A History of Ancient Greek Physics

Plato and Aristotle - Danita Delimont - Gallo Images - GettyImages-102521991
Aristotle was a Greek philosopher, a student of Plato and teacher of Alexander the Great. He wrote on many subjects, including physics, metaphysics, poetry, theater, music, logic, rhetoric, politics, government, ethics, biology, and zoology. Together with Plato and Socrates (Plato's teacher), Aristotle is one of the most important founding figures in Western philosophy. He was the first to create a comprehensive system of Western philosophy, encompassing morality and aesthetics, logic and science, politics and metaphysics. Plato and Aristotle - Danita Delimont - Gallo Images - GettyImages-102521991

In ancient times, the systematic study of fundamental natural laws was not a huge concern. The concern was staying alive. Science, as it existed at that time, consisted primarily of agriculture and, eventually, engineering to improve the daily lives of the growing societies. The sailing of a ship, for example, utilizes air drag, the same principle that keeps an airplane aloft. The ancients were able to figure out how to construct and operate sailing ships without precise rules for this principle.

Looking to the Heavens and the Earth

The ancients are known perhaps best for their astronomy, which continues to influence us heavily today. They regularly observed the heavens, which were believed to be a divine realm with the Earth at its center. It was certainly obvious to everyone that the sun, moon, and stars moved across the heaven in a regular pattern, and it's unclear whether any documented thinker of the ancient world thought to question this geocentric viewpoint. Regardless, humans began identifying constellations in the heavens and used these signs of the Zodiac to define calendars and seasons.

Mathematics developed first in the Middle East, though the precise origins vary depending upon which historian one talks to. It is almost certain that the origin of mathematics was for simple recordkeeping in commerce and government.

Egypt made profound progress in the development of basic geometry, because of the need to clearly define farming territory following the annual flooding of the Nile. Geometry quickly found applications in astronomy, as well.

Natural Philosophy in Ancient Greece

As the Greek civilization arose, however, there came finally enough stability - despite the fact that there still frequent wars - for there to arise an intellectual aristocracy, an intelligentsia, that was able to devote itself to the systematic study of these matters. Euclid and Pythagoras are just a couple of the names that resonate through the ages in the development of mathematics from this period.

In the physical sciences, there were also developments. Leucippus (5th century B.C.E.) refused to accept the ancient supernatural explanations of nature and proclaimed categorically that every event had a natural cause. His student, Democritus, went on to continue this concept. The two of them were proponents of a concept that all matter is comprised of tiny particles which were so small that they could not be broken up. These particles were called atoms, from a Greek word for "indivisible." It would be two millennia before the atomistic views gained support and even longer before there was evidence to support the speculation.

The Natural Philosophy of Aristotle

While his mentor Plato (and his mentor, Socrates) were far more concerned with moral philosophy, Aristotle's (384 - 322 B.C.E.) philosophy had more secular foundations. He promoted the concept that observation of physical phenomena could ultimately lead to the discovery of natural laws governing those phenomena, though unlike Leucippus and Democritus, Aristotle believed that these natural laws were, ultimately, divine in nature.

His was a natural philosophy, an observational science based on reason but without experimentation. He has rightly been criticized for a lack of rigor (if not outright carelessness) in his observations. For one egregious example, he states that men have more teeth than women which is certainly not true.

Still, it was a step in the right direction.

The Motions of Objects

One of Aristotle's interests was the motion of objects:

  • Why does a rock fall while smoke rises?
  • Why does water flow downward while flames dance into the air?
  • Why do the planets move across the sky?

He explained this by saying that all matter is composed of five elements:

  • Fire
  • Earth
  • Air
  • Water
  • Aether (divine substance of the heavens)

The four elements of this world interchange and relate to each other, while Aether was an entirely different type of substance. These worldly elements each had natural realms. For example, we exist where the Earth realm (the ground beneath our feet) meets the Air realm (the air all around us and up as high as we can see).

The natural state of objects, to Aristotle, was at rest, in a location that was in balance with the elements of which they were composed. The motion of objects, therefore, was an attempt by the object to reach its natural state. A rock falls because the Earth realm is down. Water flows downward because its natural realm is beneath the Earth realm. Smoke rises because it is comprised of both Air and Fire, thus it tries to reach the high Fire realm, which is also why flames extend upward.

