Casey DreierOct 29, 2013

Cosmos with Cosmos Episode 3: The Harmony of the Worlds

Cosmos with Cosmos was a weekly series that encouraged Society members to re-watch Cosmos with a shared group, a cosmo(politan), or other drink of their choice. The Planetary Society published weekly episode discussion pieces to complement the original series before the Neil deGrasse Tyson-led 2nd season in 2014. You can currently watch the original Cosmos streaming on twitch.

I'm often asked to justify the study of the solar system given the larger problems of the world. There can be a strange hostility to spending money and time on this seemingly-esoteric field or for sending a robotic probe to a planetary body. And there are some people who just shrug and say "so what?" when talking about astronomy.

This is a major, major problem, and not just in astronomy and planetary science. If the majority of the public doesn't feel a benefit - or even a connection - to science, then we risk losing the institutional support that sustains this profound advance of human knowledge in which we are so fortunate to live.

Cosmos, as a series, is a rebuke to the "so whats" of the world. It celebrates the connections between individuals and the universe, between technological advances and the sparks behind them, and how astronomy served as the prime mover of the modern world.

Sagan states this rather baldly midway through the episode as he explains the apparent motion of planets across the night sky (emphasis mine): "The real solution is that the planets are worlds, that the Earth is one of them, and that they all go around the sun according to precise mathematical laws. This discovery has led directly to our modern, global civilization."

Episode 3, "The Harmony of the Worlds," demonstrates just how this occurred, though it addresses it somewhat more obliquely than I'd prefer. The physical manifestation of this moment serves as the heart and soul of this episode: Johannes Kepler, a courageous, contradictory, brilliant man living in a time of squalor and strife.

But the episode begins with a focus on astrology, a memetic virus that has infected human thought for thousands of years.

Sagan joyously demolishes the pseudo-science of astrology, and not just with strong, logical arguments, but by highlighting the provincial small-mindedness of the subject. The sequence contrasting the magnificent strangeness of the planets with their astrological doppelgängers is beautifully done. The "regal" nature of astrology's Jupiter is small potatoes compared to the whipping winds of its great red spot, three times the size of Earth. Why choose astrology when the astronomical reality is far more grand?

Astrology is, in some ways, wonderfully human. It epitomizes our deep contradictions and insecurities: the need to feel important and also powerless to fate; the desire to know our future so we may alter it; to explain away our faults but to take credit for our ability. It is the inverse of modern astronomy. In astrology we are the main characters; in astronomy, insignificant bystanders in the great cosmic destiny.

We leave astrology behind and cut to Sagan in the desert, building a campfire (a nice symbolic moment), where he introduces us to the idea of predictability behind certain physical behaviors in the world. This idea of predictability, as I discussed in the Episode 1 writeup, is the fundamental conceit of science - it's why we have a cosmos (order) instead of a chaos.

As Sagan directs us to the night sky, we see the familiar constellation of the Big Dipper among the stars. But then a new pattern of lines laid over the new stars creates something unfamiliar. The subsequent patterns even more so. Displaying the alternate constellations over the same set of "big dipper" stars is another subtle attack on astrology as well as an important reminder at our own cultural chauvinism.

The constellations tend to be taught to us at a young age. For many people, their education in astronomy ends there. It's what they take with them into adulthood. Constellations are what people always ask about at star parties or during dark nights over the glowing embers of a fire. People internalize ideas taught to them as children and, as Sagan implies, these human-made patterns may be conflated with the actual science of astronomy. But they are arbitrary projections of human culture onto the sky above us. There's no reason they have the patterns they do, beyond that we share some cultural history with the first peoples to apply that interpretation of them. Tragically, what most people know about the night sky is the least important - and least scientific - quality.

Ancient Egyptian Usra Major Constellation
Ancient Egyptian Usra Major Constellation One of the more creative interpretations of the same set of stars as the "big dipper."Image: Cosmos

Astrology, so concerned about which constellation is rising when and what star is in what constellation, loses all basis in reality upon the realization that other cultures have completely different ideas about what those constellations are. This is it's fundamental flaw: subjectivity.

Astronomy, as we see in this episode, is the opposite. It depends on the objective reality of the night sky. The idea that any thinking person will eventually reach the same conclusions regarding properties of the stars as any other - regardless of their culture. There is no Egyptian astronomy (or European, or Indian, or alien, etc). Few moments are more important to the history of science than the separation of subjective and objective interpretations of the night sky.

Kepler straddled this divide, this watershed. He had deep respect for data but never truly abandoned his theory of the geometrical relationship between the orbits of the planets. He embraced numerology and astrology, working for large portions of his life as a court astrologer, but simultaneously used mathematics to represent natural behavior. His work would ultimately destroy the respectability of his astrological career.

