Middle English, cloud, sky, from Old Norse skȳ cloud; akin to Old English scēo cloud
- Date: 13th century
- 1 : the upper atmosphere or expanse of space that constitutes an apparent great vault or arch over the earth
- 2 : heaven
- 3 a : weather in the upper atmosphere
- b : climate <temperate English skies — G. G. Coulton>
The sky is the part of the atmosphere or of outer space visible from the surface of any astronomical object. It is difficult to define precisely for several reasons. During daylight, the sky of Earth has the appearance of a deep blue surface because of the air's scattering of sunlight. The sky is sometimes defined as the denser gaseous zone of a planet's atmosphere. At night the sky has the appearance of a black surface or region scattered with stars.
During the day the Sun can be seen in the sky, unless obscured by clouds. In the night sky (and to some extent during the day) the moon, planets and stars are visible in the sky. Some of the natural phenomena seen in the sky are clouds, rainbows, and aurorae. Lightning and precipitation can also be seen in the sky during storms. On Earth, birds, insects, aircraft, and kites are often considered to fly in the sky. As a result of human activities, smog during the day and light radiance during the night are often seen above large cities (see also light pollution).
In the field of astronomy, the sky is also called the celestial sphere. This is an imaginary dome where the sun, stars, planets, and the moon are seen to be traveling. The celestial sphere is divided into regions called constellations.
For only when you experience the stillness are you in complete knowledge of His presence and only as you carry your understanding of grace with you into your arena are you capable of maintaining that quality which allows you to prevail with men in such a way as to maintain your own sense of balance and solidarity -- that is to say: your head in the clouds and your feet on the ground -- and this condition is evidence of a well-unified personality operating in the fullest capacity known to him at that time. - Tomas