Ancient Greek Astronomy Facts That Aspiring Astronomers Will Adore

Ancient Greek astronomy was a marvelous gift given by the Greeks to the world.

Ancient philosophers and astronomers from Greece are known for their rich contributions to the study of the sky, stars, and heavenly bodies.

The Greek philosopher Heraclides of Pontus, a disciple of Socrates, was the one who proposed numerous solutions to celestial phenomena and the structure of the universe. Pythagoras, the famous philosopher, discovered around 500 BCE that the evening and morning stars are the same thing—the planet Venus. Pythagoras is also known for his famous geometric Pythagoras theorem that he proposed.

The Greeks are the ones who described the movement of the planets, stars, the moon, and other celestial objects moving around in space. They attempted to calculate the size of the planet Earth and different space phenomena with the help of geometric and arithmetic knowledge.

The Greeks used to call a comet 'Kometes', which translates to a head with long hair.

The Greeks were the ones who started astronomy and what we today refer to as ancient astronomy. Ancient astronomers used to take the help of many tools, like the position and movements of the stars and sun, and through them, they used to perform astronomical measurements.

Aristotle, Plato, Socrates, and Ptolemy are considered to be the most important and earliest astronomers who contributed a lot in every field of science and astronomy.

The Greeks did some cool astronomical wonders, like calculating the size of our planet, the distance between the Earth and the moon, determining the size of the moon, and calculating the size and distance of the sun.

It is said that beginning in the fourth century BCE and continuing into the early years of the Common Era, Indian astronomy was inspired by Greek astronomy, as evidenced by the Yavanajataka and the Romaka Siddhanta, a Sanskrit translation of a Greek work distributed in the second century.

After Aristotle, many scholars contributed to the richness of Greek astronomical knowledge. For example, Copernicus was one of the greatest scholars after Aristotle, who is known for his rich contribution to Greek ancient science and astronomy.

If you want to explore and read more such interesting facts, do check out these ancient Greek medicine facts and ancient Greek sports facts here at Kidadl for some enriching knowledge.

Experiencing The Sphere Of The Earth

The Ancient Greeks were considered to be smart and knowledgeable in almost every field. The Ancient Greeks were the first to observe and learn about the sky and astronomy, and Greek astronomers were the first to refer to our planet as a spherical Earth.

The Ancient Greeks are considered to be one of the founding fathers of astronomy. They briefly studied every aspect related to the sky and astronomy and were the first to discover that the shape of the Earth is spherical and not flat.

The concept of a spherical Earth first emerged in Greek philosophy around the sixth century BCE. There are a lot of ancient Greek philosophers who attempted to explain the reason behind the spherical shape of the planet Earth.

For example, Pythagoras said that the Earth and all the other planets must be spherical. He noted that a geometrical sphere was the most harmonious shape, and he thought the universe and space were harmonical in nature.

Plato and Aristotle were the ones who gave concrete, scientific, and detailed explanations of the reasons behind the spherical shape of the Earth.

When Plato returned to Athens and decided to open his school, he taught his students that the Earth's shape is spherical and that if one went above the clouds, he would see the Earth as a furry ball with various colors and ranges.

Aristotle was also a disciple of Plato and believed in Plato's theory of the spherical shape of the planet Earth.

Aristotle gave some scientific and observational arguments to support his claims of the Earth being spherical in shape.

He argued that every part of the Earth gravitates toward the center, eventually forming a sphere through convergence and compression.

He also argued that our planet projects a circular Earth's shadow on the moon during a lunar eclipse.

The fact that the shadow of the Earth is round in shape during a lunar eclipse was enough in terms of astronomical observations to prove that the Earth was spherical. Yet, Aristotle gave another argument in favor of the Earth being spherical, saying that at different latitudes, different constellations are visible.

In the third century BCE, Greek astronomers rejected the flat Earth theory and established the fact that the Earth was spherical as a physical fact that cannot be denied and is backed by observational astronomy.

The Wandering And Fixed Stars In The Celestial Region

As per the Greek astronomers, the celestial sphere has a fundamentally different nature than the terrestrial. Greek astronomers observed that most of the celestial, heavenly bodies seem to be fixed stars, and they don't have any planetary motion as such, and they appear to move altogether at exactly the same speed.

Greek philosophers deeply studied the planetary motions of celestial objects and lunar eclipses. Ancient Greece was the hub for major astronomical discoveries and gave great astronomers and philosophers to the ancient world.

By looking at the night sky, ancient astronomers observed two primary types of celestial bodies: the wandering stars and the fixed stars. A large percentage of visible things appear to be moving at the same pace and present themselves in exactly the same position night after night.

These are the stars that never change and are called 'fixed stars'. They appear to move in synchrony.

Aside from these, seven objects acted differently: the sun, moon, and planets Venus, Mercury, Mars, Saturn, and Jupiter all followed their eccentric circles. These were the wandering stars, according to the ancient astronomers.

The entire cosmological model was contained within a large sphere in this arrangement. The sphere was divided into two main sections: a heavenly domain on the outside and a terrestrial realm on the inside.

The moon's orbit served as a dividing line between these two sections. While the Earth was in a state of flux, the heavens remained consistent.

Aristotle claimed that the heavens were made of a fifth component, the quintessence and that the heavens were a realm of perfect spherical motion. The motion of the wandering stars was guided by a system of movers in the celestial spheres.

Each of these moving stars was supposed to have an 'unmoved mover', or the thing that propels them around the heavens. Many Greeks believed that this mover was a deity who corresponded to a specific entity in the skies.

