A close look at supercritical carbon dioxide CO2
Why Worldbuilding Stack Exchange recommends it
Worldbuilding Stack Exchange answerers link it when they need a visual demonstration of CO2 as a liquid and then a supercritical fluid, for speculative solvents and planetary atmospheres.
Recommended by 0 people across 0 different months, 2018 to 2022.
What it is
Ben Krasnow of Applied Science builds an aluminum and acrylic pressure vessel, fills it with dry ice, and heats it so the CO2 passes through liquid-gas coexistence into a supercritical state. He explains what supercritical CO2 is and where it is used, such as decaffeinating coffee and dry cleaning.
What people said
Cites Willk · 2018-02 · Worldbuilding Stack Exchange · on “Gasses as a biological solvent”
Supercritical CO2 [LINK] might fit the bill. CO2 is a gas, and people are familiar with it as a cold solid: dry ice. But it can be a liquid and under pressure, also a weird state called a supercritical gas. from linked wikipedia [LINK] It is polar like water. It can dissolve things like water (or better) and for that reason is being used as dry-cleaning fluid and other industrial solvent uses. It can flow like water but also sort of like a gas. [LINK] [this video] When the vessel is heated, the CO2 becomes supercritical -- meaning the liquid and gas phases merge together into a new phase that has properties of a gas, but the density of a liquid. Venus may have once had lakes and rivers of supercr
Cites Adrian Colomitchi · 2020-03 · Worldbuilding Stack Exchange · on “Planet where animals capable of flight couldn’t evolve?”
Flight: aerodynamic (winged) vs aerostatic (buoyancy) propulsion yes/no (e.g wing flapping/gliding, zeppelin/balloon) Putting the things this way, one discovers that conditions believed impossible or hard for flight may actually be easy (depending on other factors) no air or too low pressure will surely make any kind of flight impossible or too taxing. note : even at 0.1% of Earth's atmospheric pressure, flight is still possible [LINK] - except large wingspan and light body may prove too high an evolutionary cost for a biologic organism. Too costly for buoyancy too, it will require very large volumes. violent atmosphere dynamics (read "storms") may be a serious impediment for flight evolutio
Cites Tangurena · 2022-09 · Worldbuilding Stack Exchange · on “Is it possible to place a permanent probe on Uranus?”
This YouTube shows the transition of CO2 from liquid to gas and to a supercritical fluid: [this video] It is a region where the distinction between liquid and gas no longer exists. Supercritical CO2 is a very useful substance. Among its many uses, decaffeinating coffee is probably the one we have encountered.