Harrisburg telegraph. [volume] (Harrisburg, Pa.) 1879-1948, 1919-01-06
kindly give information on the


.+.irst-Does. the earth revolve
ss,out the sun from west to east in
\ accordance with it's own revolution
~n ITS own axis?
Second-Do the planets aL re-
voive about the sun chch in the di-
rection of its own revolution. In
other words does the earth or any
planet revolve about the sun in a
direction counter to it's own revo-
luton?
Third-Do the planetary moons
revolve on their own axes or are
they like earth's moon in this re-
spect?
These questions all appear to be
very simple. but l certainly do not
know the answer to them, and be-
leve that the average person, like
myself out of school for many
years, mikht like to be Frightened
SIDNEY STEVENS.
Millinocket, Me.
i. Yes, the revolution of the
earth around the sun like it's rota-
ton on it's axis is performed from
west to east. This direction is
purely conventional, and the notion
of it arises from our sense of the
CnCu!oF nlOtlOilS 10 WHICH IL Is uuC.
TO Il man looking down upon oue
of the poles of the earth ithe
'north"),' the rotation would be
suspended above the other pole
(the "south") the rotation would
be- from left to right.
Take small globe out OF its
bearings and set il spinning from
west to east" as indicated by its
geographical features; then turn
~ 4.~f,, 4p,ts s,.1
face, and you will perceive the
curious apparent reversal of its
rotation, due entirely to your re-
ferring it to. your inner sense Of
direction.
just so, the revolution Of the
earth and the other planets around
the sun would be from right to left
for Il person looking down upon the
solar system from point north"
of its plane, and from left to right
FOR one who regarded 1t from the
south" side.
You get q similar effect by. look
ing at q spinning wheel alternately
from opposite sides. To man on
one side of a road the wheel is
running to the left; to a man on
the other side it is running to the
right, but the one mans right" and
the others left" are purely per-
fine the actual motion Of the wheel.
Hang the observer up by the heels
and what was right becomes left.
But note that west" and east
are not referred, like right" and
left" to our personal impressions,
but to the rotary motion of the
earth. Thus west and east have the
same sense on both sides of the
equator, and the earth's rotation
takes place from west to east for all
the earth's inhabitants, no matter
in which hemisphere they live. This
is because mankind have agreed to
consider the direction of the sunset
west and that of the sunrise east.
Nevertheless, with regard to fixed
outer space, what is west for us is
east for our antipodes. Just as right
and left are impressions of direction
referred to the human brain as Il
source, SO west and east are impress
sions of direction referred to the
rotation of the earth, and both are
correspondingly restricted in their
application. i
2. All the planets, without eXcep-
ton, revolve around the sun in the
same direction, and all, except two,
rotate on their axes in that direc-
ton, west to east" The two ex-
ceptions are the outer planets,
Uranus and Neptune. There is
some doubt about the exact inclina-
tion of the axes of tlsose planets to
their orbits, but the axis of Uranus
appears to lie nearly in the plane of
it's orbit, so that its rotation is per-
formed almost at right angles to its
motion around the sun, while the
axis of Neptune it tipped so far over
backward" that its rotation occurs
from east to west, although the
planet revolves around the sun from
west to east. For Uranus a very
curious result follows, because every
summer, in either hemisphere, the
sun must pass nearly through the
polar zenith, the ecliptic lying across
the middle of the polar zone, while
in winter the sun is never seen with
in that zone.
In the satellites of the planets we
have Il few more examples of oppo-
sition to the general direction of
motion in the solar system. The
four satellites of Uranus follow the
example of that planets rotation by
revolving around their primamry
nearly at right angles to the plane
of its motion around the sun, while
the one satellite that Neptune is
known to possess also inlimtates it's
master by revolving from east to
west. In addition to these, there
are three other satellites, includ-
ing the two outermost of Jupiters
nine, and the one most distant of
Saturn's nine, which, unlike their
sisters, reVolVe from east TO west.
1t is significant that just as the
only planets that contradict the gen.
eral law of rotation in the solar sys-
tenn are the most distant ones from
the sun, so the only satellites that
contradict the general law of revo-
luton in the systems to which they
belong are the most distant ones
from their planets.
.. TO your third question u per-
fectly definite answer cannot be
given. Observations have not abso-
lutely determined whether or not
the satellites generally rotate on
their axes. AS far as it goes the
evidence, mainly inferential, Is that
they all Cor all the large ones) prob
ably rotate, like our moon, only
once i'm the course OF n revolution.
This would result in their keeping
the same face always toward the
primary, as happens with the moon,
and it would probably be conse-
quence of tidal friction.
Notwithstanding the exceptions
that have been mentioned, the mo-
tons both of revolution and rota-
tion in the solar system are so