To Aru Majutsu no Index II - Episode 19 Discussion / Poll

[SuzushinaYuriko]

So many topics I want to comment on...

Most of Kihara's strategy involves keeping Accelerator mad at him. If Accelerator actually employed half the stuff he learned when he killed 10,000 versions of "Misaka lite", Kihara would be dead by now. Let Kihara hit him (at much reduced force since he's literally pulling his punches), then grab his hand and reverse his blood flow. Game over.

It's almost like the whole universe consists of staged matchups... Accelerator is not allowed to fight magic enemies and Touma is not allowed to fight science enemies. Railgun is not allowed to fight anything important unless it's her series. For instance, I fail to see how she'd manage not to be involved with the golem in Season 1, given her general aggressive nature in seeking out challenging fights. She could NOT have failed to see the darn thing... it was 5 stories tall and very nearby!

Go to the light novel thread and skip back a few pages. We had an entire argument revolving around that scene which lasted for two days, with plenty of good points brought up by both sides.

And about the stage matchup scenes, Touma has fought Accelerator, and as for the rest I can't say anything because those would be spoilers. Touma is the magic protagonist, Accelerator is the science protagonist, and Misaka is a side character, so they're simply fulfilling their general roles in the story.

[Chaos2Frozen]

Most of Kihara's strategy involves keeping Accelerator mad at him. If Accelerator actually employed half the stuff he learned when he killed 10,000 versions of "Misaka lite", Kihara would be dead by now. Let Kihara hit him (at much reduced force since he's literally pulling his punches), then grab his hand and reverse his blood flow. Game over.


Actually, this was what Touma was afraid of when he fought Accelerator. He was afraid that after taking his punch, Accelerator would immediately counter with a grab to his arm.

As it turns out that wasn't the case; Accelerator was knocked back from one hit.


- Accelerator is not a tough guy.
- A single punch can mess him bad
- Accelerator is slower than Kihara (slow-mo scene remember?)
- Kihara can easily maneuver around Accelerator, never letting him touch him.

Combine all that and you can see that your 'take one hit' plan wouldn't work.


It's almost like the whole universe consists of staged matchups...

Really? A written story have matchups that are predetermined :eek: ? Say it isn't so!

[eiyuu99]

Accelerator is too used being "untouchable" with his reflection,
thus he doesn't bother learning to dodge or block.

[IppoTsuko]

In a way or another, Accelerator is like a spoilt brat in terms of battles

[giorno]

Most of Kihara's strategy involves keeping Accelerator mad at him. If Accelerator actually employed half the stuff he learned when he killed 10,000 versions of "Misaka lite", Kihara would be dead by now. Let Kihara hit him (at much reduced force since he's literally pulling his punches), then grab his hand and reverse his blood flow. Game over.

meh, taken straight from the novel, explanation for why Kihara could defeat accelerator

There's a twist in here.

After all, Kihara overwhelmed Accelerator only because he [personally developed Accelerator]. Therefore Kihara, having gathered all sorts of data on Accelerator, like personality, ability, and kinetics, has acquired only sure-kill tactics [effective for Accelerator only].

Of course, to make it succeed requires a sense for excellent body kinetics more superior from those of normal people and a genius brain able to incorporate extensive research data into battle tactics. But even as he realizes these, they are not enough to take down the only seven Level 5s of Academy City.

In the first place, Kihara wouldn't have employed [Hound Dogs] as lackeys if he really could crush Level 5s without any trickery.

[Cantelope]

As an aspiring physicist and engineer, Accelerator is one of my most favorite characters in any series sheerly because of the nature of his power. Now, I've recently gotten around to watching this episode and--as an aspiring physicist and engineer--I find it utterly inconceivable that Accelerator can be man-handled by Kihara like that (given the nature of Accelerator's powers).

*NOTE 1* I'm fully aware that this is a fictional series written by an author who has very very disillusioned conceptions about classical mechanics.

Premises
Now, thinking back on the episode, I had to think hard about the way Accelerator's power works and Kihara's "explanation" of how he bypassed redirection. I'm going to go ahead and establish some axioms here.

