Influences: Carl Sagan

General Lessons in Science

This week I discuss Carl Sagan's influence on my thinking. Rather than focus narrowly on any particular work (as I did for Richard Feynman last week), I discuss his non-fiction works.

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Carl Sagan's influence on generations of young adults makes it almost cliche to say, "I was a big fan of Sagan growing up". But, honestly, I was! My uncle gave me a copy of his book Dragons of Eden when I was 13 or 14. I finished reading that just in time to start watching the Cosmos series on TV. I added Broca's Brain and Murmurs of Earth to my personal library during high school. I credit Carl Sagan, through these books, with nudging be towards a B.S. in Physics and later an M.S. in Space Science.

Sagan's Unique Style

Carl Sagan’s popularity stemmed from his writing style. His writing was engaging and accessible to a wide audience. He would deftly tell a story as he related scientific facts. For example in Broca's Brain, he takes us on a tour of the Musee de l'Homme in Paris as he tells us about early studies in anthropology. He gives us an overview of Paul Broca's scientific accomplishments while holding the man's brain in jar of formaldehyde (to the morbid delight of every 13 year old boy).

Sagan managed to illustrate the amount of data contained in a DNA molecule playing a simple game of 20 questions. Reading Dragons of Eden, one couldn't help but gasp when presented with the amount of information in human DNA. The 5 billion nucleotides on a human chromosome is transformed into 4,000 books of 500 pages each as Sagan walks the reader through his game. The abstraction is made real by his masterful writing.

I am most captivated by his story telling, though. Carl Sagan had a way of weaving the personal into the scientific when telling us about the science. He gave me an appreciation for the qualities of character a scientist must have by relating the personal struggles of men like Johannes Kepler. Einstein's thought experiments are vividly etched in my memory as I recall the dramatization Sagan recreated riding his bicycle through the countryside.

Now the last point I want to make may be my experience. I’m not certain how many people got this from Sagan’s books. I always felt like he was inviting me to come along with him. I felt as if I was on a walk with a friendly teacher who pointed out fascinating plants and animals along the path or pointed to an object in the night sky. His explanations made me think I could learn science and make interesting discoveries. He cautioned me to avoid mistakes made by previous scientists. But these warnings were more like pointing to puddle I was about to step in.

The Substance of Sagan's Message

Style is not the sole reason for Sagan’s lasting impact, however. He also provided substance while entertaining the audience. What lessons did Carl Sagan provide to budding scientists like me?

Sagan tells the story of Johannes Kepler in the series Cosmos. Kepler's story illustrates two important lessons - Trust the data/observations that you make and abandon ideas that don't fit, no matter how cherished.

Kepler was a devout Christian who believed he could read the mind of God if only he could figure out the orbits of the planets. Starting from this mystical premise, he tried to model the orbits of the planets by nesting Pythagorean solids one inside the other. Each solid would describe the orbit of one planet. The smallest would define Mercury's orbit, which would be inside the next defining Venus's orbit and so on. The Pythagorean solids were thought to be perfect and so it was assumed that God must have use them to create the orbits.

Kepler sought to validate his model using observations, measurements of the path each planet took across the sky. Unfortunately, even the crudest measurements demonstrated that his perfect solid model of the solar system was wrong. He had to abandon his cherished model. But by following the data, he eventually arrived at the correct solution - elliptical orbits with the Sun at one focii.

Sagan also taught me not to extend data further than is warranted. Observational data is limited by the circumstances. It is wrong to apply an observation to a situation where it doesn't fit or to make wild guesses based on a fact that doesn't support it.

I learned this from the story of Percival Lowell. Lowell made extensive observations of Mars in the late 19th and early 20th Century. He was motivated by a misinterpretation of an Italian paper describing 'canali' on Mars. Lowell took this to mean 'canal' which conjures up visions of some civilization that is building canals. His notebooks are filled with sketches of light and dark patches covering the face of Mars. He noted that they changed over time. Stuck on the idea that these were engineering structures, he built an elaborate theory that intelligent Martians were building vast canals to transport water from one location to another. The observations of different colored regions on Mars were a fact. The idea that intelligent life existed on Mars was a fanciful extension that existed in Lowell's mind, not in reality.

Another lesson I garnered from his books was that science requires reason, curiosity and an active mind. At that age, I possessed the active mind and curiosity, but not the reason.

Like many teens in the 1980's, I enjoyed reading about UFOs. Magazine articles, TV shows and books I read provided 'evidence' that proved UFOs were real. I saw pictures of elaborate stone carvings from Central America that the author told me were alien lifeforms sitting inside a rocket ship. Photographs of wispy cotton-like material was presented as exhaust from their spacecraft. And of course, the US military was hiding actual alien spaceships in the Nevada desert. And with the dawn of portable video cameras, videos of a strange objects zipping across the sky were broadcast frequently. There were just so many 'facts' that seemed to fit together suggesting that UFOs really existed.

But somewhere in my readings, Carl Sagan set me straight. One of his books (I can't recall which one) had a full chapter challenging the notion of UFOs. He reasoned through each of the 'facts' I thought I knew and asked questions. That UFO exhaust - why has no one performed chemical analysis of it? He pointed out that it is more likely the grainy video I watched was a staged. Stone carvings of spacemen may just be stylized priests in headdress.

Then Sagan explained some things that he would need to see before he believed in UFOs. One of his criteria has stuck with me all these years. There are certain metal alloys that are impossible to make on Earth because gravity causes the metal components to separate before it cooled. Sagan explained that if someone brought him a sample of this alloy, he would take that as proof that UFOs existed. Only a space faring civilization could create it in the weightlessness of space.

The reader should notice that Carl Sagan doesn't dismiss the idea of UFOs as childish. He never attacked the UFO enthusiasts who published these articles. He simply examined the 'facts' they presented and showed where those 'facts' didn't quite pass the smell test. Then he provided new criteria for me to consider, phenomenon he would have to see before he believed we had been visited by aliens. His method upheld reason without demeaning my 13 year old imagination. It gently prodded me in the right direction.

This all helped me understand that science requires you to reason carefully. Make sure the 'facts' you are considering are indeed facts. It is also important to make sure the facts fit together. Observations must be integrated carefully to arrive at logical conclusions. You can't just throw together grainy videos, Egyptian pyramids, ancient stone carvings and rumors of crashed spacecraft then say UFOs exist Q.E.D.

Carl Sagan is a Titan when it comes to popularizing science. His ability to explain science in an entertaining way has influenced young adults in this century. But, as I will discuss in my next essay, something has gone wrong. Sagan’s efforts to bring science into the mainstream has had unintended consequences. Rather than foster a culture that is literate in science and respectful of its methods and limitations, it seems the important topics of the day are more contentious, causing remarkable conflict.