The author examines some basic questions as to why there should be astronomical facilities on the far side of the moon. The questions are ones of appropriateness, i.e., is this a proper use for human resources, what the real goals are, and are the present concepts the best match for the goals

Woolf, Neville

English

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LUNAR INTERFEROMETRIC ASTRONOMY:
N93-13592
SOME BASIC QUESTIONS
N. Woolf
Steward Observatory
University of Arizona
Aa.Zlmmati_
It had seemed likely that many of the key technical points would have already been
discussed now, and so I have brought some general questions for your consideration. When, or if
there is ever an astronomical facility on the far side of the Moon, I expect to be dead. (A this point
in the talk, Dr. Burke suggested that I should speak 0nly for myselfl) One cannot force the future
over long periods of time. And as George Herbig once commented, in 100 years everything which
we now know will be seen to be obvious, irrelevant, or wrong. Nonetheless, we have to move from
the here and now, and the focus of our enquiry has to be whether we are doing something
appropriate. Is this a proper use for human resources? What are our real goals? And is our concept
the best match to our goals?
We are proposingan activitythatisveryexpensive,and beforethe startwe must answer a
fundamental question."Why do you not use thismoney insteadto feedthe starvingbillions?"
The same questionwas ineffectasked about the anointingatBethany (John 12.8)and the reply
was thatthe poorwillalwaysbe with us. Our answer today can be more detailed--andmore
hopeful.
But first let me say that as astronomers our goal is surely to improve the quality of life, not
the quantity. Up to a point quantity has survival value, but beyond that point--and we are well
beyond that point--we pose a threat to humanity's own survival. We are such a large fraction of the
terrestrial ecosystem that in our attempt to survive a disaster we are likely to destroy the recovery
potential of the system. Our model is the reindeer population of St. Matthews island (Klein 1968).
In this ecosystem a small introduced population expanded to the point that in a food shortage the
deer killed off the potential for their future food. The entire population then died of starvation.
I am undoubtedly one of a very few astronomers who have computer-modelled famine.
That is, I have studied the effects of environmental stochasticity producing a fluctuating food
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supply, and that food supply causing population fluctuations. There will be a sigmoidal curve
relating the fractional food adequacy to the death rate. And this cure allows the prediction of the
number of deaths from the number alive and the available food. Undoubtedly past history of food
supply and details of the food distributionmust modify the shape of the curve, but this is a start in
such models. I got into this study from astronomy, first by trying to understand the growth of
quasar nuclei, then by modelling the population of the Mt. Graham red squirrel--but that is another
story.
From the models, I can tell you that giving food and medical attention to people can be
helpful in a famine--if help is in a small enoughquantity. It is also possible for it to result in an
increase in the number of people that will, in the future, die of starvation. Rather surprisingly, the
risk of the population is reduced if the food is unevenly distributed. It is only possible to eliminate
starvation by population control, that is by deliberate reduction of the birth rate or increase of the
death rate. With a population balanced at an appropriately reduced level, feeding the Starving
masses becomes unnecessary. Without population control, the action is unhelpful because it only
sets the stage for the next famine. That is, with population control there is no problem: without it
there is no solution.
science does not always give us new options; witness the laws of the thermodynamics and
the limiting speed of light. In th e area of population we learn that the real choices are between
involuntary birth control, involuntary euthanasia, and involuntary starvation. There is no doubt
in my mind that involuntary birth Control is the most favorable of these choices. The mechanism
is up to the couple, or country, until the limit is reached. Then it becomes a matter for everyone
else.
Whether it is better to have a well-fed 100 million or 10 billion starving people is our choice.
There has always been a human choice whether its goals are to produce heaven or hell. i would
suggest that all past religious and ethical systems have indicated a choice in favor of the former,
and there is no doubt which choice points which way. Malthus explained the problem in 1798. It is
about time everybody paid attention.
True charity seeks to change the problem, not to perpetuate it. Any resources we put into this
problem:should go first into inculcating the message of "Never Again," and secondly in trying to
ease the pain during the transition. With population control it is possible to build a better life here
on Earth, and on the Moon.
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Without it all we can do is watch more suffering while perhaps fooling ourselves that we
are helping because we are spending our resources doing something that appears superficially to
help others. It is possible for such activities to be stupid rather than moral. Likewise there is no
simple moral issue involved in deciding whether to spend money on astronomy.
The Annronriateness of a Lunar Base and Colony
The second question is whether astronomical study is the reason for humans making a
new colony on the Moon. I believe that the colony should exist regardless of whether there is an
observatory, but running an observatory is an appropriate colony activity.
The ammonoid fossil on the clasp of my string tie was one of a group of creatures that
existed for far longer than there have been primates on Earth, and like us the ammonoids were
one of the commonest creatures of their day. They vanished as part of the catastrophe 65 million
years ago that appears to have been precipitated by a collision with some small astronomical body.
But not all catastrophes are the same. An earlier and even more dramatic extinction event seems
quite different (Holser et al. 1989), and we have to wonder what potential ends to humanity lie
beyond our current horizon of understanding.
Here on earth we are concentrated into 10-s AU 2 in area. If we develop a self-sufficient
colony on the Moon, we have expanded into an area 1000 times greater, and with the risk of
extinction substantially reduced. I believe that humankind is special. We are the first to store
knowledge and understanding from one generation to the next. We hold that knowledge in trust
for the entire universe, at least until we encounter some similarly recording entity. That trust
