One of Johannesburg’s most enthusiastic members is Werner Kirchhoff, who
recently gave a course of lectures to U3A members. He has kindly provided us
with a condensed version of his text to enable those who did not have an
opportunity to attend his talks to benefit from the wide extent of his knowledge
and expertise.
‘MAN MUST MEASURE
THE SCALE OF THE UNIVERSE -
HISTORIC AND MODERN DETERMINATIONS.’
Produced for THE UNIVERSITY OF THE THIRD AGE
To CELEBRATE the INAUGURATION of S A L T
The SOUTHERN AFRICAN LARGE TELESCOPE
It is always a sincere pleasure for me to attempt to share with others the enthusiasm I
have for the beauty and logic of astronomical knowledge. Therefore allow me to expand
the purely factual review of the historic and modern techniques of giving scale to our
Universe, and to express and philosophize on the meaning of this knowledge.
For us humans on this minute planet, where our life is so infinitesimally small on the
scales of universal distance and time, the discovery of more and ever more astronomic
facts helps our knowledge to grow proportionally greater in advancement and
understanding.
Modern astronomical achievements demonstrate the tremendous power of the human
brain to conceive and prove extremely complex theories from initial simple observations.
This through highly disciplined logic, and then create, through new technologies, devices
so powerful to allow the amplification of minute energies from vast distances into
something clearly discernible, understandable and additional to our knowledge. This
again allows further technological innovations, thereby accelerating our mind nearer to
the as yet still unknown truths.
These concepts have come to me from early encouragement into astronomy by my
father in the 1940’s, then by my professor in navigational and geodetic astronomy,
Professor Arthur Bleksley, in the early 50’s and subsequently by the Director of the
Harvard and Smithsonian Astrophysical Observatory, Dr. Fred Whipple, under whom I
worked for many years. Having had this honour, I would like to quote liberally from his
and other seminar discussions including some led by Carl Sagan.
We are living in the space age. Man has broken the tyrannical bounds of gravity that
confined him so long to earth, only a tiny speck in the cosmos. Now man’s machines and
devices travel across the gravity barrier in the early exploration of a universe so vast that
it defies comprehension. No longer are man’s eyes and instruments blinded by the black
curtain of atmosphere that shuts out most of the incoming messages of radiation from
outer space. Now vehicles shot beyond this atmosphere contain instruments that can
‘see’ the universe by the ultra-violet light, X-rays, infrared light and radio emanations that
could never penetrate our cloudy, opaque and tremulous atmosphere.
Man has developed a great insight concerning the sources of energy in the universe.
Reactions in the nuclei of atoms that keep the stars burning for billions of years are now
well enough understood and controlled to turn the wheels of industry. Although the stars
have not shown man directly the secrets of their radiation we have learned from them
that such secrets exist.
The stars have served as beacons to give man the hope and assurance that by
continuous delving into nature’s treasury of knowledge he might expect to find answers
to questions involving practical power sources as well as evolutionary secrets hidden for
hundreds of millions of years.
Some might argue that for the first time in man’s history astronomy has taken its rightful
place, because problems of nature, the past, the present and the future of the physical
universe represent the greatest challenge to man except perhaps man himself. But the
significance of astronomy in man’s upward climb from the cavemen must not be
discounted in the dark ages of the past. Every sunrise presented the miracle of the
newly born sun in some older philosophies, while each sunset represented its death.
The stars have reflected man’s own concepts, aspirations, fears and hates in countless
different forms in past cultures. Only rarely do the stars and planets stand for evil, the
undesirable or the dreaded. Usually the heavenly bodies mirror the idealism and hopes
and aspirations of man and reinforce his will towards life and progress.
The many thousands of years during which the heavenly bodies were primarily religious
or superstitious symbols testify to man’s weakness in cutting boldly with logic as a sword
through the jungles of superstition. One may question seriously whether science and
technology would have developed at all on a cloud-bound planet where no direct signs
of the outside universe were manifest except for the alternation of night and day. Without
the sun, moon, stars and planets to prod his spirit, mankind might still consist of a few
hundred thousand persons gnawing on bones in the warmer caves of the planet.
