Science + Pop Culture, writing

Science Tangents: Avatar: The Last Airbender

I started rewatching the wonderful ATLA on Netflix — binging, of course — and made it to the penultimate episode of season 1 (aka Book 1) before I thought about any science no-nos.

That’s pretty impressive for a show that upholds the much-outdated idea that fire, water, air, and earth are elements.


Anyway, here are a few things that made my brain go “No, that’s not right.” even while watching a clearly fictional — or rather, fantastic — story.

Book 1: Water

Come the end of this Book, we’re at the North Pole, or the version of the North Pole in the ATLA universe. Whose world looks like this:


I don’t know if it’s ever established that their world is flat/spheroidal.1 Lots of fantasy doesn’t bother with that, unless you’re Tolkien, who explains that the world (a.k.a. Arda) was flat, until partway through the Second Age when a bunch of haughty humans decided to invade the lands of the little “g” gods to steal their immortality, and big “g” God killed them all as he ripped off the undying lands and made the rest of the world round. Fun times.

It’s not clear exactly when the season finale takes place, except that it has to be after the Winter Solstice, when Roku warns Aang about Sozin’s Comet, which will return by the end of next summer. And Appa starts shedding for spring partway through Book 2. So it’s still winter up there.

In the real world, where the Earth is round (approximately an oblate spheroid), this is a time when everything above the Arctic Circle never sees the light of day. That’s because the Earth’s seasons originate from the fact that the planet rotates about an axis that isn’t quite “upright”.


This axial tilt, aka the “obliquity”, changes over time because the Earth wobbles; it sits currently at about 23.44º.2

In a polar winter, there’s still a bit of sunlight that eeks out from the horizon during some hours, but at best you get some kind of twilight. So, it’s probably too bright at the ATLA North Pole in the “daytime”, but only to a pedant like me. And even for a pedant like me, it’s not enough of a booboo for me to ruin the moment.

Instead, what kicked me out of my suspension of disbelief was the Moon. Specifically, the following exchange about it:


Yue: The legends say the Moon was the first waterbender. Our ancestors saw how it pushed and pulled the tides, and learned how to do it themselves.

Katara: I’ve always noticed my waterbending is stronger at night.

[NB: most people don’t know that the Sun also causes Earth to have tides. Now you know and can impress people at parties.]

In the real world, the Moon and Sun aren’t opposite one another. One isn’t always rising when the other sets, and vice versa.

For example, today where I live the Moon rose just after noon, and will set at about 4am tomorrow morning. Sunrise was at 7:01am and will set at 7:51pm. So there’s about 8 hours of overlap when they’re both above the horizon.

Moonrise shifts by roughly a half-hour every day, so in one week it will be more of a one in, one out arrangement. At the end of October, the Moon and Sun will rise at about the same time.

The reason for this is the Moon’s orbit around the Earth (which determines its position in the sky relative to the Sun) takes 28 days to complete. A full moon, which we see in these episodes, is as far away from the Sun in the sky as it can be, so it will rise at sunset.

Please ignore that 1. the Sun should be white, and 2. the obviously inaccurate placement and shape of Earth’s continents. Just enjoy the Oreos…

In other words, there’s nothing wrong with the events of this season finale. At least there wasn’t anything wrong until the very end. The Full Moon is out, now Sokka’s girlfriend, and it’s day.3


That moment sealed this post’s fate, but it was Katara’s exclamation that set it in motion. If it’s supposed to be the presence of the Moon in the sky that amplifies her waterbending, it doesn’t only do so at night. During the other lunar phases, it’ll do so during the day, too.

It also doesn’t make sense that a Full Moon amplifies Katara’s power at all, because that just means the Earth is bathed in more (reflected) sunlight. And the Sun helps with firebending.

Boom. Scienced.

It’s almost as if we’re dealing with a world so nonsensical that putting a fish in a bag turns the Moon red.

Oh wait.


Book 2: Earth

Sticking with the Moon, in episode 10 we learn solar eclipses happen in this world. And there’s one a few months away, which may provide a day in which to pound the Fire Nation army into dust.4

This is thanks to an old school planetarium, which tracks the motion of the Sun and Moon. (No planets, though. Are there planets in this franchise?)


At the moment of the eclipse, the two tracks line up forming a crosshair, and the Sun and Moon can move in opposite directions to meet up. It’s kind of hard to see in the screencaps, ’cause…ya know…they aren’t moving.


This is wrong, at least in the real world, but it’s something I’m pretty sure you wouldn’t catch unless you had a degree in astronomy/astrophysics,5 or were a serious amateur backyard astronomer.

It all comes down to the ecliptic. The plane that all the stuff (planets and moons and asteroids and whatnot) orbits the Sun in.


Our world may not be flat, but the Solar System basically is; the Moon’s orbit is angled about 5 degrees from the ecliptic.

Also, the Moon orbits the Earth in the same direction that the Earth orbits the Sun.

