In my world everything is formed from the following fundamental elements. Air, Water, Fire, Earth, Nature and Mana. I wanted my creations to be able to travel faster than the speed of sound with no sonic boom, so I decided that Air would be generated instead of just being present in the empty space.

So when you talk, you generate air with your vocal chords. When there is a breeze, it is a combination of thousands of plants moving in unison to create the breeze. And when it storms it is a mixture of fire from the sun, water and its evaporation and plants moving when hit by water which create great gusts of wind.

Anyway the end result is that Air Friction doesn't really exist. If someone travels faster than 300m/s there is no sonic boom unless they created a huge column of air behind them to propel them that fast in the first place, or they ran into Air that had been generated by someone else.

So I was wondering, if there would be any significant changes to modern society if Air Friction didn't exist. (All I can think of is that ground vehicles might be more efficient and planes would need to operate off a different principle.)

Edit: Some Clarifications on my World

  • Its a world with magic. This doesn't mean I can just hand wave everything because I want to. There are rules and consequences of such rules. For the purpose of this question, Air in my world is generated by movement or magic and then dissipates. This for me means there is a lack of air resistance (there might be more consequences)

  • Gods. Life didn't evolve. It was created. The Gods too just appeared. You can think back to some old mythologies, where beings just existed in the void.

  • The concept of space doesn't exactly exist. There are meteors, but they are the result of continent sized floating islands colliding with each other and exploding. Gravity is also localized around the earth element and is uniform, extending out from the continent in all directions. I haven't figured out a distance, but once you are out of range, you are essentially floating in space with no way back unless you use magic.

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    $\begingroup$ Interesting question. I'm curious though about what happens to the 'generated' air. Does it eventually dissipate into nothing again? One would assume that without such a mechanism air would eventually build up and cause the friction you're avoiding. Also, are you describing an absence of air friction or an actual absence of air? Parts of your question seem to imply the latter, which would result in a very different answer. $\endgroup$ – Tim B II Dec 10 '18 at 5:53
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    $\begingroup$ Where did you get the idea that sonic boom is generated by friction? $\endgroup$ – L.Dutch - Reinstate Monica Dec 10 '18 at 6:03
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    $\begingroup$ definitely avoid rains at all cost and forget umbrella $\endgroup$ – user6760 Dec 10 '18 at 6:27
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    $\begingroup$ When there is a breeze, it is a combination of thousands of plants moving in unison to create the breeze Plants will not move in that way. Plants move in response to air currents, not the other way around. To do this your plants would need something akin to muscles and a reason to move. It would also mean that the breeze oscillated because the plants would first move one way then have to move in the other to return to the starting point. And they'd have to be synchronized to generate a breeze, otherwise the random motions would cancel each other out. $\endgroup$ – StephenG Dec 10 '18 at 7:21
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    $\begingroup$ Even if the plants did this synchronized movement thing (seriously ?) then they get one movement and have to move back without disturbing the air. Also note that a breeze moving over a field moves the grass but the breeze is not significantly reduced, demonstrating that the movement of plants will not generate enough energy to create the breeze. The best way to handle breezes is to ignore them for story purposes. Don't get bogged down in detail your audience don't need for story purposes. Story and character first, broad strokes everything else. Like every sci-fi show ever. $\endgroup$ – StephenG Dec 10 '18 at 8:03

No air friction means that anything doing an atmospheric entry will strike the ground with full force.

According to a professor from Cornell University:

Estimates for the mass of material that falls on Earth each year range from 37,000-78,000 tons. Most of this mass would come from dust-sized particles.

A study done in 1996 (looking at the number of meteorites found in deserts over time) calculated that for objects in the 10 gram to 1 kilogram size range, 2900-7300 kilograms per year hit Earth. However, unlike the number above this does not include the small dust particles. They also estimate between 36 and 166 meteorites larger than 10 grams fall to Earth per million square kilometers per year. Over the whole surface area of Earth, that translates to 18,000 to 84,000 meteorites bigger than 10 grams per year. But most meteorites are too small to actually fall all the way to the surface. (This study was led by P. A. Bland and was published in Monthly Notices of the Royal Astronomical Society.)

If that mass of meteorites did not burn up in the high atmosphere, we'd be in trouble.

Just so you know, the slowst of those particles that get destroyed by air friction hit the Earth at speeds in the order of eleven kilometers per second. Most are much faster than that.

Not only it would constantly rain space dust on our heads, it would rain at hypersonic speeds. Any life would only form underground.

