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A salutary tale
In search of planet Vulcan: the
ghost in Newton’s clockwork
Universe. R Baum and W
Sheehan. XVI+310 pages,
Plenum Press, New York, 1997.
$28.95. ISBN 0-306-45567-6.
The history of the relatively recent
past can often make absorbing
reading. In search of planet Vulcan
is such a book. Do not let it put
you off that it is based on the minutiae of celestial mechanics – Baum
and Sheehan weave an irresistibly
beguiling tale.
They start at the beginning in preNewtonian days and trace the
development of planetary theory
rapidly to Newton and his theory
of Universal Gravitation. They
record Newton’s immense disappointment that he did not achieve a
satisfactory account of the Moon’s
motion. We then look at the magnificent work of the French mathematicians of the 18th century, who,
after giving Universal Gravitation
an initially frosty reception, became
its greatest apologists. Their work
not only led to a theory of the
Moon’s motion, but to Le Verrier,
that dynamo of 19th century celestial dynamics.
While the achievement of Adams
is well acknowledged, it is Le Verrier that dominates the book. His
and Adams’ success in predicting
the existence of Neptune was seen,
perhaps in overblown terms, as the
final crowning glory of Newtonian
theory, and that achievement drove
Le Verrier to tackle the last of the
great unsolved Newtonian problems – the advance of the perihelion
of Mercury. As with the discrepant
orbit of Uranus, he believed that
the solution lay with an, as yet
undiscovered, planet between Mercury and the Sun. Similarly to his
prediction of Neptune, he predicted
an intramercurial planet at least as
massive as Mercury and the hunt
for Vulcan was on.
Not surprisingly, the observers
obliged and transits of the Sun
were reported, unexplained transits
from the past were exhumed and
confident predictions of future transits were proposed. Vulcan persistently failed to oblige with a predicted transit. Searches at total
solar eclipses were usually negative,
apart from the observations of Watson and Swift at the 1878 total
solar eclipse. Later photographic
surveys at total eclipses failed to
show a candidate Vulcan. The
April 1998 Vol 39
Out of sight: the infrared sky, a jumping-off point for Internet exploration of the universe.
astronomical community ceased to
believe. Einstein in 1915 showed
that general relativity accounted for
the advance of the perihelion of
Mercury beautifully. Unlike Neptune, Vulcan was an unnecessary
hypothesis.
Was it all futility? Was the prediction of Neptune the triumph it
appeared to be? It was not in the
least futile to try – before Einstein’s
theory of general relativity. But was
it the triumph of Newtonian theory
– probably the extent of the triumph was overblown as the “prediction” and discovery of Pluto was
ultimately shown to be. But were
all those experienced observers really as deceived or over-excited by an
actual solar eclipse as they were
alleged to be by their detractors?
Baum and Sheehan invite us to
wonder about those who thought
they had observed Vulcan in these
days of better appreciation of
comets and earth-crossing asteroids
– perhaps we might be less judgmental than their peers.
It was an irresistible read – just
the thing for a stormy Christmas
vacation. But the book led me on to
yet more unfortunate speculation:
what might be the equivalent at the
end of the 20th century of Vulcan
at the end of the 19th century?
Who now is the “successor” of the
overbearing Le Verrier and the
supremely self-confident Watson,
Swift, Peters, and all the others
active in this tale of derring do?
And who indeed in the 21st century
will confound us all like Einstein
did in 1915? I have my own actors,
but read the book, enjoy a splendid
tale and, yes, have a little fin de
siècle speculation too – it is wonderfully cathartic.
D McNally.
Web wanderings:
a telescope of
one’s own
Remote access to telescopes is one
approach to using Internet connections fully: schoolchildren, for
example, can point and receive
images from major instruments,
giving them the insight into the glories of the sky that is generally
reserved for professionals. This is a
powerful tool to draw people into
astronomy and one that will be
increasingly useful as such links
increase.
But such access can be almost as
valuable when what is available is a
bank of images. If the interface is
useful, access fast enough and there
are sufficient images, you can
explore the known sky from the
comfort of your terminal. This is
what Skyview, the Virtual Telescope
from NASA’s Goddard Space Flight
Center and the High Energy Astrophysics Science Archive Research
Center provides. At this Web site,
http://skys2.gsfc.nasa.gov/, you can
choose your wavelength (from a
range such as “radio”), or choose
your instrument, select an area of
sky, and the image appears. Access
is reasonably fast, the images come
with good captions and information about the instruments that
were used, and the scientists
involved get clear credit.
There are also three levels of
knowledge assumed at the interface.
If you choose the “nonastronomer” option, all you need
specify is the frequency of radiation
and an area of the sky such as
“Orion”, or “1987A”. Beautiful
images appear, with explanations.
There is a comprehensive glossary,
defining and explaining terms and
concepts, so that the process of
exploring the sky becomes informative as well as awe-inspiring. You
can use right ascension and declination to specify your region of interest if you prefer, making this a great
way to expand knowledge for those
who are familiar with the night sky
in visible light.
The basic interface gives the
option of choosing images on the
basis of sky surveys or instruments,
while the advanced option includes
all this plus the option of overlaying your chosen image with classic
star maps, such as the Palomar Sky
Survey. There are also choices for
parameters such as the brightness
scaling and so on.
I found this a fascinating tool for
my own learning and exploration.
It set off all sorts of guesswork and
hypothesis-testing: Why should that
object show up so strongly in the
infrared? What does that strong
radio source look like? And of
course, it is so easy to take such
astonishingly powerful information
retrieval systems for granted. I soon
found myself wanting the option of
a sky survey overlay on all the
images, to help me find my way
about. I also wanted what I suspect
are unreasonable things: to be able
to overlay or in some way directly
compare images in different wavelengths, something that I suspect
would not be helpful in most cases,
but I wanted to try.
All in all, this is a great way to
discover the sky, explore it further,
entrance other people and generally
help to explain what it is about
astronomy that is so fascinating – a
real eye-opener, in every sense.
Sue Bowler.
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