My Little Pony: Friendship Is Magic/Setting Science and Magic/WMG

Because pony physics are a bit weird, guesses will creep up. If you have guesses on other things then:

"Shared Universe guesses go here

Pony guesses go here

Guesses about Equestria itself go here

Guesses on Equestrian Culture go here

Dragon guesses go here

Guesses on other species go here"

"Go back to the Main Setting Guesses page here"

"and you can still go back to the Main WMG Page, here"

The universe runs on friendship.
Literally. The physical laws of the universe is actually thinly held together. They break down constantly and require maintenance. Usually, they are held stable by magic. However, over 1000 years ago, Equestria figured out how to harness the power of magic, turning their realm into an Utopia, but at the cost of physics within the land slowly decaying. The royal family, possible the then young princess Celestia, gathered all ponies together, and organized them, taking over the responsibility of ensuring the season turns as supposed to, as well as such things as gravity and speed of light. This also nicely helped solve the recent unemployment problem.

Clouds are actually gaseous non-newtonian liquid instead of water.
Non-newtonian liquids become solid when pressure is applied to them, and allows one to walk on water if done carefully, as seen in several YouTube videos. Clouds in Equestria are gaseous forms of these liquid, which allows them to remain airborne but still have enough liquid to be solid when comparably-light pegasi walk on them. The spell Twilight uses in "Sonic Rainboom" is really a spell that reduces earth ponies' weight to that of pegasi.
 * Also explains why repeatedly stomping on a cloud causes it to dump its water onto whatever is below it.

Gems in Equestria are actually a type of fungus.
They occur only a couple of inches below soft ground, which makes no geological sense, and there never seems to be a shortage of them despite the fact that dragons must eat huge amounts of them. Therefore, we can assume they're actually growing and regrowing regularly.

Jewels and gems grow like plants in the MLP universe.
This explains why they're often found buried only inches underground, and why they are still so abundant even though dragons eat them. If gems didn't grow like plants, they would've disappeared a long time ago with the way dragons eat them.

The reason the ponies need to control the plants, animals and weather is because Discord is imprisoned.
Discord was/is the physical manifestation of Chaos... which, isn't just "everything goes wacky," it's a necessary attribute of physics. Much as superheated pure water can't turn to steam until an outside force perturbs it or introduces a tiny contamination, without Discord's presence, Equestria doesn't have enough natural chaos in it to trigger the formation of clouds, or of raindrops/snowflakes/ice crystals, or the shifting pattern of winds, or the ebb and flow of plant or animal lifecycles. But given a choice between having to crank the ecosystem over manually or having a mad god loose in it, the ponies made the obvious choice. It's also an explanation for the Everfree... it's the last natural source of Chaos left in Equestria, and so is kept as a nature preserve.

Ponies have access to electricity...
...but NOT to fossil fuels. Thus the existence of a hydro-electric dam and various minor electric appliances is possible, but the existence of cars and other major industries as we know them is NOT possible. This is not a case of environmentalism, mind you, but a simple matter of discovering electricity before gasoline (although environmentalist ponies are probably happier for that).
 * Not that they'd need fossil fuels, since they DO have access to everything they need to generate electricity. They have windmills and water turbines, and it's not hard to imagine that solar panels exist. Unicorns have been seen using their magic to power machines. Organic waste can also serve as a fuel source. Even if fossil fuels did exist, there are enough alternatives in place to make drilling for them pointless.
 * If the world is assumed to be relatively young, created by magic or gods sometime in the last million years, there are no fossil fuels to find. The ecosystem hasn't been around long enough to make any.
 * That's kind of mixing your paradigms. If the world was indeed spontaneously created ex nihilo at some point, there's no reason it couldn't have come with fossil fuel depots (or functional analogs if one wants to quibble about the definition of "fossil fuel") already included.

The dam in The Mysterious Mare-Do-Well produces magic
Almost exactly like a more local version of the Lux Font of the Rac Conan Diamh(sp) in Tales of the Questor, right down to the use of invisible ley lines rather than cables on poles to transmit the power.

Equestria's technological devices are actually powered by earth pony magic.
That's why the locomotive in "Over a Barrel" needed a team of earth ponies to pull it, and that's why the ponies working the construction equipment in "The Mysterious Mare-do-Well" were all earth ponies. The locomotive was pulling the train, but it needed a team of earth ponies galloping before it to power the boiler.
 * I always thought they were trying to conserve coal or something.

The main power source for magic-run machines are gems.
We've seen them used for a lot of things already (decoration, food source for dragons, presumably they have momentary value). So for gems being a source of power for machines wouldn't be a huge stretch.
 * A slightly more specific explanation could be that some types of gems can harness ambient elemental energies in the magical aether;in other words, a Fire Ruby can be used to make actual fire. There could also exist Water Sapphires, Wind Emeralds, Shadow Amethysts, and for straight-up power supplies, Lightning Topaz.

