The Physics of Airbending

The Physics of Avatar: The Last Airbender and The Legend of Korra

Let’s continue our journey into the physics of bending with the element of freedom, air.

I recommend you read my first four posts on the physics of Avatar and Legend of Korra if you haven’t already. It will be important for understanding the rest of this series.

Moving Air

Our running hypothesis throughout this series has been that benders control their elements using electromagnetism. For airbending, this means taking advantage of an effect known as electric wind, also called ionic wind. Electric wind happens when an object with a strong electric field repels charged particles in the air around it. These charged particles then collide with neutral particles and rip away their electrons. This starts a chain reaction called a corona discharge — also called an electron avalanche — where atoms are broken up into electrons and positive ions which go onto to collide with and ionize more particles. Electric wind occurs because even atoms that aren’t ionized can still be dragged along after being struck by charged particles. By controlling the motion of enough initially charged particles, airbenders could control the direction of electric winds and create complex patterns in the flow of air. This lays the groundwork for all the powers we see airbenders display across Avatar and Legend of Korra.

Electric wind could also explain why the air appears to be visible. You may think it’s just an animation decision so the audience can see what’s happening, but there are many times when characters in the show seem to be able to see incoming airbending attacks.

One possible reason the air is visible is because of the corona discharge mentioned earlier. Corona discharge is visible to the naked eye because it breaks down some amount of air into a plasma that emits light. Another explanation is that the air being bent is at a higher pressure than the surrounding air because of the forces being applied by the bender. The refractive index of a gas determines the angle at which light will bend entering it. You can see the effects of light being bent as it moves between mediums of different refractive index. For example, you can see the distorted image of a straw partly submerged in water. The refractive index of a gas is directly proportional to its pressure, so higher pressure air may look visibly different from the surrounding air if the pressure difference is great enough. A similar effect would occur if the air being bent is at a significantly lower pressure than the surrounding air.

One downside to airbending in this way is that the ionization of air creates ozone, which is both a greenhouse gas and bad for the human body. To combat this, airbenders could use electromagnetism at the scale of atoms to break down ozone into oxygen atoms, which they could force to recombine into plain old oxygen molecules.

Heating or Cooling Air

We’ve already talked about how waterbenders, earthbenders and firebenders use electromagnetism to change the temperature of their elements. Airbending could work in a similar way by using electric fields on the nanoscale to slow or accelerate the motion of individual air molecules and change the air’s overall temperature. However, airbenders could also change the temperature of the air they bend by rapidly changing its pressure. Applying a lot of pressure and forcing molecules closer together would heat up the air. This may be how airbenders can warm themselves with just their breathing no matter the climate they’re in. They’re breathing in air that they’ve heated with their bending.

As for cooling, air drops in temperature when it rapidly expands, so an airbender could rapidly cool air by forcing its molecules to move apart quickly. They could then use this cooled air to cool down objects.

Another way to cool objects down with airbending is wind chill, which wouldn’t even require the air itself to be all that cold. Wind chill, or convective cooling, is when objects lose their heat energy through collisions with air molecules. This process occurs when objects are standing still, but once they begin moving they collide with more air molecules and lose more heat. The same thing happens if air molecules move at high speeds relative to objects, so airbenders could cool objects down just by creating fast enough winds around them.

Increased Speed and Agility

Airbending as a martial art involves quickly moving out of the way of attacks. Airbenders are in a special position in terms of their ability to improve their physicality with bending. The reason why is that unlike other benders, they are constantly engulfed in their element. As such, they can push their bodies using air in order to speed up their movements and move air out of the way of their bodies to reduce drag forces. Aang is described in one episode as being able to run faster than the wind. This is also how airbenders are able to jump great heights and slow their descent.

Sensing Disturbances in the Air

Similar to earthbenders sensing vibrations in the Earth, airbenders can sense disturbances in the air caused by moving objects. They likely do this by ionizing air molecules around them and creating a wide reaching, but weak, electric field around them. This field is pushed and pulled by the motion of charged particles in the nearby air, alerting the airbender of nearby atmospheric disturbances. The airbenders would be able to sense the forces on this electric field by creating small electric fields on the surface of their bodies which interact with the larger field.

Air Propulsion

Air propulsion works in a very similar way to the fire propulsion I mentioned in my last post. Airbenders ionize a region of air and create a moving electric field to push and pull the positive ions produced away from them in the opposite of the direction they want to move. The resulting electric wind is then corralled using airbending so that it can only escape in one direction. Due to Newton’s 3rd law of motion, the airbender moves in the opposite of the direction they thrust the air.