1. Accelerator - The basis of redirection is that his power automatically reverses incoming vectors at "random". I say "random" instead of harmful because he can eat, drink, and see (remember that the way our eyes work is that light reflects off of objects into our retinas)--yet things like the sunlight etc. are reflected away.

2. Kihara is a normal human, without modified bones or muscle structure. As far as the wikia is concerned, this would appear to be the case.

Redirection
Now, I believe Chaos2Frozen's explanation of the way redirection works, and how Kihara bypassed it is a good summary in layman's terms of what exactly transpired in Kazuma Kamachi's (the author) imagination. Here's an appended quote to refresh everyone's memory:

Redirection automatically reverse the vector of anything it deems as harmful in the opposite direction. Kihara simply reverse the direction of his attacks at the last nanoseconds before Redirection kicks in and instead reflect the attack right into Accelerator.

Now, this should somewhat make sense to anyone not entirely familiar with physics; however, to those with trained eyes this makes absolutely no sense, and I'm about to explain why (by the way, dragon132004's diagram on page 12 made absolutely no sense, but kudos for trying, the time-axis was a nice touch but had utterly nothing to do with anything at hand).

What it means to Punch (A Physics Refresher)
Let's ponder for a moment about what it actually means to punch someone. When you punch someone, basically the specifics of what's happening is a series of muscles contracting and relaxing to exert a force on your fist *NOTE 2*. If we recall our 2nd or 3rd day in physics class, we'd remember that the definition of a force is the acceleration of a mass, in this case the acceleration of a fist. When the fist actually reaches the target and hits them, what actually determines the amount of damage done is not the amount of force the fist is experiencing at impact, but the momentum of it.

Why is getting hit by a train moving at constant velocity more scary than getting hit by a car that has been accelerating for only 1 second? (The key proponent here is that the train is experiencing a net force of zero and the car is experiencing non-zero net force)

We remember from class that the answer to this is: "because the train has a hell of a lot more momentum than the car (unless the car accelerates to very very very large speeds in the one second interval)." *NOTE 3*

Now, back to the fist flying towards my dear pal Accelerator's face. When you want to punch someone, the reason why you fire your muscles as hard as you can is because you want to exert as large a force as possible on your fist: the goal is to make the velocity of your fist as high as possible before colliding into your target's face (trying to reach maximum momentum).

What determines the amount of damage when you hit someone, is how quickly your fist decelerates from it's previous momentum. This is generally called the "impulse" in physics courses. Recall *NOTE 3*, and you can see that in order to decelerate an object to zero momentum (zero velocity) it takes a certain amount of force (deceleration is negative acceleration). Depending on the time it takes to decelerate, the amount of force an object must experience to reach zero velocity can be very very large (a train, for example because the mass is very large; and an electron for example because of how fast it is).


Where Shit hits the Fan
Finally here's where Kihara's little strategy starts falling apart. Apparently he merely pulls his fist back right when his fist is in the AIM field where the vectors are automatically redirected, thus making his fist that is experiencing a negative force *NOTE 4* now experience a positive force.

Let's imagine the FBD of Kihara's fist right before it strikes Accelerator, inside of Accelerator's AIM field. There are two vectors of interest here *NOTE 5* momentum and net force. When Kihara says he's "pulling his fist back" right before striking, this is just vague enough to mean several different things:

1) Fist momentum is positive, net force is negative.
2) Fist momentum is zero, net force is negative.
3) Fist momentum is negative, net force is negative.

Scenario 1: After redirection, momentum is now negative, and net force is now positive. Basically, axes are reversed. Fist is flying towards Kihara's face, but is experiencing deceleration (probably won't reach target). In order to hit Accelerator, the amount of force must be great enough that the momentum changes from negative to positive (with respect to Accelerator), and the fist must attain a good momentum to deal respectable damage to Accelerator's face. Now, apparently the order of magnitude that Accelerator's redirection operates is in nanoseconds. NANOSECONDS. That's 1x10^-9. The amount of force in the impulse (change of momentum) in a nanosecond to make ANY number change magnitudes will destroy every bone and muscle in your body. *NOTE 6*

Scenario 2: After redirection, momentum is still zero, but net force is now positive. On top of *NOTE 6*, if the force is too small Kihara's best hope is that Accelerator's weakness is a soft caress on the face.