Equestria is on the verge of an Industrial Revolution
But they lack the motivation for it. We see that they have automation to a degree but the inferior quality of the products has yet to be overcome by the need for sheer quantity. In the real world that need was supplied by aggressive colonization, trade with ignorant native populations and periodic wars. We have yet to see any other nations besides Equestria and it seems like war is a thing of the distant past. Although it appears that at least two frontier towns have been founded in the last century and trade with the buffalo or zebras may provide some incentive for industry within the next generation or so.
 * Well, they do have video games as of "Hearts and Hooves Day"

The solar system in which Equestria exists is heliocentric/Celestia and Luna actually don't move the sun/moon, but rotate the Earth on it's axis.
In the intro for the show (here), there is a glass window on the right of Celestia that seems to depict an Earth-like planet in a heliocentric orbit — although we cannot see the orbit of the Earth-like planet, the small, ringed planet in the upper left corner does seem to depict its orbit around a sun (whose existence is implied by the rays in the image), so we can safely assume that the Earth-like planet is also orbiting around that sun. Assuming that the Earth-like planet is a portrayal of whatever planet on which Equestria exists, this strongly suggests that the Equestrian solar system is in fact heliocentric.
 * PS. After watching bits of Return to Harmony, more stained glass windows seem to suggest a heliocentric orbit. If the Equestrian universe is in fact heliocentric, this ultimately means that Celestia and Luna are rotating the Earth on it's axis, instead of moving the sun/moon. Alternatively, Celestia and Luna's jobs are to keep Earth from crashing into the sun (Celestia) and the keep the moon from crashing into Earth (Luna).
 * Begs the question, though, why knowledge of what the princesses actually do doesn't seem to be more widespread. Why, given the state of astronomy in the setting (with our own Twilight Sparkle being an astronomy nerd not above lecturing her friends for their educational benefit herself), is the old "their magic raises the sun and the moon" story still around and apparently unchallenged if that's not in fact what happens? (Sure, under another regime I could easily see that sort of knowledge getting suppressed if it's inconvenient to the rulers. Neither princess strikes me as the type to do that here, though, especially when whatever role it is that they're playing in maintaining the day/night cycle clearly is vital and thus arguably something they'd have reason to be proud of...)

Equestrian apples undergo fermentation while still ripening on the tree.
This not only settles the whole alcoholic vs. non-alcoholic cider question, it also explains why the Apple family's apples and related products are so popular all over Equestria. Just as appears to be the case in real life, ponies are as a rule less affected by alcohol than humans...but they're still quite capable of enjoying it.

On the Relative Power Levels of All Characters in Equestria
This is a list of characters/setting elements in Equestria, organized by magnitude of power. Feel free to add your own notes and observations on the topic.

The base list, which I have come up with, goes as follows:


 * The Elements of Harmony
 * The Power of Love (i.e. Cadance + Shining Armour)
 * Discord
 * Nightmare Moon
 * Celestia
 * Luna
 * Cadance
 * Twilight Sparkle
 * Shining Armour
 * Rainbow Dash
 * Fluttershy
 * Rarity
 * Applejack
 * Pinkie Pie (sans Rule of Funny)

This is my logic for the above order. Feel free to comment/discuss:


 * The Elements are canonically the most powerful force in Equestria. They trump literally anything, despite the fact that there are somewhat strict requirements to using them.
 * The Power of Love comes next, as of the Royal Wedding. Chrysalis (the Changeling queen) is able to trump Celestia with siphoned love, and at the end Cadance's love was capable of overpowering the entirety of the Changeling hordes. It's as yet uncertain whether Love would trump the Elements, but I rank them lower because the Elements are more reliable, being as they are physical artifacts that can be gathered by the Mane 6 at any time, while Love is almost useless to anyone except Cadance and relies heavily on Rule of Drama for effect.
 * Discord comes next. It's implied that he could easily overpower Celestia without the Elements on her side. He pretty much toys with the entire cast until the Elements come into play. At the moment, I would be willing to bet that The Power of Love would trump him, being almost equal with the Elements.
 * Nightmare Moon is also capable of overpowering Celestia. However, I rank her lower than Discord because, well, Discord is the embodiment of Chaos, while NM is a corruption of Luna.
 * Celestia comes next, naturally, followed by Luna. As the younger of the two, I estimate Luna to be less powerful; additionally, Nightmare Moon was only able to overpower Celestia because she received a power boost from whatever being corrupted her, thus implying that Luna was weaker to begin with. Cadance follows her two aunts/great-aunts/whatever, as she's far less powerful than them without The Power of Love.
 * Placing one of the Ruling Sisters above the other is kind of dodgy. How much older Celestia is, and whether that means anything is unknown. The only time that they competed against each other, both were augmenting their power. The extent to which the Nightmare Moon state increased Luna power, if at all, was never made clear.
 * Cadance really shouldn't be up with Celestia and Luna. Regardless of whether one believes that Celestia and Luna are especially powerful winged unicorns or that it takes time to reach that level of power, Cadance never displayed power above that of the average unicorn. She was defeated offscreen by Queen Chrysalis, was unable to even try to escape without Twilight's help, and Twilight did most of the work while they were escaping. She did use the Power of Love to help Shining Armor cast out the changelings, but Shining Armor is crazy powerful on his own, so that wasn't a solo showing. Outside of the very rare situations where somepony can be revitalized by the power of love, she should probably be down with the mane five, or in the swing tier with Spike.
 * Twilight Sparkle's magical potential has been commented on repeatedly. I rank her higher than her brother because her special talent is Magic, and you can't get much broader than that, while Shining Armour's talent is supposedly defense or some such. Her brother is still the most powerful unicorn after his sister, however.
 * Suggest placing Queen Chrysalis here. She defeated Cadance without trouble, but used subterfuge to subvert Shining Armor instead of capturing him outright.
 * Rainbow Dash's Rainboom has serious destructive potential, making her far more powerful than the other Mane 6. After her comes Fluttershy, who can easily keep pace when angry or upset. Rarity outclasses Applejack and Pinkie Pie on the basis of having magic, and Applejack has repeatedly demonstrated her physical aptitude. Pinkie comes last, but with a qualification; when Rule of Funny is in play, she demonstrates Reality Warper potential, and in this state could probably outclass the rest of the cast.
 * Fluttershy usually only keeps up with Rainbow Dash when Dash wants her to. Fluttershy did manage to fly faster than Rainbow dash while under extreme duress, with extreme effort, and for a short period of time, but that was when Rainbow Dash was in an altered mental state, which likely had a detrimental effect on her abilities. She also has the stare, but she can't really use that on command. Fluttershy's lack of aggressiveness, combined with her inability or unwillingness to use her abilities on command makes her the weakest of the five under most circumstances. Rarity does have magic, but it is limited in scope and power, and she prefers to use her hooves in a serious fight, though she is a strong fighter like that. Applejack is, well, the jack, and is capable in a wide variety of situations with a number of athletic skills. Pinkie Pie, even without the Rule of Funny, is still very fast and agile, but more importantly, has access to and skill with a number of useful machines that she might have built herself. Finally, she has Pinkie Sense, which doesn't isn't just for laughs.
 * Suggested Mane Five order Rainbow Dash, Applejack/Rarity, Pinkie Pie , Fluttershy.
 * Swing Tier: This tier is for characters that switch massively between power levels. Spike fits here, as he usually has below average physical abilities and a weak Breath Weapon, with only his natural armor to balance it out, but under the right circumstances can become an adult, shooting him up to around Rainbow Dash or even Shining Armor's level.
 * Cadance would fit well here, due to the situational utility of her only strong ability. Chrysalis would also be a good fit, due to her explicitly variable power level.

