Evening star., 1940-09-26
Of Stars, Men
And Atoms
Notebook Of Science Progress
In Field, Laboratory
= And Study
BIZ Thomas r. Henri.

By Thomas r. Henry.
On the morning Of November II will
take place one of the rarest of celestial
events-a transit of Mercury.
Shortly after sunrise in Eastern North
America the nearest and, with a single
exception, smallest of the family OF
planets will pass across the face of the
sun. Capt. j. F. Hellweg, superintend-
ent of the United States Naval Observa-
tory, has sent out an appeal to amateur
astronomers all over the United States
to make observations of the event.
Mercury passes between the earth and
the sun about 10 times every century.
There will be nine more such transits
in the Goth century, but all except one,
that of 1878, will be practically unob-
servable from the earth. Such an event
affords an opportunity to check up on
the orbit of Mercury, important for an
exact theory of the mechanics OF the
solar system. 1t moves in an eccentric
path around the sun. This eccentricity,
as reported from previous transit obser-
vations, was one of the chief arguments
advanced Is years ago by Albert Elm
stein in support Of the theory of rela-
tivity.
There will be four instants when Mer-
curry can be seen IN contact with the
sun, according to the instructions sent
out by the Naval Observatory At the
time of the first contact Mercury begins
to impinge on the suns disc 1t will be
black spot about 1920 the size of the
morning sun. About a minute and q
half later the planet will appear as
black drop hanging on the, suns limb,
like drop of water about to fall into
space. At this instant, according to the
Naval Observatory instructions, thread
OF light becomes visible between the
planet and the suns limb This is the
instant Of the second contact.
Although this phenomenon is well de-
fined, the time Of its occurrence as
determined from previous observations
is uncertain by more than 10 seconds.
The boiling of the suns limb, particu-
larly when low in the sky, makes obser-
vations difficult. Sometimes the thread
Of light appears to be made and broken
several times in quick succession.
Five hours later a similar sequence
OF events takes place in reverse order
as Mercury passes of the suns disc
Here the phenomenon to be observed
is the breaking of the thread of light
hotm al
The results of observations of previous
transits says Capt. Hellweg, have always
suffered from the too small number
obtained
"Observations Of transits of Mercury"
he says. ARE uncertain by amounts ap-
preaching half a minute of time be-
cause of the atmospheric conditions on
the earth. The uncertainty can be
reduced sufficiently only by obtaining
a great number of observations and
averaging the different results. The
ingress will be visible over most of North
can be observed in Europe or Africa. 1t
is therefore doubly important that as
tronomers who are so situated that they
can observe this transit allow nothing
within their control to interfere with
their observations"
This planet always has been difficult
to observe Very close to the sun,
caught in the intense glare Of the solar
radiation 1t Is known that 1t must be
a place of such intense heat that no
living thing could possibly exist on 1t.
There are certain surface markings
which can be observed and which show
that the planet always must turn the
same baked face to the sun. Clouds
observed there cannot possibly be due
to water vapor, like those of the earth
or the planet Venus, and must be great
masses of dust raised by hurricanelike
winds into the high atmosphere
Astronomers have shown by the vari-
ations of light that the planet must
have very rough and uneven surface
Its rocks appear to be, from the light
reflected from them, of volcanic origin.
The varying distance from the sun
tends to disintegrate the rocks exposed
to the great heat. Much of it is ex-
perature, ranging over hundreds OF
degrees centigrade.
Mercury" wrote one astronomer, rs
probably parched desert with nothing
to mitigate the intense glare Of the sun
on its day side, seven times as fierce
as We receive on earth. The condition
of its surface is so unfavorable to life
that any living thing is practically un-
imaginable"
1t long has been recognized that the
orbit of Mercury best checked by its
transits across the face of the sun, did
not quite fit the theories of gravity as
propounded by Sir Isaac Newton Up to
quarter of century ago astronomers
assumed that the difficulty was with
errors of observation, rather than with
the theory.
One of the revolutionary conclusions
Of Einstein was that, due to the peculiar
position of the planet so close to the
enormous mass of the sun, its orbit
would vary considerably from that in
herent in the formulas of Newton, but
that it would fit his own strange caIcu-
lations. Observations up to the present
have seemed to support his contention
and have been one of the chief bull
warks of the theory of relatively. The
finer observations expected this fall may
have an important bearing on them
Sees Alien Symbols
In Prize Sculnture