But there's a delightful irony in this. Though astrology traffics in the arrogant falsehood of the stars' influence on our lives, the motion of the planets have exerted a powerful influence on the course of human affairs.

Planetary motion occupies an accessible, inbetween state of natural movement. Unlike falling objects here on Earth, for example, they are slow and their positions are relatively easy to measure with primitive instruments. They move in a vacuum, so their velocity is simple - no need to worry about drag, shear, or other fluid dynamics to disrupt motion. But their movements are just complex enough to defy simple explanation. Think if Earth had been the outermost planet - would we have progressed beyond the Ptolemaic concept of an Earth-centered universe and circular orbits? The planets are the perfect compromise between complexity and the possibility of measurement. Their strange retrograde motion and elliptical orbits - particularly that of Mars - compelled Kepler to ponder and eventually overturn long-held beliefs about how they moved.

Like Mars, Kepler was eccentric. It was only because of his then-unheard of commitment to the accuracy of his theoretical predictions that drove him to demote the planetary orbits from perfect circles to ellipses; to state that planetary velocity was not constant, but sped up and slowed down depending on their proximity to the Sun; to understand that there was a basic mathematical relationship between the length of time to complete an orbit and their distance from the Sun.

There's no easy answer to why Kepler was so compelled to tie his theory to his data, or, as Sagan puts it, to "combine imagination with observation." Perhaps it was his unwavering respect for Tycho Brahe's data. Or a quirk in his analytical mind. Or that the reformation dramatically altered the validity of sacred, unalterable truths.

Kepler's Astronomia Nova
Kepler's Astronomia Nova Johannes Kepler's book, first edition.Image: Casey Dreier

Regardless of why, the important thing is that he did. It was this connection of theory to the real world that opened the door for Newton, born 12 years after Kepler died, to run with the concept. Starting with the idea that mathematics describes the patterns of nature, he developed the concept of gravity, uniting Earthly forces with the previously impregnable heavens. Without delving into too much historical speculation, I'd hazard to state that Newton would not have developed as much as he did without Kepler's groundbreaking work.

The show does a decent job of showing Kepler's story. The historical reenactments are probably a little too clean for that day and age (literally, Kepler didn't like to bathe), and Brahe's golden nose could use a little more work, but the story is well-told and compelling. It ends on a down note as Kepler wanders in the countryside, an old man who never achieved his dream of discovering the true geometrical theory of the universe. But as I said before, it's actually a beautiful story. He triumphed over the age he lived in. He set in motion a series of events that ultimately did more to reduce misery in the world than anyone could have dreamt of. He began the technological revolution.

Technology, of course, depends on science that comes from careful observation. The concept of collecting data and matching it to theory is now so ingrained to us that it's easy to forget that this had to be invented. Sagan calls Kepler the "spark that started the scientific revolution," but I think that's not quite right. Copernicus was the spark. Kepler was the first bright flame - both in spirit and intellect - that tore through the desiccated husk of medieval thought, allowing the mind to be reborn.

Stray Observations

  • Kepler was right in the middle of the The Thirty Years' War, which by some estimates massacred the local population in rates similar to World War II. It was a nasty time to be alive. But there's something beautiful about his revolutionary ideas springing forth from such a miserable period in human history - inspiring, really. Even in the darkest times of our civilization, the mind can still flourish, though rarely.
  • My wife points out (correctly) that the episode barely spends any time with Tycho Brahe, without whom Kepler would never had had the data necessary to make his discoveries. Also, Tycho would be a lot more fun to hang out with.
  • Statistically speaking there's a planet with a civilization that never progressed beyond medieval physics.The distributions of the orbits of its sibling planets just happened to match some arbitrary, pleasing geometric pattern.
  • In the quick detour to the ruins of the Anasazi people in New Mexico we have another answer to the "so what" question. Astronomy was embedded into daily life, serving as timekeeper for major activities: planting, harvest, and religious rituals. It was deeply important to the lives of ancient peoples. How strange, in a way, that as our technology advanced our direct connection to the stars faded, ultimately going so far as to obscure their existence by the television-tuned-to-a-dead-channel glow of our urban skies.
  • There is a fundamental irony to Kepler's life. He labored for decades to understand the motions of the planets, discovering along the way his three laws of planetary motion, all in the service of his incorrect thesis that the spacing of the planetary orbits was determined by the shapes of the five perfect solids. He created the science of astronomy almost by accident.
  • A great book about Kepler is Arthur Koestler's The Sleepwalkers (though I assume not 100% historically accurate, it's a joy to read).
  • Tycho's dwarf's name was Jepp.


  • "A reminder of the 40,000 generations of thinking men and women who preceded us, about whom we know nothing, upon whom our society is based."
  • "The desire to be connected with the cosmos reflects a profound reality. We are connected, not in the trivial ways that the pseudoscience of astrology promises, but in the deepest ways."
  • "These are known as laws, some of which are already known to us."

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