Ship floating on nothing! :: Physikshow Uni Bonn
Why Worldbuilding Stack Exchange recommends it
Worldbuilding Stack Exchange answerers and commenters link it as a quick visual proof that a very dense gas can hold up a light object and stay separated from ordinary air, which they use when reasoning about floating things and dense atmospheres.
Recommended by 1 people across 1 different months, 2015 to 2019.
What it is
A 31-second clip from the Physikshow at the University of Bonn in which an aluminium foil boat appears to float in mid-air above a container filled with sulfur hexafluoride, a gas much denser than air. It is a short physics demonstration with no narration beyond the description.
What people said
Recommends Starfish Prime · 2019-09 · Worldbuilding Stack Exchange · on “What would be needed to scientifically be able to stand on cloud?”
Short boring answer: nope. Even a really, really dense gas ( tungsten hexafluoride [LINK] , 12.4g/l at room temperature... actual tungsten gas might be denser, but it would be at a hazardous 6203K) is much less dense than the lightest solids (solid hydrogen, 86g/l, at a chilly 14K or lithium, 534g/l at room temperature). You could cheat by using carefully structured solids like aerogels (as low as 1.1g/l) in a dense atmosphere but aerogels are only low density because they are mostly made of air. Therefore any cloud-trapeze aid using aerogels is basically equivalent to making a lighter-than-air balloon, so you may as well do that instead. So slightly longer but no less boring answer: no, unl
Cites Ethan Strider · 2015-03 · Worldbuilding Stack Exchange · on “What would happen if Earth had oceans of dense gas instead of water?”
This sulfur hexafluoride boat experiment [this video] would certainly indicate that there can be a strong separation between the normal atmosphere and a dense gas. However, I have no familiarity with the gas, so if the container is left uncovered, does the sulfur hexafluoride dissipate or stay in the container?
Cites Ethan Strider · 2015-03 · Worldbuilding Stack Exchange · on “What would happen if Earth had oceans of dense gas instead of water?”
Excellent answer! What if there was enough water on earth to maintain a relatively similar climate; however, there was also a layer of xenon, or sulfur hexafluoride over the top of every body of water. Would the dense gas cause the water to stay warmer for longer? How significant is the mixing of the dense gas with the surrounding gases? This sulfur hexafluoride boat experiment [this video] indicates that there can be a strong separation between the normal atmosphere and a dense gas.
Cites Chloe · 2017-04 · Worldbuilding Stack Exchange · on “How can we have dragon-sized butterflies?”
Make the air density greater than it is on Earth. Aluminum foil can float on sulfur hexafluoride. With greater air density, you can have greater buoyancy. [this video]
Cites Hans Z · 2018-02 · Worldbuilding Stack Exchange · on “How to put a lake on the ceiling?”
The lake is not made of water. Or, the air is not made of nitrogen, oxygen and carbon dioxide. Theoretically, if the shimmering, glistening liquid on the ceiling of the cave had a density that was less that of air, it would float above the air in the cave like oil on water: [LINK] There are some ultralight materials out there already like aerogel [LINK] . Similarly there are some ultradense gases out there like sulfur hexaflouride [LINK] , pictured here [this video] with a foil boat floating on top of it. Note that if the gas was indeed an ultradense gas, then when Joe steps into it he will rapidly begin to asphyxiate due to lack of oxygen.