and the gentle illumination of our nights.

The distance of the Sun has, moreover, been confirmed by other means,
whose results agree perfectly with the preceding. The two principal are
based on the velocity of light. The propagation of light is not
instantaneous, and notwithstanding the extreme rapidity of its
movements, a certain time is required for its transmission from one
point to another. On the Earth, this velocity has been measured as
300,000 kilometers (186,000 miles) per second. To come from Jupiter to
the Earth, it requires thirty to forty minutes, according to the
distance of the planet. Now, in examining the eclipses of Jupiter's
satellites, it has been discovered that there is a difference of 16
minutes, 34 seconds in the moment of their occurrence, according as
Jupiter is on one side or on the other of the Sun, relatively to the
Earth, at the minimum and maximum distance. If the light takes 16
minutes, 34 seconds to traverse the terrestrial orbit, it must take less
than that time, or 8 minutes, 17 seconds, to come to us from the Sun,
which is situated at the center. Knowing the velocity of light, the
distance of the Sun is easily found by multiplying 300,000 by 8 minutes,
17 seconds, or 497 seconds, which gives about 149,000,000 kilometers
(93,000,000 miles).

Another method founded upon the velocity of light again gives a
confirmatory result. A familiar example will explain it: Let us imagine
ourselves exposed to a vertical rain; the degree of inclination of our
umbrella will depend on the relation between our speed and that of the
drops of rain. The more quickly we run, the more we need to dip our
umbrella in order not to meet the drops of water. Now the same thing
occurs for light. The stars, disseminated in space, shed floods of light
upon the Heavens. If the Earth were motionless, the luminous rays would
reach us directly. But our planet is spinning, racing, with the utmost
speed, and in our astronomical observations we are forced to follow its
movements, and to incline our telescopes in the direction of its
advance. This phenomenon, known under the name of _aberration_ of light,
is the result of the combined effects of the velocity of light and of
the Earth's motion. It shows that the speed of our globe is equivalent
to 1/10000 that of light, _i.e._, = about 30 kilometers (19 miles) per
second. Our planet accordingly accomplishes her revolution round the Sun
along an orbit which she traverses at a