Whatever the answer to this question, the astronomical development in our earth
cultures, has inevitably been a representative measure of the progress of the culture
generally.
Some may mourn that in our modern space age accurate measurements and clearer
vision are dispelling many of the mystic veils and charming imagery of our past
ignorance. In contrast, truth is beauty and that an understanding of, space, time and the
physical universe can only lead to a more interesting and captivating view of the
universe. It may even lead to man’s better understanding of himself.
Space is now as much a part of our arena of technology as is the atmosphere, the
oceans or even solid earth. The peculiar problems of life in zero gravity, the problems of
operating in a vacuum, the hazards in space from meteoritic impact, the dreaded Van
Allen belt of radiations only 600 miles above the earth’s equator, the problems of rocket
propulsion and the peculiar difficulties of returning to earth through the atmosphere at
speeds of several miles per second, are all real and practical aspects of astronomy
today. These and other problems of space technology demand a great increase in our
astronomical knowledge and understanding. While it is true that a bird does not need to
study aerodynamics, chemistry or optics to survive comfortably in our atmosphere, it
must be pointed out that it has taken a hundred million years of natural selection to
produce this unconscious adaptation to practical survival.
It is hoped that man can continue to progress at a much more rapid pace in his conquest
of space. To do this he must utilize to the full his intelligence, which, to become fully
effective, must operate from the firm foundation of knowledge and understanding
accumulated in basic studies of the universe. If man is to exploit the heritage of our past
and look forward to uncovering new wealth of understanding in the future, he must begin
with study, continue with study and follow with contemplation and with experimentation.
The study of astronomy will give the satisfaction of understanding far more clearly than
before the true significance of explorations of the universe made from astronomical
observatories, from space satellites or from exploratory missions into the depths of our
solar system. These accomplishments will then become significant realities to him and
not merely reports of incomprehensible activities by ‘geniuses’ and ‘mad scientists’ or by
military forces of dreaded import. These scientific triumphs will become understandable
in terms of man’s conquest over nature and his climb up the ladder of evolution towards
goals that are yet undreamed of.
Much of this introduction, sounding so current, comes from the staff seminar discussions
given at the Harvard Smithsonian Observatory, in the 1960s. It has been my
philosophical guide for the past forty years and my motivation to perform many of my
functions at this observatory and to try to spread this experience per the motto of the
Smithsonian Institution: “for the increase and diffusion of knowledge among men”.
These philosophical truths, many coming from our director Dr. Fred Whipple have now
also been enhanced by observational proof. For example, his own personal theoretical
model of comets being “dirty snowballs” was proven by the encounter of the Galileo
Spacecraft with Halley’s Comet. The very successful interplanetary missions of the
Voyagers, a program he advised President Kennedy on, have also shown the truth of his
philosophy.
BUT EVEN MORE SPECTACULARLY by the recent July 4th 2005 DEEP IMPACT into
COMET TEMPLE. A spacecraft hurled a half ton discuss with a velocity of 30 000
km/hour into the 10km diameter comet nucleus. This blasted a 100m crater excavating
10 00 tons of ice and dirty soot representing the original primordial raw materials from
when the comet formed at the birth of our solar system. And CARL SAGAN postulated
that it is the impact of many of these, dirty-snowball comets, in the early formation of
earth that gave us our water and oceans and the starting blocks of life, the dirty
hydrocarbons.
Having quoted Dr. Whipple stressing the need to study, experiment and observe, allow
me to now proceed to the subject - THE SCALE OF THE UNIVERSE.
Here I will speak more from my level as a Surveyor and try to show how human brain
power applied over several thousand years in a tremendous exercise of
interdependence of knowledge and cooperation has brought about the “age of
electronics” and much of our modern technology. “Man must Measure” has applied since
the earliest of cultures and many of our systems, especially time and angle, were
devised even prior to Babylonian times. The simple question of why a right angle has 90
degrees, and not, say 100 grades as modern computations would desire, cannot be
answered by most in today’s world. Yet it stems from one of our simplest observations,
that of the ever recurring yearly seasons. How many days total in January, February and
March? Ninety in the first quarter of our year; that is, the earth moves one degree per
day in its orbit around the sun.
