Evening star., 1949-10-05
Exact Planet Movements
Figured by Astronomers
Navy and Yale Scientists Report
Results of Mathematical Studies
Bv Thomas r. Henry

Results of Mathematical Studies
By Thomas r. Henry
NEW HAVEN, Oct 5.-The solar systems
nine spinning planets moving in orbits
around the sun are being reduced to new
order by vast cooperative project between
United States Naval Observatory and Yale
University astronomers.
Each planet. including the Earth. moves
in a path almost, If not quite, dictated by
strict application of the law Of gravity. The
sun pulls strongly in one direction. Fellow
planets pull them in other directions This
is the theory, and observations over the past
two centuries of their positions at given
instants are very close to what would bs
predicted from the theory.
Now observations are much more exact
and numerous than during the 10th century.
The object of the present work, which In
wolves the use of recently perfected mechan-
ical calculators which will do in few hours
work which would require months Of the
time of skilled mathematician, Is to pro-
duce far more perfect astronomical tables
for the use of mariners and other astron-
omers.
Astronomical D-Day.
January s, 1941, was the astronomical D.
day. Then the precise positions and veloci-
ties of all nine planets were determined at
given instant. From these data, using the
gravitational equations, the positions were
extended backward to 1870 and forward to
1860. The backward predictions now are
being checked with the actual observations,
which will be slightly off, and forward with
the observations made from night to night
at different observatores all over the world.
There already have been some notable
results. The orbit of the planet Mercury
around the sun is extremely eccentric.
Among the observations which never have
checked with theory are those Of the planets
"perihelion," or the point in its orbit where
it approaches closest to the sun. This varies
slightly from revolution to revolution, but
it should be possible to check its position
precisely for any Mercurial year.
The discrepancies were one of the major
arguments for the theory of relativity ad-
vanced by Albert Einstein. 1t did give exact
predictions. Opponents, however, advanced
the argument of incorrect observations. But.
says Prof Dirk Brewer Of the Yale Observa-
tory the reductions of the observations on
Mercury in the new project, which now have
been completed by DR.. Gerald M. Clemence
of the Naval Observatory staff, appear to
vindicate completely the claims of Einstein.
The effect is barely within the limits of
measurement.
1t is impossible to demonstrate it for Venus,
nearest planet to the earth and the second
nearest the SUM- because it has an almost
circular orbit which remains almost inva-
riable year after year. DR.. Clemence's work.
however, gives strong evidence that the same
effect is found in the elliptical orbit of the
Earth. 1t hitherto had been unsuspected. It
is about fifteenth as great as in the case
of Mercury.
Prof Brewer himself is working especially
on the outer planets, Jupiter, Saturn,
Uranus, Neptune and Pluto. These have
enormously long orbits, compared to Earth,
Mars or Venus.
Problems Of Interest.
Among the problems Of interest is that Of
the existence of tenth planet. still farther
away from the sun than Pluto and Alto
gether too minute for telescopic observa-
ton. It's existence may eventually be DEM
onstrated from positions OF Neptune and
Pluto which do not agree with theory. DR..
Brewer has found no evidence OF anything
of the sort in the positions Of Uranus which
has made two complete circuits OF the sun
since it was discovered in 1880. It does not
yet appear in the positions OF Neptune, but
this distant planet has covered only about
three-fourths Of its orbit since its discovery
In 1846. Pluto. discovered only 20 years ago.
would not be expected to show anything. 1t
requires $50 years to cover its path around
the sun.
The project, DR.. Brewer said Is expected
to provide new tables Of planetary move
ments based on improved mathematical
formulas which will stand up for centuries.
BY them, it is expected, 1t will be possible
to predict the precise position Of any planet
in its orbit at any second.
Only the work on Mercury has been COM
pleted. That on Venus is nearing completion,
while that on the Earth Is well under way.
Next March DR.. Brewer announced. there
will be conference in Paris. to which he
and DR.. Clemence will be the American dele
gates, to revise all the present astronomical
constants on which predictions are based.
These include such data as the distance Of
the earth from the sun. the mass ratios Of
earth and moon, etc.. which are especially
essential in the split-second prediction Of
eclipses. Some of those now accepted have
been considerably changed by observations
since 1896, when the present tables were
adopted.