Producing and Amplifying Sounds

Sounds are waves that change the pressure at different locations in the air, so an airbender would be able to produce and manipulate sound by controlling the vibrations of air molecules. If they produced sound waves that constructively interfered, then the sounds would become amplified. Airbenders could also produce sound using a varying amount of corona discharge. In the video below, an experimenter actually uses corona discharge to actually play music:

Control of sound waves can also be used to produce standing waves, which introduces the possibility of airbenders performing sonic levitation. Sonic levitation is the process of using sound, or more specifically acoustic radiation pressure, to cancel out the force of gravity and hold objects in midair. It is also called acoustic levitation. This process occurs when the areas of high and low pressure air created by overlapping sound waves actually hold objects in place. By changing the sound waves, you shift the location of the high and low pressure points and the objects move with them.

This brings us to…

Flight

There are four types of flight across Avatar and Legend of Korra for us to discuss.

Airbenders Lifting Themselves with Wind

This is the simplest way for airbenders to keep themselves suspended in the air. It simply involves airbenders bending air upwards underneath them to cancel out the force of gravity. They can then create winds to push them in the directions they want to be moved.

Appa’s Flight

Appa wouldn’t be able to rely on air currents pushing himself upwards against gravity because the winds he would create would be so strong that we would definitely see their effects in the show. What he could do instead is use airbending to create an area of lower air pressure above him so that he would be lifted up by the pressure underneath. This idea may work because if the air pressure underneath him times the surface area of his body that experiences that pressure is greater than the air pressure above him times the surface area experiencing that pressure, he would feel a force upwards. If this force is equal to that of gravity, he’d float. If it was greater, he’d rise. If it was only slightly lesser, he’d slowly descend. Nickelodeon actually has a video that discusses how this works:

To push himself horizontally, Appa could create strong winds or use the air propulsion technique we discussed earlier.

Glider Flight

Glider flight is likely a combination of the two types of flying discussed above. This would be similar to how planes fly, since they make use of both differences in air pressure above and underneath their wings and the impacts of air molecules with the wings pushing them upwards.

Zaheer’s Flight

In many instances, Zaheer’s flight probably involves a combination of pressure differences, strong winds and air propulsion as well. However, Zaheer has also been shown quietly levitating in place without any noticeable air flow around him.

Here, we see the return of sonic levitation. If Zaheer can produce the right amplitude and frequency sound waves, he could hypothetically lift himself using sonic levitation. Since air molecules only vibrate back and forth due to sound waves, this process wouldn’t produce any noticeable air currents.

Spirit Projection

Spirit projection is when an airbender(pretty much always Jinora) creates an image of themselves separate from their actual body that can speak and observe their environment. We already discussed that airbending involves corona discharge, which means partially ionizing the air. This partial ionization emits light which could be used to create the glowing image of a spirit projection. We also saw that plasma can be used to create sound waves, which explains how spirit projections can speak. All that’s left is to understand how a spirit projection could relay information about its environment back to an airbender. In my first post on Avatar and Korra, I talked about how benders would likely need to connect to their environment, using quasiparticles to measure the physical properties of their surroundings. So it could be that airbenders send out quasiparticles along with their projected images in order to gather information about a location. However, this doesn’t explain why Jinora sometimes projects her image to locations where she only wishes to observe what’s happening without her projection being noticed. What’s likely going on in these instances is that Jinora doesn’t actually project her image to these locations. Only the audience is seeing her. She merely observes these locations by sending quasiparticles to them which then return to her carrying information.

Drawing Energy from the Atmosphere

Earth’s atmosphere is turbulent due to its uneven heating from the Sun. That’s what creates wind. In previous posts, I talked about how benders could harness energy from the motion of particles around them through electromagnetism. The same could be true for airbenders. First, they’d ionize a small fraction of the air molecules around them. Then, these particles would get dragged along with the wind. The accelerated charges would then push and pull against the airbender’s electric field, transferring energy to them.

That concludes our analysis of the physics of airbending.

In my next post, I’ll be looking at miscellaneous aspects of the Avatar world, such as spirits and energybending, and seeing what hypotheses can be made about them. As always, let me know about any ways I can improve my hypotheses from this post or better explain them.

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