Which leads to another problem: air friction takes a lot of energy from sound. Without it, any sound would last much longer. With the closed space of the underground acting as a insanely large array or resonance chambers, any sound would be deafening - and the buildup of energy there would make underground caves shake and collapse.

I see that after my answer, you edited your question to include this:

The concept of space doesn't exactly exist. There are meteors, but they are the result of continent sized floating islands colliding with each other and exploding.

I am not amused by answer-invalidating edits, but in this case I'll keep playing. Chicxulub was orders of magnitude smaller than a continent. What your islands lack may lack in speed, they more than compensate for in mass. The first collision of the type you describe will obliterate the planet, even at low speeds - our own tectonic plates move a few meters per year and we get biblical-proportion earthquakes here and there. In your case, it will be like dropping a couple tectonic plates from up high.

You may rethink that and handwave it away with more . But that just becomes a growing snowball of magical handwaving, and you'll just end up ignoring all answers because magic solves everything.

By the way, the cherry at the top of the cake comes from this comment:

definitely avoid rains at all cost and forget umbrella – user6760

Without terminal speed (which depends on friction), each water droplet from a rain will be striking you like a bullet.

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    $\begingroup$ No more shooting stars, only silent death. Though: would a frictionless fluid still be subject to compression heating? $\endgroup$ – Joe Bloggs Dec 10 '18 at 9:50
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    $\begingroup$ actually, objects burning up by entering the atmosphere is mostly due to compression heating and not friction. Many people mistakenly attribute this phenomenon to friction, but that’s not actually correct. see also quora.com/Why-does-a-spacecraft-heat-up-during-reentry $\endgroup$ – Ivo Beckers Dec 10 '18 at 10:10
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    $\begingroup$ The answer is, oddly, no. As the frictionless gas can ‘move out of the way’ stupidly efficiently, any energy transferred from the object to the gas goes into moving the gas, not compressing it. Compression heating will only really come into play just before whatever it is hits the floor... $\endgroup$ – Joe Bloggs Dec 10 '18 at 10:27
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    $\begingroup$ I don't think the sound part is quite correct. If the air is created when speaking, it would be a ridiculously small volume of it. When expanding through empty space, the density of it would be reduced proportionally to a factor of 3 of the distance traveled. That would mean that at 1 meter, the sound would be heard easily, as density would be the standard in earth. But at 10 meters it would be 1000 times smaller. That means almost no sound propagation, as volume is dependant on density. $\endgroup$ – spcan Dec 10 '18 at 10:28
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    $\begingroup$ I think, anyway.. a back-of-the-envelope fluid flow equation gave me a nonsensical result at least... I hate superfluids. $\endgroup$ – Joe Bloggs Dec 10 '18 at 10:30

Simple answer

For 'no air friction', read 'in a vacuum'.

Any physics that relates to movement in a vacuum will apply when considering frictionless air.

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    $\begingroup$ By the bright side, all that textbook physics would finally apply in real life. $\endgroup$ – Renan Dec 10 '18 at 14:17
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    $\begingroup$ @Renan And the bright side would carry different meaning too without the atmosphere to refract the light $\endgroup$ – Anketam Dec 10 '18 at 16:47
  • $\begingroup$ @Anketam refraction has nothing to do with friction. $\endgroup$ – Renan Dec 10 '18 at 17:39
  • $\begingroup$ @Renan I was referring to vacuum in the answer, in a vacuum there is no sky. $\endgroup$ – Anketam Dec 10 '18 at 18:49

I doubt complex life would have formed in such a world. If air exerts no force when flowing on objects, it would not move the surface of water bodies, not creating waves.

This would severely limit the gas exchange with the atmosphere, resulting in less available gases for water lifeforms.

Also, there would be no nutrients carried by the wind when blowing land dust over seas and lakes, and with no nutrients such as phosphorus sea plants would not thrive. Fewer or no plants means again fewer or no oxygen for aerobic water organisms.

Consequently, no land dwelling creatures.

  • $\begingroup$ OTOH, maybe plants generate the air to spread their pollen instead. See: the question and wind. $\endgroup$ – Draco18s no longer trusts SE Dec 10 '18 at 16:55

Your world is scary

There are a few initial problems with your world.

