The CGI-heavy cinematic world of Alita: Battle Angel, the big-screen adaptation of Yukito Kishiro's popular manga series Gunnm, is chock-full of the kinds of cyberpunk toys most of us only dream about. But while much of the technology in Alita is futuristic, it's deliberately grounded in the real-world technology of today, per producer James Cameron's vision for the film.

(Mildest of spoilers for Alita: Battle Angel below. You can read Sam Machkovech's largely spoiler-free review here.)

Set some 600 years in the future, the cyberpunk world of Alita: Battle Angel is a dystopian society where people in Iron City scavenge for anything useful—especially technology—in the Scrapyard, which holds everything dumped from the floating city of Zalem, where the "elite" reside. There's a series of tubes where products are sent from the Iron City to Zalem (in exchange for the latter's refuse), but otherwise the two worlds never really mix. The Scrapyard is where a kind doctor finds cyborg Alita's head, holding her carefully preserved human brain. He knows immediately he's looking at highly advanced technology from three centuries earlier, lost in time, and rehabilitates her. The plot follows her journey from amnesiac innocent to fierce warrior.

We'll leave aside the problematic (from a physics standpoint alone) floating city of Zalem—although the concept of a space elevator is very much a topic of current research and grand hopes. Every movie gets a limited number of what the industry calls "buys:" story elements that are not expected to be realistic, but the audience will hopefully suspend its disbelief and accept them as part of the background. That's what puts the fiction in science fiction.

In this scavenging economy, people find old technology in the Scrapyard and repurpose it. Sensors are pretty much ubiquitous in 21st-century life, found in appliances, televisions, cars, airplanes, medical devices, and so forth. According to Matt Gould, a field application engineer in the aerospace unit of TE Connectivity, which specializes in sensor technology, they would be equally critical to the realization of the kinds of futuristic cyborgs depicted in Alita.

"A lot of the mechanical features that you see on the cyborgs are grounded in reality. You've got gears and actuators," said Gould. "And then you go down to the way these exaggerated limbs communicate with the human brain."

Once and future tech

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TE Connectivity/20th Century Fox

TE Connectivity/20th Century Fox

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Single-wheeled and electric bikes already exist, for instance; the movie's design for them was just modified to look cooler and more futuristic. Per Gould, contactless connections could distribute the battery power efficiently in lieu of a gas-powered internal combustion engine, along with a gyroscopic balancing system. Alita's Berserker cyborg body—technology rare even in her futuristic world—is tough enough to withstand impact but also super-flexible to enable her to move freely. We already have "smart armor" made with unusual materials that are flexible, yet harden in response to impact to protect the wearer. We also have a number of self-healing materials—another unique feature of Alita's Berserker body.

She would need haptic sensors to feel anything she touched (like her love interest, Hugo's, face) and nano servo motors to give her full range of motion. Neural power links would be needed to transmit energy from Alita's cyborg "heart" to her cyborg body, along with high-speed databanks to connect her brain to her body. The heart itself is a miniature reactor (think Tony Stark's miniaturized arc reactor that powers his Iron Man suit), purportedly capable of powering Iron City for years. That, alas, is still far in the future, although there are several competing large-scale designs in development for fusion energy around the world. (The economics of scale just aren't there to make it a viable energy source.)

As for the brutal game of Motorball—a hybrid of roller derby and Death Race 2000—Gould argues that those rocket skates could be propelled by microturbines, augmented with tiny MEMS-based gyroscopes and speed sensors to track her velocity and changes in direction. There could also be gyro sensors and magnetics to motorize the ball itself, making it move more erratically and increase the challenge to the players.

This is also a world filled with human/cyborg hybrids. Because life is so hard down below, many residents augment their bodies, sometimes simply with neurally controlled prosthetic limbs. Those who become Hunter-Warriors (basically cyborg bounty hunters) and/or those who compete in the fictional sport of Motorball go much further. They replace various body parts with prosthetics that include any number of creative weapons or useful devices to give them an edge. We're nowhere near that kind of technological capability, but the seeds of such augmentation are already in place, thanks to cutting-edge research in robotics, prosthetics, exoskeletons, brain-computer interfaces (BCIs), and so forth.

The robotics revolution will be the inverse of the computer revolution.

Aaron Ames, a mechanical engineer at Caltech who specializes in robotics, thinks the robotics revolution will be the inverse of the computer revolution. "Computers started out as these monolithic things that fill rooms, then they were on your desktop, then they were in your pocket," he said. "I imagine robots going the other way. They start in your pocket, taking an actuator and putting that in a phone. [A smart phone] already has all the processing you need in many respects, and it will grow from there into more elaborate applications."

