11  In the confined space of an Easy-Bake oven, a 100-watt bulb can create a temperature of 325 degrees Fahrenheit.

12  Light has no mass, but it does have momentum. Later this year the Planetary Society will launch LightSail-1, attempting to capture the pressure of sunlight the way a boat’s sail gathers the wind.

13  Laser beams bounced off mirrors left behind by Apollo astronauts show that the moon is moving 1.5 inches farther from Earth each year.

14  Visible light makes up less than one ten-billionth of the electromagnetic spectrum, which stretches from radio waves to gamma rays.

15  Goldfish can see infrared radiation that is invisible to us. Bees, birds, and lizards have eyes that pick up ultraviolet.

16  Photography means “writing with light.” English astronomer John Herschel, whose father discovered infrared, coined the term.

17  Shoot now: The “golden hour,” just after sunrise and before sunset, produces the prettiest shadows and colors for photographs.

18  Day and night are everywhere the same length on the vernal equinox, which occurs this year on March 20.

19  Auroras light up the night sky when solar wind particles excite atoms in the upper atmosphere. Oxygen mostly shines green; nitrogen contributes blue and red.

20  But to the Inuits, auroras are spirits of the dead kicking around the head of a walrus.

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