Bedtime Stories For The Mare In The Moon

by Needling Haystacks

Chapter 5: The Tale of the Sonic Rainboom

Here, we have 2 stories to tell. The first is the relatively short legend of the Sonic Rainboom, the second is a construction of the events that are much more recent: less than two decades ago. The former is such a dimly-remembered legend, that I cannot say too much about it. Further, out of respect for the participants (who are still around), I do not make any poetic turns of phrase or imposition of narrative structure to the latter event. Thus, these may be a bit dull to read, but then they are short.

The Legend:

Many years ago, before Equestria was founded, there was a Pegasus named Firefly, who could fly very fast indeed. Through practice, she got faster and faster, until she could fly so fast that a loud boom would accompany her flight. But then, one day, another Pegasus flew into a snow cloud by mistake, and their wings froze. As her friend plummeted towards the ground, Firefly dived after her. In this case, not only was there an explosion of sound, but there was also one of color. A rainbow appeared behind her as she flew, and she was able to catch up to her friend and move set her on the ground without injury, the rainbow trailing her as she went. After much practice, Firefly was able to create this “Sonic Rainboom” at will, forming rainbows wherever desired nearly instantly. But no other pony was ever able to replicate this feat, and in the passing of time, the skill was lost.

The Fact:

Some years ago, at a Young Flyers camp in Cloudsdale, a phenomenon so similar to the legends occurred that it could hardly be anything else. For some time, until the parties in question came of age, the names of the participants were kept anonymous. Now, it is known that the creator of the Sonic Rainboom was one Rainbow Dash. She was goaded into a race by two colts, Hoops and “Dumb-Bell” (not his real name, but apparently what he goes by). A traditional “go through the hoops” race, there was one “power dive” checkpoint. During this section, she left her competition in the dust and broke the “magic barrier”. A rainbow-colored circular shockwave radiated out from the low point of her dive, and afterwards a rainbow trail formed behind her as she flew, eventually petering out. The event was seen for a long distance across Equestria, reaching not only Canterlot, but all the way to the Diamond Mountains and the Rock Plains.

Analysis:

We can say little with regards to the ancient legend, except by comparison with modern events. However, we should note that Firefly is not universally accepted as the name of the pegasus in question. For instance, the version told among the pegasi of the Cloud Mountains has her name as the apropos “Swift Wing”. Some versions hold that the pegasus was male (with similar names), while the griffons claim that it was actually a griffon who first achieved this feat! The griffons give “Greta” (for female) and Groucho (for male) as possible names. Firefly being the name most commonly told in Cloudsdale, I will stick to that hereafter. As a side-note, the famous General Firefly was supposedly named for the Firefly of legend.

With regards to the incident in Cloudsdale some years back, there are a few points to note before we consider the Sonic Rainboom itself. The first is the filly who performed this feet. While still young, she has placed in the top three in a number of racing competitions since then, though her current occupation is as a weather pony. With regards to that last point, for those who do not know, unless one can get one of the coveted slots in one of the professional teams, it is difficult to make ends meet as a pure 'flier'. The best-known of these teams is the Wonderbolts, though there are others. There are even a handful of solo performers who make a living appearing at private events.

Next, Ms. Rainbow Dash has yet to reproduce the feat. While her cutie mark, according to her, actually appeared after the start of the Rainboom, the fact that its appearance was near then suggests that the magic 'boost' that occasionally accompanies a cutie mark's emergence (regardless of the bearer's species) may have played a role. There have been a number of attempts to get her to repeat the feet, including one I undertook myself. That makes a mildly interesting anecdote in and of itself. However, because it was ultimately unsuccessful, I do not feel that that anecdote fits here. I will include it in an appendix, for the interested reader1.

Now, since unlike the tales from previous chapters, this one has been replicated recently enough to be in many living memories, we can be a bit more definitive in our analysis. But first, a brief overview of terms for my non-pegasus readers. The 'ring race' is a flying competition whereby the contestants must pass through rings in a specific order. For young fliers, they are generally made of cloud to avoid injury, but metal rings may be used for more advanced fliers. For the event in question, they would have been cloud since the participants were young. Next, the “power dive”.