After that, it's pretty much fair game.

The Friendship Is Magic's universe's God is making sure that the main six ponies stay close.
It's been shown that caused the other five to get their cutie marks. I bet that the My Little Pony Friendship Is Magic universe's God is keeping them snug and close so it has an Ace when things skew to a sour side.
 * Yes, her name is Celestia.
 * This Troper's views of Princess Celestia's interactions with the mane cast have always been tinted with the idea that she sees them at least partly as the Elements of Harmony. Rewatch the end of "Fall Weather Friends" with that view. Why would Celestia go to Ponyville to see the falling leaves, when she can do the same thing in Canterlot? Because Honesty and Loyalty are risking a falling out, making the Elements weaker.
 * I thought her name was Lauren Faust.
 * But she's no longer 'executive producer'.
 * It's some unknown entity above Celestia, Luna, and even Discord.
 * It's HARMONY.

The universe uses a virtue system like Exalted.
Tying in to the guesses about Elements of Harmony having inherent flaws to them as well, it could also be that having an element renders you vulnerable to an Exalted-style Limit Break. Instead of Exalted's four virtues (Compassion, Conviction, Temperance, and Valor), this universe uses six (Friendship, Honesty, Kindness, Generosity, Laughter, and Loyalty), each with their own Virtue Flaws and Limit Breaks. Naturally, a pony that embodies an element/virtue would have the most dots in it possible, leading to some truly spectacular Limit Breaks. Just for fun, let's look at what each of the Mane Six's Elements and possible Limit Breaks could be....
 * Rarity - Generosity - Give Too Much: The character is overwhelmed by her giving nature and proceeds to work herself to the bone in an effort to please every friend she has, regardless of her physical, mental, or emotional health.
 * Applejack - Honesty - Unbroken Promises: The character tries too hard to keep every promise, oath, and agreement she has made, disregarding all other concerns.
 * Pinkie Pie - Laughter - No One's Laughing With You: The character drops into a psychotic depression, firmly convinced that others don't actually care about her or the things she does to cheer them up.
 * Fluttershy - Kindness - Overbearing Kindnesses: The character becomes driven solely by the need to care for others, and to have them care for her in return, to the point where she becomes a terrifying figure of smothering over-affection.
 * Rainbow Dash - Loyalty - Pain of Testing: The character, torn between two mutually exclusive loyalties, finds herself unable to make any decisions and flees her responsibilities.
 * Twilight Sparkle - Magic - Lack of Understanding: The character, driven to frustration by her inability to understand the workings of something, becomes obsessed with unraveling its secrets.
 * Rainbow Dash is the only one we haven't seen in-series. Her loyalty was tested in Giffon the Brush Off, but she kept her head. All her issues have related more to her strong personality than her element.

Pony magic forms a field around each pony and has similar properties to electricity.
Specifically, they both are strongest on angled surface. Long pointy things are used as lightning rods, because the electric energy on any surface is the strongest wherever the sharpest angle is. The sharpest angle on a unicorn would be its horn, and because it is so close to their brain, the energy interacts with their brainwaves, allowing to control it directly. The sharpest angle on a pegasus is its wings, and because of this, the majority of their magical abilities come from their wings.
 * And on all ponies, the magical field around them allows them to manipulate any object they can physically touch. At the Grand Gala, we see the pianist pony play the piano, without using fingers. During the parasprite infestation, Pinkie is able to play an accordion without actually touching the keys. And on numerous occasions, we've seen ponies pick things up using only a single hoof.
 * So, ponies have tactile telekinesis? That...would actually make sense, especially when having the regular version is canonically already part of the unicorns' hat.

Earth pony magic manifests as a sixth sense, which is related to their special talent.
It's been confirmed that earth ponies have a magical connection to the land, i.e. Sweet Apple Acres grows better when run by earth ponies. The reason for this is because all earth ponies have the innate ability to simply know how to use their talent best. For example, with her special talent being apple farming, Applejack's "earth sense" tells her precisely when her apples are ready to be harvested. It also tells her how to buck each apple tree so that the majority of the fruit falls into her baskets.
 * Taking the above into account, this can be used to explain Pinkie Pie's "Pinkie sense." Remember, her special talent is making others happy. Most of her various twitches tell her of some sort of danger in the immediate future, and it's awfully hard for someone to be happy when they are hurt. The fact that her "earth sense" manifests as physical twitches is because, well, she's Pinkie Pie.

