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Science Challenge #5

(Responders are from many places in the U.S. and even from overseas)

Question 1.Which of the following elements (gases that occur normally in Earth's atmosphere) on a dry day makes up about 80% of the air we breathe?

Argon, carbon dioxide, helium, hydrogen, krypton, neon, nitrogen, oxygen.

(Our air also normally contains water vapor, hydrocarbons, hydrogen peroxide, sulphur compounds, in very small and variable amounts.)

Question 2. What is the term used for the warming of the Earth that is thought to be caused by the presence in Earth's atmosphere of an abnormally high level of carbon dioxide and other gases that allow passage of heat from the sun to the Earth's surface but reduce the radiation of heat back into space?

If it takes about eleven and a half days for one million seconds to tick away, will one billion (U.S.) seconds take close to one year, ten years, twenty years or thirty years?

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