A power dive is a gravity-assisted maneuver where the pegasus actually moves faster than the free-fall velocity. There are some complications to that statement, as we shall see in a moment. Many pegasi can do this without thinking. There has been analysis of this maneuver for at least as long as recorded history. “Analysis paralysis,” where thinking about how one does something renders one unable to do it, proved something of an impediment, but it has been well studied by this point. The invention of high-speed magic photography in the last few years has allowed further analysis of the actual physics of the process.

In the beginning of a power dive, the pegasus begins to free fall by angling downward and tucking in the wings. As they continue to accelerate, they must progressively tuck in their wings in order to achieve maximum streamlining. At a certain point, some feathers have to actually “pop” up in order to disrupt turbulence that would otherwise form. This last point is rather complicated, so I shall not bore the reader with the details. Mind you, this all occurs in a very short time. Once within a certain distance of the ground, the wings must be progressively extended to slow down enough to 'make the turn' and avoid impact with the ground. [see B. Ponyz [sic] and Horse B. et al., “Diving-Flight Aerodynamics.”]*

The process I have just described is something falcons and other birds can do as well. For them, they are technically in free fall the entire time, they are merely minimizing drag from the air. Pegasi are a bit different. I suspect most of my readers have never considered how pegasi fly, assuming it is the same process used by birds. To some extent it is, but a pegasus's body-mass-to-wingspan ratio is simply too high to fly without rather furious flapping, and anyone who has observed a pegasus in flight will know that this is simply not what most pegasi do. Instead, the innate magic of a pegasus allows them 'push off' against the air via and expenditure of magic. In addition, they can 'swim' through (or 'push off of') the magic field that permeates our planet to some extent. There are limits: at high altitudes, there is less air to push off of. The reduction in the magic field is minor by comparison, but 'swimming' through the field alone is not enough to keep a pegasus afloat. Thus there is an upper limit to flight, as I mentioned back in the first chapter.

The result is that pegasi can, in principle, reach even faster speeds than a falcon when in a power dive. Typically, the acceleration distance and time are short enough that the speeds cannot exceed that of sound, much less that of magic. That assumes, of course, that the pegasus in question tries to avoid crashing in the typical manner. Apparently, leading up to the Sonic Rainboom, Ms. Rainbow Dash became so engrossed in the race that she neglected to decelerate longer than would ordinarily be safe. According to Hoops, her nickname at the school was “Rainbow Crash”, as apparently this was a habit of her. When flying around clouds instead of the ground, it is typically less of an issue.

I mentioned above the speeds of sound and magic, and I must take some pains to describe what I mean here. The speed of sound is, logically enough, the speed at which sound travels. In thunderstorms, the lightning is always visible before the thunder is audible. This is because sound travels more slowly than light. By having a pegasus trigger a lightning strike at known distances from the observer and measuring the change in delay over the distance, one can find the speed of sound. Note well: the speed of light is so much faster that the lightning's visual transmission can be said to be instantaneous for any distance over which it is visible. It is about 770 miles per hour at sea level, and generally decreases as you go up in altitude. There is a temperature dependence, so there is some variation as well as altitude transitions where it decreases. There are also other ways of measuring it, but as this chapter is already heavy on the science, I will not bore the reader with further details.

The speed of magic is, as one might guess, the speed at which magic travels. Here, however, we have to take some care. The EFFECTS of spells typically travel much slower than this speed, being limited both by what the unicorn wants to do and by limits on their ability to follow these effects. The classic example of this is unicorn kinesis: an ability possessed by most unicorns to move small objects via magic. The object itself may move quite slowly, or even stay still, suspended in the air. The speed I mean here is that which carries this effect from the unicorn's horn to the object, typically signified by a similar glow surrounding the two. This does have a limited speed, though for simple kinesis that speed is so fast that the response is essentially instantaneous.

If, however, a unicorn were to, say, send a zap of magic over a long distance, then one might be able to tell how fast that zap moved. The unicorn would have to be careful that this zap was PURE magic, since if he or she instead used magic to create lightning or sound, the effect would move at the speed of those phenomena. One could also measure the delay moving an object at a great distance, though here since kinesis is generally restricted to line-of-sight one must be sure that there is sufficient open area. These measurements are a bit trickier, so the speed of magic is known with less precision, but it is about 900-1000 miles per hour. The greater uncertainty makes it difficult to be sure, but it seems to vary little with altitude, tested via unicorns casting a 'walk on clouds' spell first, then the test spell.

