Heaven and Hell: Lessons from a Neighboring Planet

"Worlds can have cautionary tales. Venus is one of them."

NASA image of Venus

Ever since I was a child I was intrigued by the planets, but Venus was always a mystery. So bright in the sky, so close... and yet so inaccessible.

On October 26, 1980, the fourth episode of Cosmos, Heaven and Hell, was broadcast for the first time. In it, Carl Sagan reveals the true nature of Venus: a planet scorched by extreme temperatures, with a dense, poisonous atmosphere. But beyond the planetary science, what grabbed me was the profound message of this story.

This episode is not only a lesson in astronomy, but a warning. A mirror in which we can see the future of the Earth if we don't take care of our own world.

Heaven and Hell struck me for its rawness and its beauty. Sagan has the unique ability to take complex scientific data and give it an emotional, almost poetic feel. Here we learn not only about Venus, but also about Earth, and how the fate of a planet can depend on choices made...or ignored.

I was surprised to discover how much had been fantasized about Venus in the past: exotic jungles, oceans under thick clouds, even alien life. And yet, when the probes arrived and revealed a hostile, fiery, unbreathable world, science had to face that uncomfortable truth. It was not the Eden we expected, but a hell we had projected without knowing it.

But the most powerful thing about this episode is the connection to our own future. The greenhouse effect that turned Venus into an uncontrollable furnace is not just a distant phenomenon: it is a process that we have also activated here on Earth. And while there is still time, the warning is clear.

Image of the venus greenhouse effect: misistemasolar.com

One of the parts that impressed me the most was the account of the Tunguska incident. Carl Sagan manages to convey with awe and humility how small we are in the face of the power of the cosmos. The idea that, in 1908, an explosion as powerful as hundreds of atomic bombs leveled an entire forest in Siberia, without leaving a visible crater, left me thinking about how fragile our existence is. That scene reminded me that the sky is not only beautiful, it can also be unpredictable.

Some images of the Tunguska incident in 1908 and a drawing that tries to recreate how the incident was seen.

Sagan does not judge, but neither does he remain neutral. He explains with disturbing serenity what could happen if we continue to ignore the signs: that our atmosphere becomes a trap, that the planet we love becomes uninhabitable. That got me thinking for a long time. Science, understood in this way, is not just knowledge: it is consciousness.

This episode made me appreciate even more the importance of space exploration. To go to other worlds is not to flee from our own, but to learn from them in order to protect the one we have. Venus, in her tragedy, becomes a silent teacher. And Sagan, with his way of telling, invites us to listen to her.

The Venera 13 probe was the Russian mission capable of capturing these wonderful images.

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Some interesting curiosities:

• The dense atmosphere of Venus is composed mainly of carbon dioxide, which produces an extreme greenhouse effect.

• The pressure on the surface of Venus is more than 90 times that of the Earth, equivalent to being 1 km under water.

• Sagan worked directly on the analysis of data from the Venera (USSR) and Mariner (USA) probes, which provided the first real images of the planet.

• The episode combines scientific images with animations that help to imagine the climatic evolution of Venus.

This episode taught me that science is not only a search for knowledge, but also for wisdom. That looking to other worlds is not an escape, but a way to better understand our own.

Venus is not just a planet. It is a message. An example of what can happen when an equilibrium is broken, when the atmosphere becomes a prison, when living conditions disappear. It did not happen overnight. It was a gradual but irreversible process.

Sagan speaks to us with serenity, but also with urgency. He reminds us that the Earth, although alive and diverse, is not invulnerable. That if we do not heed the warnings, we could be headed for our own climate hell. But it also leaves an open door: the possibility to act, to understand, to change, although we must remember that on October 26th, 2025, it will be 45 years since Carl issued this warning.

Key topics of the episode:

• The scientific exploration of Venus

• The greenhouse effect and climate change

• The evolution of astronomical knowledge about other planets

• The consequences of environmental ignorance

• Scientific responsibility for the future of the planet

After watching Heaven and Hell, I was left with one certainty: the exploration of the cosmos is not just an act of curiosity. It is a necessity. Because by learning about other worlds, we may be able to save our own.

So much for this fourth installment of this wonderful documentary series, which chapter after chapter shows that, to this day, it is still very relevant. Or, at least, it should be for all of us, for many of the messages it conveys.

In the next chapter, Blues for a Red Planet, Carl Sagan takes us to Mars, a world that has fascinated mankind for centuries.