The Cosmos, is a thirteen part documentary produced written and presented by Carl Sagan aiming to expand public understanding of science. It is one of the most successful series and is perhaps the best one for telling the fascinating history of science reaching audiences in 60 countries since it has been aired. It inspired generations to become scientists from all over the world.
It was written with such poetic vigor that in title of every episode there is an attractive metaphor for the basis of our civilization: Science. “Cosmic Fugue” is one example. This sophisticated musical term encapsulates the character of life and non-life evolving in the universe we are trying to understand through science. The history of musical sophistication and elaboration of fugues overlap with re-birth of science.
Sagan does a good job of anchoring us on our planet. Before understanding the vastness of the universe we must understand events taking place at human-scale first. As an evolutionary biologist, I see this second episode of the series as by far the most dense and challenging among others. It introduces the concept of evolution, not only in biological sense but also in cosmological and geological scales.
The episode starts with some curious questions regarding the origin of life both in our world and elsewhere in our universe:
All life on Earth is closely related. We have a common organic chemistry and a common evolutionary heritage. As a result, our biologists are profoundly limited. They study only a single kind of biology, one lonely theme in the music of life. Is this faint and reedy tune the only voice for thousands of light-years? Or is there a kind of cosmic fugue, with themes and counterpoints, dissonances and harmonies, a billion different voices playing the life music of the Galaxy?
Understanding evolution is a prerequisite in understanding the diversity of life. There are four major forces of evolution namely migration, mutation, genetic drift and natural selection. Among them, natural selection is perhaps the easiest to understand because the end products are visible. Dr. Sagan does a superb job of giving an example for artificial selection which is a special case of natural selection. The story of the Japanese crab of the Heike provides a compelling case.
Sagan then moves on to cosmological calendar where the entire 13.7 billion years of cosmological evolution is fitted within an earth year. Sagan’s cosmological calendar inspired many evolutionary timelines based on the same theme. Some are static and plain highlighting key evolutionary events. Others are interactive and have lots of information to facilitate further learning. Using an animation evolution of life from single cells to humans is also demonstrated. This visualization style later has been adopted by many documentaries produced after including the BBC’s Walking With Monsters series.
In the second half of the episode Sagan takes us into a journey inside a blood cell where we reach the nucleus. We enter inside through a nuclear pore and observe the DNA replicate itself using enzymes. During this copying process errors occur in rare occasions and the DNA accumulate mutations leading to hereditary changes. DNA replication is an essential part of life. It forms the basis for flow of genetic information inside living cells known as the Central Dogma. After exploring a complicated modern living cell we get introduced to a historical experiment designed to understand how life might have started on earth. The Miller-Urey experiment (1952) helped us to understand how building blocks of life could have been synthesized from simple molecules. The experiment was able to detect organic compounds made from inorganic ingredients by creating the conditions and adding the chemical elements present on the surface of the early earth back more than 4 billion years ago. The Miller-Urey experiment expanded our view on origins of first life and lead many scientists to design more experiments and see steps necessary to make the first replicating molecules (pre-RNA) from simple prebiotic molecules and how first cells might have evolved to form membrane-bound compartments. Experiments also explore how the first replication systems might have evolved. The update at the end of the episode refers to this view of RNA world hypothesis getting stronger.
Sagan had a firm political stance against nuclear armament and warned against the effects of nuclear war on global climate. His efforts played a big role in thawing of relations with the Soviet block and eventually bringing an end to the cold war. He was also a strong advocate of life outside our planet. There are two biographical books about him written by Keay Davidson and William Poundstone.
Cosmos is a profoundly influential scientific documentary series and a sequel with 13 new episodes aired in 2014.