CHAPTER VI

JUPITER, THE GREATEST OF KNOWN WORLDS


When we are thinking of worlds, and trying to exalt the imagination with
them, it is well to turn to Jupiter, for there is a planet worth
pondering upon! A world thirteen hundred times as voluminous as the
earth is a phenomenon calculated to make us feel somewhat as the
inhabitant of a rural village does when his amazed vision ranges across
the million roofs of a metropolis. Jupiter is the first of the outer and
greater planets, the major, or Jovian, group. His mean diameter is
86,500 miles, and his average girth more than 270,000 miles. An
inhabitant of Jupiter, in making a trip around his planet, along any
great circle of the sphere, would have to travel more than 30,000 miles
farther than the distance between the earth and the moon. The polar
compression of Jupiter, owing to his rapid rotation, amounts in the
aggregate to more than 5,000 miles, the equatorial diameter being 88,200
miles and the polar diameter 83,000 miles.

Jupiter's mean distance from the sun is 483,000,000 miles, and the
eccentricity of his orbit is sufficient to make this distance variable
to the extent of 21,000,000 miles; but, in view of his great average
distance, the consequent variation in the amount of solar light and heat
received by the planet is not of serious importance.

When he is in opposition to the sun as seen from the earth Jupiter's
mean distance from us is about 390,000,000 miles. His year, or period of