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Our concept of the cosmos, its basic structure and its origin, is called cosmology, a word with Greek roots. Before telescopes were invented, humans had to rely on simple evidence of their senses to get an idea of the universe. Ancients Human developed cosmologies which combined his direct vision of heaven with a rich variety of philosophical and religious symbolism.
At least 2000 years before Columbus, educated people in the eastern Mediterranean knew that the earth was round. and a mathematician who lived 2,500 years ago. He believed that circles and spheres were “perfect shapes” and suggested: that the earth should therefore be a sphere. As proof that the gods liked spheres, the Greeks cited the fact that the moon is a sphere using the evidence described below.
The writings of Aristotle (384-322 BC), the teacher of Alexander the Great, summarize many of the ideas of his time. They describe how the progression of the moon phases – its apparent change in shape – results from seeing different parts of the moon in sunlight. Hemisphere during the month (see earth, moon and sky). Aristotle also knew that the sun must be further from the earth than the moon, since the moon occasionally passes exactly between the earth and the sun, temporarily hiding the sun from view. . We call this a solar eclipse.
Aristotle made compelling arguments that the earth must be round. First, when the moon enters or leaves the earth’s shadow during a lunar eclipse, the shape of the shadow visible on the moon is always round. Only a spherical object always creates a round-shadow. For example, if the earth were a disk, there would be times when sunlight strikes on it & its shadow on the moon is a line.
As a second argument, Aristotle stated that travelers traveling a considerable distance south can observe stars that are not visible further north. And the height of North Star, the star closest to the north celestial pole, decreases as the traveler moves south. Flat earth, everyone would see the same stars overhead. The only possible explanation is that the traveler must have moved on a curved surface of the earth that shows the stars from a different angle.
One Greek thinker, Aristarchus of Samos (310-230 BC) even suggested that the earth move around the sun, but Aristotle and most of the Greek scholars rejected the idea. One of the reasons for their conclusion was the idea that they would be observing the stars from different places in Earth’s orbit as the Earth moved around the Sun. As the earth advances, nearby stars should change their position in the sky relative to more distant stars. Similarly, when we are in motion, we see that foreground objects appear to be moving against a more distant background. When we take the train, the trees in the foreground seem to change position relative to distant hills as the train passes by. We constantly use this phenomenon to estimate the distances around us.
The apparent change in direction of an object caused by the movement of the observer is known as parallax. We call the change in the apparent direction of a star due to earth orbital motion of the Earth’s stellar parallax. The Greeks made a dedicated effort to observe the stellar parallax and even enlisted the help of the Greek soldiers with the clearest vision, but to no avail. The brightest (and presumably closest) stars just didn’t seem to change as the Greeks observed them in spring and then again in autumn (when Earth is on the opposite side). of sun).
That meant the earth wasn’t moving or the stars had to be so far away that the parallax shift was immeasurably small. Such a vast cosmos required a leap of imagination that most ancient philosophers were unprepared for, and so they withdrew to the safety of the earth-centered view that would dominate Western thought for nearly two millennia.
