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Knows that the scientific account of the universe comes from studying evidence about its contents and imagining, with the help of mathematical models and computer simulations, how the contents got to be the way they are.

Length of the Day

The length of the day is something we take for granted. Yet, much can be learned about the day -- and the way the Earth moves -- from careful observations of the Sun and a more distant star, over as little as 24 hours, with a home-made viewer and a good clock.

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