gives us a responsibility to avoid extinction. It is somewhat like Pascal's reason for believing in
God. However low the probability of extinction in the near future may be, and however high the
cost, the benefit of being prepared against it is so high as to weigh the odds in favor of that course of
action. The Moon is potentially our ark.
With the potential for the Earth to become humankind's tomb, I do not believe that it is
appropriate to build an isolation shelter here. Also, I do not believe that space stations allow
adequate shielding of humans. Here on earth we are benefiting from a mass layer of 1Kg per
square cm above our heads. Large amounts of matter for shielding are available on the Moon, but
not in a space station. I do not see a substitute for the Moon.
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For similar reasonsweneedto somewhatredirectourenergies.Whatkinds of
astronomicalprocessesmightput usatrisk? Forexample,is thereanystageofdevelopmentof a
mainsequenceSun-likestarthat could precipitate a catastrophe?
 mMat£z 
Enough. It is time to turn the searchlight in the other direction. So it is all to be for that
great store of knowledge of which science is a major part? What about the fun we are getting?
Some space cowboys just want the ride. Other telescope cowboys want to ride the giant aperture.
Some want to design it, plan it, build it, sell it, talk about it, ride to power using it, go out in a blaze
of glory with it. We are human, and have the usual mixed motives. And even if things are done
as well as they possibly can be done for science, there will be those kinds of side effects. Is it the
greatest treason to do the right thing for the wrong reason, or is it an greater treason to fail to do the
right thing? I must agree with Chesterton that if a thing is worth doing, it is worth doing badly.
One does the best one can with the available resources.
There isno substituteforprojectingthe consequencestohelp decidewhether a courseof
actionleadstoofarastray.The scienceneeds todirectthe plan,and be atthe centerofthe designof
the interferometers.We shouldnot be surprisedor dismayed by minor diversions.
As we plan forhigherand higherresolutionobservationsofthe universearound us,we
findthat gettinga 10ng'well-controlled,and predictablebaselinebecomes harder and harder.
The Moon isvery specialinprovidingcontrolledbaselinesofup to3,000km withoutthe associated
seeingproblems we have here on Earth. While shortbaselinesarefineforcuttingour teeth,itis
those baselines that beckon, and suggest that lunar interferometry is not just another quickie
project, but rather a long-term effort for more than one generation.
We need to be very careful and thoughtful about the justification of the facility. We have
already seen at this conference that the public can all too easily be sold on any project to look for
planets around other stars, and particularly to look for evidence of life on those planets from the
presence of oxygen. Interferometers and large telescopes both offer opportunities for this kind of
search as well as a host of interesting additional science benefits. Unfortunately, the search for
planets is quite specialized and very difficult at any wavelength. Searches for planets need the
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experience and sophistication that are best developed by using lower precision devices first. The
natural and appropriate order is to delay the planet search until our techniques are better under
control.
S0ecial Asnects of Ootical Interferometry
There seem to be two aspects of optical interferometry that are quite special. The first is that
the optical region offers strong spectral lines as well as continuum. Even a cursory study of the
beautiful radio maps of energetic galaxies reveals the limits to interpretation because these is no
spectral line information. For our optical two-element interferometers it is easy to apply spectral
dispersion at right angles to the fringes. When we have a multi-element 2-D interferometer, we
need to plan on the method of beam interference to preserve this possibility.
The second point is that optical wavelengths are so short that potential angular resolution is
incredibly high. A 1500 km baseline at a wavelength of 5000A is equivalent in resolution to about
1AU at 5 cm wavelength. With that resolution we could place 100 resolution elements across the
disk of our Sun even if it were 1Kpc away! One hundred resolution elements are just enough for
seeing sunspots. We could similarly study the surface detail of the nearest white dwarf stars. The
baseline is still a little shy of resolving the velocity of light surface of the Crab Nebula pulsar. It
just resolves the Schwartzchild diameter of energetic galactic nuclei.
For the galactic nuclei, the region where the material is expected to be optically thick at
optical wavelengths is much larger, and interferometers with baselines of 10-100 m can yield
information on orientation and structure of such regions. Even shorter baselines will start to
yield the structure of the line emitting regions and allow us to relate such structures to the position
angles found for radio lobes and jets.
Such observations are pointed in a direction that has been our current rationale for the
study of astronomy. The universe reveals to us a range of conditions that are not met on Earth or
available in even the most sophisticated laboratories. Astronomical observations allow us to
check our extrapolation of laboratory experience and theoretical calculation and improve our
understanding of the laws of physics and their consequences.
I would like to suggest that with our basic reason for going to the Moon--to guarantee
human survival--astronomy starts to have a different and certainly more human-oriented
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significance.We clearly need to shift gears to recognize this. For example, we should be very
attuned to detailed confirmation of our understanding of the evolution of solar-type stars. Are
there any nasty surprises that occur at intervals? Would observations of surface details in many
such stars be of help? Are other stars in our galaxy going to produce unpleasant surprises?
The advent of lunar astronomical observing will prompt a reorientation of astronomers
toward different goals. We hope it will also orient us toward different ways of doing things and
thinking about things. I do not believe that when the time comes we will find it irrelevant that we
are fundamentally inhabitants of Earth, and humans concerned with human survival. We can
hope that by then it will be obvious.
.
,
References
Holser, W:T.; Schonlaub, H-P; Attrep, M.; Boecklemann, I_; Klein, P.; Magaritz, M,;
Orth, C.J.; Fenninger, A.; Jenny, C.; Kralick, M.; Mauritsch, H Pack,E.;Schramm,
J.M.; Statteger, K; Schmoller, R. 1989. Nature 337:39.
Klein, D.R. 1968. Journal of Wildlife Management 32:350-367.


Lunar interferometric astronomy: Some basic questions

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