What now? This seems like basically an assertion backed by a completely nonspecific justification. I don't think you've established anything here.
The spell effects are certainly not within our natural laws. A few example: shape change can drastically increase or decrease your mass. Disintegrate destroys matter or energy. Teleportation effects move the target instantly, faster than light. Those ones are just off the top of my head, and though you can come up with an argument that counters each (e.g. "Teleport actually moves you at light speed"), it's harder to come up with an argument that doesn't also contradict the wording of the spell ("Instant" yo).
I have my own explanations for each of those spells. I'll readily admit they are very forced, and some of them awfully convenient to support my theory there. More on this later.
You seem to be mixing up how you think magic in D&D works with how it works by the RAW. If you want to say that it works in accordance with real physics in your game, that's fine, but I don't think that's backed up in the rules..
...
As far as I know, nowhere does the game give you a round or two of life post-decapitation. Your whole argument seems to rest on real world stuff, rather than on in-game stuff, so I think it's pretty shaky.
You're right, it isn't. It was more that I had do come up with
something at one point, and this was the first idea I came across that worked, however shakily.
The kind of players I play with - the kind I
like to play with - tend to rip the game system apart for fun. That's not a problem for me the way most DMs think of it. I do the same thing, and I enjoy a good challenge. It's not perfect though, as every once in a while you meet an idea that is completely legit within game rules but cannot be countered.
At that point, the one who wins is the one who does the trick first. It takes away the soul of the game and everyone would eventually go home for the day in disappointment. Figuring out a system that can't be broken was only one of the many necessities to keep my players interested and the campaigns intact.
I try to keep the game as realistic as the abstract system allows it for the same reason. You can't 'cheat' in the real world - this is more me playing it safe than anything else. I grudgingly accept there are infinite possible explanations, a fraction of which are balanced, and I shouldn't have phrased my explanations in a way that suggested it was the only right way to do it.
But alas, while possible, I don't have the time, nor the smarts to invent and test a whole new set of basic rules. Thus I picked the best alternative readily available.
I recommend the same should you ever run a campaign like I do. It's a lot more easier than coming up with a system from scratch. And (to my pleasant surprise) realism reduces the power gap between magic users and fighter types! Especially ranged fighters, the poor things.
Originally I changed gravity to simply fill in another hole. You have to admit, D&D's rules for gravity, collision, and by extension, ranged weapons, are silly.
Pathfinder's guidelines(I formally thank Paizo for using the word 'guidelines' as opposed to 'rules', because referring to them as such would give me a seizure), present a rare exception in that they are even worse, requiring an object to be
as large or larger than a halfling to hurt you when it falls on you. Never mind that size has jacksh*t to do with weight or mass. Even weirder, they do know it, as right after the table they point out heavier objects should deal more damage! Except when they are small. Logic? Also, damage is dealt differently if the object is dropped as part of a trap. Somehow. (though I admit the creation of a singularity each time a trap is made would explain the horrendous price tags on the damn things.)
Then a player pointed out archer builds would kick ass under my new ruleset. And indeed they do! A realistic take on gravity and collision immensely increases their damage output - they are still miles behind a magic user focused on direct damage, but they can keep up with them! And I never had to nerf anyone! That was fantastic to realize.