The Moon was destroyed twice in Dragon Ball. The first time was during the Tenkaichi Budokai when Kamesennin reverts Goku's Great Ape Transformation by firing a Kamehameha straight at the Moon. The second time was when Gohan underwent his own Great Ape Transformation and Piccolo destroys the Moon to stop Gohan's rampage.
The Dragon Ball characters' lives seemed to carry on as normal when the Moon ceased to exist, but what sort of influence would losing the Moon have on the real world?
There are a couple other things I really wanted to ask about. During Vegeta's battle with Goku, Vegeta creates an artificial moon to undergo his own Great Ape Transformation. I want to know if it is possible to create an artificial moon with real world technology. And what on earth are the "Blutz Waves" Saiyans need to undergo the Great Ape Transformation...?
Once the questions start coming, they don't stop! To put an end to the madness, we consulted Kentaro Terada, a professor at Osaka University.
Interviewee: Kentaro Terada
Osaka University Graduate School Professor since 2012. After obtaining a PhD in Physics from Osaka University, Terada worked as an assistant professor and then professor at Hiroshima University before his working at Osaka University. His fields of research include Earth and Space Science and Planetary Geosciences. When asked what inspired his research into space he responded, "I was fascinated by the laws of the universe when I was in high school".
Interviewer: Yuuka Higaki
Editor and writer. For as long as she can remember she has always been more of a humanities student, with her weakest subject being science. Since becoming an adult, she is starting to appreciate the fun of science through various forms of entertainment like manga.
—Just to start off with a quick question, what exactly is the Moon?
Kentaro Terada (hereafter, Terada): That's a good question. First off, if you go by the dictionary definition, there is only one Moon.
—"Dictionary definition"? What do you mean by that?
Terada: Well in the Earth and Space Sciences, we call all objects that orbit planets "satellites". The Moon and other planets' moons are natural satellites, and the word "Moon" refers only to Earth's Moon. Under the definition of natural satellites, there are currently about 300 in our solar system.
—Wow, 300! When you put it that way, I guess there would be a lot of moons in addition to our Moon.
Terada: Sometimes objects like small rocks get really close to Earth, and then fly off in some other direction. Since you could also call these "Earth's natural satellites", it would be fair to think of them as being a kind of moon. Rocks like this don't have to be all that big, there are even some that are only about 2 to 3 meters in size. If you call things that small moons, then it's not such a big deal to be able to destroy a moon.
*Hereafter, the word "Moon" will be capitalized when talking about Earth's Moon, and will be left lowercase when referring to other planets' moons.
—N-not that big of a deal... Would destroying the Moon be like that?
Terada: No, I think it would be very difficult to destroy the Moon. Let me try to explain it using some research into the destruction of asteroids as an example.
It is theorized that a long time ago, an asteroid that collided with the Earth caused the dinosaurs to go extinct. According to calculations, this happens about once every 100 million years. As it's been about 66 million years since the last collision, it wouldn’t be surprising if another collision were to happen soon.
If that happens again, we'd be in deep trouble. So, there is a lot of ongoing research into finding out if there is a method of destroying an asteroid if one were to come flying towards Earth. But it's really difficult to conduct that sort of research. Whenever an asteroid is destroyed in a simulation, it always goes back to practically its original size within 2-3 days.
—Why does it return to its original size?
Terada: Due to Newton's Law of Universal Gravitation, objects tend to be attracted to each other. Therefore, even if we were to destroy something, all the remaining little pieces would eventually come back together again. It might be slightly smaller than the original object, but I think it would be difficult to break something up and have it stay as pieces.
If you want to remove all traces of an object, you'd have to break apart and scatter the pieces with an incredible force. Kamesennin and Piccolo's attacks must have been infused with some special property or contained a tremendous amount of energy.
—So that's how unusual those attacks were... What in the world is the Moon even made of?
Terada: Both the Moon and asteroids are basically just made of stone. So, breaking up the Moon would be akin to breaking up a ginormous rock. Here are some basic facts about the Moon:
Terada: So, Moon rocks and Earth rocks are very similar. We know that the Moon is gradually moving away from the Earth, so conversely, the Moon must have been much closer to the Earth originally. This is where the Big Splash Theory (Giant-Impact Theory) comes from.
