Although these scholars managed to make important contributions, the lack of experiments to confirm them did not allow them to become laws. In many cases, his theories about the behavior of nature were interspersed with philosophy. This has caused that it is spoken of natural philosophy to qualify its works.
An example of this mixture between science and philosophy was the work of Aristotle. This author left a series of works that combined philosophical theses with physical and astronomical hypotheses. His theories were based on observation, but without developing any kind of experiments. Aristotle continued to maintain that all natural laws had their origin in the gods.
Other important authors were Leucippus and his disciple Democritus. Both rejected supernatural explanations about nature and claimed that all events had a natural cause.
With the Greek civilization the figure of the thinker and philosopher appeared. They wondered about the final cause of life, nature and the universe from various points of view.
Some of them made important contributions to physics, based on their observations. However, the scientific method was not yet developed , so its theories could not be confirmed.
Thales of Miletus
Thales of Miletus (624-546 BC) is considered the first mathematician and astronomer of ancient Greece. For some authors, this makes him the first scientist in history.
Thales rejected the use of mythology as a central element in the explanation of the universe. Instead, he sought natural explanations that would allow him to construct theories.
Although none of his works have been preserved, several contributions in the field of physics are attributed to him. Thus, he created a method that allowed him to measure the pyramids of Egypt by comparing their shadows. His system was later applied to navigation. This measurement system assumes that Thales was knowledgeable about the bases of geometry.
On the other hand, Thales of Miletus held that the origin of the entire universe, the first element of matter , was water.
Pythagoras, Empedocles and Anaxagoras
Pythagoras (569-475 BC) is known for his contributions in the field of mathematics, a discipline closely linked to physics. Already in his time he claimed that the Earth was circular. In addition, he argued that it was the center of the universe and that the Moon was inclined towards the Earth’s equator.
Another of his contributions to astronomy was the assertion that the “Morning Star” and the “Evening Star” were, in reality, the same planet: Venus .
For his part, Empedocles promulgated a theory that affirmed the existence of four principles of reality: water, air, fire and earth. These, according to the author, were in constant motion and were united or separated by the influence of spiritual forces: hatred and love.
Despite the contributions of the previous ones, many authors consider Anaxagoras (500 – 428 BC) as the first physicist in history. This is because his investigations into nature were based entirely on technique, memory and experience.
Anaxagoras offered a rational explanation for eclipses, as well as for brain respiration. He was also the one who started the study on the anatomy of the brain.
Some of his theories, such as the one that explained that the Sun was a mass of burning iron and that the Moon was a rock from the Earth and that it only reflected sunlight, led him to be accused of heresy.
The most recognized figure within the natural philosophy of Ancient Greece was that of Aristotle (384-322 BC). His philosophical and cosmological theories, continued by his followers, are called Aristotelian physics.
Aristotle used systematic logic to develop his theories. According to his work, there were two different worlds: the celestial, formed by invariable ether; and the terrestrial, in which the natural movements take place. This movement was caused by what he defined as an immobile motor. This was identified with the divinity.
Principles of Aristotelian physics
For Aristotle, all elements had the will to change their position with respect to the center of the Earth, a point that he also considered the center of the universe.
To reach the desired position, objects were influenced by a force that moved them up or down. Consequently, they developed a motion at constant speed in a straight line.
This philosopher affirmed that there was a relationship between the speed and the density of the medium in which the object was moving. The higher the density, the lower the speed.
Aristotle denied that matter could be composed of atoms, since if this were the case, there would have to be empty spaces, something that he rejected.
In the field of astronomy, Aristotle held that the planets and the Sun were perfect spheres and that they never changed. The planets also moved in a circular motion.
The mathematician, engineer, astronomer and physicist Archimedes was the author of one of the best known principles among those developed in ancient times.
This principle, which bears his name, states that when an object is submerged in a liquid, even partially, it experiences an upward thrust equal to the weight of the dislodged liquid.
In addition, he was also the author of some research on the lever, understood in physics as a simple mechanism that serves to transmit force. Archimedes expressed his possibilities with the famous sentence “give me a foothold and I will move the world.”
Its meaning is that with a good fulcrum and a suitable lever the force necessary to even move the world could be transmitted.
Despite the importance of Aristotle, one of the most important contributions to physics was not made by him, but by Leucippus, in the 5th century BC. C.
This philosopher, whose work was later continued by his disciple Democritus, was the creator of atomism. According to his theory, if matter divided if it ceased, in the end a particle would be obtained that could no longer be divided: the atom.
That small particle was, for these authors, the one that formed all the things that surrounded them. However, at that time it was impossible to prove.
Heliocentric and geocentric model
Another important contribution was made by Aristarco about the year 300 BC. His observations led him to affirm that the Earth moved around the Sun.
This assertion was, generally, rejected and the majority continued thinking that the Earth was immobile and that it was the center around which the rest of the celestial bodies revolved. This was the basis of the geocentric model promulgated by Ptolemy (85-165 AD) and which remained the most widely believed for 1400 years.