Only when the moon, Earth and the sun are perfectly aligned is the moon 100% full. And sometimes — once in a blue moon — the moon is full twice in a month (or four times in a season ...

A new moon occurs when the moon is directly between Earth and the sun, with its shadowed side pointing towards us. You can see a new moon when it crosses the face of the sun during a solar eclipse.

On 16 September, the world will mark the International Day for the Preservation of the Ozone ... The ozone layer is a thin shield of gas in the Earth’s atmosphere that protects the planet ...

Earth Day encourages environmental awareness ... The holiday occurs during the month of Nisan on the Hebrew calendar, usually in March or April. It's observed with formally structured seders ...