The Hatching Dragon Test is meant to be an Unwinnable Training Simulation.
Fluttershy's initial reaction shows that baby dragons are probably extremely rare. We don't see a single baby or adolescent dragon elsewhere. My conclusion is that hatching the dragon is designed to be an impossible test for a young unicorn. To see how they will react to not having enough magical power when under extreme stress. This would be a test to judge the character of talented unicorn and help ensure Equestria doesn't have any evil wizards. Twilight's Sonic Rainboom-induced magical seizure might have been the first time in millennia that the test was successfully completed.
 * Taking it further, Spike's egg was a fake, meaning Twilight hatching it was an Achievement In Ignorance.
 * Indirectly supported through "The Secret of My Excess": knowledge on dragon growth and their greed is not well known (Twilight can't find it in books, and neither a pony doctor or a vet know about dragon biology, so she's forced to a more obscure fountain of information, Zecora), suggesting that knowledge of dragons is limited due to their rareness and/or longevity. If Celestia was handing out baby dragons for every student that passed through her school for the last thousand years a dragon, you'd think this would have been well covered by then. Twilight's performance was beyond unexpected.
 * Supported by Word of God: According to Faust, she used the test for specific fillies that she thought had unique magical abilities, and one which Twilight actually passed. Celestia would go on to raise and train Spike while Twilight continued in school, eventually giving Spike to her as her assistant.
 * In "Dragon Quest," Twilight told Spike that he had been given to her as an egg, suggesting that Spike had been with her ever since. There's no evidence in the show that Spike was raised by Celestia.
 * Perhaps Celestia did most of the actual work when it came to raising Spike, with Twilight playing with him and 'helping', like a child with their first pet.

In addition to the above, the Hatching Dragon test was meant to reveal the suitable Element of Magic.
Anypony who possessed enough power to actually succeed at it would be taken by Celestia as her personal student, and on eve of the fateful day would be sent to Ponyville to make some friends…
 * So it's like the test to determine the next Avatar?
 * Confirmed by Word of God - it was only used as a test of magical power for a select few, Twilight being the first that passed it.

The cloud-walking spell from "Sonic Rainboom" never wore off.
The flight spell was mentioned to only last for three days, but the cloud-walking spell wasn't even stated to be temporary. For all we know, Twilight Sparkle, Applejack and Pinkie Pie can still walk on clouds.
 * Pinkie Pie still needed the balloon to sing her invitation to Rainbow Dash for Gummy's birthday. But that episode does not give hints of continuity, so it could go either way.
 * Pinkie would've needed the balloon (or some other flight method) just to get to Dash's place.

Friendship is magic… similar to how Madoka verse emotions are magic.
Cutie Mark = Soul Gem, Cutie Mark Failure Syndrome is the transformation from Soul Gem to Grief Seed, and Nightmare Moon is Luna’s witch form. The ‘outside influence’ in that instance was Kyuubi, and Twilight and co are the Madoka’s of their universe. They didn’t get rid of the system, they used Twilight’s revelation/wish that Friendship IS Magic to focused the contract entirely upon the Elements of Harmony, creating Cutie Mark Shaped Soul Gems they can draw power from/subsequently channel power into. These ponies are saving the universe, one lesson at a time.

The three pony types each have their own kind of magic, but they aren't exclusive to that pony type.
Earth pony magic, unicorn magic and pegasus magic all exist. Unicorn magic is what lets unicorns cast spells, earth pony magic is what lets earth ponies work with animals and plants, and pegasus magic is what lets pegasi fly and perform special effects. Usually this magic occurs most strongly in the associated pony type, but not exclusively. Rainbow Dash has plenty of pegasus magic, letting her fly really quickly and perform lots of special tricks like the Sonic Rainboom and the Atomic Rainnuke, but very little earth pony or unicorn magic. Fluttershy, on the other hand, has a moderate amount of pegasus magic, letting her fly but not terribly well, but she has quite a bit of earth pony magic too, giving her her bond with animals. Applejack has a huge supply of earth pony magic but almost no pegasus or unicorn magic, making her physically very powerful and successful at her work, but she's the only character with no real special powers. Pinkie Pie has some earth pony magic, and a certain amount of unicorn magic, which powers her Pinkie Sense (and other things, depending on how you interpret her abuses of Cartoon Physics). Without a horn, she can't actually cast spells, so her unicorn magic manifests as strange supernatural powers that aren't really under her control.

Friendship isn't just nice, it's SURVIVAL
Not only has it saved Equestria twice, but being nasty, non-empathetic, or antisocial can cause everypony to be frozen into starvation or worse! The ponies brace each other up and remind each other about this regularly, and now we know why Celestia assigned her best student, Twilight Sparkle, to study it.

Earth Ponies can't make an agricultural surplus without Pegasi weather control.
Although they think they can, and the ancient Pegasi and Unicorn leaders also thought that their races could manage to make one without Other Pony Races assistance.

Celestia and Luna don't move the heavens unaided.
Instead, they are actually channelling the powers of all the unicorns.

Unicorn Magic, Earth Pony Magic and possibly Pegasi Magic all work under different principles.
As off "Family Appreciation Day", Earth Pony Magic appears to work with the principles that things need to be influenced in such a way to produce the desired results. Especially when working with a magical crop like Zap Apples. This seems to work similar to Discworld's Witch Magic. It's also been repeatedly shown that Unicorn Magic works by cause and effect, and it seems to be studied in the same way that quantum physics would be studied. This is similar to Discworld's Wizard Magic. Not really sure how Pegasi Magic might work since we haven't really seen enough of how Pegasi society is run aside from weather control and cloud walking.