The Big Splash Theory is a theory that is well supported by researchers. It theorizes that when the Earth was brand-new, it collided with another celestial body about half its size. This caused a part of the Earth's surface to break away, and that part is what formed the moon.
—So the part that broke off didn't just get pulled back to Earth, it became the Moon instead? It must have been a really powerful impact that broke the piece off!
Terada: When the Moon was formed, it was much closer to Earth, about 1/20th of the current distance (3 times the Earth's radius away). It has since been moving away from Earth to its current distance of 380,000 km. There have been other pieces of the Earth that were broken off like that in the past, and many asteroids made of iron or rock several hundred km in length have been broken apart.
— So Kamesennin and Piccolo's actions destroyed the Moon and prevented it from reforming. In a sense, I guess that'd mean those attacks possessed the level of force explained in the Big Splash Theory.
Terada: This scenario would be hard to recreate artificially in the real world. Another important point to consider is that if the Moon were to break apart into pieces, huge meteorites would fall onto Earth. That would be extremely dangerous.
—Yeah, humans and animals would be severely injured if they got hit.
Terada: No, that's not the scope I'm talking about. (Laughs) When the dinosaurs went extinct, it is thought that a 10 km long rock hit the Earth. Considering the Moon has a diameter of 3,400 km, it would be safe to assume that 10 km fragments are quite likely to form. If even one of those hit the Earth, it would probably cause the extinction of all mammals.
—How does having the Moon affect the Earth normally?
Terada: The easiest way to see the influence are tides. The height of the ocean when it rises and falls is due to the gravitational pull of the Moon.
This is a little off topic, but the Moon is actually a very special natural satellite.
—What's so special about the Moon?
Terada: As I mentioned earlier, there are about 300 moons in our solar system. Out of all those moons, the Moon is the only one that is so proportionally large to the planet it orbits. Mars has two moons, but they are only about 1/309th the size of Mars. Jupiter has a moon called Ganymede and Saturn has a moon called Titan, and each of them are about 5000 km in diameter, but since Jupiter and Saturn are about 10 times the size of Earth, they are only about 1/27th and 1/23rd the size of the planets they orbit respectively.
If you think about it in those terms, the Moon, which is about a quarter the size of the Earth, is extremely large proportionally. So, it's fair to say that the Moon has a significant influence on the Earth. The tides are also a direct result of the Moon's large size as compared to the Earth.
—Oh, so the fact that the Earth has such a large Moon is quite rare even within the solar system!
Terada: Yes, you could say that it is the most important feature of the Moon. Going back to your original question, Earth's seasons are also influenced by the Moon. The reason the Earth has four seasons is because it rotates around the sun with its rotational axis tilted about 23.4 degrees. The important point here is that the axial tilt remains stable with almost no fluctuation.
Thanks to this stability, summers are always hot, and winters are always cold. And this axial tilt stability is all thanks to having our large Moon nearby.
It's been 4 billion years since life appeared on Earth. Over time, the relatively stable climate has allowed us humans to evolve. In that sense, it was extremely lucky for humanity's survival that there is such a large Moon so close to Earth.
—It seems that the Moon is indispensable, both for the Earth and for us. So, if the Moon were to disappear, just what would happen...?
Terada: Well, as I said earlier, there would be no tides without the Moon, mudflats would disappear, and the entire ecosystem of the ocean would be seriously disrupted. Also, the climate would be totally messed up, too. The places where most humans currently live could become as cold as the North Pole, or as hot as around the Equator.
This isn't as directly related to the environment, but arts and culture as we know it would never be the same. This is because the subjects of paintings, songs, haiku and other poems, and more would disappear. For example, you would probably never be able to go under the Torii Gate at Hiroshima Prefecture's Itsukushima Shrine or see the whirlpools in the Naruto Strait caused by the tides. It would especially affect those in tourist areas.
The Tenkaichi Budokai announcer was also concerned about the cultural impact of the Moon disappearing.
—If we lost the Moon, how long would it take for those changes to manifest?
Terada: The tides would stop almost immediately, say within a day or two. But I'd think it would take several tens of thousands of years for the climate to change due to Earth's axial tilt going askew.
—So, if the Moon were to disappear, it's not like humanity itself would go extinct today or tomorrow. However, tourist attractions would disappear, and the ocean's ecosystem would change, which would make it impossible to catch the food we've eaten up until now.
