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# A Snapshot of The Earth Today

While compared to the rest of the Universe, the Earth is tiny, but to us its size is quite impressive. Because the Earth is so large compared to the lifeforms that live on it, it is difficult for those lifeforms to study and understand it. A small hedgehog lives his life carefully going from one place to another looking for food. The hedgehog has no idea that there are vast continents, islands, and oceans filled with life. It does not understand the processes that cause the sky to spill rain upon it from time to time. It is only familiar with the things that surround it.

Until only very recently in human history, even the intelligence of human beings did not allow us to understand the planet we live on. One example of our struggle to understand the world around us evident in our understanding of the shape of the Earth itself.

Look out your window. What shape does the Earth appear to be? You know it is round because you have been taught about its global shape, but as you gaze out the window, what shape does it appear to take? Using just our eyes as a tool to understand the world around us, the Earth appears to be flat, and to go on in all directions forever. For many thousands of years, our ancestors believed that they lived on a vast endless flat plane.

Eventually, as the tools and technologies advanced, scientists began to understand our Earth a little better. The ancient Greek scholar Eratosthenes used trigonometry to calculate the shape and size of the Earth. By measuring the angle of the Sun’s rays in one city, and then measuring the angle of the Sun’s rays in another location, and then using these measurements, Eratosthenes calculated that the Earth was approximately 26,700 miles in circumference. This is just a few thousand miles off of the real measurement of 24,900 miles. This is the first time that anyone, either animal or human, had accurately measured and understood both the size and shape of our planet.