Also it seems that you don't need to be a certain breed to practice that breed's magic. Fluttershy appears to have the same sort of abilties that Earth Ponies might have (Influencing animals to do what she wants them to do, The Stare etc.) Perhaps it all depends on the correct mindset.
 * Pegasus Magic probably makes it so that everything they build/create doesn't dissipate/fall through the clouds.
 * We know "WHAT" it does, what isn't known is "HOW" they do it. Is it different from the other two methods of pony magic?

Many of the steps in the Zap Apple Jam ritual are unnecessary.
The Zap Apple Jam ritual is cargo cult science at its best. Granny Smith obviously doesn't understand why it works, only that it does. Its various steps include: (a) Steps that were never necessary, but Granny Smith wasn't willing to risk removing them, (b) Steps that were once necessary but which aren't anymore, (c) Steps which Granny Smith made up to obfuscate the process and keep her family's monopoly secure, (d) Steps which Granny Smith made up specifically to troll the youngsters of Ponyville, and (e) Steps which are actually necessary. She may not even remember which ones she made up anymore. I'm pretty sure the bit with the bunny suits is just to mess with the kids.

The most powerful forms of magic in Equestria manifest rainbow light.
The Elements of Harmony, the Sonic Rainboom, The Zap Apples... not to mention the use of rainbow in a powerful Love Potion. To ponies, a rainbow kaleidoscope of color could symbolize pure harmonious power: since each pony has their own color pallete, and unicorn magic is color-coded, a rainbow could combine the strengths of all ponies.

Using magic burns calories.
This is probably how all the ponies are capable of eating such huge amounts of sweets and sugary treats without significant weight gain.

Everypony and their mother has a connection to an incredible magic power
The Elements of Harmony are just the most understood ones
 * During the royal wedding Cadence and Shining Armor defeated the Changelings through The Power of Love
 * And the CMC will wield the Fire Of Friendship

In Equestria, moving the sun and the moon isn't quite as big a deal as it might seem.
This is a land of magical talking cartoon ponies, after all. A sufficiently powerful non-winged unicorn wizard (especially one with a suitably related cutie mark) could in principle learn how to do it; what makes Celestia and Luna in particular uniquely suited to the task isn't so much raw power as their extended lifespan, which circumvents the need to find and train a new pony for such an important job every few decades or so.

Magic fights don't tend to last long, because ponies are glass cannons.
Horn-blasts are really powerful so, essentially, whoever hits first wins. This would explain why Twilight Sparkle is capable of defeating a Changeling with a single blast, why Celestia's duel with Chrysalis was so short, and why the Royal Guard went down so quickly against the Changelings.

The power of the Elements of Harmony are hereditary.
Pinkie's grandmother taught Pinkie at a young age to "Giggle At the Ghosties" as a subtle way of teaching her how to properly wield ancient power of Laughter. No word yet about what the other characters' parents have taught them.
 * Twilight's parents encouraged their daughter to practice magic.

Everypony has a connection to one of the Elements of Harmony.
However, they don't always have a very strong connection to them, thus leaving the ability to wield the Elements to those who do, and who have a strong friendship with the other five strongest wielders. After all, it'd have to be an awfully Contrived Coincidence that all six Elements of Harmony end up living in the same exact town...
 * It's neither contrived nor coincidental: Recall that this universe's God-monarch walks among her people. Is it too farfetched to believe she had set up a Batman Gambit to save her little sister?

Two or more of the elements of Harmony can be combined to create other good forces.
And these forces can be used to cure the world of other evils. Of course, All of them combined creates the greatest power of them all, but these lesser powers still have their uses. For instance:
 * Kindness + Generosity = Mercy/Forgiveness
 * Honesty + Loyalty = Family
 * Laughter + Magic = Joy
 * Magic + Kindness = Abundance
 * Generosity + Honesty = Guidance
 * Laughter + Generosity = Playfulness
 * Laughter + Honesty = Roasting?
 * That's actually brilliant. Hope we see that in future episodes...

What the Elements of Harmony actually DO.
This is something of a weird thought I had regarding the various Elements of Harmony when they're by themselves, feel free to add your own thoughts/guesses for these:
 * Magic: Grants the wielder extraordinary magical aptitude, obviously.
 * Honesty: Makes the wielder impossible to deceive or trick, possibly even through magical means.
 * Granted Applejack was tricked by Discord, but then again Discord's effects around Sweet Apple Acres near the start of episode one of the two-parter shrugged off Twilight's Failsafe spell.
 * Kindness: Grants the wielder a sort of empathy with Nature, giving them a general understanding of how ponies and other animals work and letting them communicate. This may not work if done for selfish reasons, since you can't exactly be kind if you're selfish.
 * Generosity: Allows the wielder to find and/or make things easier; as you can't give gifts without either finding or making them first.
 * Laughter: May allow the wielder to awaken the soul of a person; bringing joy to those who may have trouble finding it themselves.
 * Loyalty: May give a general increase to the wielder's physical skills, allowing them to be there for their friends, no matter what.

I realize that I'm reaching for some of these, but these are just first draft ideas.

Anypony is an Element of Harmony.
All it requires is for the pony to have a personality that fits one of the elements. However it requires very specific circumstances to use, as the pilot showed. The point is that the mane cast is not some form of Chosen Ponies, the entire gang could be replaced by entirely different ponies as long as there was somepony there to represent each of the specific elements.
 * With one more caveat that they have to be good friends. Since it's an established part of series cosmology that "friendship" and "magic" are synonyms, naturally the pony who gets the fancy tiara is going to have to have a fairly good relationship with the other five, and they with each other. You can't just throw any random sextet of thematically-qualified ponies together and get an Orbital Friendship Cannon.