These two facts together mean that the Sun and Moon always move across the sky in the same direction, tracing out roughly the same path. They both rise in the east and set in the west.

Scienced…in regards to an episode featuring a giant, talking owl spirit…

M.A. Seeds, The Solar System, 5th Ed., Thomson/Brooks-Cole, 2007.

Additionally, in the following episode (where Sokka drinks the cactus juice) Aang tries to collect water from a cloud and gets basically nothing. An average cloud weighs about a million pounds, most of that water. I only mention this because most people think clouds are wispy, weightless things because they float. But no. They’re massive.

There’s another thing you can fascinate people with at a party.

And extra bonus: here’s the animators correctly demonstrating the color of the Sun:


Book 3: Fire

In episode 3, we learn that the solar eclipse will only last 8 minutes. Doesn’t seem very long – certainly not long enough to win an entire war against an entire nation. And yet, in our world, they’re often much shorter.

The exact length of time you experience totality (i.e. the moment when the Moon is so perfectly lined up with the Sun you get to see its atmosphere, aka the corona) depends on your exact location on the ground.

Here’s a map from the 2017 solar eclipse that crossed the continental US:


That grey sliver is the path of totality. Inside this region, you actually got to see the full eclipse. Anywhere outside of it and the Sun’s bright enough that you/the Fire Nation Army wouldn’t notice all that much of a change.6 The closer to the center of that ribbon that you’re standing, the longer the eclipse would last.


I was in Nebraska for the event. Specifically Kearney, which if you look closely enough you’ll see is solidly on the 2 minute line. If we had been a little further north, we could have gotten the maximum 2:40. That’s the longest anyone in the States would have had, had they decided to battle some firebenders.

Photo credit: my dad

The length also depends on several other factors. Longer eclipses happen when:

  1. The Moon is as close to Earth as possible (i.e. “at perigree”)
  2. The Earth is as far away from the Sun as possible (i.e. “at aphelion”)
  3. The path of totality is closer to Earth’s equator, so the ground is rotating as fast as possible against how fast the Moon is orbiting us.
  4. The path of totality is closer to the part of the Earth where the Sun is directly overhead (i.e. “the subsolar point”)
  5. The path of totality is as horizontal (i.e. following lines of latitude) as possible.

According to one paper, the longest totality between the years 2000 B.C. and 7000 AD is 7 minutes, 29 seconds. in 1973 one lasted over 7 minutes, but the next that long won’t be until 2150.

The next total eclipse that crosses North America will have a maximum totality of about 4.5 minutes. This one in 2027 will be over 6 minutes, and the one in 2028 that crosses through my current city will be over 5.7

Screen Shot 2020-09-26 at 10.38.29 PM

As for what happens during the eclipse, I don’t know why the Mechanist had everyone put on “eclipse glasses” for totality (and not for looking at the eclipse itself, just for general seeing purposes). That’s when you don’t have to wear those special glasses!

Credit: NASA/Mamta Nagaraja
Credit: NASA/Mamta Nagaraja

But how ’bout that space sword?


Meteorites aren’t one-size-fits-all. They come in a range of compositions. The two main types are ‘stony’, meaning they’re primarily made of silicon-based minerals, and iron, meaning they’re primarily made of uranium (I’m hilarious…it’s iron and nickel). You can also have a blend, but something like 95% of the meteorites found on Earth are of the stony variety.

Iron meteorites are my favorite because the crystals have millions of years to grow into Widmanstätten patterns:

Credit Jim H, CC BY-SA 2.0

A few swords have been made from meteoric iron over the years. Tentetsutou (i.e. “Sword of Heaven”) was made by Japanese swordsmith Yoshindo Yoshiwara; it’s on display at the Chiba Institute of Technology. (I don’t know the year he made it, but it’s been some time in the past half century…)

In 1814, Britain’s James Sowerby made a very curved blade (67 cm long) for Russian tsar Alexander I out of a meteorite that landed in modern-day South Africa. It was basically a thank you gift for his help defeating Napoleon. Took 10 hours to make, and 5 years to deliver.


In the 1600s Mughal Emperor Jahangir had two swords and a dagger made partly from a meteorite. The pattern in the metal you can see in the dagger (“pattern welding”) comes from the fact that multiple metal sources were used.


King Tut was buried with a space knife, too. (You might wonder how we can tell these old blades have space-based origins. It’s ’cause they have a higher nickel content.)

And then, of course, the guy from Man At Arms made a replica of Sokka’s sword. He had to use extra steel because the meteorite material was too brittle, but it looks cool.

If not black.

In fact none of these blades are black. Meteorites look black after they impact because the outer layer of the rock forms a crust as it barrels through the Earth’s atmosphere. Simple erosion will wear that away, so making a sword out of it definitely will, too.

Taking a brief moment away from all the space stuff, in Ep. 13 we get a glimpse of a rainbow of fire colors thanks to two firebending masters (aka dragons).


