In episode 40, where did they get the material to put that turtle float around The Nirvash?
Was that Charles' gun that Holland left in the Nirvash, as seen in episode 44? If so, why would Holland leave them that specific gun?
That was Charles' gun. It seemed to be very powerful (able to shoot through LFO armor on its first appearance), so perhaps Holland knew that and left it just in case. Plus, he knew that Charles and Ray meant a lot to Renton, so that could've been a factor as well.
I always wondered... everyone in this show all have mostly non-japanese names, so it makes me wonder why the natural language in the show is Japanese? You'd think they'd read english everywhere. Did Japan defeat the US or something?
Short answer: It was made for the Japanese, so the language spoken and read in the show would be Japanese. Long answer? I'm not really sure; on one hand there is no US or Japan. After the Scub took over the world and the humans came back from space to live on Earth, nothing would've been the same. I'm thinking that they kept their language and when they came back to Earth, they separated like they used to be, with certain places using certain languages, but due to spending so much time close together in space, language conventions were shared - hence, the characters' English names even though they still speak Japanese.
Another possible explanation is that it's set far enough in the future that any existing languages would have changed enough to be unrecognizable (or to have died out entirely and replaced with new ones) so for the sake of convenience writing and speech is represented by Japanese rather than whatever the lingua franca actually is. The names could simply be traditional or a translation intended to give the sense of how the names might sound to native speakers.
Just what is the "Limit of Questions"? I just watched through the whole series all over again, and I don't believe they ever gave a straight answer. The most they alluded to was that it was related to Quantum Mechanics, and that if the "Limit" was reached, it would be the end of the world as we know it.
Quantum mechanically speaking, information storage capacity is a function of system entropy. There is, in turn, a maximum entropy for any given volume, which is the entropy of a black hole enclosing that volume (equal to Boltzman's constant times the surface area divided by the Plank area (~10^-70 m^2)). In context, however, the whole premise makes no sense.
The "Limit of Questions" is a concept inspired by a Sci-Fi novel called Blood Music written by Greg Bear (who's referenced in the series through Doctor Bear), which explores the concept of reality as a function of observers, itself a part of the Anthropic principle. To put it bluntly, the Coralian 'observers' are inherently incompatible with our reality, and threaten to make it unstable and possibly even destroy it if they were to awaken all at once.
Why didn't Dewey kill himself earlier even though a good part of his plan relied on taking the bullet train to heaven?
The Dead Man Switch was his Plan B, the primary plan was to destroy the Command Cluster and let reality eat itself while he watched. Dewey had to be around to personally shepherd that part to completion. Those meddling kids forced him into a Thanatos Gambit.
Why did it take half the series for anybody to call Holland out on assaulting Renton? What did they think he was doing to him the first few times? Trying the kill a bug on his face?
They were calling him out, in a fashion. The Gekkostate, despite their seeming indifference to Renton, do care about him. So while most of them aren't willing to fight against their leader as much as Talho does, they still argue wit him to go easy on him. They complained about Holland sending him to the brig, tried to break up the fight between hi and Renton just before the Charles and Ray arc, and Talho repeatedly calls him out.
If Renton and Eureka are two completely different species, HOW THE FUCK ARE THEY EVEN ABLE TO INTERBREED AND SUCCESSFULLY HYBRIDIZE? Their most basic physiology shouldn't even allow it!
First off, are Coralians people? They're clearly not any subspecies of Homo sapiens and dictionary definitions generally specify that only human beings can be considered people. Even if we broadened the definition of "people", as we probably should in this case, these people still wouldn't be human nor any other species of monkey. Humans are a subset of apes, so if you're not an ape, you can't be human. We're also a subset of mammals in the same way and for the same reason. Not every mammal is human, obviously, but every human is a mammal and if you're not a mammal, then you can't be human no matter how intelligent or civilized you are. Regardless of how much Eureka, Sakuya, and Gonzy look like human beings, they are not part of the human gene pool. They and other scub-based organisms evolved separately from mankind, unrelated, independently, on a distant planet before arriving on Earth. They are something else. One of the cardinal laws of evolution: Thou shalt not grow out of thy ancestry.
Second, Eureka Seven is hardly the only offender. On Star Trek, we have humans, Vulcans, Romulans, Klingons, Cardassians, Borg, Ferengi, and other sentient races; Dragon Ball has humans and Saiyans (We never see any hybrids of humans and Nameks, for example); The World of Narue has humans and Narue's unnamed species; Please Teacher! has humans and whatever Mizuho is supposed to be; Doctor Who has humans and Time Lords; ad infinitum. In any case, all the humanoid races in these franchises are based on the same template, each bearing their own unique modifications such as weird ears, funky foreheads, extra organs, strange hair/eye colors, and definitive behavioral disorders. They're all essentially the same thing and the fact that they can all interbreed suggests that they must be closely related subspecies at least within the same genus and all derived from the same source. But if they all evolved independently, separately, unrelated, each on different planets, then their most fundamental physiology should be dramatically different.
THEY CAN'T ALL BE UNIQUELY ORIGINAL YET SUPERFICIALLY IDENTICAL, INTERNALLY INCOMPARABLE, AND GENETICALLY COMPATIBLE ALL AT THE SAME TIME! In our biological reality, there can be instances of convergence where members of once-divergent subclasses or other taxa later play identical roles and adapt accordingly (e.g., wolves, hyenas, and thylacines; birds, bats, and pterosaurs; sharks, dolphins, ichthyosaurs, and thalattosuchians; scimitar cats, barbourofelids, nimravids, creodonts such as Hyaenodon, and the distantly related sparassodont Thylacosmilus, among others), but they'll never become the same and can never hybridize. It doesn't matter how much they look alike on the surface. The physiology of an organism determines what it is. The more distantly related they are, the deeper you have to look for similarities, but if they're related at all, then the deeper you look, the more similar they'll be.
Eureka is not a Scub Coral, she's a humanoid Coralian. She did not evolve naturally - she is an artificial organism that was intentionally designed by superintelligent aliens for the specific purpose of communicating with humans. It is not totally out of the question that they gave her a human uterus and a pair of human X chromosomes in order to facilitate that mission.
Why did Holland wanted to be Eureka's partner so much when their were other ways to save the world?
For one, there were really no other ways to save the world besides becoming the Chosen One and for two, Holland felt responsible and guilty for just about every problem that the world was dealing with at the time because all of those problems were caused by Dewey, his own brother.