The Elements Of Harmony are incapable of killing.
They've been used four known times to defeat a major threat. All four times, the effects were non-lethal. First two and the last time, it merely neutralized the threat by imprisoning it, despite the fact Celestia and Luna clearly wanted to be rid of Discord once and for all. As the Elements Of Harmony representing the Power of Friendship, they can't be used to kill.
 * That's actually brilliant. Though they are certainly capable of scary things. Just ask Discord.

The Elements of Harmony one thousand years ago…
First of all, Celestia and Luna weren't the only users of the elements, there were six, just like the mane six. But The Corruption that made Luna into Nightmare Moon also corrupted the other 4 representatives, Celestia being the only one able to resist. Each one shared the leadership of all equestri until The Corruption appeared. Luna was able to resist it long enough to help her sister to seal their friends. The previous generation could have been:
 * Celestia = Magic: being this one the stronger of the elements, she was able to resist The Corruption, and use the elements.
 * Luna = Loyalty: her love and devotion for Celestia, made her ablo to resist it until the bitter end. later becoming the opposite of her element and the last one to be sealed.
 * Discord = Laughter: He said Pinkie's element was his favorite, and seems to have put special effort in her Mind Rape. He could have Mind Raped Luna before having been sealed.
 * A Dragon = Generosity: he could have been somekind of "Dragon King" and the one who made the theorized "Dragon egg's deal" with the princesses.
 * A Griffon = Kindness: he/she could have, like Fluttershy, been able to talk with animals and helped to bring friendship with all species in equestria.
 * Ursa Major = Honesty: first, a humongous eldritch Mama Bear made out of stars is not prone to trickery, and second, the Ursa stars are used for navigation in our world.
 * I'm a fan of the notion the original Elements of Harmony were the gods of the other races, but they fell apart after Luna's betrayal.

The Elements of Harmony are, to some extent, Magic Feathers.
Consider what Celestia says to Twilight at the end of "Elements of Harmony": "I knew you could do it....I saw the signs of Nightmare Moon's return, and I knew it was you who had the magic inside to defeat her, but you could not unleash it until you let true friendship into your heart [emphasis added]." In other words, the magic that defeated Nightmare Moon, and Discord as well, came from inside Twilight Sparkle. After all, there are presumably other groups of close friends among the ponies of Equestria, and presumably others who embody the virtues of honesty, loyalty, generosity, kindness, and laughter. Those are not unique traits. And if all that was needed was a close group of friends to activate the Elements, well, Twilight, as of the beginning of "Mare in the Moon", is the last pony you would send: she has no friends, and shows no sign of wanting any friends. The one thing Twilight had was incredibly powerful magic. She needed to make friends so that she could unleash that magic. Finally, consider the fact that the elements did seem to have been destroyed, only to take on new forms to suit the new bearers, and that the sixth element just appeared for Twilight: those are simply the form that the magic takes, not the substance.

The jewelry referred to as the Elements of Harmony are just a Magic Feather
Their only power is as a psychological crutch to make the actual elements easier to use for the ponies who embody them. They are, in fact, mere projections of the actual elements, which is how they reformed in the pilot. Discord never actually stole them or relocated them, he just made the magic feathers disappear, and then let them reform once he felt the situation was perfect to break Twilight.
 * Alternatively, what Discord was actually doing was suppressing the Elements, which is why he was so incredibly confident; the jewelry he let Twilight find was really fakes after he destroyed the old ones. When she revived their Friendship it broke the suppression, and gave the fake jewelry the same "glow when element is used" effect due to that being what they were expecting to happen.

Elements of Discord/Chaos will be simple opposites of Elements of Harmony
Kindess vs. Malice, Generosity vs. Avarice, Loyalty vs. Betrayal, Honesty vs. Deceitfulness/Deception, Laughter vs. Despair/Gloom, and Magic/Friendship vs. Oblivion/Isolation. Alternatively, Magic will be a common element with Twilight Sparkle ending up on a precipice between them as part of an ongoing seasonal plot/undercurrent (provided another skilled magic user doesn't show up, or they don't just use Trixie).
 * Also, the Element of Betrayal and the Element of Deceit will both be Heel Face Revolving Doors, and the Element of Malice will be either The Chessmaster or a Magnificent Bastard.

Conversely, the Elements of Discord will instead be corruptions of the Elements of Harmony.
Loyalty being twisted into slavish devotion, Generosity being twisted into self-destructiveness, Kindness being twisted into obsession, Honesty being twisted into utter tactlessness (to the point of either revealing secrets or insulting the target), Laughter being twisted into mockery, and Magic/Friendship being twisted into darkness/toadyism.

The Elements of Discord will be the following...
There have been many WMG theories that there would be the "Elements of Discord" that would oppose the Elements of Harmony, and Word of God confirms that a villain named Discord would appear in season 2. My theory is that past "bad guys" of the series will be given these elements. After Discord is defeated by the Mane cast, he decides to recruit others to defeat them and counter their Elements of Harmony. The Diamond Dog(s) will be the element of Greed, since they were willing to hurt others to get their diamonds. Gilda will be the element of Betrayal, since she was so quick to abandon Rainbow Dash for shallow reasons. Trixie will be the leader, using the element of Dark Magic. Diamond Tiara will be the element of cruelty (opposite of kindness) since she lacks compassion and respect. Two other ponies will be introduced who will follow the elements of Gloom and Dishonesty. However, by the end of the second season the Mane cast will purge them of the dark magic that took ahold of them and they will good guys.
 * Though not without making the fans cry. Bonus points if the wielders of the Elements of Discord become Woobies, Destroyers of Worlds.

