The "Movie Physics" of Back to the Future Part II

By David Konow

And why the DeLorean has to speed up to 88 miles per hour to time travel.

One of the things we love about science fiction movies is the storyteller's take of futurism. Films set in the near future take on the challenge of imagining a world filled with technological and cultural changes, and yet are still recognizable and relatable to the viewer. Movies like Blade Runner, Minority Report, and A.I (hey, all based on Philip K. Dick works!) fast forward us in time to create a setting that can be used to reflect on the problems of the present, and adorn that setting with props and effects that signify "the future." Those gadgets in turn have inspired a generational of roboticists, computer interface designers, and even toy makers.

With 2015 right around the corner, we wanted to take a look back at one of armchair futurtists' most beloved movies, Back to the Future Part II. With technologies like Google Glass, video-recording drones, and ubiquitous video conferencing software, it does seem like BTTF II was particularly prescient in its wacky vision of the future. So what's it like for a screenwriter to see elements from one of his movies coming true twenty-five years after its release? We talked to BTTF scribe Bob Gale about how he and director Robert Zemeckis went about predicting the future, how you can make an audience believe in time travel and hoverboards, and just exactly why Doc Brown infamously pronounced the word gigawatts 'jigawatts.'

We first asked Gale if he was surprised that some of what was predicted in Back to the Future Part II has come to pass. "Well yeah, I kind of am," he says. "There's a lot of stuff we did a lot of research on, like using your thumb to make a money transaction, what the money would look like, that kind of stuff was all being theorized about back in the day. The video conferencing, there was a rudimentary form of video conferencing that that already existed back in 1989. So a lot of this stuff was me and Bob Zemeckis saying, 'Let's try to take these ideas to its logical conclusion.'

"One thing that's kind of interesting, is it's like what came first, the chicken or the egg," Gale continues. "We know that people who saw the movie have thought, 'Is there a way to invent a hoverboard?' Then people are out there trying to figure that out. We did the tie-in with Nike to make the shoes, then they started thinking, 'Maybe we can [actually] make these things.' Some of what we predicted may be coming true because people who saw it in the movie were inspired and thought, 'Maybe there's a way to make it come true.' The guys at Mattel that worked on the hoverboard replica were excited about it, they wanted a hoverboard just like everyone else."

Of course many people would really love the hoverboard to come true, and a recent Funny or Die video raised the hopes of many fans before it finally sunk in that it was a goof. "Bob Zemeckis gave an interview where he said, tongue in cheek, that the hoverboard had been around for years and parents groups have kept it off the market because they were afraid kids would get hurt," Gale says. "People believed that, and Mattel was really pissed off at us for a number of months, maybe as long as a year, because people started calling the company saying, 'I want that hoverboard man! You can't keep that off the market!' We didn't think people would believe that, then there was that Tony Hawk video and people believed that too."

In imagining the hoverboard, Zemeckis and Gale put a lot of thought and consideration into how this invention could actually work if it existed in the real world. "This was when there was a lot of experimentation with magnetic levitation, like mag lev trains for rapid transit," Gale explains. "So we thought, 'Okay, it picks up magnetic waves from the center of the earth. That might be why it may not be able to work well over water.' We thought about all that kind of stuff: If cars fly, what would the traffic laws be like?"

"We thought about all that kind of stuff: If cars fly, what would the traffic laws be like?"

Another scene in the film that recently came true is drones zooming in and capturing the news. "The USA Today drone that came in to take the photo when the gang was being arrested, we thought we were just being goofy with that, and now it's actually going to happen," says Gale.

Yet one Back to the Future innovation Zemeckis and Gale did not see coming were smart phones. "We completely missed that idea, even that everybody had their own personal phone," Gale tells us. "We had that incorporated into the glasses at the table where they're watching movies in their glasses and getting phone calls, that's pretty much Google Glass. I was also sure that we would not have flying cars, that's one concept that I think is a constant source of disappointment to people! There might be a way to make flying cars, but how practical is it, and what are some of the other issues we would have in society if we had them? Everybody's already scratching their heads about self-driving cars, so flying cars? I don't think we're going to get those."

"Why 88? Just because it was an easy number to remember."

In directing films, John Landis has referred to a theory he called "movie physics," which basically means if you present something nonsensical realistically enough, audiences will believe it. "For us, movie physics is important," Gale says. "There has to be rules for how the time machine works. It has to be traveling at 88 miles an hour. It doesn't work at 87, it doesn't work at 86, it has to be 88. Why 88? Just because it was an easy number to remember. There was no other reason than that. Once you lock yourself into a rule, you need 88 miles an hour and you need 1.21 jigawatts all at the same time. As long as that all happens, you can travel through time in a DeLorean!"

"We did research," Gale continues. "A lightning bolt really can generate 1.21 gigawatts of electricity. In the movie we pronounced it jigawatts, it was misspelled in the script with a J instead of a G. The first time I heard the term, we called up an electrical engineer or a physicist, to find out how much electrical energy is actually in a lightning bolt, and that's how he pronounced it. It's not an incorrect pronunciation. The giga prefix comes from the Greek word gigos, which is where we get 'gigantic' from. So this guy pronounced it with a soft g – jigawatt - and it's actually an acceptable pronunciation. That's the indication that we had just enough scientific information in there to make it sound plausible, and if somebody looked it up they could say, 'Well yeah, that's not entirely wrong.'"

In creating the future world of 2015, Zemeckis and Gale had specific ideas and regulations they wanted to stick to as well. "We didn't want to have a dystopian future because that's not what the movie was about. We wanted people to be optimistic about the future, and we wanted the future to look like a pretty fun place to be in.

"One of the things that we were conscious about is when you see movies like Blade Runner, The Shape of Things to Come, and Metropolis, they've torn down the past and the present, and everything has been newly built, or recently built. That's not the way it works. If you took somebody from 1940's New York and transported them to 1980's New York, yeah there'd be a lot of things different, but you'd still be able to find your way around. The streets would still be the same. So we didn't tear down the past. We wanted you to feel it wasn't an alien place, that you could recognize it."

It's also important to explain science, even nonsensical science, in a way that audiences can digest it. One of the best scenes in Back to the Future II in this regard is when Doc Brown explains to Marty how an alternate version of 1985 was created when Biff Tannen stole the time machine.

"Part of it is the fact is when you have Christopher Lloyd explaining it, it's automatically going to be a lot of fun!," Gale says. "When I was writing that stuff, knowing that Chris was going to be saying it, I could write it with Chris's voice in my head. A great actor always makes it better, that's why they get the big bucks. The thing about exposition is that it needs to come at the right time. We had enough stuff going on in Back to the Future II at that point where the audience was ready to sit down and listen to an explanation. That's the sense of drama you have to have, where you know when it's time to explain something. If we explained it too early, it would have gone over people's heads."

One of the best compliments that has ever been paid to Back to the Future is that Carl Sagan was a fan, and he told Robert Zemeckis it was his favorite time travel film. "That was real flattering," Gale says. "I think it was because we so clearly demonstrated some of the elements of time travel, like the duplication paradox in part one. We took it seriously, and explained it and showed it in a way that was really happening."

While some of what Zemeckis and Gale created in Back to the Future II came to pass, it's always much harder to predict what movies will be remembered and enjoyed in the years to come, and what movies will fall by the wayside. The fan goodwill for the first Back to the Future will always be strong, and in recent years we've seen that Back to the Future II is still a big fan favorite in its own right.

"It's always flattering when you know that people are watching your work and getting a kick out of it," Gale says. "I never get tired of hearing about that."