Book Review: Cosmos by Carl Sagan

I am thoroughly ill-equipped to write this review because Carl Sagan was a giant with many talents and Cosmos is his magnum opus. I write this book review with much awe and wonder – feelings that are constants while reading this masterpiece.

Cosmos by Carl Sagan is a timeless journey. Unlike most books on scientific topics that stick to one domain, Cosmos is like a tapestry, as Neil DeGrasse Tyson puts it, weaving in itself astronomy, biology, chemistry, geology, history, anthropology and philosophy. This magical carpet takes you through the most incredible times and places, revealing a deep connection between the destiny of human species and the Cosmos.

While it traces much of the cosmic evolution, exploring topics such as origin of life and of human intellect hand in hand, the most striking theme of the book remains around the mankind’s struggle for it’s quest of knowledge and how they were overcome.

One of my favorite chapters “The harmony of worlds” explores this theme. In this chapter, Sagan tells us the story of Johannes Kepler, whose laws of planetary motions are taught in early physics classes, but never much appreciated for the milestones they were in our understanding of Physics. (Using Kepler’s third law, Newton mathematically deduced the nature of the gravitational force.)

In the chapter, the constant conflict between religion and scientific inquiry is highlighted by Kepler’s own vision of God. Kepler received a religious training in his childhood. It was his quest for understanding God’s creation that led him to study the Cosmos.

Sagan writes, “But God became for him more than a divine wrath craving propitiation. Kepler’s God was the creative power of the Cosmos. The boy’s curiosity conquered his fear. He dared to contemplate the Mind of God… “

…”In the geometry of Euclid he thought he glimpsed an image of perfection and cosmic glory. Kepler was later to write: “Geometry existed before the Creation. It is co-eternal with the mind of God.. Geometry provided God with a model for the Creation.. Geometry is God Himself.”

At first, Kepler (and other astronomers at the time) had imagined the planetary orbits to be circular because circle (and sphere) was considered the perfect shape, worthy of God’s creation. However, when he tried to fit his model to the most accurate observational data available at the time (collected by Tycho Brahe which makes for another interesting part of the story), it failed. A circular orbit could not explain the Mars’ retrograde motion accurately by a variation of eight minutes.

Confronted with the difficult decision of whether to rely on his model, that he had worked on for a long time, or on the observed positions of the planet, Kepler writes:

“.. If I had believed that we could ignore these eight minutes, I would have patched up my hypothesis. But, since it was not permissible to ignore, those eight minutes pointed the road to a complete reformation in astronomy.”

Eventually, Kepler was to find that an elliptical orbit perfectly explained the planetary motion. His complete regard towards accuracy of empirical evidence and preference for facts over illusion paved the way for astrophysics, as Sagan illustrates beautifully with these lines:

“It was the first non-mystical explanation of motions in the heavens; it made Earth a province of the Cosmos. Kepler was the last scientific astrologer and the first astrophysicist. ”

These and many more beautiful insights are abound in this wonderful book.

Reading this book gave me a brand new appreciation for the many observers and astronomers on whose shoulders our present understanding of the cosmos rests. It gave me a fresh new outlook towards the Cosmos and our miniscule existence within its grandeur.

Most importantly, it gave me brand new enthusiasm to look up into the sky and wonder!

Cheers!