Railgun’s Physics and Other Bits

So, I just finished watching episode 12 of To Aru Kagaku no Railgun, and for all that it was a bit talky in the final battle, explaining what we were seeing (as if we couldn’t figure it out ourselves), it was a very satisfying episode. There are still some dangling plotlines, but no loose ends.

We did not get to see what Uiharu’s power is, and that’s the only disappointment.

On the other hand, Mikoto was a tour de force. I lost track of how many ways she used her power in this battle, and every one of them made sense — although one of them was quite subtle. I’m putting them behind spoilers as they give away the final battle.

1. She threw electrical blasts, of course.
2. She threw objects to break the monster’s tentacles (she also used lightning bolts to do that, but I’m basing the object toss on the metallic sound)
3. She used the “iron sands” not just as a whip/sword, but as a hemispherical defense. Surprisingly, it wasn’t solid, but was a rotating series of blades cutting off any tentacles that approached.
4. She built a shield out of rebar-filled concrete (which she did last episode), but this one was much bigger.
5. She threw one electrical blast at very high power and sustained it for at least 30 seconds, until the clash with the monster’s shield generated enough heat to cook it.
6. Of course she used her railgun shot.
7. She apparently used her electrical blasts as a sensor of sorts, as she knew exactly where to fire the shot that destroyed the core; it was not obvious at all. I assume that the flow of electricity around it was distorted and she felt that.
8. And the one that really made my eyes pop was when she was thrown at a concrete wall, and should have gone splat. I fully expected her to crater it, then walk away, at which point I would call BS. (There was no precedent for it in the show, which has been pretty good about people being able to take no more than a normal amount of damage.) That’s not what happened — instead as she flew toward the wall, she suddenly flipped about, slowed down, and landed feet-first on the wall, standing sideways.

She’s previously established that she can walk on a concrete wall by establishing a magnetic field around herself and use the rebar in concrete as her anchor point. That only takes one field, around herself, to pull her towards the metal. To do what she did here, she had to generate two fields, one around the rebar in the wall, and one around herself, and make them of the same polarity, so they’d repel each other — and then drop the one around the wall (or reverse its polarity) to stand there.

All in all, my reaction was similar to Steven’s. “No, she wasn’t fighting you seriously, and you better be damn glad of it!”

Now, some speculation, and a few dozen dead catgirls will probably result.

First, what exactly is Mikoto doing? Is she focusing and controlling the movement of electrons, or is she creating them? The latter violates a few laws of thermogoddamics. So we have to assume she’s controlling the movement of electrons and/or magnetic particles around herself. It’s quite possible that she’s using a flow of electricity to create the magnetic fields, but she has to gather those electrons from somewhere; logically, that’s the area around her, which means that she’s concentrating electrons in one area, while stripping them from another.

And that is why she’s always surrounded by a nimbus of electricity when using her powers, tends to knock out electrical devices for blocks around when she cuts loose, and a few sparks always loop around her afterwards. The electrons will always try to flow, like water, “downhill.” Only in this case, downhill is “towards areas that lack electrons” or more accurately, “to areas the Railgun just stripped the electrons from.” This is why she had to warn the doctor away; given the level of blasts she was about to throw, she’d have to drain a goodly area of its electrons, making everything around her have a positive charge, while the target would have a huge negative charge.

A term for these positively charged objects in the presence of an object with a high negative charge might be “anode.” A better one would be “lightning rod.”

Second, given the level of control and power she’s exhibited, she might become capable of replicating Magneto’s trick from X2: killing someone by yanking all the iron out of their blood. Or for that matter, by simply immobilizing their blood, and letting them asphyxiate.

The former suggests that Accelerator should steer clear of her, if she develops this ability — if she got the drop on him, it wouldn’t matter how much repulsion he’s got up. By default, he leaves his defense set to “repel” and anything that touches him rebounds back toward the attacker. But he’s defenseless against someone yanking the iron molecules out of his blood, because even if his power works (not a given), the effect will be to make the iron just take off in the opposite direction. It would be just as deadly — his capillaries are shredded by millions of iron molecules. So then he’d have to spend his remaining moments of consciousness keeping his blood flowing properly…assuming his brain hadn’t been similarly perforated, which it would be.

And let’s not even think about what Kuroko would do to the Accelerator, since anything she’d teleport inside of him wouldn’t actually be moving. No defense he has would be effective against a handful of nails appearing in his brain. Given that Kuroko might go just that far for her Oneesama (if she explained why, and that Judgement was powerless to do anything about it), we have to assume that Mikoto simply didn’t want to bring another person into it. Good assumption given Touma’s difficulty in convincing her he could help.