Interstellar, as everyone has noted, is a stupendously ambitious movie. It’s also pretty complicated—and not just because of the science involved. If you’re like us, you probably walked out of the theater with a bunch of questions. We try to answer a number of them below.

Who are the mysterious “they” people keep referring to?

Assuming Cooper (Matthew McConaughey) is right, “they” are our descendants, who have evolved to exist in five dimensions. Because they exist in five dimensions (time being the fourth dimension), their experience of time is not linear in the same way that ours is. They create the wormhole and the tesseract that saves Cooper.

I don’t understand the ending. If “they” are descended from humans, and Cooper saves humanity, then how could “they” exist in the future if Cooper hasn’t saved humanity yet? Or, as Vulture put it, “you can’t travel back in time and engineer your own salvation.” Right?

A lot of science fiction, at least, would disagree with you. The ending of Interstellar seems to present a “bootstrap paradox.” In short, this is a type of time paradox in which a chicken sends an egg back in time, which egg then becomes that chicken. A popular example is The Terminator: In the first movie in the series, Kyle Reese is sent back in time by John Connor to protect Sarah Connor, John Connor’s mother. The paradox is that Reese turns out to be the father of John Connor—by sending Reese back in time, John Connor created himself. (Similarly, by going back in time to try to kill John Connor, Skynet leaves behind the advanced robotic parts that lead to the creation of Skynet.)



Without time travel, whether such a thing is possible remains theoretical, but it’s something theoretical physicists do argue about. (If you’d like to read more, theoretical physicist Kip Thorne has a whole chapter about this in his book The Science of Interstellar.)

What’s a tesseract? Isn’t that the thingy from The Avengers?

Yes, in the Marvel Universe, the Tesseract is an Infinity Stone—an object of extraordinary power. In our universe, however, tesseract is the geometric term for a four-dimensional cube. If a cube is the three-dimensional equivalent of a square, a tesseract is the four-dimensional equivalent of the cube. (Again, the fourth dimension being time.) You can read more about this here, but the important thing is that the tesseract is a space built by “they” so that Cooper can communicate with Murph.

Why does Dr. Mann (Matt Damon) try to kill Cooper and escape?

Because it’s only a matter of time before they figure out that he’s been lying about his planet and putting the whole future of the human race at risk just to save himself. By killing Cooper and stealing his ship, he can escape the planet and no one else will ever know what he’s done. (He may also be a little deranged, and they may not have enough resources for everyone to survive.)



Could habitable planets actually orbit a black hole, as they do in the film?

Not as far as we know. As our colleague Phil Plait asks, “Where do the planets get heat and light? You kinda need a star for that.” What’s more, in order for the water planet to have such extreme time dilation (one hour there equals seven years on earth), it would, Plait writes, “need to be just over the surface of the black hole, and I mean just over the surface, practically skimming it.” But because of way black holes affect space, no planet could have a stable orbit that close to one. Plait addresses additional problems with the science in the movie in his own piece about the film.



Update, Nov. 9. 2014: Plait has retracted some of his complaints about the movie, noting that he had based his calculations on the assumption that the black hole is non-rotating. Things are different with a black hole that‘s rapidly spinning: “From what I can find, there is a stable orbit around a rotating black hole that can produce that kind of time dilation, so I was wrong there,” Plait writes.

Is that really what black holes look like?

According to Kip Thorne, a renowned astrophysicist who served as a producer of the movie, yes. In fact, Thorne told Wired that the rendering of the black hole by the movie’s computer effects artists taught him new things about the ways black holes behave. The effects team based their visualization—“the product of a year of work by 30 people and thousands of computers,” Wired reports—on Thorne’s equations. When they did, the accretion disk, “agglomerations of matter that orbit some black holes,” appeared all around it: “above the black hole, below the black hole, and in front of it.” Thorne wasn’t expecting this, but says that he now sees that this is what his equations dictate. Wired calls it “the most accurate simulation ever of what a black hole would look like.”

What’s up with the blight? Why is corn the only crop left on earth?

Interstellar is vague about what has rendered the Earth nearly uninhabitable, though there is some suggestion that global warming is the culprit. (At one point, a character blames “the excesses of the 20th century.”) Science writer Alan Weisman, author of The World Without Us, told us that “corn might do a little better” than other crops—particularly wheat and rice, which, along with corn, are the world’s most popular crops—in the conditions shown in Interstellar, but that it wouldn’t be by much. Corn, Weisman explained, has an advantage over rice and wheat in that it’s more efficient in processing solar energy. Still, all grains are vulnerable, and Weisman says it’s “extremely unlikely” that any grain would have much chance under Interstellar’s conditions. And, sure enough, the movie suggests that corn, like okra, will not survive much longer.

Why does Murph (Jessica Chastain) burn the corn field?

Up to that point in the movie, Murph has tried to convince her brother Tom (Casey Affleck) that if he and his wife and son don’t leave the farm, they will all die. (They’ve already lost one child to an illness, apparently due to the quickly deteriorating conditions.) Tom refuses to heed her warnings, and, in an act of defiance, she sets fire to the crops to force them to leave.

What’s the poem that Michael Caine is always reciting?

That’s “Do not go gentle into that good night,” by Dylan Thomas. The popular villanelle was first published in 1951, two years before Thomas died, and it has been featured in a number of movies and TV shows.

Is it true that some of the best yachtsmen in the world don’t know how to swim?

Cooper comforts a crew member who is anxious about exploring space for the first time by saying that some of the best solo yachtsmen don’t know how to swim. Is Cooper operating on 90 percent honesty here, or is this 100 percent true?

Expert yachtsman Dennis Conner, four-time winner of the America’s Cup Race in the ’70s and ’80s, has said he never learned how to swim. His friend, the quadriplegic racer Paul Callahan, can’t swim, either, and he still earned the title of 2012 Yachtsman of the Year from the New York Yacht Club. For the record, though, learning how to swim is generally encouraged for aspiring yachtsmen: F.W. Pangborn, then vice-president of the New York Yacht Racing Association, wrote in 1890 that “one must learn to swim and to row before he graduates into the ranks of the yachtsmen.” And William Ricketson, a communications manager for U.S. Sailing, informed us that while sailing clubs across the country are “free to decide whether to include swimming as part of their courses on how to sail … the vast majority of professional ‘sailors’ and ‘yachtsmen’ are proficient swimmers,” at least in his experience.



Read more about Interstellar in Slate.