The Washington times. [volume] (Washington [D.C.]) 1902-1939, 1922-02-15
DON'T BE FOOLED
is BEST ANTIDOTE TO SUPERSTITION
Prof. Serviss Has Hopes That Human Race
Will Eventually Distinguish Between
Science and Charlantry.

the earth, by employing two we'll
known rules, which / shall state
after having first expla ned what
is meant by such Q conjunction.
Only the inner planets, 1. e.,
Mercury and Venus, which are
Inner" because they are nearer
to the sun than the earth Is,
and consequently revolve around
it in orbits enclosed by the orbit
OF the earth-only these two
planets can, technically speaking,
be in conjunction with the earth.
They are in. that position when
they are in line or nearly in line
between the earth and the sun.
When Mars, an outer planet, is
in line with the earth and the
sun, the earth is the middle body
of the three, and Mars is said,
then, to be in opposition, 1. e.,
opposite in position to the SUN.
What is really meant by saying
that, on the occasion in question,
Mars and Mercury will be in con-
junction with the earth is that
Mars VIII be in oppos ton to the
sun at the same time when Mer-
curry Is in conjunction with the
sun.
Now for the way to tell when
any planet will be either in con-
junction or in oppos ton. For
convenience / borrow these rules
from Moulton's Introduction to
Astronomy" but you could easily
derive them for Yourself from
mere arithmetic relations:
Let p be the sidereal period Of
the planets revolution ii. e., the
actual time that II takes to make
one trip around the SUM: let A be
the sidereal period Of the earth's
revolution 1865 days., and let 8
be the planets synod period
meaning the time required for il
to pass from one conjunction, or
opposition, to the next. Then we
have for our rules:
us equals Up minus lie, for
an interior planet.
Is equals lie minus Up, for an
exterior planet"
The first rule will tell us how
Thus: Mercury's sidereal period
is eighty-eight days, and the
earth's sidereal period is 365
NayS NulSI vi
days.. Then. s, representing Mer-
cury's synodic period. we have
from the rule, Is equals 1888
minus 1856. Now, work that out
and you find that s equals about
ll6 days. This shows us that,
starting from any known commune
ton, Mercury will, on the aver
age, again be in conjunction
about 116 days later.
The second rule will give US,
In like manner, the time that
elapses between two successive
oppositions of Mars. The sidereal
period of Mars may be taken as
6S5 days. The equation will then
be IS standing this time for the
synodic period Of Mars: is
equals 1865 minus 1857. This
worked out gives us, for the
value of about IT'S days, so that
the average period from one op-
position Of Mars to the next is
about two years and forty-eight
days.
These figures, as already indi-
Gated, are only approximate, for
two reasons-first. because we
have for simplicity, employed
only approximate, for two reasons
first, because we have for sim.
plicity, employed only round fig.
ures for the revolution periods,
and, second, because, owing to &c.
centricities of the planetary or
bits. the length of the synodic Pc
RODS varies somewhat. In the
case of Mars the period varies in
the extreme as much as six
weeks.
Mercury's conjunction with
Mars occur, on the average,
every 101 days. Combining these
various periods you can readily
find out about how often the
earth, Mercury and Mars will be
in line with the sun.