Evening star. [volume] (Washington, D.C.) 1854-1972, 1901-08-24
EXCEPTIONAL EARTHSHlNE
UNUSUAL VISIBILITY OF NEW MOON
BEING INVESTIGATED.
Cancellations Reached by Prof. Cleve-
land Able of the U. s.
Weather Bureau.

From the New York Tribune.
There are two sets of conditions under
which it is possible to see light on the moon
which comes from the earth. One OF these
exists at the time Of total eclipse of the
moon. when the earth is directly between
that body and the sun. Enough solar radi-
alton. passing through the ring OF atmos-
phere around the earth, is bent from its
natural path to illuminate the moon family
even while it Is in the earth's shadow. The
moon will sometimes be dim and dusky
during an eclipse, and sometimes 1t has
fairly bright copper color. The degree OF
Illumination depends upon the clearness or
cloudiness of the earth's atmosphere in the
regions where the bending occurs.
The other situation is produced when the
moon gets between the earth and the sun
at the time of new moon" The side OF
the earth which Is turned toward It's satel-
lite Is brightly Illuminated by the sun.
whereas the side of the moon which is d.
rected toward the earth receives no SUM-
light at all. A little light. however, Is
thrown back from the earth's surface to
the moon. This phenomenon Is reflection;
the other one was refraction.
Moon On March %.
The amount of reflected light Is variable.
as we'll as that which Is refracted. What
is called ''earthshine" is much brighter at
Gently been directed to a statement made
by G. E. Lumsden, president Of the local
astronomical society in Toronto. on this
subject. He reports that on the evening OF
March p, when the moon was nearly new.
the dark portion was so distinctly visible
that several of the most prominent forma-
lions. seas and mountain ranges could be
identified with an opera glass. The part of
the earth which was turned toward the
moon at that hour embraced western Amer
lea, the Pacific ocean and eastern Asia. Mr.
Lumsden has asked for information tend
causes were at work in this quarter of the
globe to account for the unusual degree Of
Illumination.
Prof. Abl,e's Suggestion.
The matter has been investigated by the
United States weather bureau and it now
reports that Of the area which was con-
cerned in producing the earthshne about
Is per cent was land and So per cent was
water. Four-tenths Of this land is covered
with cloudiness in March. on the average,
and about four-tenths with snow. Over
the ocean the normal percentage Of cIoudi-
ness for the same months Is about SIX
tenths. Log books of Pacific steamships
have been consulted to see If there was an
unusual amount of cloud on March %. The
lower side of cloud is likely to be dark,
but the top is white when in flood of sun
shine. Hence it is assumed that the greater
the cloudiness the more powerful would
have been the reflection.
No definite evidence of the prevalence OF
more than the ordinary amount on the date
mentioned has been secured. But granting
that there was enough to raise the proper
ton to seven-tenths, Prof. Cleveland Able
doubts whether the difference would ac-
count for the observed effect.
He suggests another explanation, how
ever, which clears up the mystery in a
rather more satisfactory manner. The
| moon at perigee is only 221 900 miles from
the earth, while at apOgee she is 253, 600
miles off, OF course. the closer she comes
the more strongly she will be Illuminated
by earthshine. It is estimated that the
brightness at the least distance would be
81 per cent greater than at the greatest.
This Is far greater variation than is likely
to occur in the amount Of terrestrial cloudi-
ness, and the almanac shows that the
moon had just passed perigee at the time
when Mr.. Lumsden made his observation.
Still, the cause here specified should oper-
ate with equal power once month. 1t
would seem. therefore, that there must
have been a somewhat rare combination OF
astronomical and meteorological influences
at work to produce earthshine Of excep-
tional intensity. The moons position in
her orbit does not completely explain the
facts