There are ways to exceed the speed of sound. A bare handful of pegasi throughout history have been able to just barely exceed the speed of sound. In recent times, besides Ms. Rainbow Dash, there is also Captain Spitfire of the Wonderbolts. There have been a dozen or so others known to have possessed this ability, but it would be tedious to list them here. With the exception of Ms. Dash, however, none were able to go enough beyond this speed to exceed the speed of magic.

The end of a good bull whip (my apologies to our bovine friends, but that is the name most know it by) can also exceed the speed of sound, which is what causes the distinct “crack”. Interestingly, a carefully made whip wielded by a sufficiently skilled hoof can actually exceed the speed of magic. This does not create a Rainboom, though. Neither does lightning, which is strictly speaking caused by electrically charged particles called electrons. I will not go into that particular nuance here, but it can be found in many college textbooks. From this we can conclude that a Rainboom requires not only exceeding the speed of magic, but also an entity that has an innate magic charge. Using magic to drive a whip does not work, as the driving spell is itself limited by the speed of magic. It is possible to imbue a whip with magic, and then crack it in the normal way, which produces a bright 'spark'. It is a useful trick in stage magic, and perhaps in some sort of Daring Do-esque adventure, but still not a full Rainboom. Likely, the concentration of magic must be sufficiently high and/or the speed maintained long enough for a full Rainboom to occur.

There are two visual and one audible components to a Sonic Rainboom. The audible component is a lightning-like “boom”, which can actually cause a blast wave that can knock things down, if done too close to the ground. The two visual components are an initial “blast wave” circular rainbow pattern and a rainbow “trail” which follows the direction of flight. With respect to the first, based on the accounts of those who are there, the blast wave appeared to travel perpendicularly to Ms. Dash's direction of travel. The appearance of this blast wave is now officially recognized as when a Sonic Rainboom has really occurred. The rainbow “trail” began at or just past the initial break-point and persisted for some time, with additional 'track' being added as Ms. Dash continued to fly at high speed, stopping when she slowed down below a certain point. Of note, while the initial blast occurred during a power dive, the trail continued to exist as Ms. Dash flew upward again.

There was apparently also a visual cue that the Rainboom was forming. When Ms. Dash was approaching the critical speed, both she and Hoops say they saw a sparking “envelope” that was mostly white with streaks of rainbow colors. This envelope probably narrowed and increased in intensity leading up to the boom: they were not paying particularly close attention to such subtleties at the time. This is interesting in that it has been hypothesized that at supersonic speeds a “Mach cone” will form around the traveler with an opening angle that narrows as they go more times the speed of sound. In this case, the cone seems to have formed before she reached the speed of magic, though perhaps after she reached the speed of sound. Captain Spitfire has said that she has observed the beginnings of such an aura forming during some of her higher-speed flights. Ms. Dash, for her part, hedged her words more, but is fairly certain that she has observed this aura or cone forming during some of her attempts to create another Sonic Rainboom.

The best model of the Rainboom is thus that when the speed of magic is approached by a magically charged body, there starts to be a conversion from magic energy to light energy, and possibly sound, creating the sparking and possibly crackling aura. It being difficult to hear when flying at speed, it is not certain of this aura makes a sound. After the speed of magic is exceeded, the conversion is continuous and directed, pointing away from the direction of travel. At the 'break point', there is a sudden, massive conversion as the local magic field and the pegasus's innate magic first adjust.

A useful analogy is a tightly wound watch spring. If over-wound then suddenly released, the results can be rather dramatic, but if one end remains tethered, it will subsequently settle into a must smaller and stabler oscillation (the end bouncing back and forth, in other words). Similarly, when the pegasus's innate magic first 'breaks through,' so that it travels faster than the local magic field, there is a big release of energy, but once this barrier is broken, there is instead a smaller, steader stream of energy released.

Possibly related is the aforementioned fact that the rainbow trail continud even after Ms. Dash began to climb against gravity. It seems that she actually maintained faster-than-magic speeds during at least some of that time as well. Typically, gravity slows one down during a climb. In this case, it seems that the conversion of magic energy, directed away from the direction of flight, gave her a 'boost' that enabled her to maintain speed. This is a most fascinating effect, and I do wish it could be studied further. If there were an easier way to harness it, it may be possible for, say, trains to maintain high speeds with minimal expenditure of coal, magic, or pony power. Though the repeated use of this effect would probably temporarily drain the local magic field. However, since the conversion of magic energy of all unicorns throughout history has not shown any negative effects in this manner, the draw-back would likely be only temporary.

