Season 4 and some of Twilight's peeks into the distant past of Equestria leave me even more curious about this matter than ever before. I tried simply researching at first, but there was hardly anypony able to address this matter satisfactorily. As such I've chosen to analyze the topic myself. what you read below I originally typed up for the /r/mylittlepony/ reddit, where I was told that this would be a good place to put my analysis.

For the most part, everypony on the web seems to believe that Celestia and Luna are Goddesses. I do not think this is true. If they were, then there would be no age gap. They would begin their existence at the same time: during the creation of the world. Additionally, they would be nigh invulnerable. Twilight and many others have expressed panic at the sight of harm to Celestia, implying that if enough harm came to her, she would likely die. In the Season 4 premiere (Spoilers!), Twilight weeps tears of sorrow for what she believes to be the death of Celestia at the hands of Nightmare Moon. I will go ahead and admit that I'm aware of the fact that certain versions of polytheism permit gods to be born at different times, ascend from mortality, and even die (Greek Mythology for example). But Celestia and the rest of the Alicorns edge too far on the side of mortality to be veritable Gods. They are Royalty. They cannot leave physical form. They require protection in the form of a castle and armored guards. They eat food. And yet, they are ageless. In a thousand years, Celestia has not aged a day. She has also survived all threats made against her during this time. That is to say that if she's been threatened multiple times over the course of 1 year (the year encompassed by the show), then it probably wasn't all just rainbows and cupcakes for the 1000 years prior.

And then there's Luna. Why is she still physically smaller than Celestia? Would she still look this way had she not been essentially frozen in time for a full millennium? Or would she have instead grown to the same size and stature as Celestia? Was Celestia once the same size as Luna? Unanswered questions like these teach us a little bit about the possible Alicorn aging process (or at least those of Celestia and Luna, the two "Original Alicorns"). The premiere's glimpse into the past tells us that Luna was no younger in form back when facing Discord, roughly hundreds of years before her banishment. That is, I'm fairly certain I recall a canon source that stated that the downfall of Discord preceded the banishment by at least a few hundred years. If not, then at the very least Nightmare Moon came to be sometime after the Princesses had managed to build a Kingdom, complete with the castle they lived in, as well as fill the diary discovered by Twilight. So, assuming Luna is in fact still growing, and that Celestia exemplifies the fully matured Alicorn, then it takes an incredibly long time for alicorns to grow to maturity.

Now, this part gets messy when it comes to whether or not you believe that there is a fundamental difference between "original alicorns" like Celestia and Luna versus "anointed alicorns" like Twilight and Cadance. My understanding, however, is that Cadance became a princess, and was then able to mature to the same physical stage as Luna in the same amount of time it took the Mane 6 to grow from fillies to mares (a highly debatable but ultimately very short period of time for alicorns). How about for now we just pin the tags "medium" on Luna and Cadance, "Large" on Celestia, and "small" on town-faring ponies. Does it take all Alicorns this short a time to grow from small to medium? Or is one of the prime differences between anointed and original alicorns that anointed ones age faster, possibly even dying from old age? Granted, it would explain why there were zero anointed alicorns in Equestria at the beginning of the show's timeline, whereas now there are two. Perhaps over the years there have been many unmentioned ponies who were anointed and died of old age. I find it fairly unreasonable to think that Celestia would rule alone for so long just to immortalize two princesses in a flurry while already regaining her sister. And if Cadance is an ageless princess, then is Shining Armor an ageless prince? I'm not saying that there most certainly is a difference between original and anointed alicorns, but just imagine Twilight and Cadance living practically forever just like the princess who made them what they are, and inevitably outliving their friends and spouses; watching them die. Not very MLP, wouldn't you say?

