cover off the hole in the ground? There was some speculation
that
>>the cover exceeded escape velocity, and a remote chance that
it
>>might have survived the blast and entered a solar orbit.
This isn't likely. Think about it. Escape velocity is about
25,000 mph. The cover would have had to pass through 100 miles
of atmosphere without a significant loss of energy, or simply
disintegrating.