We (as viewers of the series) are already familiar with Azula’s blue variation of firebending, supposedly indicative of her skill. Along with her lightning bending, it’s associated with her “cold” personality, though blue flames are actually hotter than every color but purple.

Anything that has any measure of temperature (i.e. it has atoms that are moving around, and the faster they’re moving on average, the higher its temperature) emits electromagnetic radiation—which is better known as light.

Visible light is only a tiny part of the electromagnetic spectrum which ranges from radio waves at the longest, to Hulk-creating gamma rays at the shortest. So plenty of objects that have a measureable temperature (e.g. you) emit light, but it’s mostly if not entirely invisible to eyeballs.

By Philip Ronan Gringer CC BY-SA 3.0

But it’s not just one wavelength of light. It’s a bunch of different wavelengths of light in different abundances all at once, which depends on the temperature. Long ago, scientists figured out the actual equation which best models that electromagnetic emission, as well as the wavelength that’s emitted most frequently (i.e. where that equation hits its maximum).

Apparently I am incapable of not connecting any ATLA science tangent to space, so here’s the curve for our Sun, which peaks across the part of the EM spectrum that humans just so happen to be able to see:8


The Sun’s “surface” (i.e. its photosphere…it’s a giant ball of plasma it doesn’t have an actual surface) has a temperature of about 5500 ºC. The colors of light combine in different amounts to make it look white overall. Anything that’s glowing red hot is actually cooler than that—its curve peaks at a longer wavelength. Anything glowing bluer is hotter.


You’ll notice that the Sun actually emits more greenish light than it does any other. But because it doesn’t just emit green light prevents it from revealing that fact, visually. The way you get green flame (as well as various other colors) works differently and depends entirely on what fuel is burning (in the following image’s case, copper sulfate), which does not apply in the case of firebenders.

Credit Søren Wedel Nielsen CC BY-SA 3.0

And finally, Sozin’s Comet, the astronomical event we’ve been waiting for all series. Which per evil buff Luke Skywalker will provide the firebending ability of 100 Suns.


What a real-world comet has in such abundance compared to the real-world Sun is…basically nothing. And they definitely aren’t a goodness, gracious, great ball of fire that only hangs out for two half-hour episodes of fighting.

But they are pretty sweet as far as glowing space rocks go. They start out as frozen hunks of rock, ice, and dust a few kilometers is size. Their comas and tails are created as they get close enough to the Sun that ice turns directly into a gas and shoot up up and away at enough speed to carry plenty of dust away, too. You actually end up with two tails (like Tails, but lets not jump franchises…), one for the gas and one for the dust.

By SimgDe - Own work, CC BY-SA 4.0,
Credit SimgDe – CC BY-SA 4.0 

The coma forms first — basically the comet’s version of an atmosphere — which can expand to the size of an entire star (hundreds of thousands of kilometers across), and then light from the Sun (as well as small but mass-having particles) actually pushes on the matter in the coma away to form the tails. Yeah, light can push stuff.

Then, while sunlight bounces off the dust tail, sunlight gets absorbed by the gas atoms’ electrons and kicks them free. This creates a plasma, which glows.

All this happens when the comet is near the Sun, which means it’ll be pretty close to the Sun in the sky from Earth’s perspective. So day-to-day, you can only really see it for brief periods after sunset and before sunrise. But the comet’s still out there for weeks at a time, until it gets far enough away from the Sun to turn back into a dusty snowball.

Whether or not someone uses one to take over the world is still up in the air.

1. The sequel series, The Legend of Korra, confirms that the world is round.
2. Our moon actually helps keep the amount of change in Earth’s obliquity (between 22.1–24.5º over 41,000 years) relatively small. Over on Mars it can vary over 60 degrees over the course of millions of years.
3. One small bonus is that their Moon appears bigger when it’s closer to the horizon. This is an optical illusion that happens in the real world.
4. Why firebenders lose their bending during an eclipse and not during the much more frequent case where the Sun’s light gets blocked by a massive planetary body (i.e. night time)…or while they’re deep within a cavernous collection of lava tubes…is anyone’s guess.
5. To be honest, there are probably a lot of people with such a degree that might not notice, too, especially if their research focuses on stuff beyond our solar system, like quasars or whatever. 
6. In other words, the fact that King Bumi also experiences totality all the way in Omashu, allowing him to retake his city from his temporarily powerless firebender captives (as portrayed in Episode 19), is an amazing coincidence…
7. I’m departing the country many years prior to this, but hopefully I will have at least one friend that will let me stay with them (and I have the actual money to fly all the way back to NZ…)
8. This is not a coincidence. This is thanks to it being evolutionarily useful to be able to see the light that the Sun emits the most of, as opposed to, say, x-rays, which the Sun does emit (in smaller quantities) but is blocked almost entirely by our atmosphere.

Here’s the Sun being the wrong color again:

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