—There was another scene I wanted to ask you about. Vegeta creates a small artificial moon during his fight with Goku and he says "But only when [the sunlight] is reflected by the Moon does it contain Green-Spectrum Radiation [Blutz Waves]... When the Moon is full, that radiation exceeds 17 million zeno units."
—These "Blutz Waves" exist in Dragon Ball, but is there anything like them in the real world?
Terada: This is difficult to interpret... Vegeta says, "moonlight is only sunlight reflected", but when I thought about it again, I think that Blutz Waves are actually the reflected light of sunlight. Since, the reflected light from sunlight are electromagnetic waves, if Blutz Waves are some kind of wave, then they'd be electromagnetic I think... Take a look at this diagram of the different views of the Moon.
Image provided by Professor Terada and Osaka University
Terada: Our usual view of the Moon is on the bottom left here. Or in other words, this is the view of the Moon in visible light. There are a lot of different kinds of electromagnetic waves, like radio waves, infrared rays, x-rays, and gamma rays.
When the Moon is viewed using radio waves, it looks like the one on the upper left, but if you look at the one right next to it it's completely white. That's how the Moon looks when viewed with submillimeter waves. The sun emits various kinds of electromagnetic waves, and when they hit the Moon and are reflected back to us, we can see totally different phenomena just like these images show us.
—In Dragon Ball, Vegeta explained that "When the Moon is full, that radiation [from Blutz Waves] exceeds 17 million zeno units." But in the real world, are the strength of electromagnetic waves changed by the waxing and waning of the Moon? Does it have some sort of effect on us?
Terada: The strength does change. Just like when we can see a half-moon or crescent moon, invisible light (electromagnetic waves) only shines in parts exposed to sunlight (like the moon viewed in submillimeter waves or gamma waves). If there was a full moon, there would be a lot more reflected light reaching the Earth.
―Oh, speaking of which, right after that scene Vegeta created a small moon. Is it possible to create an artificial Moon in the real world?
Terada: Like I said before, according to the dictionary definition of "Moon", there is only one. But, if you were to expand the definition to include all satellites (natural satellites and manmade) that orbit planets, then you could say we are already making moons of sorts.
—I never thought about it that way...
Terada: If you mean a moon made of rock like the Moon, if you released a rock from a manmade satellite orbiting the Earth, it will also start to orbit the Earth. You could create a moon made of rock like this. So, I don't think it's that amazing that Vegeta made a moon. It would be much more difficult to destroy the Moon.
—Now you put it that way, I guess there is value in creating a moon that can bring about a Great Ape Transformation rather than just using the plain old Moon.
—Professor Terada, if you got the chance to go to the Moon, is there something you'd want to investigate up there?
Terada: There is! In 2017, I discovered that Earth's oxygen reaches all the way to the Moon. People from all over the world wanted to interview me.
—How did you discover that?
Terada: Well, first off there's something called solar wind. Solar wind is a wind that blows from the Sun at about 500 km per second. It can even reach the Earth, but it is largely stopped because the Earth is protected by an electromagnetic field. But sometimes some of the solar wind leaks in and collides with the Earth's atmosphere. When this happens, it causes a glow that can be observed from the North and South Poles, or in other words, the auroras (northern/southern lights).
—Wow, I didn't know that...
Terada: I thought, if there is that much wind coming to the Earth, wouldn't it also carry oxygen away from the Earth? I decided to review the data from the lunar orbiter Kaguya (also called SELENE).
Then I saw that when the Sun, Earth, and Moon were aligned, or in other words when there was a full moon, the amount of oxygen per 100 km around the Moon increased. This suggests that the Earth's oxygen is transported downwind to the Moon.
We estimate that the oxygen created on Earth takes about 20 minutes to reach the Moon. Next time there's a full moon, try to remember this as you're gazing upwards.
—I don't think I'll ever look at the Moon the same again!
Terada: There's a lot of stuff about the Moon that even children would be excited by. So I think the Moon is a good entry point to get people interested in science.
Going back to that initial question, if I got the chance to go to the Moon, I'd want to confirm whether the Earth's oxygen actually makes it that far. However, I'm a tad claustrophobic so I don't think I would do so well on a rocket...
—Well, if you ever get the opportunity, I'm sure you'll manage! (Laughs)
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