- published: 04 May 2016
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The sky, also known as the celestial dome, commonly refers to everything that lies a certain distance above the surface of Earth, including the atmosphere and the rest of outer space. 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. Usually, the term sky is used from the point of view of the Earth's surface. However, the exact meaning of the term can vary; in some cases, the sky is defined as only the denser portions of the atmosphere, for example.
During daylight, the sky appears to be blue because air scatters blue sunlight more than it scatters red. At night, the sky appears to be a mostly dark 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. 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 pollution during the night are often seen above large cities.
Angels, in a variety of religions, are regarded as spirits. They are often depicted as messengers of God in the Hebrew and Christian Bibles and the Quran. The English word angel is derived from the Greek ἄγγελος (aggelos), a translation of מלאך (mal'akh) in the Hebrew Bible (Tanakh); a similar term, ملائكة (Malāīkah), is used in the Qur'an. The Hebrew and Greek words originally meant messenger, and depending on the context may refer either to a human messenger (possibly a prophet or priest, such as Malachi, "my messenger", but also for more mundane characters, as in the Greek superscription that the Book of Malachi was written "by the hand of his messenger" (ἀγγήλου)) or to a supernatural messenger, such as the "Mal'akh YHWH," who (depending on interpretation) is either a messenger from God, an aspect of God (such as the Logos), or God Himself as the messenger (the "theophanic angel.")
The term "angel" has also been expanded to various notions of spirits found in many other religious traditions. Other roles of angels include protecting and guiding human beings, and carrying out God's tasks.