The heart-shaped beacon in Hearth's Warming Eve acts as a core to the Elements of Harmony
Much the same way the Master Emerald is the core of the Chaos Emeralds. The only way to permanently destroy/depower the Elements of Harmony would be to somehow extinguish its flame. This is not an easy task, since there would be a lot of friendship and harmony to destroy.

The Elements of Harmony are simply Equestria's weapon of last resort against supernatural threats. Despite their fancy name, they actually have no other powers.
Consider: We never actually see or hear of them being put to non-combat use. Between the fights against Nightmare Moon and Discord in the show, Princess Celestia clearly just kept them in a box in her palace. And before the start of the series, they've apparently been sitting undisturbed in those old ruins for quite some time. Even assuming for argument's sake that Celestia lost the ability to use them herself right after banishing her sister to the moon, she could have readily assembled a group of trustworthy, qualified ponies to do it for her far earlier. So why didn't she...unless, of course, there's no real use for the Elements in times of peace?
 * Maybe only a certain few ponies have the power to use them, like benders in Avatar: The Last Airbender?
 * Celestia has, in principle, the entire pony population of Equestria to draw upon at any time. For her to be chronically unable to put a team of Element bearers together, suitable candidates would have to be extremely rare (even relative to benders, which are actually not that uncommon in the Avatar world), probably to the point that less than six would have to be born within each generation...which would then beg the question why the Elements don't see more use now that the opportunity exists for once. So that's probably not it, or at least not the only reason.
 * Possibly only the Magic element is rare.
 * That's actually the reason given in canon. In order for the Element of Magic to unlock, there must be harmony between its would-be bearer and that of each of the other five Elements. It's rare because this information is NOT stated in any records pertaining to the Elements of Harmony. That's something the pony trying to unlock them needs to learn and understand on their own.
 * Maybe the elements Cast From Hit Points

Equestria’s most powerful races and the Elements of Disharmony.
"Alicorns: Betrayal.

Dragons: Cupidity.

Draconequi: Mockery.

Windigos: Malice.

Changelings: Deception.

????????: ????????."

They must be saving the best (or, you know, worst) for last.

The Elements of Harmony are more effective when used by larger groups.
At some point, the entire population of Ponyville, or even Equestria, will have to use the Elements together.

The Sonic Rainboom is some sort of time-space shift.
It sends them to a seperate alternate universe every time it's used, and it's incredibly risky. Think in The Cutie Mark Chronicles.
 * This Troper JUST finished writing a fan fiction on that premise, without having seen this post.

Sonic Rainbooms warp reality.
First off, their very animation implies that they involve breaking a barrier that is not intended to be broken. Thus, the effects of pulling off such a move need to be seriously taken into consideration. They seemed simple at first when it was first seen in "Sonic Rainboom", briefly knocking witnesses out of character such as turning Fluttershy excitable and Rarity humble.

But this takes on a whole new layer of meaning in "Cutie Mark Chronicles". Applejack managed to miss the actual Rainboom and Rarity didn't behold it herself, so they were largely unaffected. Fluttershy was only minorly affected, causing her to remain calm and brave even as the other animals panicked. But then we get to later stories, and we realize that this Rainboom was directly beheld by both Twilight and Pinkie. The results? Twilight suddenly found herself tapping into an immense power she couldn't control, forcing Celestia to take her under her wings to help her. And Pinkie Pie, an otherwise normal earth pony beforehand, became the Cloudcuckoolander and borderline Reality Warper (exceeding the powers of known unicorns and pegasi) that she is today.

We were lucky the first two times. Who knows what could happen if such acts of breaking the rainbow barrier continue unchecked?


 * Alternatively, this is the standard effect of breaking the rainbow barrier... But if too much of it is used, it'll reduce the world to cloying saccharinity, sapping the intellect of all ponies and destroying their individuality in the process. In addition, it will turn at least certain pegasi into earth ponies... Raibow Dash and Scootaloo first and foremost among the afflicted. If the rainbow barrier is breached too carelessly and too often... this may be what Equestria reverts to!
 * It was broken a 3rd time in Lesson Zero, so we may be getting there…

The Sonic Rainboom is magic.
The prismatic wave (the rainbow-colored shock wave) is caused by the sonic pressure wave compressing the ambient magical energy of Equestria along with any magical energies emitted from the entity that obtained supersonic speeds. This compression would cause the magical energies to become temporarily visible and even enter a high intensity state. The contrail (the stream of rainbow that flows behind) is an after image blur, the long duration of such made possible by the large quantities of exhaust energies shed by the pegasus from the natural thrust vector magic they unconsciously use to obtain supersonic speeds. As such, the contrail is largely harmless though potentially very pretty. The contrail's coloration would be dependent on the coloration of the pegasus. The high intensity energies within the prismatic wave would have properties similar to Comic Book radiation, namely they would give things exposed to them strange powers and abilities. This probably only effects creatures that already have at least some degree of magic (to help explain why plants and such seem to be unaffected) and any powers or abilities gained would follow along the natural paths of magic for the affected creature (so ponies would gain powers in relation to their special talent.) Let's look at the mane six: With Rainbow Dash's Second Rainboom, it can be assumed that whatever spared Rainbow from being affected by the first Sonic Rainboom would be the reason why she, Rarity, and the Wonderbolts were unaffected by the second one. Also the second rainboom was close to the ground and the high intensity energies might not have reached all the way up to Cloudsdale, which is why nopony in the stadium was affected (as far as we know) by the high intensity energies.
 * 1) Pinkie Pie is the only one whose story shows that she was caught by the full force of the shockwave, and therefor would have received a maximum dosage of the high intensity energies. Pinkie Pie's special talent is making ponies smile (Parties are just a good way to make large numbers of ponies smile at once). This would be why Pinkie Pie can access Toon Physics, which allows her to perform feats and use abilities that defy explanation by modern unicorn magic, provided they are humorous or make for a good gag.
 * 2) Fluttershy was in the middle of the forest when the prismatic wave went over head. The trees of the forest might have somehow prevented most of the energy from reaching the ground, causing most of the high-intensity energies to pass overhead, though some might have leaked down to Fluttershy. That would explain her 'Stare,' which certainly is a strange ability and can is generally used to influence animals, linking it to her special talent.
 * 3) Applejack was in Manehatten at the time and didn't even see the prismatic wave. All she saw was Rainbow Dash's contrail heading in the direction of Ponyville.
 * 4) Rarity saw the prismatic wave pass overhead, but between her and the origin point of the wave, was the Rock, which would have acted as a windbreak. The gems inside the rock could have absorbed any energies that came in contact with it, increasing the effective size of the wind break effect.
 * 5) Twilight Sparkle was in Canterlot and seemingly far from the Sonic Rainboom. So her magic would have been unaffected by the prismatic wave, though the loud boom startling she was trying to use her magic (possibly coupled with whatever subtle shifts in Equestria's ambient magical fields the Rainboom would have caused) caused whatever was blocking her from accessing her titanic pools of magical power to break loose.
 * 6) Rainbow Dash was at the epicenter of the sonic rainboom, though it could be argued that the rainboom started just behind her and propagated at a slower speed than what RD was flying at. As such, Rainbow Dash would have had minimal contact with any high intensity energies.

