Why is it that some magic spells require bursts of magic (Ex., red bolt for Stunner) to reach a target before the spell works, while other spells do not require a targeted burst of magic or even line-of-sight (Ex., Summoning Spell)?

I believe that the answer lies in the fact that every being has an innate resistance to outside magical influence, with the resistance being stronger the more powerful that being is. Spells like Wingardium Leviosa (presumably) apply force to the outward surface of a being/object. However, spells like the stunner attempt to change the state itself of a being, acting on the inside. I believe that an outside magical influence is automatically repelled by the body's magic, and if the incoming magic steadily increases (or simply acts constantly), then one's own magic would have time to react and counter the intruding magical force. Therefore, Wizards discovered ways of concentrating magical energy into a burst that needed to hit the target to affect it. When a burst spell hits its target, it 'unloads' its magical energy too fast for the body to react, thus bypassing the body's automatic magical defense. The situation is similar to a frog being slowly boiled, only in reverse. The target's innate magic will (logically) always be greater than that of the one who cast the spell (force is always less the farther you have to reach), so the 'frog' will have no problem gradually countering your sustained flow magic. Overpowering bursts are needed to overcome this barrier (and concentrated burst are required to block it - magical shields).

I do not know if conscious control is possible over the one's innate resistance to foreign magic; ie., if a Wizard is Summoned, whether the Wizard in question would be able to simply concentrate on not being Summoned to trigger his defense, or whether it is completely unconscious. My personal opinion (not backed, or disproved, by Canon) is that the resistance is involuntary, but can be augmented by a Wizard's conscious thought.

Of course, the success of this theory depends on whether or not Transfiguration spells require bursts of magic to hit the Wizard's target before taking effect. I cannot remember an example either way, but common sense says that yes, a burst of magic is required to hit a target. Otherwise, duels would merely be 'Who can transfigure their opponent into a poodle first?'

A question that point brings up is whether or not so called (by me, only, so far) 'sustained flow' spells are blockable. If two people are dueling (Gred and Feorge) and Gred attempts to Levitate Feorge, who has a Protego shield up, will the spell take affect? Can you block Summoning Spells (another sustained flow spell)? If not, why wouldn't Gred just Accio Feorge's wand?

So indeed, such is my theory. Any thoughts are welcome, most especially one's that disprove it (so I can make a better one).

 

You can block Accio with Protego. Harry blocked it with Protego in the Department of Mysteries I think....

 

He did. It is because some spell effects are instantaneous. You are stunned. There is no process of being stunned; it is immediate. But to summon, it takes a little while to get to you, so you have to keep pulling.

 

While I may not have the answers to your questions I know where you can find them. The HP Lexicon has an entire section on Magical Theory.

Edit: The magic in HP has always been, to me, very much like "sorcery" in David Edding's Belgarid series; The Will and the Word. Translated into HP terms magic is Will, Word, and Wand-waving. Yet, it seems that the stronger a person's will and desire for something to happen then the easier it is for the other "rules" to be bent or broken, or for them to overcome someone else's spells. Thus, to put it into even simpler terms, all magic in HP is Will vs. Will. If I want you floating in mid-air bad enough then the strength of my spell will overcome your protego.

Just my concept of it at least.

 

The way I understand it is that a magical shield blocks any foreign magic from getting within a certain area around you (whether that's spherical or just an arc is uncertain), so a Wingardium Leviosa would be able to break through, but a protego cast while it is in effect would sever the tie and drop the person.

A stunner on the other hand is a bolt of red light that doesn't need a continuous flow of magic to sustain, so it isn't a contest of will, more like a split second reaction from the target body's magic to either fight it off or allow it to take effect. This would also explain why highly magical creatures (like dragons and giants) are able to fight off stunners that aren't powerful enough, like in GoF where it takes eight wizards to take down the Hungarian Horntail.

I honestly don't think will has that much to do with it when it comes to fighting off spells. It may have a small effect, but I expect that the amount of raw power you can channel into the effort would have more effect. That Harry couldn't break out of Dumbledore's petrfication spell gives some credit to this, as Harry's will was solely bent on getting out of that spell, but Dumledore's magic was greater than his, so Harry couldn't get out, and couldn't save Old Dumbles.

Transfiguration, I imagine is a burst type spell. Its a one off event that lasts for a period (or indefinate - we don't know), otherwise the wand wouldn't be able to cast more spells while the transfigured object was still... Transfigured. Imagine it like a lumos spell compared to Avada Kedavra - lumos ties up the wand so it can't cast anything else (continuous flow) while the AK is a burst which can be fired while the other spell is still in the air (burst).

Aekiel

 

The whole idea of willing oneself out of things like Stunners or body-binds is born of Fanfiction. As far as I know, it's never been indicated in canon that Petrificus Totalus can be broken by the person it is placed upon. I don't think in that kind of situation it's a matter of Dumbledore's magic being greater than Harry's so much as that spell if cast successfully will do it's job no matter what. When I see sentences where Harry struggles against a spell like that, I see it more of the kind of thing where someone gets tied up and struggles fruitlessly against the ropes.

 

If that was so then the dragon would have went down to one stunner, not eight. It may be the way dragons' minds work, or it may be because they're highly magical and their innate resistance to foreign magic would need the combined stunners of eight wizards to overpower.

Even Hagrid, who has never shown signs of being magically powerful (though that's probably because he wasn't taught past third year), was able to throw off several spells because of his giant blood and magic.

I take this to mean that its more about the magic inside of you than your actual will and mind. So if you could force up enough magic (or summon it, or channel it, or whatever) to overcome the hostile spell I would assume you'd be able to fight it. Though being unconcious would probably put a dampener on that .

Aekiel

 

People try and think to deeply into these things. Fanon and canon are not the same, yet people try and merge them together. If you keep it seperate, and the ideas seperate, then it makes life so much simpler. How in the hell is Harry going to, in the course of a year, learn enough about magic to beat Voldemort or his death eaters in a duel? He couldn't beat Snape, who doesn't know his arse from a whole in the ground in comparison to Voldy or Dumbles. Unless we keep this discussion in the fanon area of the Potterverse, I fear that we will be dissapointed by what Rowling hands us in the last book.