(July 14, 2025 at 8:50 pm)Thumpalumpacus Wrote: Carl Sagan back in the 70s proposed an idea to terraform Venus starting with seeding the clouds there with single-celled lifeforms in order to slowly change the atmosphere, and thus undercut the runaway greenhouse that made it too hot to support life. I don't remember the details. I think he floated it in The Dragons of Eden; I could be wrong about that as well.
Sagan proposed that Venus could be cooled by dispersing photosynthetic organisms in its atmosphere that could convert it from CO2 to transparent (and breathable) oxygen.
But it would not have worked for a number of reasons. There are no plants that actually live in an aerial habitat. Perhaps they could be engineered, but Sagan's proposal faces a bigger problem because his concept grossly overestimated the amount of water available on Venus. Photosynthesis involves combining water molecules with CO2 molecules, but on Venus there is much more CO2, than water, so even if you could actually find organisms to perform the reaction of photosynthesis on a mass scale, you would simply rid Venus of the small amount of water it retains while leaving the large bulk of the CO2 in the atmosphere basically untouched. It would take the equivalent of a global ocean 200 meters deep to provide enough water to react away the CO2 in Venus' atmosphere via photosynthesis. But we now know that Venus has only enough water to cover itself with a layer 5 cm deep. So Sagan's idea could not have worked because there just isn't enough water on Venus to do the job.
The only way to cool Venus is to block the Sun with a huge solar sail that would shield over 90 percent of the Sun's rays for a period of about 200 years. But the planet would still be incredibly dry.
Interestingly, the early Venus featured oceans of water, but at temperatures somewhere around 150°C or 300°F. The pressure of the thick atmosphere prevented these oceans from boiling away. And the early Sun was only about 70 percent as luminous as the Sun is today. But after a billion years or so, the Sun's luminosity increased to 80 percent of its present value, and it boiled the water from Venus.
teachings of the Bible are so muddled and self-contradictory that it was possible for Christians to happily burn heretics alive for five long centuries. It was even possible for the most venerated patriarchs of the Church, like St. Augustine and St. Thomas Aquinas, to conclude that heretics should be tortured (Augustine) or killed outright (Aquinas). Martin Luther and John Calvin advocated the wholesale murder of heretics, apostates, Jews, and witches. - Sam Harris, "Letter To A Christian Nation"
