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The distances to the sun, moon, and stars: How did the ancients calculate them?
In the ancient cosmology, the movement of celestial bodies is not only an astronomical phenomenon, but also the center of the world view. Ancient Greek natural philosophers such as Aristotle and Plato proposed different celestial sphere models to explain the movement of the sun, moon and stars. These models placed celestial bodies in rotating transparent spheres. The celestial spheres in these cosmic models are nested in each other, eventually forming a complete cosmic structure.
These celestial bodies were thought to be made of a tenuous substance that was undetectable but fundamental to the movement of all celestial bodies.
The earliest thinking about this came from Anaximander in the sixth century BC, who viewed the sun and moon as circular openings, symbolizing the vents of fire. These rings of fire form rotating wheels around the earth, and the fixed stars are the spherical shells formed by many wheels. Subsequent scholars, such as Aristotle and Ptolemy, went further and combined the motions of these celestial bodies with concepts from geometry to form more predictive models.
Ancient scholars calculated that the sun is about 4 million miles away from the earth, and assumed that the distances of other planets and the stars also corresponded to this model.
As time goes by, this model of nested spheres is constantly challenged in deeper philosophical and scientific discussions. Especially during the Middle Ages and the Renaissance, when scientists such as Copernicus and Kepler proposed the heliocentric theory, the movement of celestial bodies in the celestial sphere model also underwent dramatic changes.
Copernicus moved the earth from the center of the universe to the position of the sun and proposed a completely new cosmic structure. Nevertheless, his work On the Revolutions of the Celestial Spheres still used the term "celestial sphere", reflecting the continuity of the ancient model. At the same time, Kepler further proposed a model of the elliptical motion of planets, showing movements that could not be explained by the traditional celestial model.
Through these developments, scientists have come to understand that the quantitative models that the ancients relied on do not accurately reflect the real universe. Today, scientists use modern technology to measure the distances between planets and find that these distances are far beyond what the ancients originally thought, and the true size of the universe continues to be revealed.
Modern astronomy tells us that the boundaries of the universe are constantly expanding outward, far beyond what the ancients could imagine.
By the end of the Renaissance, the traditional celestial model was basically overturned, represented by Newton's theory of universal gravitation, and replaced by a more precise understanding framework that follows the laws of nature. This change is not only an advancement in scientific theory, but also a deep reflection on humanity's understanding of its own position.
Ancient humans' calculations of the distances to celestial bodies now seem full of mystery and artistic imagination. These historical explorations have given us a deeper understanding of the universe. However, such developments tell us that the pursuit and thinking of larger questions continues. How will we understand this vast universe through new scientific discoveries in the future?
