When did Aristotle realize the Earth was spherical?

Answer 1

He thought that all earthly matter was drawn to the centre of the Earth through natural motion, so a sphere was the most natural shape. He noticed that the shadow of the Earth was curved during lunar eclipses, and he noticed that travelling significant distances North or South allowed you to see different stars.

Answer 2

Ancient Greeks were the first to understand that the Earth was probably spherical rather than flat. They saw that the star constellations seems to be lower in the horizon as they travelled more north: that gave them a clear indication that the Earth was spherical. They also measured the distance from Earth to the Moon, the distance from Earth to the Sun and many other things, just by using Euclidian geometry and simple geometrical rules (similar triangles especially).

Answer 3

During a lunar eclipse earth's shadow passes across the surface of the moon. It is quite clear the earth is round, when this happens. There are also other bits of evidence. It does not take someone who is traveling long to realize that the horizon appear equidistant on most plains, no matter how far one moves. There are some places around the world where the curvature of the earth is quite apparent. It used to be apparent to me on my way home--I could see the tops of mountain ranges on the distant horizons, but not all the way down to their bases. Earth's curvature hid the base of the mountains from view. Also, even more clearly, the masts of sailing ships (which the Greeks had) would be visible before the boats themselves.

The Greeks at the time of Aristotle actually measured the distance to the moon in terms of earth diameters, based upon the length of time it took earth's shadow to cross the lunar surface. The calculated 60 diameters, a figure that was quite accurate. What they did not know was how big the earth was, at that time. A couple of centuries later Eratosthenes, the clever Greek who was head of the Library at Alexandria, figured out a way to measure the breadth of Earth. His figure was pretty close to the currently accepted value, and thus the Greeks developed a pretty good concept of the size of the solar system. Aristarchus, who lived around the time of Aristotle, also developed a heliocentric (sun centered) model of the solar system, which placed the sun out some 20 times further than the moon, but most educated Greeks rejected his model.

Answer 4

He thought all Earth was drawn to the centre point from which it originated, so a sphere was the only natural answer, he noticed that during lunar eclipses the Earth's shadow was round, and he noticed that when you went a significant distance North or South, the stars that you can see change.

Answer 5

Aristotle noticed that the shadow of the earth on the moon during a lunar eclipse is spherical, and that some stars/constellations that were visible in the south were not visible in the north, and vice versa. Both of these observations could be explained with a spherical-earth model. (http://en.wikipedia.org/wiki/Spherical_Earth#Classical_Greece)

Another clear giveaway sign that every sailor knows is that when you sail away from land, the bottoms of the buildings disappear while to tops of the towers - and even the mountains farther away - are still in view.

Or, from the top of the lighthouse, you can see the ship's sails before the hull becomes visible.

Answer 6

Aristotle wrote about the fact that the Earth was spherical, but the idea didn't originate with him. He probably learned it while a student of Plato, but it could have been earlier than that.

The concept that the Earth was round had been "common knowledge", at least among the educated Greeks, for at least 100 years by the time Aristotle was born. It's not entirely clear who first proved this, but it was probably someone in the 5th or 6th century BC, possibly Pythagorus or one of the Pythagoreans.

Answer 7

I don't know why he thought that, but it would be dangerous very. If the world was flat people could fall of the edge and the force of gravity might be too late

Answer 8

Answer in process....

Answer 9

Aristotle believed the earth is round.