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CAN WE LEARN THE TRUTH
Very early on, we thought the stars at night were pinholes in a black shell, and a big light from outside shined through the holes. The Earth was the center of the universe, and the sun was a really hot ball traveling around us. Scratch that. We actually thought the sun went down in the west, circled behind the mountains to the north, and came up in the east. We can't forget about that poor turtle. Gods drove some of these sky things around, and to say the Earth wasn't the center of it all was heresy.
Thousands of years ago, some thinkers did come up with some rather clever methods. For instance, they already knew the Earth was round because of a few observations: they saw the round shadow of the Earth on the moon during a lunar eclipse, they saw different stars when they traveled north or south, and they even found a way to measure the size of the Earth.
One scientist of the day had a pole, let's say six feet long. Another scientist traveled many miles north carrying another six-foot pole. They agreed to stick their poles into the ground four inches at noon on a certain day and measure the shadows. (Because the sun is so far away, its rays are practically parallel.)
As you can see, if the Earth is flat, the shadows are the same length, but on the round Earth, they are not.
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