But, how big was the Sun and its orbit around us, how big was the world? At the time of
Greek philosophy it was also accepted that the earth was most probably spherical and
some very good determinations of its size were made.
The most remarkable deduction was that of Eratosthenes - probably about 230 BC.
Eratosthenes had records at his Alexandria Library, stating that at the northern summer
solstice in June, at Syene (Aswan) on the Tropic of Cancer, the sun shone vertically
down wells, i.e. reflected straight back up. Whereas in Alexandria (793 km north, of the
first cataract of the Nile), the sun just illuminated the north-face of the Obelisk having 15
pyramid points. Thus it was obvious to Eratosthenes that the angle subtended at the
centre of the earth - between Alexandria and Syene - was 7 degrees or say 1/50th of the
Earth’s circumference. The distance between the two localities was well established,
over centuries of Egyptian culture, from messenger-runners, and accepted as 5 050
itinerary stadia of 157m or 793km, thus giving a polar circumference of 39 650km. This
was within 1% of the modern value of close to 40 000km (Napoleon defined the metre to
be a ten-millionth of the distance from the Equator to the Pole.)
The remarkable accuracy of this and other dimensions of moon and sun sizes and
distances was lost in the decline of Greece, and with it, the philosophical logic of the
time. [Their determination is given later.] It was not till two thousand years later, that
Copernicus again showed the world to be spherical and orbiting around the sun. But only
with Newton’s postulation, based on his laws of gravity, was the earth considered
elliptical in polar section. Newton’s concept was proven when, under Louis XV the
French Academy of Science financed major expeditions. One to equatorial Peru for
comparative measures of terrestrial length along meridian arcs, with others made in
Northern Lapland and Southern Africa to show a variation of length for a given angular
latitude difference.
We, in South Africa, are fortunate that in 1751 a very meticulous observer, the Abbé de
la Caille came to Cape Town. He established his observatory in the courtyard of a house
in Strand Street, and, there, laboured unremittingly. In the course of little more than a
single year of actual observation, he compiled the material for his catalogue of 10 035
stars, made observations of the moon and the planet Mars from which, in combination
with corresponding observations in the northern hemisphere, he derived the then most
reliable values of the lunar and solar parallax. Within the same short period he also
measured the first arc of meridian in the Southern Hemisphere, and made observations
of Jupiter’s satellites from which he derived a very approximate value of the longitude of
Cape Town. When it is remembered that de la Caille did all this work single-handed,
without the help of computers etc., one is lost in amazement at the energy and capacity
of the man. In the course of a single year, he laid the foundations of sidereal astronomy
in the southern hemisphere, he pointed the way to the geodetic survey of South Africa,
he indicated the lines of research which subsequent astronomers at the Cape have
followed, he rendered many scientific services to the Dutch Government of the day
(including a sketch-survey of Hout Bay), and won the friendship and love of all who knew
him.
Despite his very accurate observations, his measurement did not agree with theory as
the arc was too long for its latitude difference and only the extended arc by Thomas
Maclear in 1840-1848 proved the earth’s ellipticity. Subsequent meridian arcs showed
the geophysical anomaly of plumb line deviation - especially by the massive Table
Mountain, which erroneously affected the Abbé’s determination of the latitude for his
southern station on Strand Street.
The dream of Surveyors in those days was to have angels fly with distance measuring
chains to relieve the very burdensome task of accurate base length measurement. Here
was a major interactive requirement, but only recently solved.
I was most fortunate to have been a student guest at a 1948 Survey Seminar, held in the
Hillman Block at Wits University. The discussion was between Surveyors who had
invited the Radar experts, including Dr. Hewitt, to discuss the possibility of using Radar
for accurate surveying. The question then asked by Dr. Hewitt was whether Surveyors
could accept a repeater return rather than a passive reflection from a far terminal.
