Once a well-known scientist gave a lecture on astronomy. He talked about the motion of the Earth, the Sun, and our whole galaxy. In the end, a woman got up and claimed that this whole idea was preposterous. She said that the Earth was a round disc on the back of a great turtle. When asked what this turtle was resting on, she responded by saying that is was turtles all the way down!
A massive tower of heavenly turtles?
Obviously, this funny theory was wrong, but it has deeper implications. What seemed extremely logical to this woman, we see as wrong to the point where it’s comical. The questions we ask now may seem extremely obvious to later generations or may seem as ridiculous as a tower of turtles.
Does this make the current work immaterial?
NO! if anything, it makes it all the more important to study the universe so that we can reach a point where we know where we came from, where we are, and where we are going.
This post discusses the process of the evolution of a theory that is widely accepted nowadays. It is, of course, the evolution of the “round Earth theory”
The original belief was that the Earth was a flat disc floating about in space. However, even in 300 BC, Aristotle hypothesized that the Earth was a round sphere. He based this on two important reasons:
- Eclipses on the Moon are caused by the Earth coming in between the Sun and the Moon. This shadow was always round. He reasoned that the Earth had to be round. If not the flat disc may make elliptical or elongated shadows based on the planes of the Earth, Sun, and Moon.
- Observations show that the North star moves lower on the horizon the further south you go. The north star appears directly overhead to someone on the north pole, but if you move south it appears lower and lower on the horizon.
These two suggest that the Earth is round. Furthermore, he said that The Sun and all the heavenly bodies revolve around the Earth and the Earth was the center of the universe.
This was elaborated by Ptolemy who predicted the motion of heavenly bodies. He theorized that the Earth was at the center of the universe with 8 spheres surrounding it(for the different heavenly bodies).
However, there was an inherent flaw in this system. The moon appears large at some times and small at some times. Ptolemy realized this and explained that the Moon follows a very complicated path that shows this effect.
A simpler explanation was given by a man named Nicolaus Copernicus.
He said it was in fact the Earth that moves around the sun along with the other planets. This theory was disregarded for almost a century till when Galileo Galilei and Johannes Kepler publicly supported this theory. They smoothed out some inconsistencies in this theory by explaining that the orbit is elliptical and not circular. This allowed them to accurately measure the movements of heavenly bodies. They believed that it was a magnetic force that kept the Earth and other planets in orbit. But this was not reconciled by the elliptical orbital theory.
Finally, it was explained by Sir Isaac Newton in a paper that is considered one of the most influential papers in history, Principia Mathematica.
In this, he not only hypothesized the presence of a force called gravity but also explained the motion of heavenly bodies and developed the mathematics needed to measure this motion.
This revolutionary paper completely changed the world’s understanding and perception of forces and the universe.
This was the development of the “round Earth theory”. This post has been inspired by “The Brief History of Time” by Stephen Hawking. Stay tuned for more!