Scenario 3: This is impossible because of *NOTE 6*. He has to change the momentum of his fist within the AIM field. The best case scenario here is that the bits and pieces of what used to be his arm before it exploded into a bloody mess gets redirected towards accelerator and forces him to take a shower.

I eagerly implore other posters to help me swallow what I conclude to be Kihara's utter bull-shit, but if there is no answer then I guess the only thing I can do is wait for him to get destroyed along with his ridiculous deus ex machina in a few episodes when he is transformed into a projectile.

Phew, that was quite a bit to type but I felt like I needed to get that off my chest.


*NOTE 2* Your entire arm actually experiences a myriad of forces, but we're chiefly interested in the effects of the fist on Accelerator's face, so let's just worry about the way the resultant vector of these forces are like when they reach Kihara's fist.

*NOTE 3* Momentum is defined as a moving mass, e.g. mass w/ velocity. We can see plainly that a force (acceleration of a mass) changes the momentum(velocity) of an object.

*NOTE 4* Negative force means acceleration in the opposite direction, where positive means towards Accelerator's face, and negative is directly away.

*NOTE 5* Momentum of the fist, the net force on the fist, and torque on the fist. We're ignoring torque, because it holds no relevance to this scenario.

*NOTE 6* Let's say start velocity of a 1 kg mass is -10 mps, and ending velocity is 10 mps (respectable speed for a fist imho). The average impulse in 1 nanosecond is 10-(-10)/ (10^-9) = 20x10^9 = 20 BILLION Newtons. To put this into perspective, that's about enough force to launch a Saturn V rocket into space two hundred thousand times, and Kihara must exert this force on himself in a nanosecond. I guarantee the results will not be pretty.

[giorno]

this would be better discussed about here http://forums.animesuki.com/showthread.php?t=92229

and while you're at it, care to tackle the whole building bullet feat as well? it'd be interesting to know exactly what should have happened there...

[Cosmic Eagle]

-physics-

That's what I've been saying all along. Kihara changing momentum of fist in nanoseconds is either retarded or he's fucking strong to the point like Angel strong....which he obviously isn't

[Mr.Kyon]

-physics-
That's a work of beauty :love:

[I_am_Kami]

To cantelope.


You sir are smart. Though I'm pretty sure even the author knows it's bullshit for a normal human but looking now it seems kihara is the mike Tyson of science. That's probably the inspiration. Why ? He has a tattoo on his face and his style is boxing

[Cantelope]

this would be better discussed about here http://forums.animesuki.com/showthread.php?t=92229

and while you're at it, care to tackle the whole building bullet feat as well? it'd be interesting to know exactly what should have happened there...

Eh it's not really a dissection of his powers, but moreso a dissection of why Kihara's ability to hit Accelerator is pure nonsense. Since this is purely episode specific, I decided to leave it here for anyone curious.

As for the building bullet in episode 21, I'm assuming that the general basis of the act was that as he pushes up on the building, the building exerts a normal force in an equal but opposite direction back down on his arm. Accelerator redirects that normal force back upwards in the same direction as his arm, and in turn the building now exerts a new normal force downwards the same magnitude as the combined new upwards force from the previously directed vector. In this fashion, the amount of upwards force doubles until it's large enough to rip the building of its foundation and then all of the force is redirected in the desired direction of launch.

Clever application of his powers, which I like, and it's somewhat believable if you accept what I call the "magic" of fiction (unfortunately Kihara is far far beyond acceptable levels for me). What would probably happen in reality is that, because the force being exerted upwards is only being redirected from his arm, is that the amount of pressure on that small area would simply cause his arm to begin slicing through the building like butter, instead of lifting the entire building from the ground.

Imagine trying to pick up a cake with just a single finger, without the assistance of a plate underneath it. Your finger would simply tear the cake apart, because it isn't able to push back on your finger as hard as your finger is pushing upwards. In the same fashion, the amount of force the support beams in a building can exert downwards is also limited, and I'm confident that a single steel beam cannot exert a downward force equal to the entire weight of the entire building.

We can easily escape this thought process by accepting the "magic" of fiction. I choose to pretend that all of the support beams in Academy City are made of carbon nano-tubes. A very expensive city, but eh, it helps me sleep at night.

