242, 243:—
Percy Bysshe Shelley
The sun’s unclouded orb
Rolled through the black concave.
Beyond our atmosphere the sun would appear a rayless orb of fire in the
midst of a black concave. The equal diffusion of its light on earth is
owing to the refraction of the rays by the atmosphere, and their
reflection from other bodies. Light consists either of vibrations
propagated through a subtle medium, or of numerous minute particles
repelled in all directions from the luminous body. Its velocity greatly
exceeds that of any substance with which we are acquainted: observations
on the eclipses of Jupiter’s satellites have demonstrated that light
takes up no more than 8 minutes 7 seconds in passing from the sun to the
earth, a distance of 95,000,000 miles.—Some idea may be gained of the
immense distance of the fixed stars when it is computed that many years
would elapse before light could reach this earth from the nearest of
them; yet in one year light travels 5,422,400,000,000 miles, which is a
distance 5,707,600 times greater than that of the sun from the earth.