The revolution could start with exoskeletons, which Ames considers the most likely means by which robotic augmentation will find its way into the public sphere. His lab is developing an exoskeleton to enable paraplegics, for instance, to walk, along with providing robotic assistance for other motor impairments. One of the biggest mechanical challenges is figuring out how to implement hard, rigid actuators and similar devices with the soft, mushy human body (the realm of so-called "soft robotics"). The mechanics need to be synergized with carefully tailored algorithms, which in turn must sync with the dynamic movements of the human body.

That's much more difficult than it sounds, because just the simple act of walking is incredibly complicated from a mathematical standpoint. "It's hard to explain to the public how hard it is, because we take it for granted," said Ames. "But walking is one of the most difficult things a robot can do." It's basically controlled falling: with every step, we catch ourselves from falling flat on our faces by restoring our balance. It's a periodic motion, just like plants orbiting the sun, and we understand those motions very well. But planets aren't contending with a constantly shifting terrain: grass, pavement, rocky ground, or ice, for example.

I, Cyborg

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Jennifer Ouellette

Jennifer Ouellette

Caltech

TE Connectivity

20th Century Fox

TE Connectivity

TE Connectivity

YouTube/Caltech

Translating that complexity into something that can interface with robotic assistive devices like an exoskeleton is a daunting task. Ames builds walking robots in his lab that can "learn" the appropriate stride for the greatest stability and lowest energy expenditure in real time, thanks to carefully designed optimization algorithms. One of them, dubbed Cassie, even went for a stroll around the Caltech campus.

But the movements are slow and inefficient compared to human movement. "There's been no power device with onboard actuation that will actually increase the efficiency of walking for a person, which means we still haven't figured out this formula" said Ames—never mind the formulas for running, jumping, dunking a basketball, or zipping along a Motorball track at near-supersonic speeds.

Ames's group is also developing a robotic powered prosthetic leg that can sense automatically how fast the user is walking and adjust its stride to match. The leg sports a flexible ankle that can move in two directions for a more natural, fluid gait. His Caltech colleague, Richard Anderson, was one of the first scientists to create neurally controlled prosthetics via implanted brain-computer interfaces. The current crop is predominantly for arms, according to Ames, because arms have some inherent stability.

"If you overshoot a little in your movements, you're not going to fall over," he said. Neurally controlled prosthetics for legs, on the other hand, present an enormous challenge, because they don't have inherent stability.

There's also an inherent challenge in the BCIs themselves since the implants require brain surgery with all the associated risks, including coma, bleeding inside the brain, seizures, and infection. The devices also degrade over time. Should a device malfunction, more surgery would be needed to repair or remove it. The risk is worth it for paraplegics (or people with severe epilepsy), but safety concerns will likely dissuade many people from implanting a BCI in their brain—at least in the near-term future.

“It’s a beautiful dream, but I think we make the mistake of expecting computers to be like us.”

Alita herself, of course, is almost entirely cyborg. Only her brain is human, connected to her mechanical and electrical body. We are nowhere near achieving that level of neural control, according to Ames, or uploading an individual's consciousness. "It's a beautiful dream, but I think we make the mistake of expecting computers to be like us," he said. Artificial neural nets may mimic the brain's many layers and weighted signals passing through the network of nodes. But the human body is so much more complicated. He draws an analogy with the invention of airplanes. Airplanes don't precisely mimic nature with flapping wings; they achieve lift through different means.

Another Caltech scientist, Joel Burdick, is researching the use of spinal cord stimulation as a form of neural control. He's found that applying a voltage to the spinal cords of paraplegics can elicit movement from their otherwise paralyzed legs. That's just one example of how much broader our notion of neural control could be.

"Our brain only does part of the work when we're walking," said Ames. "There's a lot of spinal cord control that's happening, and that circuitry is different than the circuitry in our brains."

Alita: Battle Angel is struggling in the domestic box office this weekend for a variety of reasons. That's a shame, because in addition to being a genuinely entertaining, action-packed adaptation of the original manga, it offers a reasonable vision of what cyber-technology in the future could look like.

"When I'm watching a sci-fi movie, I'm saying, OK, it's unrealistic, but how could it be made realistic? What are the steps we could take to enable us to do these things?" said Ames. "That's what science fiction is about: asking what's possible. It forces you to ask creative questions."