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Discoveries > Earth


Earth: a planet like the others?
Above, the Grand Canyon on Earth from space.
Below, the valley Marineris canyon on Mars.
Credit NASA 

As soon as becoming aware of the environment , mankind wished to know what was around , what was the shape of the Earth on which they lived? Aristarchus of Samos (310-230 BC) was the first considering a round Earth rotating around its axis. Observing lunar eclipses and interpreting the phenomenon as the projection of the Earth's shadow on the Moon, it was a proof of the roundness of the Earth. It took a long time (until Copernicus and Galileo) to admit that most definitely, the Earth moved in the space around the Sun. 

In fact, the demonstration is not simple. The evidence of the rotational motion of the Earth around its axis is given by the flattening of the poles due to the centrifugal force. Evidence of the motion of the Earth around the Sun is more complex: it is the observation of the stars and the detection of annual parallax which demonstrated this motion.