Following Aristotle's Footsteps: The People That Looked to the Stars


Humans have always been curious on the space surrounding our home planet. Since the beginning of our species we have contradicted one another on the motion of planets and the science of the universe. We currently believe in much of the scientific exploration from long ago on gravity, astronomy and the motion of the planets. Noted theorists, scientists and astronomers from ancient times through the Scientific Revolution are credited for such findings. From Aristarchus to Newton, the laws of gravity and force were developed slowly and meticulously.

A force of attraction between all matters is called Gravity. Although it is the weakest force known in nature, gravity holds solar systems and galaxies together. Ancient Greek philosophers believed motion of planets and stars did not have to do with Earth at all. Space was considered the heavens, which was the realm of the gods. Everything in the heavens was perfect and unchanging. Aristotle, one of the philosophers explored more in depth below, believed planets and stars continued on a “natural” motion. He believed that there was an actual force keeping them moving, but not touching. What we know today to be gravity was discovered and somewhat invented by the ancient Greeks up to the 16th century. At that time, theorists believed objects needed to be touching in order to effect each other. Further studies by Galileo and Newton later changed the understanding of what gravity actually is- a force without touch.

Aristarchus of Samos (310-230 B.C.E.)

Aristarchus of Samos was a Greek theorist who is credited with discovering the ratio of distances between the Earth and the Moon and the Earth and the Sun. Through these measurements Aristarchus was able to determine the radius of the Earth and the Moon and discovered a proportional relationship between the two. Using other theorists diameters of the Moon, Aristarchus could calculate the Sun, Earth and Moon’s size and the distance between them all.

Aristotle (384-322 B.C.E.)

Aristotle was born in Stagira, North Greece in 384 B.C.E.. He began his studies in medicine prior to studying philosophy with fellow theorist, Plato. Following their studies and Plato’s passing, Aristotle tutored Alexander the Great who later conquered Athens. After the battle, Aristotle opened Lyceum, his own school until fleeing political conflict to Euboea. Science credits Aristotle for understanding matter and potential energy. He named souls within living creatures, where plants have the lowest level souls, animals can feel with their souls but only humans have reason, thus having the highest level. Zoology studies by Aristotle include distinguishing the difference between animals through anatomy observations and classification. He created genera and species still used today. Similarly, his studies in meteorology included nature of the planet and oceans, not only weather for the first time. Also, he theorized that the universe is eternal; it always has been and always will be.

Claudius Ptolemy (127-145)

Born in Alexandria, Claudius Ptolemy was an astronomer, mathematician and geographer. He believed that the Earth was in fact the center of the universe and wrote The Mathematical Collection on Astronomy, now called The Almagest. The 13 books explain in detail astronomical concepts on stars and objects within space. Ptolemy extended on the work of Hipparchus within the motion of the Sun, Moon and other planets. His studies outlined retrograde motion, star calendars, and debunked three dimensional space theories before writing five books on optical phenomenons.


Nicolaus Copernicus (1473-1543)

Nicolaus Copernicus was born to a German family, although was a Polish child due to political upheaval. He was an astronomer and mathematician that theorized that the sun did not move at the center of the universe. Copernicus did not believe Ptolemy’s model on the universe and was the first to suggest that the Earth revolved around the sun, not the other way around. He determined the distance of the planets according to their orbit size. From this data, he developed a heliocentric model making him the initiator of the continued Scientific Revolution.


Tycho Brahe (1546-1601)
Tycho Brahe was born to a noble family in Denmark in 1546. Brahe was first a law student during the time of Galileo’s period of study. He chose to live a life of astronomical studies as a teenager when he viewed an eclipsed moon for the first time. Believing the heavens and space to be perfect and never changing, Brahe’s studies changed drastically in 1572 when he saw a nova exploding. From then on, Brahe would spend the rest of his life collecting space data, without the help of a telescope. Using a compass and a sextant, Brahe discovered over 1000 stars, and he is credited for teaching Kepler and collecting data alongside the theorist on astronomy.

Galileo Galilei (1564-1642)

Born to the well-known musician of the time, Vincenzo Galilei, Galileo Galilei was born in Pisa in 1564. An Italian mathematician, physicist and astronomer, Galileo acknowledged Copernican’s theories on space. Both scientists believed the sun did not revolve around the Earth, rather the Earth orbited around the sun. Prior to their mutual understanding, there was a long-held belief that Earth was the center of the universe. People believed in ancient times that the planets and stars revolved around the Earth. Galileo’s revolutionary belief resulted in his trial at the Roman Inquisition. Sentenced to house arrest, Galileo spent the last 8 years of his life serving time. Galileo is best known as the founder of experiments and mechanical physics. His most famous invention is the telescope and with this new technology, Galileo was able to discover the rings around Saturn, moons around Jupiter, lunar craters on the Moon and spots on the Sun.

Johannes Kepler (1571- 1630)

At the time of Brehe’s death, Kepler was still his assistant and student. After he passed, Kepler continued with Brahe’s work, using is data to formulate the laws of planetary motion. Also known as Kepler’s Laws, the laws of planetary motion proved that planets revolved in elliptical paths around the sun. This contradicted the original belief that the planets moved in circular paths. Similar to Brahe, Kepler also viewed a much larger supernova in 1604 that inspired future work. He was the first to explain how a telescope actually worked, explained the tides caused by the Moon and determined Christ’s birthday. With all of Kepler’s studies available, Newton was then able to determine general gravitational forces laws.


Sir Isaac Newton (1643-1727)

The founder of modern physics, Sir Isaac Newton was an English physicist and mathematician. When the plague of 1665 shut down Newton’s research at Cambridge University, he took his studies home with him. From his own home, Newton developed circular motion theories. After two years Cambridge re-opened allowing Newton the opportunity to combine his studies with Kepler’s laws. Using observations made on tides, comets and the motion of the moon and calculus by Kepler, Newton ultimately created the universal law of gravitation and was credited with the math study.

Bibliographical Resources