“Give me the place to stand, and I shall move the earth.”
The Flat Earth
The oldest mention of the flat earth is found in the Hebrew_Bible and in Babylonian_civilizations. This concept spread among almost all civilizations of that time. This concept entered into Greek philosophy mainly with Pethagoras(600BC).
But in India, we can see idea of spherical earth and flat earth are existing at the same time. Many of the early medival era ‘Purana’ present a flat earth cosmology. Probably an influence of the Greeks, after arrival of Alexander_the_Great in northwest indian subcontinent, Hindu, Buddhist and Jain cosmology adopted this idea.
However, the flat disc shaped earth is not the only cosmology presented in these texts. The fifth chapter of the historically popular text Bhagvat Purana , for example, includes sections that describe the earth as a sphere, wherein the authors explain that the phenomenon of sunrise, sunset, the rise and setting of moon and planets from the spherical shape and the movement of astronomical bodies.
Hebrew Bible believes that the world is flat and covered by a solid doom called firmament in which all the sun, moon and stars are embded. The texts on the Egyptian Hiarogliphics also describes Nun (the ocean) and Nbwt (dry land).
The Geocentric Model
The flat earth model wasn’t a satisfying answer explaining the curved sea horizon or lunar period. So, they want to know, pushed human race forward for a better model of universe.
In Geocentric model, it was assumed that earth is a sphere and it is the fixed center of the universe. It also assumed, the other planets, sun, moon and stars are are revolving around earth on their own transparent spheres. This idea originated mainly from the apparent movement of sun and the ancient idea of symmetry at that time.
The idea of earth entered universe can be found in the works of Anaximander (600 BC) and later Plato ( 4th century BC) emperically grounded this concept in his book Myth of Er. Eudoxus of Cnidus was Plato’s assistant. He developed a less mythical and more scientific explanation of Geocentric universe.
Aristotle was a student of Plato. He worked on Eudoxs’ model and further elaborated it and presented Aristotelian model of universe in his book De Caelo et Mundo. We can find influence of his work among Islamic world through the writings of Al-Ghazali and Fakhr al-Din al-Razi. He also influenced European science.
Ptolemy (100-170 AD)
Ptolemy was a great figure in science and philosophy of the pos-medival time. He was from Alexandria, a city of the then Roman province of Egypt. And was a student of Aristotle. He clearly gave the Geocentrism theory in his book Almagest. Almagest was one of the most popular books ever wrote. It used to do astronomical studies for more than 1200 years !
The Geocentric theory was not for ever. With the invention of telescope the story changed totally. It failed to explain some cosmological phenomenans like stellar_parallex (relative movement of cosmic bodies seen in the sky). But the truth was not a fewer steps away. The seed took a large time to grow up and fruit.
Heliocentric Model of Universe
Heliocentric model of the universe deals with such a set up where all planets are moving around the sun. It was much more accurate and first actual explanation over the universe ever given by one.
In 390 BC, ancient Greece, the heliocentric idea was first given by philolaus. But he said, only Mars and Jupiter are revolving around sun. Next, nearly 100 year later Architas of Samos gave a precise heliocentric model nearly at 270 BC. In ancient times some more Greek scholars though about a sun centered universe. Sclecus was one of them.
Medival Islamic World
There are a lot names in the list of medival muslim scholars who doubted on Ptolemy’s model of universe. Famous aincent arabic scientist Alhazen’s book Al Shukūk alā Batlamyūs or “Doubts Concerning Ptolemy ” criticizes his earth centered planetary model. He also wrote “the movement of sun and moon and all other cosmological objects we see, are actually apparent movement. The earth is moving itself, on its on axis and also around the sun.
In the 12th century, some Islamic astronomers developed complete alternatives to the Ptolemaic system (although not heliocentric), such as Nur ad-Din al-Bitruji, who considered the Ptolemaic model as mathematical, and not physical. Al-Bitruji’s alternative system spread through most of Europe in the 13th century, with debates and refutations of his ideas continued up to the 16th century.
The Ptolemaic system was also received in Indian astronomy . Aryabhata (476–550 AD), in his magnum opus Aryabhatiya (499 AD), propounded a planetary model in which the Earth was taken to be spinning on the axis and the periods of the planets were given with respect to the Sun. He accurately calculated many astronomical constants, such as the periods of the planets, times of the solar and lunar eclipse , and the instantaneous motion of the Moon.
Later in medival times, Nilkanta Somayaji (1444-1544) presented Aryabhata’s helinestic model with more mathematical accuracy in his book Tantrasangraha (1500).
Later Medival Period
There were lot of people who worked on heliocentric model. Maragha observatory of Ilkhanis era and later developed as Samarkand observatory at Timurid era of Persia, played a great role researching on non-Ptolemyic model.
Nicholas of Causa, Al-Bitruji, Al- Tusi etc. are important names in this field, before Copernicus. Copernicus used such devices in the same planetary models as found in Arabic sources.
Nicolaus Copernicus published the definitive statement of his system in De Revolutionibus in 1543. Copernicus began to write it in 1506 and finished it in 1530, but did not publish it until the year of his death.
Later, works of Tycho Brahe, Jhonas Kepler, Galeilo and his telescope , Newtonian laws showed this theory it’s path to accuracy .
We know very few of the universe. Probably not even 0.000001%. From the wrong ideas to the actual explanation, science took almost 2600 years to be corrected. So its really uncertain that when we will know the whole universe.
A Physics Enthusiast, An Entrepreneur and A Motivational Speaker, Krishan Kumar, A multi-talented personality has been portraying the role of a Science Communicator for the past 4 years. He has the utmost passion for Physics. He is truly in fact, a physicist-in-process. He is also the Co-Founder of CosmosNow (India’s First Independent Astronomy Magazine) and Fastika (A Delivery System Startup).