But a clear, cloudless day-time sky is blue because molecules in the air scatter blue light from the sun more easily than they do red light.

BBC: rainbow

The abundance of such compounds tells us that the sun grew up less than 1 light year away from a massive star that exploded.

FORBES: Searching for the Siblings of the Sun

One recent study of more than 450 Sun-like stars within about 325 light-years of Earth indicated most had high iron content in their photospheres, or on their surfaces - again, evidence the stars had gorged themselves on planetary material.

BBC: Star 'eats' a planet

The researchers estimate that the two light sources come from black holes between 20 million and one billion times more massive than our Sun.

BBC: Dancing black hole twins spotted

Bringing more light than a traditional window that can crack or leak during typhoon season, the bottle bulbs refract the sun's rays to create 55-watts worth of light.

CNN: Plastic bottles light up lives

Because they are so far away, by the time their images traverse the universe at the speed of light and arrive here for Schmidt to see them, more time has passed than the Earth and the sun are old.

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