All wroooooong.

Just did some reading and apparently he redirected energy from Earth's linear angular momentum into launching the building. The kinetic energy of a massive rotating body is Iw^2, which in the case of Earth is roughly 2.57x10^29 (257 quintillion billion) joules. The change in energy, or work, in this case is enough to slow the rotation of earth by 5 minutes, which means the angular velocity w is now 7.29754x10^-5 (calculated from 2*pi/(24*60*60 + 5*60 seconds). The new rotational energy of Earth is roughly 2.55x10^29 joules, meaning Accelerator has about 1.78x10^27 joules to work with (enough energy to launch a Saturn V rocket completely out of Earth's gravity well 237 trillion times).

Needless to say, if he redirected all of that energy into a building, the result would be catastrophic for the entire city, I hope is self-evident. Think about it, we're talking 1.78x10^24 kilojoules of energy here. This is the equivalent energy of 21,141,001,293 (21.1 billion) nuclear explosions.

So if you're asking me what would happen realistically, I can't really say for certain. Most likely the building would be destroyed so utterly that we'd see nuclear fission as the chemical bonds between every compound in the building get torn apart in the high energy environment, and subsequently the atoms also breaking apart. The explosive force would be so destructive everything within a radius of about 3000 miles would be completely obliterated.

Scary to think about.

That's a work of beauty :love:
I'm glad you enjoyed it.

To cantelope.


You sir are smart. Though I'm pretty sure even the author knows it's bullshit for a normal human but looking now it seems kihara is the mike Tyson of science. That's probably the inspiration. Why ? He has a tattoo on his face and his style is boxing

You flatter me, but thank you. Does Mike Tyson work for NASA, launching 120,000 kg rockets into space with his punches? If so, Kihara could very well be the Mike Tyson of science, but I'm inclined to believe otherwise--no disrespect to Mr. Tyson intended, and I acknowledge how amazing he is nonetheless.

[I_am_Kami]

Eh it's not really a dissection of his powers, but moreso a dissection of why Kihara's ability to hit Accelerator is pure nonsense. Since this is purely episode specific, I decided to leave it here for anyone curious.

As for the building bullet in episode 21, I'm assuming that the general basis of the act was that as he pushes up on the building, the building exerts a normal force in an equal but opposite direction back down on his arm. Accelerator redirects that normal force back upwards in the same direction as his arm, and in turn the building now exerts a new normal force downwards the same magnitude as the combined new upwards force from the previously directed vector. In this fashion, the amount of upwards force doubles until it's large enough to rip the building of its foundation and then all of the force is redirected in the desired direction of launch.

Clever application of his powers, which I like, and it's somewhat believable if you accept what I call the "magic" of fiction (unfortunately Kihara is far far beyond acceptable levels for me). What would probably happen in reality is that, because the force being exerted upwards is only being redirected from his arm, is that the amount of pressure on that small area would simply cause his arm to begin slicing through the building like butter, instead of lifting the entire building from the ground.

Imagine trying to pick up a cake with just a single finger, without the assistance of a plate underneath it. Your finger would simply tear the cake apart, because it isn't able to push back on your finger as hard as your finger is pushing upwards. In the same fashion, the amount of force the support beams in a building can exert downwards is also limited, and I'm confident that a single steel beam cannot exert a downward force equal to the entire weight of the entire building.

We can easily escape this thought process by accepting the "magic" of fiction. I choose to pretend that all of the support beams in Academy City are made of carbon nano-tubes. A very expensive city, but eh, it helps me sleep at night.


I'm glad you enjoyed it.



You flatter me, but thank you. Does Mike Tyson work for NASA, launching 120,000 kg rockets into space with his punches? If so, Kihara could very well be the Mike Tyson of science, but I'm inclined to believe otherwise--no disrespect to Mr. Tyson intended, and I acknowledge how amazing he is nonetheless.

just saying

http://i.telegraph.co.uk/multimedia/archive/00678/mike-tyson-404b_678997c.jpg
http://cdn.myanimelist.net/images/characters/16/110532.jpg



in the novels its said that his fighting stance was like a boxer