The Backbone of the Night: The Sky as the Origin of Human Thought

“We are a way for the cosmos to know itself.”

Stargazing is one of the oldest experiences we share as a species. Long before the invention of telescopes, before mathematics or modern science, we already looked up at the heavens with a mixture of awe, desire, and curiosity. The excerpt from the episode below captures this essence, narrated by Carl.

One of my favotite parts to the episode

In The Backbone of Night , Carl Sagan connects our ancestral past with our scientific present. We could say that the episode is, in a way, a story about the origin of rational thought and how observing the sky gradually led us to build tools, measure time, understand the cycles present in nature, and ultimately question who we are and where we are in the universe.

Sagan travels to different ancient cultures—Babylon, Egypt, Greece, Central America—so we can understand that what we call constellations today were once stories, gods, warnings, calendars, a reflection of society. People projected their worldview onto the stars, and from this dialogue between mythology and nature, science slowly emerged.

One of the episode's most revealing moments occurs when Sagan explains that, for many cultures, skywatching wasn't a hobby, but a necessity. Astronomical knowledge was essential for farming, navigation, and survival. But it was also a way to make sense of chaos (you can see this in the video accompanying this post).

So, The Backbone of the Night isn't just about astronomy. It's about how, by looking up at the night sky, we begin to think more deeply. The first compass was the firmament. And from that compass came the first steps toward systematic knowledge.

Artistic representation of different cultures that dedicated their time to observing the sky.

One of the episode's most powerful points, I would say, is the contrast between civilizations that used knowledge to liberate themselves and those that confined it to dogma. Sagan highlights, for example, the case of the Ionians in ancient Greece, such as Anaximander and Democritus, who dared to believe that matter was made of atoms or that the Earth floated in space. Ideas that, for centuries, were buried by superstition.

And yet, as Sagan shows, those sparks never went out. Science is a flame that sometimes flickers, but never completely goes out. In the shadows of history, there were always those who kept curiosity alive.

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“Science is not only compatible with spirituality; it is a profound source of spirituality.” —Carl Sagan

This phrase sums up the spirit of the episode. Because The Backbone of Night doesn't despise emotion or mystery. I'd say quite the opposite: it reminds us that true wonder isn't in the myths we invent, but in the reality we manage to discover.

The Milky Way, the backbone of the night, captured in the year 2014 from Mount Teleno in León.

Interesting curiosities

• The episode title refers to the Milky Way, which many cultures interpreted as a backbone of the sky—a structure visible on clear night sky that guided travelers and storytellers.

• Sagan explains that many words we use today—like “calculus,” which comes from calculus , “small stone”—are derived from ancient practices related to astronomy and arithmetic.

• The episode emphasizes how the sky served as a natural clock, helping to predict the seasons and regulate agrarian societies.

• The importance of the Library of Alexandria, one of the most advanced centers of knowledge in antiquity, and its tragic destruction are shown.

• Astronomical observation was one of the earliest forms of collective science, passed down across generations and cultures, long before the modern scientific method.

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Key themes of the episode:

• The role of the night sky in the development of human consciousness

• The relationship between mythology, observation and science

• The birth of rational thought in ancient civilizations

• The importance of astronomical knowledge in everyday life

• The tension between science and superstition throughout history

• The idea that science is also a form of spirituality

At the end of the episode, we're left with a strange but beautiful feeling: we know we come from a long tradition of beings who looked to the sky for answers. And that, even though we have satellites and probes today, we're still doing exactly the same thing our ancestors did, sitting around a bonfire in the dark of night.

The sky hasn't changed, and although we have, when we look at the stars, we become children again.

See you next week. In the next episode, "Journeys Through Space and Time ," Carl Sagan will guide us on a fascinating journey through the mysteries of relativity and the possibilities of space and time travel.