  1. Evaporation. A very bad thing happens when you place a liquid in empty space. If there is not anything to create pressure against a liquid, it boils very quickly. So much that if you bleed you blood will start boiling and pouring out of your body, which, as I recall from high school biology, will kill you. Also, seas and oceans and rivers will evaporate, creating either immense mists or clouds. Of course you can always say that magic pressure is applied, but that is a bit convenient.
  2. Everything that produces air will create shock waves. Supersonic shock waves are produced when supersonic and subsonic flows make contact. When speaking, you are sending an airflow into empty space, which accelerates the fluid a lot, and creates what is called Prandt-Meyer expansions (a type of shock wave).
  3. No sound. It would be a quiet world, with some spontaneous bursts due to shock waves. Sound transmits through air. If air is produced in the mouth, it can only be in limited amounts. As the density is inversely proportional to the distance^3, the amount of air carrying the information (sounds) is negligible at 10 meters away. If you do it near someone's ear, you could damage the internal organs. Also, shock waves mangle sound quite a bit, so it would be difficult to articulate and be understood. Maybe using Morse code like languages or sign languages would work.

Another big problem is described in @Renan 's answer. I recommend checking it out.

A solution to some of these problems would be for people having a "bubble" of magic around them, which is exuded naturally, and creates air continuously. That would facilitate communication and take away some of the problems of boiling liquids.


Being able to talk means that air seems to be generated in a manner that affords a pressure wave of some kind - that is to say, that it's not massless. This is a very exotic form of physics, insofar as it would involve a very exotic form of fluid dynamics.

First thing I can think of is that birds wouldn't exist in your world, certainly not birds that merely flap their wings. Birds flap their wings because of air pressure and friction, one of which they no longer have. They may 'whistle' or eject air from the front part of their wings in a manner that generates a form of jet propulsion, but there would be very little benefit to flapping in your physics.

Parachutes would also be far less efficient because they lack the ability to keep sufficient air contained to create a pressure differential that generates the resistance you need to slow down.

Jet engines would be rocket engines in another name, as there would be no air to suck in and push out the back of the engine really quickly. Conversely, propellers and even helicopters just wouldn't work, not in their current engineering incarnations.

Hot air balloons won't work either. As the air dissipates, you're in many ways operating in a vacuum meaning that whatever air you have in the balloon, it's heavier than the 'atmosphere' around you. Mind you, in a 'windy' area, with lots of trees producing breeze, they may just work but they'll be less efficient.

The real winner here is rockets; just as meteors and the like won't be slowed down on their way to Earth, rockets don't have to contend with friction in the air as they're going up. That said, re-entry would be tricky and would rely on having as much fuel for the return journey as you had to use to get up there in the first place (and that's assuming that you don't have to carry the return fuel with you) because you can't rely on air friction to slow you down.

The other winner would be baseball players. Assuming that the turbulence created by the ball (a sphere) is greatly reduced by the lack of friction, pitches would be faster and fly for longer, and hitting the ball out of the park would be a lot easier to do. You'd probably have to have a baseball diamond that turns a home run into a mini marathon.

Guns would be (almost) silent killers so make sure you have strict gun controls in this world. Speaking would be harder as you need to generate the air, so whispering in quiet conversations would actually be easier. Quiet guns and private conversations may in fact lead to a world where intelligence and espionage is an established form of warfare, as opposed to massive armies taking each other on.

This would be an interesting world for many different reasons, but the one thing that you might miss is music, or at least the ability to play it through conventional speakers. I suspect that even playing back recorded music would involve some strange take on rocket propulsion technology.

  • $\begingroup$ Baseball would be named fastball. No "trick" shots relying on a rotating ball. How boring. Football would be just as boring. Any ball would fly only in a straight courve. Again, booooring. $\endgroup$ – DonQuiKong Dec 10 '18 at 8:41

Assuming "no air friction" means "no viscosity" in scientific terminology:

Ignoring magical considerations, if there is no air viscosity, there are no resultant aerodynamic forces on any solid object.

Actually that's not quite true, because you can get a resultant force if the air is circulating around an object - but if that is happening, it will continue to happen for ever.

So, your world has no birds, because wings don't generate lift. Similarly the only "flying machines" would be rockets, which don't rely on air for propulsion. It has no weather, because any global movement of the atmosphere relative to the ground (aka "wind") will continue unchanged for ever. Your moving plants won't create a breeze, there will just be a local air movement as the air in front of the plant is pushed out of the way, and then fills up the "hole in the air" left behind the plant as it moves.

All this has no effect on creating sonic booms, because the speed of sound in the air doesn't depend on viscosity. But if you do create a sonic boom, it will travel through the air for ever, because there is nothing to dissipate its energy.

I'm not sure where all this would be going in a world-building scenario. Anything corresponding to "real life" behaviour of the atmosphere would only work because of magic - but if everything is magical and the magic acts in a consistent fashion, "magic" seems to be just a synonym for "physics".


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