Having received an emphatic ‘yes’ from the Surveyors, his Telecommunications
Laboratory with Dr. Wadley invented the Tellerumeter and the first prototype
demonstration tests were made by the Wits Survey Department in 1952. Distances of up
to 100Km could be measured to within millimetre acuracies.
Thanks to the electronic engineers, a most important tool for surveyors was invented. Its
ongoing modification over the last years has contributed vastly to survey methods and
accuracies. But I am digressing …
Back to the Greeks and their desire to determine the dimensions of the spherical earth
and the extensions thereof.
The first step to understanding the truth of the heavens is probably no more difficult than
the first step toward recognizing the spherical earth. The first step to understanding
celestial motion is to perceive that the daily motion of the stars across the skies arises
from the rotation of the Earth. This concept was formulated by Heraclides and
Aristarchus, but was not accepted by the vociferous Plato and Aristotle. As some of
Aristotle’s teachings were accepted subsequently by the then new Christian Church, the
earth remained flat and stationary and the heavens moved in circles around the earth.
Building on Heraclides’ great idea from the fourth century BC and having the diameter of
the earth, the next task was to find the distance to the most prominent of our heavenly
bodies, the Sun, the astronomic Unit.
The best the Greeks could do was recognise that the sun was very far away by earth
standards, at least 1 000 earth diameters away. It was not until 120 years ago that Sir
David Gill at the Cape Observatory could give the actual value, that the distance was
closer to 12 000 earth diameters or 150 Million Kilometres.
So how does one go about measuring the distance to the sun in the period 250 BC?
Again, observe and use your logic for deductions and combinations. Thus combining the
other major regular movements, (other than the diurnal) that of the moon in its monthly
28 day cycle around the earth, together with a less regular but fairly often visible
observation, say once a year, of the eclipsed moon, gave the answer.
The full moon, opposite the sun enters a large circular shadow, the shadow of a
spherical earth. The shadow disc appears 3-times larger than the lunar disc and,
therefore, the moon’s diameter is about one third that of the earth’s which is a good
estimate of its actual 3480km diameter. Now the distance becomes easy. The moon’s
apparent constant visual angular diameter could be measured, even with primitive eye-
ball observations, to be a half degree or say one hundredth radian, and, therefore, 100
times further away than its diameter, coming close to its actual average distance of 38
440km, a little more than one light second distant, or about thirty earth diameters.
Now, if the sun were at a similar distance form the earth as the moon then, at first and
last quarters of the lunar cycle, when the angle sun-earth-moon is 90 degrees the phase
shadow angle should only be about 45 to our line of sight to the moon. This is certainly
not the case, as visually the phase angle clearly appears very close to the 90 degs
caused by an infinitely far away sun. The Greeks appreciated this observational problem
and could visually only say that the angle was at least 89 degrees causing an angle at
the sun of probably less than 1 deg for the lunar orbit around the earth. Then the sun
had to be at least 50 x 30=1500 earth diameters from us. But as the solar disc also
subtends a half degree at the earth, then with a crude distance of only 1500 earth
diameters, (not the true 12, 000) the sun would have to be at least 15 times bigger than
the earth.
When they combined this thought of size with distance, in other words such a large
object having to spin around the earth once in 24 hours at such a large distance, would
require a tremendous velocity. A velocity equal to 1 second for the distance from
Alexandria to Syene - quite impossible. (Even our modern rockets only achieve 1% of
such velocity.) Therefore, and obviously, the sun had to be stationary and the earth had
to rotate on its axis and revolve around the sun. Remember this was all clearly stated in
the Alexandria Library, with copies also in Byzantium and Pergamon.
This vast knowledge was suppressed by the Church, and only rediscovered by Muslim
Scholars in 700+AD, and taken by them via North Africa and Spain, to Paris and Europe
in 1000AD.
With the revival of this knowledge, then finally came about with the acceptance, almost
as a protest, of the Sun Centered Theory of the genius Nicolaus Copernicus in 1500.
