The Martian follows astronaut Mark Watney as he uses science to stay alive when he finds himself stuck on Mars. Although sci-fi movies are generally seen as alien-based and sometimes ridiculous films, this one was neither. For the most part, director Ridley Scott’s creation agrees with known science.

One of the few offenses involved is the difference between Mars’s and Earth’s gravities. Mars’s mass is about a third of Earth’s, and so the gravity is as well.

“You would weigh about two-thirds less, [and so] it would be easier to run and jump,” said physics teacher Mr. Jay Walgren. In other words, someone who weighs 100 pounds on Earth would weigh about 30 on Mars. He or she could jump higher than on Earth.

“Very quickly [he would have] experience[d] muscle atrophy, which is when your muscles start to get super weak,” Mr. Walgren said. “You wouldn’t have to fight against this huge force from Earth’s gravity. At home, you’re fighting that every day, even when you’re sleeping.”

Mark Watney did lose a lot of weight and muscle mass, but it is unclear as to specifically why. Watney did not eat a lot most of his stay on Mars (because he was rationing his food), so he grew skinnier; muscle atrophy, however, also took away some of his muscle mass. The problem is that either the filmmakers did consider muscle atrophy and did not mention it, or the directors only had Watney lose weight because he could not eat much.

Not only is the gravity different on Mars, but so is the atmosphere. On Earth, we have a large cushion of gas molecules surrounding us, and so our atmosphere is thick and strong. On Mars, the atmosphere is not even 1% as dense as ours, meaning there aren’t many gases (or air) around the planet. So, the atmospheric winds could not have moved that much sand and dirt, much less the huge metal disk that hit him in the movie’s trailer.

“Even if the wind was going [twenty] miles an hour, it would feel like nothing,” Mr. Walgren clarified.

In addition, when a second storm comes and tears apart a portion of Watney’s base, he patches it with duct tape and clear plastic. “That might actually be enough to do the job in the tenuous atmosphere that does exist on Mars,” said New York Times writer Jeffrey Kluger, who reviewed the movie’s science, “but in the violent one [the writer] invents for his story, the fix wouldn’t last a day.” Thus creates an incongruity in the film as the writers wanted both atmospheres in one.

At one point in the film, Watney is stuck out in space. When he punches a hole in the hand of his suit, air spurts out like a geiser and propels him forward. Although this is theoretically possible, he would just have spun in circles unless his hand was exactly at his center of mass. It’s a very specific maneuver and would require the precision of a robot, according to Mr. Walgren. He elaborated, “It would take an incredible amount of practice [for a human to do it].”

Watney was able to do something once considered impossible: he grew potatoes on Mars. Although Martian dirt itself has a pH a little too high to grow as nice potatoes as he produced, and he would have had to compost and process the fecal matter before it was safe to grow with, the science is represented well enough, even if it is not perfect. It, again, would be quite possible.

All in all, the movie itself was pretty fantastic. With smart, sarcastic characters and a Guardians-of-the-Galaxy-like soundtrack, even if the movie’s physics could have improved, it still easily demonstrated how cool and complex science is. That is the best part of the movie: science was what saved Watney, and science was presented in a spirited, fun light that inspired an interest in its audience.