There was no attempt by Aristotle to mathematically describe the reality that he observed. Though he formalized Logic, he considered mathematics and the natural world to be fundamentally unrelated. Mathematics was, in his view, concerned with unchanging objects that lacked reality, while his natural philosophy focused on changing objects with a reality of their own.

More Natural Philosophy

In addition to this work on the impetus, or motion, of objects, Aristotle did extensive studies in other areas:

  • created a classification system, dividing animals with similar characteristics into "genera."
  • studied, in his work Meteorology, the nature not only of weather patterns but also geology and natural history.
  • formalized the mathematical system called Logic.
  • extensive philosophical work on the nature of man's relation to the divine, as well as ethical considerations

Aristotle's work was rediscovered by scholars in the Middle Ages and he was proclaimed the greatest thinker of the ancient world. His views became the philosophical foundation of the Catholic Church (in cases where it didn't directly contradict the Bible) and in centuries to come observations that did not conform to Aristotle were denounced as a heretic. It is one of the greatest ironies that such a proponent of observational science would be used to inhibit such work in the future.

Archimedes of Syracuse

Archimedes (287 - 212 B.C.E.) is best known for the classic story of how he discovered the principles of density and buoyancy while taking a bath, immediately causing him to run through the streets of Syracuse naked screaming "Eureka!" (which roughly translates to "I have found it!"). In addition, he is known for many other significant feats:

  • outlined the mathematical principles of the lever, one of the oldest machines
  • created elaborate pulley systems, reputedly having been able to move a full-size ship by pulling on a single rope
  • defined the concept of the center of gravity
  • created the field of statics, using Greek geometry to find equilibrium states for objects that would be taxing for modern physicists
  • reputed to have built many inventions, including a "water screw" for irrigation and war machines that helped Syracuse against Rome in the First Punic War. He is attributed by some with inventing the odometer during this time, though that has not been proven.

Perhaps Archimedes' greatest achievement, however, was to reconcile Aristotle's great error of separating mathematics and nature. As the first mathematical physicist, he showed that detailed mathematics could be applied with creativity and imagination for both theoretical and practical results.


Hipparchus (190 - 120 B.C.E.) was born in Turkey, though he was a Greek. He is considered by many to be the greatest observational astronomer of ancient Greece. With trigonometric tables that he developed, he applied geometry rigorously to the study of astronomy and was able to predict solar eclipses. He also studied the motion of the sun and moon, calculating with greater precision than any before him their distance, size, and parallax. To aid him in this work, he improved many of the tools used in naked-eye observations of the time. The mathematics used indicates that Hipparchus may have studied Babylonian mathematics and been responsible for bringing some of that knowledge to Greece.

Hipparchus is reputed to have written fourteen books, but the only direct work that remains was a commentary on a popular astronomical poem. Stories tell of Hipparchus having calculated the circumference of the Earth, but this is in some dispute.


The last great astronomer of the ancient world was Claudius Ptolemaeus (known as Ptolemy to posterity). In the second century C.E., he wrote a summary of ancient astronomy (borrowed heavily from Hipparchus - this is our main source for knowledge of Hipparchus) which came to be known throughout Arabia as Almagest (the greatest). He formally outlined the geocentric model of the universe, describing a series of concentric circles and spheres upon which other planets moved. The combinations had to be exceedingly complicated to account for the observed motions, but his work was adequate enough that for fourteen centuries it was seen as the comprehensive statement on heavenly motion.

With the fall of Rome, however, the stability that supports such innovation died out in the European world. Much of the knowledge obtained by the ancient world was lost during the Dark Ages. For example, of the 150 reputed Aristotelian works, only 30 exist today, and some of those are little more than lecture notes. In that age, the discovery of knowledge would lie to the East: to China and the Middle East.

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Jones, Andrew Zimmerman. "A History of Ancient Greek Physics." ThoughtCo, Feb. 16, 2021, thoughtco.com/physics-of-the-greeks-2699229. Jones, Andrew Zimmerman. (2021, February 16). A History of Ancient Greek Physics. Retrieved from https://www.thoughtco.com/physics-of-the-greeks-2699229 Jones, Andrew Zimmerman. "A History of Ancient Greek Physics." ThoughtCo. https://www.thoughtco.com/physics-of-the-greeks-2699229 (accessed June 6, 2023).