Discworld science explains the sonic rainboom.
While only Unicorn Ponies can cast spells, Pegasus Ponies display many supernatural talents of their own, and Earth Ponies have at least their cutie marks as proof of an uncanny nature. But beyond the ponies themselves, all of Equestria appears to be a land of magic. In this entry, we present evidence that the world of Equestria may in fact obey the conventional laws of physics under a Discworld-like Background Magic Field. An experiment realized by a young Pegasus Pony named Rainbow Dash literally brings new light on the subject. A recognized property of the Discworld's BMF is that any light passing through it is slowed down until its speed becomes roughly equal to the speed of sound. As a result, any moving object breaking the sound barrier will also break the light barrier. Close and distant observers can then hear a sonic boom and see a prismatic flash, always perceived as if simultaneous with each other. In the two occasions where Miss Dash created what she calls a "sonic rainboom", all witnesses described the phenomenon in terms remarkably similar to the above paragraph. We think this is solid indication that Equestria's magic may not be unlike the one studied at the Unseen University. Further investigation at Princess Celestia's School for Gifted Unicorns revealed that the first of those two "sonic rainbooms" may also have caused a thaumic chain reaction within this reputed establishment. We were assured it was contained without any long-term damage.

A sonic rainboom requires the motivation of doing something for the sake of another.
In "Sonic Rainboom", Pinkie Pie says that Rainbow Dash is the only pony ever to have done it (though this can't be literally true, as there are apparently legends), and she'd only done it once before. When? Why, when racing some colts who were bullying Fluttershy about her weak flying! And her second time? Saving the life of Rarity and the Wonderbolts! Training could possibly help a pony with the necessary speed; alone, however, it could never cause a sonic rainboom, nor could trying to show one off. I wonder, if they were to research the legends of the sonic rainboom, they might discover ponies who were just trying to help their friends...

Sonic Rainboom is a powerful, temporal boost for a pegasus' innate magic.
The pagasi magic gives them some mild physics-breaking powers like walking on clouds and flight, but they are still mostly bound by it's laws. Specifically, when a pegasus is trying to fly too fast even by Equestria's loose standards, they are pushed back by reality itself.

However, if a pegasus is determined enough, they can push themselves to break reality's barrier and cause a Sonic Rainboom (it was probably easier for Rainbow Dash, since she's the Element of Loyalty and the reason for both Rainbooms were her friends). At this point, the laws of physics give up and stop restraining the given pegasus. Let's see what kind of laws we've seen abolished:


 * Friction: The rapid gain of speed after a Rainboom is not caused by acceleration -- rather, the pegasus is no longer bound by air resistance.
 * Inertia: Rainbow Dash could make impossibly narrow turns not even losing a fraction of her speed.
 * Gravity: The reason why Rainbow Dash was able to carry three Wonderbolts and Rarity and still fly and maneuver at top speed is because weight had no effect on her.

It implies that after performing a Sonic Rainboom a pegasus could possibly do some other interesting things, like going off to space, flying around the world fast enough to make time flow backwards or usurping Celestia as the ultimate ruler of Equestria. However, none of the above occurred to Rainbow Dash at the right time.

Note that because of it's nature, Sonic Rainboom could cause any of the reality-warping effects mentioned in WMGs above.

The speed of sound in Equestria is lower than it is in our world.
Even beyond the existence of magic and tiny pastel ponies, the atmospheric physics of Equestria are rather weird. Clouds are smaller and form at lower altitudes than in the real world, for example. If the speed of sound were much lower - say, about 50 metres per second instead of 340 - then, while breaking the sound barrier would still be very difficult for fluid dynamics reasons, it's much more plausible. At the beginning of Sonic Rainboom, Rainbow Dash spends about twelve seconds diving at a roughly 45° angle at something close to the speed of sound, which would mean diving about four kilometres. It just doesn't feel like she's covering that much distance, if Fluttershy can still see her as anything but a tiny blue speck against the (also blue) sky. If the speed of sound were 50 metres per second, that's 180 km/h, which is the speed of a very fast modern car. I think that's still pretty impressive for a little pony with tiny wings.