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In the book I am writing, I am going for a a partially terraformed Venus setting. I like the concept of floating cities, but I want to be able to make it a little easier to live up there. If colonist had around sixty years or so, could they lower the temperature at 1 bar down to 80 Fahrenheit? How would they do this?

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  • $\begingroup$ At 1 bar pressure the temperature is lower than 80 Fahrenheit, not generally higher en.wikipedia.org/wiki/Atmosphere_of_Venus $\endgroup$ – John_H Oct 14 '16 at 22:06
  • $\begingroup$ That wiki needs to be updated. The temperature is actually quite higher. $\endgroup$ – Andrew Zachary Foreman Oct 15 '16 at 1:22
  • $\begingroup$ What is the temperature? Your question doesn't include it. Can you please provide a source for the temperature as now known? $\endgroup$ – a4android Oct 15 '16 at 3:56
  • $\begingroup$ I actually don't remember, but the source I read was far more credible than wiki $\endgroup$ – Andrew Zachary Foreman Oct 15 '16 at 14:17
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    $\begingroup$ @AndrewZacharyForeman Wikipedia is more credibleanthe a source that exists only in your memory. Can you provide a reference to what you think the temperature profile on Venus is, or, preferably, a paper describing how to calculate ourselves? $\endgroup$ – kingledion Oct 17 '16 at 3:02
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Wikipedia has compiled many of the leading proposals in an article on the topic. The table of contents to it lays them out nicely:

1 Solar shades

1.1 Space-based

1.2 Atmospheric or surface-based

2 Eliminating the dense carbon dioxide atmosphere

2.1 Biological approaches

2.2 Introduction of hydrogen

2.3 Capture in carbonates

2.4 Direct liquefaction and sequestration

2.5 Removing atmosphere

3 Day–night cycle

3.1 Space mirrors

3.2 Changing Rotation speed.

The mostly likely of the proposals to work on the desired time frame would probably be to impact the surface of Venus with about 2000 large asteroids.

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  • $\begingroup$ How expensive would something like that be? $\endgroup$ – Andrew Zachary Foreman Oct 15 '16 at 1:23
  • $\begingroup$ OP already dismissed Wikipedia in the comments to the question, so I'm not sure this is any better... $\endgroup$ – a CVn Oct 16 '16 at 14:59
  • $\begingroup$ @ Andrew Zachary Foreman: Wickedly expensive. Moving even one large asteroid slightly (a la movies in the genre of Deep Impact) is an epic engineering feat. But, since there aren't a lot of asteroids near Venus you'd need to move them a great distance from the nearest asteroid belt (or blow up Earth's moon in a manner that would send the fragments in the right general direction) and you'd also have to aim them much more precisely than when simply trying to prevent them from hitting a planet. If it cost 1 to 10 billion bucks each (probably low), you'd be talking about up to 20 trillion dollars. $\endgroup$ – ohwilleke Oct 18 '16 at 0:44
  • $\begingroup$ So that's just an all around bad idea. Thanks. I wonder if bioterraforming would be too much of a cop out $\endgroup$ – Andrew Zachary Foreman Oct 19 '16 at 2:17
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The temperature of the Venusian atmosphere is 72 C at an altitude of 50 kilometres (km) where the pressure is 1 bar. This could be an uncomfortable altitude for floating cities. However, the simplest solution for colonists in the floating habitats to enjoy cooler temperatures is go higher.

Height (km) Temp. (°C) Atmospheric pressure (atm)

 0                 462                     92.10

 5                 424                     66.65

10                 385                     47.39

15                 348                     33.04

20                 306                     22.52

25                 264                     14.93

30                 222                      9.851

35                 180                      5.917

40                 143                      3.501

45                 110                      1.979

50                  75                      1.066

55                  27                      0.5314

60                 −10                      0.2357

Sorry about the formatting glitch. All attempts to rectify it have failed. Go to the source enter link description here and check out the table with the heading Atmosphere alongside the section on Troposphere.

At 50 km, the temperature is 75 C and the pressure is 1.066 bar, while at 55 km, the temperature is now 27 C and the pressure is 0.5314 bar. This is a comfortable temperature, though the atmospheric pressure is lower and this means the flotation mechanism will be correspondingly larger for floating habitats. It should be easier to go higher than attempt complex, costly and unnecessary methods to lower the atmospheric temperature.

Essentially the Venusian atmosphere does it for you with increasing height and corresponding falling temperatures.

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  • $\begingroup$ OP already dismissed Wikipedia as not trustworthy, and that particular table is even tagged citation needed. So I suspect that won't do. $\endgroup$ – a CVn Oct 16 '16 at 15:00
  • $\begingroup$ You can use MathJax arrays for this type of data. $\endgroup$ – a CVn Oct 16 '16 at 15:02
  • $\begingroup$ @MichaelKjörling Thank you for the information. Never used MathJax before, so more stuff to learn. $\endgroup$ – a4android Oct 17 '16 at 3:04
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    $\begingroup$ @MichaelKjörling The OP may have dismissed Wikipedia, but its information on the Venusian atmosphere falls into line with the results from the Magellan and Venus Express missions. It seems credible enough in that case. Besides its temperatures do correspond to the OP's own comments about troposphere temperatures. $\endgroup$ – a4android Oct 17 '16 at 3:10

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