His year, or period of revolution about the sun, is somewhat less than twelve of our years (11.86 years).

His axis is very nearly upright to the plane of his orbit, so that, as upon Venus, there is practically no variation of seasons.

Gigantic though he is in dimensions, Jupiter is the swiftest of all the planets in axial rotation.

While the earth requires twenty-four hours to make a complete turn, Jupiter takes less than ten hours (nine hours fifty-five minutes), and a point on his equator moves, in consequence of axial rotation, between 27,000 and 28,000 miles in an hour.
The density of the mighty planet is slight, only about one quarter of the mean density of the earth and virtually the same as that of the sun.
This fact at once calls attention to a contrast between Jupiter and our globe that is even more significant than their immense difference in size.

The force of gravity upon Jupiter's surface is more than two and a half times greater than upon the earth's surface (more accurately 2.65 times), so that a hundred-pound weight removed from the planet on which we live to Jupiter would there weigh 265 pounds, and an average man, similarly transported, would be oppressed with a weight of at least 400 pounds.