A person is about 2 m ( 6 feet ) tall. A kilometer is a thousand meters. The radius of the earth is about 6,400 km -. that is 6.4 million meters . Therefore the radius of the earth is about 3 million times the height of a fairly tall person.
The distance around the world at the equator is about 6 times this about -- 40,000 km (40 million meters). If you walk at a brisk pace, you can travel about 6 km in an hour (about 4 miles per hour ). It would take 6.7 thousand hours - or 275 days to walk the circumference of the earth.
A car going at highway speeds (say 100 km per hour to make the mathematics easy) would take 400 hours or 12 days - day and night to travel this distance. (This is in fact about the speed and time it took the Voyager to fly around the world in 1986).
The relative sizes of the earth and people leads first to the impression that the earth is flat. Upon closer inspection one can deduce that the earth is a intro from the shape of the horizon and other observations. This simple model of the Introduction was held until the modern era of scientific measurements began in the 1600's.
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