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Exactly the question. How would glue or tape be able to stick to gas substances and remain "hanging" there mid-air.

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    $\begingroup$ Please clarify your specific problem or provide additional details to highlight exactly what you need. As it's currently written, it's hard to tell exactly what you're asking. $\endgroup$
    – Community Bot
    Jan 17 at 7:52
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    $\begingroup$ Superconducting magnetic levitation comes to mind, infrastructure and supercooling required $\endgroup$
    – Lemming
    Jan 17 at 8:09
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    $\begingroup$ Great question! Can you specify what sorts of technologies a/o thaumics are allowed? Also real, fictional or irrational physics? $\endgroup$
    – elemtilas
    Jan 17 at 8:18
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    $\begingroup$ Adhesion to gas is not the problem, it is defying gravity and the way gas flows about when something attempts to rest on it. $\endgroup$
    – KeizerHarm
    Jan 17 at 8:45
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    $\begingroup$ I am fascinated by this question, as would be many fresh apprentices on German construction sites or shop floors who fell for the practical joke to go get a "Siemens Lufthaken" (Siemens air hook). To exist, the "Lufthaken" would need exactly this adhesive. $\endgroup$
    – Dubu
    Jan 17 at 22:32

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Gas molecules have very weak intermolecular cohesive force and they are always in motion

In case of a solid material, an adhesive tape sticks to the molecules on the surface of the solid which are already very close to one another. These surface molecules are stuck to rest of the molecules of the solid because of strong intermolecular cohesive force.

In case of gaseous materials, even if the tape sticks to the surface molecules (which are already very apart), the surface molecules are very loosely stuck to the rest of the molecules of the gas because of very weak intermolecular cohesive force.

Therefore if you stick a tape to surface molecules of gas, the tape will move away because gas molecules are always in motion.

Experiment

Stick adhesive tape to a piece of solid wax. It will stick to surface molecules of solid wax.

Now melt the wax. The molecules of wax sticking to tape may remain there but all other molecules will flow away.

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It can't

A defining characteristic of a "gas" is a lack of structural cohesion. The absolute best that your hypothetical tape can achieve is to become coated with a layer (maybe even a certain thickness) of 'stuck' gas molecules. However, even if you conceptualize some sort of magic field which holds onto all gas molecules over a certain distance, once you're at that distance, the gas molecules themselves aren't "attached" to anything else.

Basically, the only way an object can remain in place against the force of gravity is to exert force against something that can't move. At that point, you aren't talking about an "adhesive", you're talking about some sort of levitation technology.

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Conceptual Tape

In old and outdated models of physics, an object was considered to be conceptually whole in and of itself.

That is, if you have a steel ball, and a magic spell to transmute steel into glass, when you turn half of that steel ball into glass, the spell is turning a steel ball into a ball that is 50:50 steel/glass.
It's not a partial transmutation because things are considered indivisible.

The whole is changed by changing part of it.

You have transformed a Steel Ball into a Steel/Glass Ball which is a distinct new form reminiscent of 50% of the original form.

Kind of a philosophical difference, but an important one for this argument.

In a similar fashion, we have the concept of "My Grandfather's Axe", or the Ship of Theseus. Where an object is conceptually still the same object even though every part of it has been removed and replaced with a fresh copy.

We also have our own bodies, which I understand pretty much completely change all their cells for new ones over the course of around a decade.
The person I am now at age 30 is literally three whole people's worth of difference from when he was born, but he's still the same Conceptual Person.

So how does this relate to taping my poster to thin-air?

Simple really.
The volume of air in the room is a conceptual whole.

You aren't taping the air-molecules, you're taping to the object comprised by the molecules.

Individual air molecules can flow and move as they like, even exiting the room and becoming part of a different space. But the whole. The concept of "Air in this room" is still intact and hasn't moved.
So you tape it to that, because obviously in order for that object to move, the room it's contained in must move too. Room hasn't moved, therefore the air-concept-object hasn't moved either and therefore with the right adhesive I can tape my poster to it. QED.

This obviously is completely impossible, but hey, it's magic tape and magic likes to deal in conceptual-space rather than real physics.

But I want it to work with real physics

Tough.
Real Physics wouldn't do this, it doesn't make any sense and any solution that would force it to be possible would no longer resemble air or glue.

