About this blog series:
I wrote a book review on Cosmos on my blog here in which I attempted to summarize one of the chapters The Harmony of Worlds. One of the readers suggested that I write a chapter by chapter summary of the whole book. I like the idea of re-reading the book in a more meaningful way and then trying to bring out the essence of each chapter.
In my mind, it can serve two purposes:
- It will make for a quick read for those who do not have the time to read the whole book. Or, even better – it may end up encouraging them to read the book themselves.
- It can become creative fodder for me to illustrate some of the central ideas from the book and present them in my own style. I am a bit unsure of how this will go, but I will try.
About the book Cosmos:
The book, Cosmos, written by Carl Sagan, was published simultaneously with a PBS TV series called Cosmos: A personal voyage that aired in 1980. Carl Sagan mentions in the introduction that the intention behind the book and the TV series was to communicate about science in an engaging and approachable way.
Cosmos is one of the best selling science books of all time. However, the book is worth reading not just because it’s a great book on astronomy or science, but because it’s a great book on the evolution of the human intellect and our journey to understand our place in the cosmos. Cosmos is written in an almost poetic style and, true to its objective, does not fail to evoke a sense of wonder with each of its chapters/episodes.
Chapter 1: The Shores of the Cosmic Ocean
“The known is finite, the unknown infinite; intellectually we stand on an islet in the midst of an illimitable ocean of inexplicability. Our business in every generation is to reclaim a little more land.”-T.H. Huxley, 1887
In this first chapter, Sagan sets the stage for two concurrent journeys through space and time.
First, is our journey through the vastness of the Cosmos which is mostly empty. It takes years for even light to travel interstellar distances and hence we measure the enormous distances in light-years. As we travel in space, we pass through a hundred billion galaxies, each with a hundred billion stars on an average. We approach our spiral galaxy, the Milky Way, where our solar system is located. Our sun is a solitary, middle-aged star. Most stars have a companion star. Then we approach the icy-cold outer planets, pass through the giant Jupiter, the stormy Mars and finally reach our beautiful planet Earth. May be there are many places in the vast universe where some recognizable form of life exists. However, for now, this is the only place in the Cosmos where we know for sure that life emerged out of rock, dust and gas.
Eratosthenes, 300 B.C, Alexandria.
The second journey takes us back in time in the third century B.C, in the Egyptian city of Alexandria. Why Alexandria? Because this ancient metropolis was the seat of knowledge in the ancient civilization with its legendary library that is estimated to have contained half a million handwritten papyrus scrolls.
In this city, there lived a man called Eratosthenes. He was an astronomer, historian, geographer, poet and a mathematician. He once read in a papyrus scroll that in Syene, that lies south of Alexandria, at noon on 21st June, vertical sticks cast no shadows. That is, on summer solstice, the shadows of temple columns disappeared and the reflection of the Sun could be seen in the water at the bottom of a deep well.
Now, this was a benign observation. But Eratosthenes was a scientist. He got curious and so he conducted a simple experiment. Does the Sun cast a shadow in Alexandria at noon on the summer solstice. He found out that, indeed, it did.
If the earth was flat, the shadows at both the places should be of the same length. But, on the day of the summer solstice, when the Sun is exactly overhead in Syene, it wasn’t completely overhead in Alexandria.
- There was only one explanation – that the surface of the earth is curved.
- Not only that, by calculating the length of the shadow in Alexandria, he could calculate that both the cities were 7 degrees away on the circumference of the Earth. (approx. 1/50th of 360 degrees)
- Now, by calculating the distance between the two cities (800 km), which Eratosthenes calculated by hiring a man to walk the distance on foot, and extrapolating it for the full circumference (800*50), Eratosthenes concluded that the circumference of the Earth must be around 40000 km.
“Eratosthenes’ only tools were sticks, eyes, feet and brains, plus a taste for experiment. He was the first person to accurately measure the size of a planet.”– Carl Sagan
Erotosthenes was not the only scholar in Alexandria.
- There was the astronomer Hipparchus, who mapped the Constellations and estimated the brightness of the stars.
- Euclid systemized geometry and later came to be known as “the father of geometry”. His Elements became the textbook for geometry from the time of its publication till the 19th century. His work and the work of Apollonius of Perga, who coined the terms ellipse, parabola and hyperbola, was later to inspire Johannes Kepler to systemize the planetary motions.
- Heron of Alexandria, invented the gear trains and authored Automata, the first book on robots.
- Ptolemy compiled much of what is today’s pseudo-science of astrology. He modelled an earth-centric universe and it took another 1500 years for most humans to figure out that he was dead wrong.
- And then there was Hypatia, who is known as the first well recorded female mathematician.
The library is believed to have been damaged by the fire after the siege of Julius Caesar of Rome. It is believed to have survived the fire, but ultimately destroyed with the decline of the city. Only a fraction of the original works survive. Till this day, there remain irreparable gaps in our historical knowledge on what was written in those half a million papyrus scrolls.
* * *
Cosmos is a Greek word for the order of the universe. It is, in a way, the opposite of Chaos. It implies the deep interconnectedness of all things. It conveys awe for the intricate and subtle way in which the universe is put together.
The maps of the world of Eratosthenes’ times are much like the maps of the Cosmos that we have today. Accurate close home, but increasingly inaccurate as we venture out further both in space and time. We have figured out a lot of mysteries, but many more remain unsolved.
Sagan ends the chapter with the following lines:
The passage from the Chaos of the Big Bang to the Cosmos that we are beginning to know is the most awesome transformation of matter and energy that we have been privileged to glimpse. And until we find more intelligent being elsewhere, we are ourselves the most spectacular of all the transformations – the remote descendents of the Big Bang, dedicated to understanding and further transforming the Cosmos from which we spring.
I hope you enjoyed reading this summary. You can receive notifications on future posts by clicking on the subscribe button below.
More comics for bookworms: https://thescribblebee.com/category/bookworm