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The sun is a kind of time machine, as this simple experiment will show.It will only work,however,on a sunny day.What to do: Cut a i inch(2 cm) hole in the center of the cardboard square.Tape the square on a south-facing window in a position so the spot of
The sun is a kind of time machine, as this simple experiment will show.It will only work,however,on a sunny day.What to do: Cut ai inch(2 cm) hole in the center of the cardboard square.Tape the Square on a south-facing window in a position so the spot of