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Date: 22-8-2020
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Date: 3-8-2020
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Night
If seeing conditions are favourable, a view of the night sky provides a far wider variety of celestial phenomena. If the Moon is visible, its brightness will dominate that of all other objects. Its shape will be crescent or gibbous or even circular. At the last condition, its apparent diameter is very close to that of the Sun. To anyone with reasonable eyesight, its surface will not be evenly bright. Areas darker than their surroundings will be noticed, so that the fancy of primitive man could see a ‘Man in the Moon’, a ‘Beautiful Lady’ or a ‘Rabbit’, sketched out by these features.
In addition to the Moon, some two to three thousand tiny, twinkling points of light—the stars—are seen, ranging in brightness from ones easily visible just after sunset to ones just visible when the Moon is below the horizon and the sky background is darkest. Careful comparison of one bright star with another shows that stars have different colours; for example, in the star pattern of Orion, one of the many constellations, Betelgeuse is a red star in contrast to the blue of Rigel. The apparent distribution of stars across the vault of heaven seems random. With the eyes becoming accustomed to the darkness, a faint band of light, the MilkyWay, catches the observer’s attention. Modern astronomers, with the aid of telescopes, know that this luminous region stretching from horizon to horizon across the sky in a great circle is made up of a myriad of stars too faint to be resolved with the naked eye. To the ancient observer, its presence inspired all kinds of speculations, none of them verifiable.
One or two of the tiny points of light may draw a closer scrutiny. They shine steadily, in contrast to the twinkling of the stars and they are among the brightest of the star-like objects. There must be some reason why they are different. If our observer is going to watch for a few hours, attention will be returned to these objects.
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دراسة يابانية لتقليل مخاطر أمراض المواليد منخفضي الوزن
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اكتشاف أكبر مرجان في العالم قبالة سواحل جزر سليمان
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اتحاد كليات الطب الملكية البريطانية يشيد بالمستوى العلمي لطلبة جامعة العميد وبيئتها التعليمية
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