This theory then gave new impetus for a revival of astronomic observations. Just as
Copernicus was the first European since Greek times to rise to the stature of
Aristarchus, Tycho Brahe, the mid 16th century Danish observational astronomer, rose
to the stature of Hipparchus, but even he, observing from a fixed earth could not accept
the Copernican theory. None the less his observations enabled Kepler, the
mathematical, theoretician, in 1605 to postulate his still accepted laws of planetary
motion of ellipses, with the sun at a focus, and the proportional ratio, of orbital
dimensions, to periods of revolution, around the sun.
At the same time, Galileo, a true experimental physicist, actually built a telescope after
its invention (whereas Kepler only worked out the optical theory). Galileo’s observations
of the phases of Venus and moons around Jupiter were the required observational proof
of Copernican theory .With Kepler’s laws and the dynamic principles of Newton, modern
astronomy was initiated.
As stated earlier, Abbé de la Caille’s observations of Mars, matched with those in
Europe in 1751, enabled a reasonable triangulation distance to be made using the 10
000 km base line of Cape-Europe. Combining the annual 686 earth days year of Mars,
with the above earth mars ditance and using the Kepler period law, an early nearly true
Earth to Sun distance was obtained.
To improve the determination, many expeditions were sent in 1760s around the world in
order to triangulate the near planets Mars and Venus. One such expedition was made by
Captain Cook, to observe the transit of Venus, and incidentally discover Australia.
Many such observations in the 18th century showed the tremendous distances to and
actual sizes of the Sun and Planets. Confirmations were observed in the 1800s with a
further observation of the transit of Venus being made in the clear skies of the
Karroo at Montague Road, now Touws Rivier, in 1882. The telescope mount is still
there as a National Monument.
However, it still left unanswered the question of what and how far were the stars.
The 19th century mathematicians, such as Gauss and Bessel, and observational
astronomer William Herschel showed that stars were probably other suns by observing
that Newton’s law of gravity existed for many binary stars. But the six monthly parallaxes
caused by our orbit around the sun could still not be observed with their instruments.
This proved that extremely far distances to stars caused such vast reductions in their
brightness and stars could be Suns.
Again at the Cape Observatory Thomas Henderson using a heliometer (split objective
telescope) measured the parallax of Alpha Centauris at just under one arc second, or
One Parsec. Subsequently with the determination of “c” the velocity of light - one parsec
i.e. the angle-earth-star-sun of one second was established to be 3.25 light years, thus 4
Light Years to the nearest star.
At the same time in 1850 another break through in astronomy was made by applying the
newly discovered Kirchhoff Laws of Spectroscopy to star light. This was the birth of
Astrophysics, and enabled the classification of stars by type and age.
And yet again, at the Cape Observatory another major contribution was made by its
director, Sir David Gill making the first photographic plates of stars through his
telescope. The result of this success was many observatories contributing to Celestial
Photographic Atlases containing 100 million stars and an actual catalogue of 6 million
bright ones. Measurements of such photographic plates - many taken in the 1930’s at
the Yale Observatory on the west side of Wits on Yale Road, have enabled the
triangulation distances of about 10 000 closest stars to be made.
This vast sample of observed stars contains many different spectral types with each type
generally having the same absolute brightness. Thus, by observing the brightness and
type, distance can be extrapolated. This has given scale to our Milky Way Galaxy and
our Sun’s position in it. The Milky Way is 100 000 light years in diameter and 10 000
Light years across in disc thickness. Observed in the spectrums of these stars were
small doppler shifts of atomic spectral lines proving the rate of movement of the spiral
arms of our galaxy.
But even more objects were photographed. Millions of fuzzy nebulae, all being galaxies
themselves. Cataloguing them showed doppler shifts at ever greater factors, to about
0,2 - i.e. velocities of 60 000 km per second with decreasing brightness.
