Pittsburg dispatch. [volume] (Pittsburg [Pa.]) 1880-1923, 1892-06-26
Astronomers of the World Will Be
Watching Them in August.
THEY WILL BE NEAREST Us THEN.
Only Sixty Miles in Diameter and Dean
swift Located Them First.
ECLIPSES EVERY DAY ON JUPITER
WRITTEN FOR THE prspArcH.I

| trst opportunity afforded Tor examining
them, inasmuch as they are so small as to
be only perceptible at close range.
Once in every Is years Mars reaches its
nearest point to the earth. Eight weeks
hence it will be within IS, ,oOo, 600 miles Of
us, whereas its greatest distance is 141 ,000,-
900 miles. Great interest attaches to the
matter, because this sister world is so much
like our own in respect to Its climatic and
other conditions that it may reasonably be
/ supposed to be inhabited, perhaps by human
beings.
When the lover swears by the earth's "in.
| constant" satellite, it never occurs to him
| to consider that there are least 20 moons in
the solar system. Saturn alone has eight,
| the biggest of them, "Titan," being nearly
| twice the size of our moon, and Jupiter
possesses four, ranging in dimensions up
ward from Europa. just about as large as
the orb of terrestrial night, to "Ganymede, -
greatest of all known moons. The latter
has diameter of 3,4SO miles. whereas the
moon belonging to this world is only 2, 160
| miles through.
Some Moons Arc Still Hot.
and cold, similar conditions are not as
sumed to govern all the satellites of the sis
ter planets. Some of those pertaining to
Jupiter are believed to emit light of their
| own, showing that they are still hot. How
| ever, astronomers are usually eager to find
| evidence of life on other spheres, even dis
| covering on the earth's attendant orb ap-
parent traces of mighty works of engineer
ing artiice-the imagined creations of races
of beings long extinct-such as the stupen-
| dous bridge that appears to span a crater of
the moon volcano called 'Eudoxus.''
Eclipses are everyday affairs on Jupiter.
Three of its satellites are eclipsed at every
revolution of that mighty globe so that a
spectator there might witness during the
Jovian year 4,50O eclipses of moons and
about the same number of eclipses of the
sun by moons. Under such conditions one
would become accustomed to a phenomenon
which occasionally appals the terrestrial
''Mimas," about half the size of the earth's
satellite, is SO close to the planet in its cir
cling that it seems to cross the face of the
latter at an astonishing rate of speed. Of
the seven others, Titan" has diameter of
8, 300 miles, 'Iapetus" 1 100 miles, sRhea"
!, 200 miles, "Dione"::a and ''Tethys" each
500 miles, while "Enceladus" and "Hy-
perion" are very little fellows. Several of
of them in the sky together, with the fam
ing ring of star dust stretched athwart the
heavens, must make gorgeous spectacle by
night on the Saturnian sphere.
Obtaining the Velocity Of Light.
Through the telescope it is very interest,"
ing to watch the shadows thrown upon
Jupiter by that giant planets moons, OBJ
servstion of the eclipses of which fur
nished the first data for estimating the We
locity of light Uranus has four little
and "Oberon" which, strange enough,
rise in the north and set in the south. A
single diminutive one belonging to Neptune
traverses the sky from southwest to north
east Neither Mercury nor Venus has any
satellite.
But the most interesting of all moons are
the two that attend Mars, each about 60
miles in diameter. That planet is just one
half the size of the earth; its surface is
divided into continents and seas, having as
much land as water; it has an atmosphere,
clouds frequently concealing its face, and
its seasons are about the same as here,
though the winters are colder. Because one
of its moons travels around it three times as
fast as Mars itselfs turns, it appears to rise
in the west and set in the east. while the
other really circling in the same direction
at a speed comparatively slow, rises in. the
east and sets in the west. Thus both moons
are seen in the heavens at the same time,
going opposite ways.
Dean Swirt's Remarkable Guesa
The most remarkable guess on record was
made by Dean Swift, who, . century before
the moons of Mars were discovered, made
Gulliver say of the astronomers of Laputa:
l.- Ill Il
volve about Mars, whereof the innermost is
distant from the planet exactly three diam
eters of the planet; the former revolves in
the space of ten hours and the latter In 21L
hours" In fact, the inner moon is 10, 600
miles from Mars whereas-the diameter of
the planet being 1000 miles-Gulliver's
estimate would place it at 1900 miles
For the outer moon he gives 20, 900 miles
for the distance, which is really 5000
miles The time of revolution for the inner
moon is actually7 hours and 80 minutes,
and for the outer one 80 hours. Prof Hall
has named these moons 'tDeimos" and
Mars who are mentioned in Homer's
ssIliad."
Hundreds of minor planets belonging to
the solar system, which are only big enough
for moons, though not such, have been dis
covered during the present century. They
are called asteroids" and the three largest
of them are "Vesta," 'Ceres" and pal
las" Many of them are only of about the
bigness of a good-sized farm. Life upon
one of them, owing to the feebleness of
gravity, would seemingly be attended with
difficulties. One ingenious romancer has
described an imaginary Journey through
upon q small asteroid, finding it occupied
by single giant The latter, being dis
pleased with some remarks made BY his
visitor, kicked him off into space SO far
that he fell within the attraction of another
sphere.
The Two Undiscovered Planets.
To solar planets yet undiscovered moons
may belong-for example, to the mysterious
"big dark sphere" beyond most distant |
Neptune, which some astronomers assert |
the existence Of A similar hypothetical |
world, alleged to have its orbit inside that |
Of Mercury, is 'Vulcan." Science has not |
accepted the latter, though two observers
Swift and Watson, working independently |
in Colorado a few years ago, simultaneously |
declared that they saw it. Watson was so
confident of his find that he built tunnel !;
in the side of q hill, pointing toward the |
tom, thinking to see the object better.
From the bottom of the well, of course, one
can perceive the stars by day with the
naked eye. But this enthusiast died with
out proving his belief. The existence of
vulcan" and the ''trans-Neptunian"
sphere has been inferred from otherwise
perturbations of the known
orbs Of the solar system.
A pretty fair notion of sizes and distances
in the solar system can be got by selecting
! level piece of ground where there is
plenty of room, placing there globe 2 feet