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  • $\begingroup$ Conceptual tape? Inconceivable! 😁 $\endgroup$ Jan 18 at 13:46
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It isn't a question answered by one simple answer. Each gas can be wildly different from the last. There is a reason we have different glue types for solids, which is much more true for gasses.

Insulation

A sponge is a simple method to hold on to certain gasses or liquids. It is nearly the same as just encasing it into something, but the material and internal 'vacuums' can pull and hold a gas close.

The best way you can see a gas held still is in insulation. Here you either remove and/or hold a gas as still as possible, preventing heat exchange. From your clothes to thick sheets in the walls, they are meant to keep in heat by (in part) holding gas still.

Bonding or changing it's state

You can bond the gas with something else. Oxygen can be bonded with just about anything. Burning something will start an oxidation reaction, bonding oxigen to the material. Another example is water. Add hydrogen to oxigen and it'll bond together to form water. This can be extracted again by, for example, electrolysis.

But this goes further. Some gasses also solidify or behave differently with cold.

Lasers, pressure and other forces

Using EM waves, magnatism or other forces you can put direct pressure on a gas, focussing it into one area. Using different properties to select a gas and forcing it into one area. Some might be transparent to some waves and others not, allowing them to be pushed. Same for magnetism.

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As others have said, gas is a fluid (which flows) and is unable to hold something up. Here is a different solution:

Flying nanobots

The glue could have embedded nanobots capable of holding or carrying your object. They might involve magnetic levitation or wing-flapping behavior.

Magic

Depending on your story setting, a magical field could keep your glue in place wherever you intend it to be.

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You want a thing to hang in air. You want to use the air to oppose gravity. There are ways to do this.

  1. Buoyancy.

lawnchair suspended by balloons

https://en.wikipedia.org/wiki/Lawnchair_Larry_flight

You can use the mass of the gas to hang something of the same volume but less massive than the gas within the gas. Things that are more massive than the volume of gas they displace fall under the gas. Things that are less massive than the volume of gas they displace will rise above the gas. Things that are exactly the same mass as the volume of gas they displace are neutrally buoyant and neither ascend nor fall, instead staying in place within the gas.

This is close to what you want.

  1. Use air resistance to slow descent.

parachutes

This is the principle behind a parachute. The weight of the object to be hung in the air is hung by virtue of a large surface area which must displace the air as it falls. By redistributing the gravitational force pulling an object down to pull on a large mass of gas the speed of fall is decreased. Larger parachutes will slow the fall through the gas more but this method alone cannot decrease the speed of fall to zero.

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Q: How would glue or tape be able to stick to gas substances and remain "hanging" there mid-air.

At 15 Kelvin it works fine

Use to hydrogen if you like, difficult to solidify, normally a gas. Freeze it. Your tape would be quite fixed ! hydrogen will be solid at that temperature, so it would always hang mid air (whether it sticks or not)

Suppose it would stick to the gas, how would you prevent your tape from flowing along ?

A gas substance does not "hang" anywhere, it will float toward lower pressure. Your adhesive tape will not "hang" or fix itself anywhere, it will (at least) float along with the gas.

.. and fall, the tape is heavier than the gas

Solids sink in gasses

Suppose you would put your gas-sticking tape inside a jar. The air won't flow anywhere.

Still, gas inside a jar consists of molecules that execute Brownian movement. This causes the molecules to move anywhere in your jar. ref https://en.wikipedia.org/wiki/Brownian_motion

In space, with zero gravity, your piece of Air-tape will be stationary inside the jar (what you want) or move around slowly. The molecules, colliding with your tape through Brownian motion would put (about) the same pressure all around the object. But on Earth, you have gravity. This will not be compensated by the Brownian motion. Result: inside the jar, your tape will fall to the bottom of the jar.

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    $\begingroup$ "gases will be solid at that temperature". no they would not be. Gases that are solid are not gases. You don't call an anvil a gas, just because the iron gas in it is colder than its freezing point. You call it a solid $\endgroup$
    – PcMan
    Jan 18 at 18:32
  • $\begingroup$ okok @PcMan changed the first part (the whole idea is crazy anyway) $\endgroup$
    – Goodies
    Jan 18 at 18:43

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