LOS ANGELES, OR POSSIBLY THE FIFTH DIMENSION — If you’re struggling to understand how the "tesseract" scene in Interstellar got Matthew McConaughey from the other side of the universe to the backside of his daughter’s bookcase — or if you’ve read anything on the Internet this week throwing shade at the film’s science in general — Kip Thorne has some choice words for you. Most of them are in his book.

“People who have declaimed on this without reading my book are completely off-base,” the renowned astrophysicist told Mashable on Tuesday.

SEE ALSO: Why scientists are in a love-hate relationship with 'Interstellar'

That book, The Science of Interstellar, is as key to understanding the film as seeing the film itself, Thorne said. With a foreward by the film's director, Christopher Nolan, the book came out Nov. 7 to coincide with the theatrical release.

The cover of KIp Thorne's "The Science of 'Interstellar.'" Image: Amazon.com

And for good reason: This deep-dive of explanations of the film’s science, which go far beyond the characters' offhand remarks used to explain some of its grandest ideas, would utterly ruin the film’s surprises.

“You have to see the film first, because the book is absolutely filled with spoilers,” Thorne said. “But when you see the film, key things are expressed in just one sentence of dialogue, and you really have to work hard to catch these things. Once you’ve seen the film, get a sense of the overall story, and see the visual effects, what I write makes a lot of things fall together and make sense.”

OK, so it’s required reading for anyone curious about how the movie's astrophysical phenomena were really supposed to work. If your head hurts already, Thorne assured us that it’s aimed at “people who have no physics background, but who are intelligent and curious.”

Perhaps the film’s largest narrative leap takes place at the end, when Cooper (McConaughey), ejected from his battered spacecraft, enters the black hole known as Gargantua. After a series of mind-bending visuals, he winds up in a chillingly surreal box that appears to be behind his daughter’s bookshelf – despite that just moments ago, he was some 10 billion light years from Earth.

“If there is a Fifth Dimension out there, in which our universe is embedded, [the tesseract] is a cube in that dimension. And in this movie, it is a transport object.”

A screenshot from the new "Interstellar" trailer. Image: Paramount

But if you rewind several scenes, our weary travelers remark — many times over — that it’s impossible to know what’s inside the black hole since no one’s ever had a peek behind that dark curtain. Don’t take that to mean that Thorne and Nolan were wildly guessing or abandoning physics when Cooper winds up in the Fifth-Dimensional environment.

“That tesseract is not inside the black hole — it’s a four-dimensional cube, with four space dimensions and time — it lives in the Fifth Dimension,” Thorne said. “One of the faces is in our universe. Cooper is scooped up in the face of that tesseract and carried into the bulk.”

Yeah, we only sort of followed that, too. But our time was limited so we let him keep rolling.

“In the Fifth Dimension, the distance between Gargantua and Earth is quite short; about the same as the Earth and the sun … whereas in our universe it’s 10 billion light years. So [the tesseract] can take him into our universe and docks beside the bedroom.”

Aha, there it is. So the inside-the-singularity part of the movie isn’t willy-nilly at all – it has a mathematical basis.

“This is really all based on some beautiful ideas; what I talk about is a ‘complexified tesseract,’” Thorne said. “It fits with our understanding of what a tesseract is … [it] fits with ‘brain worlds’ of science … [or] what I call the Fifth Dimension. There is so much science that is in there that people have puzzled about, and I don’t know any way for people to get un-puzzled other than to read the book.”