On hearing the word sky, a blue sheet appears in front of the eyes. But have you ever wondered why the sky is blue? And when ...

But why does it turn ... the sky during daytime, for example. It appears blue because air molecules in earth's atmosphere scatter blue light more easily than red. But during sunrise and sunset ...

They are outshined tonight by Mars, which is magnitude 0.5. The Red ... twilit sky, showing off a slender 7-percent-lit crescent and a disk that spans a hefty 54". Mercury, by comparison, is 10" wide ...