Aristotle's Elements And Cosmology

In ancient Greek, the Greek astronomer and philosopher Aristotle believed in four primary elements: air, fire, earth, and water. It is challenging to fully comprehend what this means since, in the present era, we think about the matter in entirely different ways.

There was no such thing as vacant space in Aristotle's philosophy. All the available areas were filled with some combination of these pieces.

Aristotle said that such components might be further subdivided into two pairs of attributes, hot and cold, and moist and dry. The components were created by combining each of these traits.

These attributes may be substituted by their opposites, which becomes how change occurs on Earth in this system. When water is heated, it appears to convert into steam, which resembles air.

As per Aristotle, the four elements, earth, water, air, and fire, had weight. According to him, the earth was the heaviest, followed by water. Air and fire are the lightest in terms of weight.

According to Aristotle, lighter components gravitated away from the universe's center, whereas heavier elements gravitated toward it. The majority of the experience included mixed entities as these aspects strove to sort themselves out to attain this order.

Earth, fire, water, and air are visible to us. Everything else in this system was interpreted as a combination of these factors.

Transition and change in our world, according to this viewpoint, come from the interaction of components. The terrestrial, according to Aristotle, is a location of birth and death, again depending on these very ingredients. The skies are their world, with their own set of regulations.

Measuring The Size Of The Earth

The ancient Greek astronomical knowledge and early astronomy of the Greek philosophers around the fifth century BCE proved that the Earth is spherical, but the size and circumference of the Earth were still unknown to ancient astronomy.

By applying basic geometrical models, Eratosthenes was the one who determined the size of the Earth and gave observational evidence to prove his findings.

Eratosthenes wrote the specifics of this measurement in a book that has been destroyed, but other Greek historians and authors have recounted his method. He was captivated by geography and intended to create a world map.

He understood that he needed to know how big the Earth was.

There was no way to find it out by walking all the way around.

Travelers had told Eratosthenes about a well in Aswan, Egypt that had an interesting property: at noon on the summer solstice, which occurs every year around June 21, the entire bottom of the well was illuminated by the sun without casting any shadows, indicating that the sun was directly overhead.

He concluded that if he understood the distance between Alexandria and Aswan, calculating the circumference of the Earth would be easy. However, determining distance with any accuracy back then was extremely challenging.

It took a camel caravan to go from one city to the next to estimate the distance between some cities. Camels, on the other hand, have a penchant for roaming and walking at different paces.

As a result, Eratosthenes enlisted the help of bematists, professional surveyors of distance trained to take equal-length steps. They determined that Aswan is around 5000 stadia from Alexandria. According to Eratosthenes, the circumference of the Earth is approximately 250,000 stadia.

The length of Eratosthenes' stadium is a point of disagreement among modern academics. The circumference of Eratosthenes' computed circumference has been estimated to be between 24,000-29,000 mi (38,624-46,670 km), based on values ranging from 500-600 ft (152-183 m).

The Earth's circumference is presently estimated to be roughly 24,900 mi (40,072 km) at the equator and somewhat less at the poles. Eratosthenes assumed that because the sun was so far away, its rays were nearly parallel, that Alexandria was due north of Aswan, and that Aswan was exactly on the cancer tropic.

While not quite true, these assumptions are sufficient to provide a somewhat accurate measurement using Eratosthenes' approach.

Ptolemy And Aristotle's Cosmic Legacy

Claudius Ptolemy was an ancient astronomy expert, mathematician, geographer, and music theorist. He wrote about many scientific treaties, and three of them became important to later Islamic, Byzantine, and Western European science and astronomy.

At first glance, the theories presented by Ptolemy and Aristotle look very similar. He was influenced by Aristotle. To make the retrograde motion more accurate, Ptolemy gave some significant theories to the universal model of Aristotle.

Aristotle's theory of the structure of the solar system, or his take on a geocentric model, was that the sun, stars, moon, and planets all orbited the Earth inside of Eudoxus' spheres. According to Aristotle, objects present in space are unchanging; they all move in perfect circles, and he considered them to be the perfect shape.

In contrast, the Earth is continuously changing. He also thought comets were part of the Earth's sphere as their motion was also not in perfect circles.

Aristotle's cosmology remained dominant in ancient Greece for a long time. In the second century BCE, Ptolemy of Alexandria came up with his geocentric model of the solar system's structure.

Ptolemy argued that the planets move in two sets of eccentric circles: a deferent circle and an epicircle.

This theory explains how the planets might go backward while remaining in their circular orbits around the Earth. Ptolemy presented an eccentric orbit where this did not suit.

An eccentric orbit has a different center than the Earth and may account for variations in a planet's brightness. The equant was Ptolemy's last gadget.

In an equant, a planet speeds up and slows down, but it appears to be traveling at a constant speed when observed from an off-center point. The planet's velocity, however, appeared to be highly erratic from Earth.

Later, with strong astronomical data and deeper knowledge of planetary motion, many new scholars and Greek astronomers argued against the geocentric model and the notion of concentric spheres. It was widely considered that his ideas were based on a fundamentally Aristotelian cosmology.

In reality, when it came to the sphericity of the Earth and its location at the universe's center, as well as the sphericity and circular motion of the heavens, Aristotle and Ptolemy agreed on many things.

As a result, an 'Aristotelian-Ptolemaic cosmology' arose in Latin Europe, including features from both ancient sources. Thus, the contribution of both Ptolemy and Aristotle's cosmic legacy can never be ignored or minimized in both the Greek tradition and modern science.

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