South Bend news-times., 1915-06-30
The Far Sentry of the
Solar System
By Garrett p. serviss.

! In these troublous times on the lit
/ tie earth it is refreshing and encour-
I aging to make an intellectual excur-
sion among the really great Orbs that
surround us. and to observe with
what grand serenity they continue
undisturbed in the pursuit of their
I wonderful ways.
At the present moment the most
distant member of the suns company,
the planet Neptune. is visible, with
the aid of a small telescope. in the
evening sky between the constella-
tiOns Geminin and Cancer. Ii is big
world, equal in size 10 So earths. II
is the OutermOst sentinel that guards
with solemn round" the biVOuac of
the solar system. Where its meas
ured PAGES fall lies the planetary
frontier. Beginning from its dark
and lonely beat. the awful sanaras OF
interstellar space stretch away. illim-
liable, though sprinkled with distant
suns like diamonds scattered over a
trackless desert.
This sentry world strides slowly on
his mighty turn. He has eight thou
sand eight hundred million miles TO
go for every circuit around his camp
fire. the sun. Ephemeral incidents
occurring IN the planetary tents that
the guards are nothing; they do not
exist for him, nor he for them. When
ent post between the Twins and the
Crab. looking down once more. from
the same point. through the pleasant
June twilight, not a living soul OF all
the millions now alive Will be left
upon the earth.
The mystic chords of memory
Will for all these. have long since
been broken. Five hungry genera
tons will have trod them down deep
Of fr1p A
hundred and sixty-fve years is the
measure of Neptune's orbital period
Yet his pace. slow i'm an astronomical
sense, is seven-fOld faster than the
swiftest flight of the destroying shell. |
AS is suitable for his position, a
watcher on the outpost, Neptune pos
sesses a range of vision unrivalled by
any other member of the solar sys-
tenn For him the parallaxes of the !
stars are 30 times as great as for the |
earth. This is because of the great |
diameter of his orbit which is nearly |
$500, ,O00,0 miles. Even the most |
distant stars must show some meas
ureable change of place in the sky |
when viewed from the opposite ends |
of a base-line as vast as that! Here |
on the earth we cannot tell how far |
away mighty Canopus is. We simply |
know he is so distant that a base-line |
1S6, 600, 600 miles long furnished by |
the diameter OF the earths orbit has |
no measurable length viewed from |
Canopusl The same is true of all but |
a very few of the stars.
But in the sentry~bOx of Neptune |
CanOpus' distance may be accurately |
known. The records kept there may |
show the range for every bright star |
and even for every star in the milky |
way. so that if a sidereal world-war !
should break out and the sun should |
feel compelled TO lombard his far-off /
brothers the solar projectiles could |
be landed with deadly effect.
There is another visual advantage !
which the sentinel Neptune enjoys /
over the planets that circle nearer to /
the sun. Since he is 30 times farther |
from the sun than the earth is he re-
ceives 900 times less solar light, area /
per area, than our planet gets. That |
is the same as saying that daylight on /
Neptune is 900 times less intense than |
upon the earth. Thus he is like a /
sentry pacing in the comparative |
darkness around the edge OF an en- |
campment in the woods unblinded by |
too near neighborhood TO the central /
fire. Still. although the sun as seen /
from Neptune is only about as great 4
in apparent diameter as an electric /
arc light, yet il gives an illumination /
between six and seven hundred times 4
as bright as that of full moonlight on .
the earth.
IL would be great to ride the cir /
cult with Neptune-to have ones \
brief terrestrial life-span enlarged by I
the scale of the long Neptunian years. /
and 10 sweep with optic glass" the /
starry battlementS from the circum- /
ference of that vast orbit But Nep- I
tune would offer a strange, uncertain I
footing for animals like us The mean 4
density of the huge planet is but
slightly greater than that of water. /
IL may be a globe Of LIQUID for all that /
we can tell. II IL has inhabitants. /
they may be fsh-like creatures.
dwelling in a bubble ocean. or they /.
may be composed of substances so |
rare that they resemble living hal /
looms, scinullating with prismatic
hues as they roll in the diminished !
sunshine or fash of the sheen OF the
stars. But II is "A long long way to /
Neptune and this world may never I
Lnpra- hat e pofUr in 4ha4