So, at this point we've diverged into two split lines of logic while regarding alicorn age: one where all existing alicorns are equal fundamentally, and one where those first two who change night and day are cut from a different cloth than their chosen student counterparts. Since my thesis is growing fairly monstrous (English was one of my favorite courses in college and I suppose I was just dying to write another 2000 word essay) I'll edit out what to logically assume if you believe in the former line of logic and just discuss the latter. Now as I addressed earlier, with Cadance there was a very short span of time involved with the movement from small to medium. Sadly if we assume that all Alicorns do NOT age the same, then this tells us nothing about how old Luna is. What we do know, is that for Luna the transition from Medium to Large takes an incredible amount of time. Possibly half a millennium give or take, since shes' already been at this stage for hundreds of years. Or perhaps instead, there is a certain rite of passage that must be taken in order to reach this Large stature, akin to that of becoming Princess in the first place, and Luna simply hasn't passed it yet. Her exploits as Nightmare Moon certainly imply that she has some growing to do emotionally still. In pretty much any case, Princess Cadance is proof that Twilight Sparkle will likely come to share Medium stature with Luna and Cadance at some point in the 'relatively' short future (almost definitely around the time the Cutie Mark Crusaders become adult mares).

I haven't even gotten started on Discord yet. He's practically the perfect ponified mix of Sheogorath, the Daedric Prince of Madness in the Elder Scrolls series and Q from Star Trek (and yes I know he's literally based off of the latter). Much like the aforementioned pair, Discord seems to be omnipotent, having virtually no bounds to his magically capabilities, and unlike Twilight, Cadance, and Shining Armor, who tire from heavy or prolonged use of magic, he seems to be rather invigorated by it. As you recall, it is part and parcel to his "stretching routine". Oddly enough, I get the impression that Discord is more a deity than Celestia herself. He can be bound, but not slain. He can leave physical form, and even disassemble himself. His "magic" is entirely different from that of all other beings in Equestria in that he needs no functional unicorn horn. He sometimes snaps to set events in motion, but that is not always necessary. Sometimes he can change himself and the world around him simply by willing it. and this obviously isn't any hard evidence, but don't you get the impression that he doesn't actually require sustenance to survive? He basically eats food sarcastically, for example consuming popcorn while wearing 3D glasses in jest of what a grand show the ponies are putting on for him. He eats his own Plunder Seeds, something likely poisonous for most earthly creatures. He also ate paper from books, primarily to get rid of them in a properly maniacal manner. As for the Princesses, so far they have only been shown eating Wedding Cake and baked goods from Sugarcube Corner, so it is possible that they only eat as a formality. I get the impression, however, that if Princess Celestia did not NEED food, and everyone knew it, then she wouldn't have set up a brunch in the first place. Once again, if you're a "hard evidence" kind of pony, then this may not hold much weight with you, and you're free to disregard it. That being said, I'm going to delve into some further speculation with zero evidence whatsoever.

Note the fairly stark differences in behavior between the Sisters and Discord. The millennia have shaped Celestia and Luna into highly cautious, aware individuals. Ponies who have fears to remain wary of at all times. Perhaps fear of death? Discord, on the other hand, is a fearless, hearty, and somewhat careless individual. Discord obviously has little concern of death. Perhaps though, what marks this difference has nothing to do with their own mortality, and instead it is the fact that the Princesses have a kingdom to protect, full of innocent mortal ponies, whereas Discord could care less what happened to anyone else even when he was the sovereign ruler of the very same land. Your opinions are your own to make. The conclusions I have come to, however, are that Discord is a malcontent deity who can neither age nor die, that Celestia and Luna are incapable of aging but can die, like some kind of demigod, and that Mi Amore Cadenza and Twilight Sparkle are something in between demigod and regular pony. And regular ponies are, well, regular ponies.

I'm also going to take a stab in the dark at their ages and propose that Princess Celestia is at least 2,000 years old. I say this because Luna is apparently 1,500 years old (1,000 years of banishment plus 300 year interval between the discovery of the Elements of Harmony and their eventual use to banish Luna, PLUS her age prior, say 200 years old), and Celestia is obviously significantly older than Luna as we discussed earlier with size and age. Until further evidence dates him, I suggest that Discord has always existed and always will.

Well, that about wraps it up! Anypony have any thoughts on the matter?