Astronomy 101 - The first astronomers

JOC/EFR - Aristarch de Samo

On this first of an ongoing series of 101 lesson articles, we will learn about the very first astronomers as documented by history. The Sumerians as well as of course, the Greeks.

The Sumerians were not the first to realize that certain points of light in the sky moved while others stayed still. But they were the first to write on clay tablets and the first to be noted in history.

While the Greeks were best at using the imagination to arrive at explanations that were theoretical and not dependent only on mythology, the Sumerians were best at predicting lunar eclipses, organizing a calendar and measuring the exact movements of planets.

The Greeks gave us the natural philosophers, who gathered together and made astronomical observations using a sundial. Thales, Anassimene and Anassimandro drew nautical charts, hypothesized on Earth's structure and the laws under which the planets and stars moved.

Then in the 6th century BC, came the Pythagoras school, in which the thought came about that the Earth must be spherical and that the movements of stars follow perfect number laws. Aristotle's fame and prestige contributed to the belief that all the planets revolved around the Earth due to the love of the 'divine immobile motor'.

Even though we know those beliefs were quite erroneous, it was quite an accomplishment to come up with such reasonings at a time when all they had was their eyes and minds to come up with answers to our surroundings and existence.

But not long after these assumptions became the accepted theories, an astronomer came along that actually chose to measure. Aristarch de Samo (310 - 330 BC) would be the first true astronomer in history as he chose logical convictions that were correct. He not only used logic, but he also utilized mathematical instruments to investigate the cosmos.

Samo was the first to deduct that the Earth and planets revolve around an immobile sun and also that the stars have to be found at huge distances from Earth. He calculated the distances from the Earth to the Sun and Moon using logical mathematical means. Even though his numbers were slightly mistaken due to the measurements done by eye that tend to be inaccurate, he tried to approach his problem solving with logic and mathematics. This was a great accomplishment for a time that philosophical means were more the norm with great scholars.

Another great scientist of the time was Eratostene de Cirene (276 - 194 BC) who using a simple mathematical calculation determined the dimensions of Earth with extreme accuracy. His value measured at 39,400 km while the real value we know today is 40,009 km.

Many more scientists and astronomers were using mathematics and logic to come up with answers to the major questions about Earth, the planets and stars. Unfortunately, many still chose to believe in Aristotle's great thesis because it was simpler to accept. So not much happened in the way of new astronomical discoveries for about 300 years.

Reference: Atlas of the Skies: Journeying Between the Stars and Planets in the Discovery of the Universe, Copyright TAJ Books, 2003.

Check back soon for more Astronomy 101 lessons of interest. Meanwhile, also keep an eye for more 101 lessons in Science, Biology and Physics. Learning is fun!