kaler

In dense portions of the Milky Way, stellar images appear to overlap, giving the e ̈ect of a near-continuous sheet of light . . . The e ̈ect is a grand illusion. In reality . . . the nightime sky is remarkably empty. Of the volume of space only 1 part in 1021 [one part in a quin- tillion] is ®lled with stars. (Kaler 1997)

kaler

The cosmos, like the sky on a turbulent summer day, is ®lled with clouds of di ̈erent sizes, shapes, structures, and distances. Some are swelling cumulus, others light, wispy cirrusÐall of them constantly changing colliding, forming, and evaporating. (Kaler 1997)