Evening star. [volume] (Washington, D.C.) 1854-1972, 1900-06-16
SOMETHING NEW ABOUT VENUS.
Rove.It Has BeeI' Learned That Its
Day Resef4bIesfO urs.


From the London Mail 81
An accomplished astronomer has Just
made a discovery in the, heavens which
merits our close attention, for it amplifies
our knowledge of the condition Of an inter-
esting neighboring world. THAT neighbor-
ing world is the beautiful planet Venus,
and that the discovery should have been
made Just now will occasion no surprise to
any one who has watched the brilliant orb
which has for weeks been adorning our
evening sky.
Venus possesses special and particular
interest from the circumstance that it Is a
globe which in many respects has a start
ling resemblance to our own earth. To be-
gin with the beautiful evening star is al
most exactly the same size as the globe on
which we dwell. The number of miles ira
versed in making voyage around the
equator Of the earth would be almost iden-
teal with the number of miles which
would make an equatorial girdle for Venus.
Nor does the resemblance between tho
earth and the planet consist merely in their
equal size. The two globes have practically
the same weight
If we imagine pair OF weighing scales so
mighty that Venus could be put into one
pan and the earth into the other no great
difference would be perceived between the
weights of the two celestial orbs. Two bill
lard balls which had no greater proper
tional difference in size and weight than
NEUTRALITY-SUSPICIOUS. The resemblance be-
tween these twin planets has. however,
been carried much further by the interest
ing discovery which has just been an
nounced to astronomers and which L Shall
now attempt to describe.
To a planet which may be the abode Of
life one Of the most important conditions
will be the succession of day and night.
Whenever the question as to the resem-
blance of another world to our earth Is
raised 1t is natural to consider how far the
inha bftants of such world. If inhabitants
there be. resemble ourselves in the enjoy
ment of the alterations of day when the
sun Is in the skies with night when the
sun is below the horizon. The change from
day to night. the change from night to day.
are of course. consequences of the rotation
of the planet on its axis. We desire to
learn how far the period which the planet
requires to complete each turn may agree
or disagree with the time required by the
earth for a like movement. To put the mat
ter more definitely. we may inquire how far
| the period required by Venus to rotate on
its axis corresponds with that period of
twenty-three hours and fifty-six minutes.
which expresses the time taken by the
earth to complete one revolution about its
axis. The determination of the length of
the day and the length Of the night to
which the inhabitants of Mars must ac
commodate their domestic arrangements
has never admitted of much doubt. Indeed.
we know the length of the day on Mars to
d
has been made so accurately because the
marks on Mars are clear enough to be pre-
cisely identified. After the lapse of years.
or after the lapse of even centuries. those
marks are still to be seen, without any
doubt whatever. in each revolution of the
planet. But for the study of the length Of
day and the length of night on Venus the
face Of the beautiful evening star offers no
such facility. This globe has no well-mark-
ed features; there are no definite spots to
| sully the brilliant mantle Of sunbeams char
acteristic Of the evening star.
One very eminent astronomer thought
that the day in Venus must be enormously
long: must in fact. last for about fifteen
weeks while the night which succeeded it
had to last for fifteen weeks more. The dis
crepancy showed that the marks on the
planets globe were not sufficiently definite
to solve the problem. Such marks as could
be seen with more or less distinctness were
most probably merely clouds in the atmos-
phere of the planet. and consequently had
no perma Some other method of
solving the problem not exposed to such
difficulties was clearly necessary.
A totally new method Of attacking the
question has been applied to Venus during
its present apparttion by the astronomer
Belopolski. He has abandoned altogether
the search for permanent marks on the
planet. He has adopted a totally different
principle. As the plant turns round. one
edge comes toward US and the other edge
goes from us. If the period be the short
one. like our own day. then the edge which
Is advancing toward us will move more
rapidly than 1t would be moving If the
period were to be expressed by months. 1t
IS easy to see that by determining the rate
at which the advancing edge Is coming to-
ward us 1t is possible to calculate what the
duration OF the whole rotation must be.
A beautiful new process permits this to
be done. Belopolski found that the edge of
the planet coming toward the earth Is NOV
ing faster than it would be If the long pc
Rod of rotation were adopted. and he has
therefore determined that we must accept
the short period. Thus a most difficult
question has been set at rest. To the other
analogies between the earth and its twin
globe Venus we have now to add that the
day and night for any inhabitant on that
world succeed each other In much the same
fashion as day and night succeed each
other on this earth.