Cosmological theories allow for the assumption that most galaxies have similar absolute
brightness thus again photometric measures could indicate their distances. Edwin
Hubble made such galactic observations in the 1920’s with the 100 Inch Mount Wilson
telescope and was able to determine the constant relating galactic distances to their
velocities away from us and each other. It is this significant observation that has
postulated the Big Bang Theory, stating that all matter in the Universe was accelerated
from a previously collapsed, extremely dense state about 13 billion years age.
Cosmological analysis of star clusters on the edge of our Milky Way Galaxy
independently determined the age of our galaxy at a similar age of 13 billion years.
It is this knowledge of the probable size of the universe, combined with current
observations, of billions of other galaxies, that has stimulated the tremendously revived
interest and expenditure in astronomy. Many new huge 8 and 10 metre diameter optical
telescopes have recently been built on the best possible observing sites.
Top of the Hawaiian Crater; on top of Chilean Desert Andes and of course our very
special S A L T, the South African Large Telescope,11 metres in diameter at Sutherland,
also in the Karroo.
Radio Astronomy and the study of some uniquely powerful radio point sources in the
1960’s, and their subsequent photographic location and optical spectra has also opened
up a new, much further horizon. These objects show red shifts of several factors of
frequency change Thus discovery of the quasi stellar radio sources, or QUASARS again
revolutionized our knowledge of the universe.
These Quasars with tremendous energy in light and radio emissions, being so very
bright, have been found with red shifts of 4 times factor, or velocities of 0,9. Times C
that is 270 000km/sec. Using the accepted Hubble constant, again ages of
approximately 13 billion years are obtained. Thus, Quasars, currently observed are
possibly depicting not only very early states of formation but also the possible extremity
and beginning of the universe.
As a surveyor, a person trained to measure, I have had a marvellous career being
involved with some of the modern developments. First with optical mechanical survey
equipment improvements, then aerial photography for mapping, then early satellite
observations for geoidal earth dimensions, then electronic distance measuring, and
computations, then lasers for distances to satellites and satellite global positioning.
And now with radio telescope observations, of Quasars from around the world,
intercontinental distances are being measured to millimetre accuracies, enabling minute
small continental drift movements to be determined. Radio-Astronomers have become
the ultimate surveyors. Using a technique of radio wave pattern interferometry Radio-
telescopes, spread around the world, record Quasar pulses simultaneously for hours on
tape. The subsequent correlation analysis gives the distances between the huge dishes,
which have changed over the past twenty years, to show continental movement.
MAN MUST MEASURE, has come all the way from Babylonia and Greece, Islam and
Europe, via ASTRONOMY, to building S A L T in the Karroo and the BIG RADIO
TELESCOPE at HARTEBEESTHOEK in GAUTENG all to show that we are moving
10 centimetres per year to the NORTH EAST.....
THIS is of no direct value to U3Aers, but has answered my sixty year quest. IT HAS
AGAIN proven the foresight of South African scientists. In 1937 the prominent geologist
ALEX DU TOIT published his work on the break up of GONDWANALAND entitled
“OUR WANDERING CONTINENTS.”
Astronomy is bringing many sciences together and reviving our interest. I therefore
suggest one way of celebrating the inauguration of S A L T would be further study of
the subjects in the above pages.
For a start obtain a copy of the new Publisher’s Choice book.
“THE STORY OF EARTH AND LIFE” A Southern African perspective on a 4.6-billion-
year journey. Written by TERENCE McCARTHY, Professor of Mineral Geochemistry,
UNIVERSITY OF THE WITWATERSRAND, JOHANNESBURG, and Prof BRUCE
RUBIDGE Director of the Bernard Price Institute for Palaeontological Research
UNIVERSITY OF THE WITWATERSRAND.
And for those interested in furthering your knowledge in greater detail go to:
The official website of the SOUTH AFRICAN LARGE TELESCOPE on www.salt.ac.za
and the SOUTH AFRICAN ASTRONOMICAL OBSERVATORY on www.saao.ac.za
YEA WITS!! HAPPY STUDIES
Werner Kirchhoff November 2005
011 880 0477 wkirch@iafrica.com