This is Chris Wayans's map of a terraformed Venus:

enter image description here

While there have been questions in this Stack Exchange on how to make Venus more livable for us humans, one question stands glaringly absent, and that concerns sunlight. Since Venus orbits the sun from a distance of 67,200,000 miles, the star's view from the sky would be 150% the size of how the sun would look on Earth, and "daylight", as it is, is 2.23 times brighter.

In the event that someone wants to seed Venus with plants, would this amount of sunlight be too much, or would the photosynthetic floral colonists find ways around it?

  • $\begingroup$ Never mind the sunlight, what are you going to do about the atmosphere? Couldn't you just put the plants under semi-transparent domes? $\endgroup$
    – pjc50
    Jan 6 at 10:41
  • $\begingroup$ This question is set past that point. $\endgroup$ Jan 6 at 14:50
  • $\begingroup$ .. so, past that point, what is the composition and density of the atmosphere? Does it have permanent cloud cover (as currently), just with water instead of sulphuric acid? $\endgroup$
    – pjc50
    Jan 6 at 15:15

Move your agriculture closer to the poles.

If your daylight is 2.23 times brighter, then using some basic trigonometry you can determine that your sunlight will be about the same at the 63rd parallel on Venus as it is at the Equator on Earth due to the obliqueness of the sun's rays.

Venus would probably still be uninhabitable because the super heating at the equator would cause MASSIVE storms, but perhaps you can combine this with Willk's high albedo idea and basically turn the equator into a contiguous, highly reflective wasteland just meant to radiate the extra equatorial heat back into space.

  • $\begingroup$ Equatorial salt plains belt? Although that would require prior belt of sea. $\endgroup$
    – PTwr
    Jan 6 at 10:26
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    $\begingroup$ I think we can safely assume laying down a large salt bed is within the technological capabilities of those terraforming the entire planet. $\endgroup$
    – chepner
    Jan 6 at 13:54
  • $\begingroup$ It does not need to be silicon based. You could just sequester all of that atmospheric CO2 into giant mountains of shiny white plastic: 2 birds, 1 stone. $\endgroup$
    – Nosajimiki
    Jan 6 at 23:08

Venus reflects most of the sunlight that hits it.

The % of sunlight reflected from a body is called the albedo. https://en.wikipedia.org/wiki/Albedo

Venus has a high albedo!

The albedo of Venus is close to .7, meaning it reflects about 70 percent of the sunlight striking it. When the moon is close to full in Earth’s sky, it can look a lot brighter than Venus, but the moon reflects only about 10 percent of the light that hits it...

Venus is bright (it has a high albedo) because it’s blanketed by highly reflective clouds. The clouds in the atmosphere of Venus contain droplets of sulfuric acid, as well as acidic crystals suspended in a mixture of gases. Light bounces easily off the smooth surfaces of these spheres and crystals. Sunlight bouncing from these clouds is a big part of the reason that Venus is so bright.


Earth has an albedo of 30%. Daylight brightness in the original OP was calculated by distance from the sun. So if Earth is 1 and Venus is 2.23, 70% of 1 (subtract the light reflected according to albedo) is 0.7 and 30% of 2.23 is 0.669. Just about the same!

Yes - new Venus is not the old Venus! It is different! I could imagine that the terraforming enterprise would change the sulfuric acid cloud cover of Venus, and so reduce the albedo. The problem I have answering is that I have no idea how one would terraform Venus or what this terraformed and so radically different Venus is like.

In the end: my proposal is that one can keep Venus cool and in the shade by keeping a high albedo either through preserving the clouds that are there, or thru terraforming jiggerypokery.

  • $\begingroup$ Kim Stanley Robinson's 'Mars' trilogy has some tips on terraforming Venus. They include placing an orbital mirror to block sunlight, causing the atmosphere to freeze and then encasing all that acidic CO2 in synthetic diamond. Sounds like a bit of a job. $\endgroup$
    – DrMcCleod
    Jan 6 at 8:56

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