"I can feel confident 124 days is an accurate amount of time. I wrote my own software to do a simulation," Weir explained. He paused. "Yeah, I did a lot of work on that."
It's hard to believe that Weir doesn't work for NASA: computer simulations, mathematical calculations and chemical studies all go into his work. But Weir is not literally sending a man to Mars, he is a novelist doing research for his recently published first book, a sci-fi thriller called "The Martian," which was released in bookstores last month.
The Martian is a uniquely hyper-real space adventure, fusing sound science (as gathered by Weir) with straight-shooting storytelling to yield a story of survival on Mars. The story follows wise-cracking astronaut Mark Watney, who is forced to survive after he is unintentionally abandoned by his crew after a dust storm forces them to retreat back to Earth.
In the novel, Watney is faced with no connection to Earth, few resources, and seemingly insurmountable obstacles. Told through Watney's mission log, "The Martian" tells a story of one man's brains, his ingenuity, and his unrelenting will to survive against all odds.
Weir said he wanted to bring sci-fi readers a fulfilling experience, and his unique attention to scientific detail sets the piece apart from many other novels in the sci-fi genre.
"The problem I have when I am reading sci-fi is that it will go by some hand-wavy science explanation, and it will set off all the alarms in my head," Weir said. "I wanted to make a story that was as scientifically accurate as I possibly could. What I really want is for readers to unquestionably believe the science presented to them and not have to second-guess it."
Much praise has followed "the Martian." Critics categorize the novel as a gripping Robinson-Crusoe-cum-MacGyver tale set in space and applaud Weir's ability to meld scientific fact with pulse-quickening fiction. And true sci-fi fans simply seem to delight in Weir's reverence for geekdom: he does the extra work to create a story that feels hyper-real.
It makes sense that accuracy would mean a lot to Weir. He is a software engineer by trade. As early as age 9, he toyed with computer programs at school. By 15, he worked as a lab assistant at Sandia National Laboratories and taught himself to write code. By his early 20s, he was a professional computer programmer, and now, at age 41, Weir develops software for Silicon Valley tech firms.
But Weir loves science fiction as much as he loves science fact. From early childhood, he developed a love of classic sci-fi books as well as a self-professed "dorky" fascination with space travel, orbital dynamics and astronomy that still sticks with him today.
Take, for example, the fact that, though many of his software simulations on space were for "The Martian," a number of them are just for Weir's own curiosity.
"I made a gravity simulator, where I put millions of rocks out into space and just let them all affect each other gravitically. It formed a big solar system," Weir said. "That was something I built for fun."
Weir's professional writing career also initially began "for fun."
After a first failed attempt at a becoming a writer while in between computer programming jobs in his early 20s, Weir decided to keep writing as a hobby.
In recent years, as he discovered self-publishing over the Internet was increasing in popularity, he decided to join the trend.
"I started writing fiction and just putting it up on my website," Weir said. "'The Martian' was just one of the things I was working on. I was posting it in serial format for free, for people to read. It was really popular."
Soon Weir began receiving emails from fans about "The Martian," requesting he release it in an e-book format. The requests prompted Weir to self-publish a Kindle version on Amazon in 2012, while keeping it available for free on his site.
"That's when I learned the amazing, unbelievable reach into the readership market that Amazon has. Way more people bought it from Kindle than downloaded it, for free, on my site," Weir said.
The Martian rocketed to the top of Amazon's online best-seller charts soon after its release. Such acclaim and Internet buzz caught the attention of Random House publishers, spurring a book deal, a literary agent and a hard-copy publication last month. And it doesn't stop there — "The Martian" has received a recent request for movie rights.
"I'm really excited. I would love it to happen," Weir said. "But Hollywood studios buy movie options like I might buy Tic-Tacs. It is still only a small probability that they would make a movie out of it. But I can hope."
It seems that the biggest compliment for Weir, however, has not come from Hollywood, but from Houston. A self-professed "fanboy" of NASA, Weir mentioned his feelings of pride and gratitude upon receiving positive feedback on the book from Mission Control after the book's release.
"Before the book got out on Kindle, I never had any interaction with NASA at all. Now, I have had lots of emails from astronauts and NASA personnel, which is really cool," Weir said. "They are commenting on the accuracy, and how it is a pretty accurate portrayal of what astronauts are like."
In the wake of his success with "The Martian," one will likely find Weir still experimenting with space phenomena on his computer, dreaming up his next sci-fi story.
"I'm a big fan of how this stuff works," said Weir. "I love that. That's the kind of guy I am."