I can't be bothered arguing with someone who knows full well the equation they have posted is made up nonsense.
Feel free to leave the discussion at any time.
If you really thought I was wrong, you'd have posted a breakdown in this thread of how all the components of the equation are correct, and why they're in there, because I could not have possibly countered that.
How could I possibly do that? It seems you have read the relevant wiki page more carefully than I have, since you have claimed it to say things that I cannot find anywhere on the page, yet you do not comprehend that the equation is only an approximation and therefore not (completely) correct.
Furthermore, it is derived from a basic premise, as I have already explained. Equations are not pieced together symbol by symbol; I can not explain how a "component" of the equation is correct any more than I can explain how I make phone calls using a microphone.
Your skating around defending the equation and merely concentrating on attacking my correction of a blatant mistake says rather a lot, I think.
I do not need to defend anything. I have never laid claim to that equation being anything more than an approximation, and an approximation of a hypothetical phenomenon at that. I certainly have not presumed to state its self-evidence and ridicule anyone who questions its validity.
By contrast, you have come into this thread with a "correction", showing obvious ignorance of the concepts you claim to be correcting. When asked to justify your position, instead of rationally explaining how you came to the conclusion that the equation was incorrect, you resorted to ridiculing me.
I have also never attacked your "correction", only your position. Your correction may be perfectly valid, but if you are unable to justify why it is valid, or how you established that it is valid, then you cannot expect to be taken seriously.
And I think the readers of these fooras are perfectly capable of making their own minds up about the accuracy of your equation.
"Bendy light specialist". 
Irrelevant.
I thought we'd all agreed that the equation was simply the equation for a curvy line, with the fine feature of concavity, in case anyone wants to minimize it.
Yep, that's what I tried to tell Parsifal, but he pretended not to be able to understand it.
If you understood the subject matter at hand, it would be quite plain that this is what I have been trying to tell you. However, I see no evidence of pretence on your part.
As you claim to understand what the equation represents, please go ahead and pick any non-zero value for the Bishop constant. Now plot a curve based on your "corrected" equation and see what concavity that has. Then pick another value for the Bishop constant, and see what concavity you get.
Come back and tell me when you find a value that produces a non-zero concavity. I will be very curious to know what it is.
Also, it seems you have overlooked the need to respond to any of my requests for substantiation in this thread. Since you appear to be new to debating, I will give you a hint: It does not make your argument appear stronger to avoid defending it.
I will quote each such request again here so you can respond to them now. I do not intend to respond to any more of your posts until you at least make a sincere effort to do so. In the interest of brevity, I will only post the first instance of requests that I have raised multiple times without an answer.
In the mean time, there's an error in the equation - the right hand side should be a 4th root, not a 3rd.
Please justify this statement.
No, not irrelevant at all. Just because I rephrased the text does not mean that it doesn't give the information that a value of zero for Y represents no curvature. Trying to make out that the exact words I used aren't in the article is poor argument indeed.
Quote me the part of the wiki that supports your claim, then. I don't care about the specific language, just quote me what led you to this conclusion.