There is some question as to whether the energy from the initial aura comes from the local magic field or the flier. Ms. Dash and Captain Spitfire say that once the aura appears, it gets much harder to fly faster, possibly going a long way towards explaining why the Sonic Rainboom had not been seen in well over a thousand years. This means that the magic field is resisting them. It might be best, then, to consider this effect like the brakes on a train hitting the wheels. This resists the train's motion (slowing it down) while kicking up sparks. In this case, the 'brake' is not part of the 'train', but as the energy of the sparks comes from both wheel and brake in a sense, so here the energy of the auro likely comes from both the pegasus and the local field, as the two 'rub up against each other,' creating a 'magic friction'.

On another note, Ms. Dash has a rainbow-colored mane and tail, and had such before performing the Rainboom. I do not know if that is serendipity or some sort of cutie mark-like magic linked to her ability to perform a Rainboom in the first place, but she and some observers claim that her mane and tail seemed to actually be part of the rainbow trail that formed following the initial boom. This raise the question: if, say, Captain Spitfire were to perform as Sonic Rainboom, would the trail be orange, like her mane? Would her mane turn rainbow-colored, either permanently or temporarily? Or would there be a disjoin between the two? In that case, would it be a gradual gradient, or a sharp cut-off at the end of her actual mane? Without more data, we simply cannot tell.

What we CAN say is that this is evidence favoring the hypothesis that a pony's mane and tail are particularly imbued with magic. There are two or three pieces of evidence besides this. First, Celestia's mane and tail remain in perpetual motion without any apparent conscious effort on her part. As she generally wakes and sleeps without attendants present, it is unknown if this effect persists in her sleep, which would fairy well confirm it as an innate magical properties. Understandably, this has been a prickly point for scientists to bring up. I understand a Ms. Neighther** asked once, but while permission was granted she decided against conducting the observation for fear it would destroy what remains of Celestia's privacy. The next two pieces of evidence are debatable, but most likely at least one of them is true. The first is that a pegasus's mane and tail (and fur, actually) seems to automatically align themselves so as to improve flight, something that does not seem to happen to, for instance, an earth pony or unicorn plummeting towards the ground. Naturally, the latter part of that is not especially well studied, particularly on the fur level, but it seems to hold for what incidences have been caught on camera. The second is that in rare instances, certain ponies are able to manipulate their hair to some extent, often subconsciously [Pinkie Pie, “The Art of Fun”, chapter 7, “Hares and Hair”]2.

I believe I have now said all that can be said for now. Now that it has been proved that the Sonic Rainboom is possible, I think it only a matter of time before someone, whether Ms. Dash or somethng else, creates one again. When this happens, there will perhaps be even more to say. I hope the reader will forgive the length and single-mindedness of this chapter. As stated near the beginning, this is the only legend mentioned in this book that has recurred in the living memory of ordinary ponies, and consequently there is the most to say about it. In the next chapter, we turn to the subject of magic artifacts other than the Elements of Harmony.

Notes to the 2nd Edition:
1: This appendix comes after the chapters of the original edition, but before the chapters new to the second addition. This may be confusing to some, but it allows returning readers to easily find the new material.

2: I understand that Ms. Pinkie Pie and Ms. Rainbow Dash are both linked to the Elements of Harmony now. I also hear that an acquaintance of mine, Professor Doctor Rock (the Professor is a title, the Doctor is part of his name. Confusing, I know), is currently thesis advisor to Ms. Pinkie Pie's sister, Ms. Maud Pie. It is, indeed, a small world.

Author's Note:

*The bit on power dives relies on this paper: Diving-Flight Aerodynamics of a Peregrine Falcon (Falco peregrinus). Benjamin Ponitz , Anke Schmitz, Dominik Fischer, Horst Bleckmann, Christoph Brücker. Published: February 5, 2014. http://dx.doi.org/10.1371/journal.pone.0086506 . Yes, Ponitz and Horst are their actual names, serendipitously. It took only a bit of tweaking to ponify them.

**Neighther is derived from Noether (pronounced "noy-ther", rhymes with neither), as in Emmy Noether, the early 20th century mathematician who happened to be female. Definitely one of the top 10 most influential mathematicians of the 20th century, and arguably in the top 3. Also, one of the Jewish intellectuals forced out by Adolf Hitler's regime. Look her up, her story is fascinating.