We're living in the future with shiny tech -- and plenty of duds

"Back to the Future, Part 2" promised us flying cars and a fusion energy machine that ran on garbage. We got social networks for dogs and a vibrating fork instead.

Robert Zemeckis and Bob Gale, the masterminds of the B2TF trilogy's scripts, didn't anticipate the hundreds of gadgets, gizmos and apps that make the movie's Black & Decker pizza-making hydrator look downright practical. Since "Part 2" debuted in 1989, technologists have poured blood, sweat and tears into flops, flameouts and gimmicks that would have defied the imaginations of even Hollywood's most creative writers.

Want an example? Check out the HAPIfork, a battery-powered utensil that vibrates in people's mouths to warn them when they're eating too much. No surprise, B2TF -- celebrated Wednesday because the main character travels to October 21, 2015 in the movie -- didn't predict something like the HAPIfork would be central to life.

Other inventions started with promise but have been relegated to punchlines after public response proved flat. Remember Segways? They were meant to revolutionize cities by eliminating car congestion but preserving the freedom automobiles provide.

Now, they're the preferred mode of transportation for mall cops across the country.

Even some of the stuff "Part 2" foresaw hasn't turned out the way Zemeckis and Gale imagined. In the movie, Michael J. Fox, the star of the series, watches TV and makes calls through a pair of goggles. Google Glass, the smartphone-powered eyewear, held at least some of that promise when the search engine giant unveiled the smartphone-powered eyewear in 2012.

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Alas, the $1,500 eyeglasses have been discontinued amid a controversy over privacy and how they would be used. Glass was so controversial that eight members of Congress sent a letter to Google CEO Larry Page inquiring about the potential to "infringe the privacy of the average American."

A Google spokesman declined to comment. HAPIfork and Segway representatives didn't respond to a request for comment.

Silicon Valley types say we can't expect every invention to be a home run, like the hoverboard McFly flew around town on. Fizzles are inevitable and, more importantly, part of the process of innovation.

"Industries that don't encourage that probably won't innovate as quickly," said Hung LeHong, an analyst at technology research firm Gartner. "The industry learns at the expense of others."

Indeed, chasing bad ideas can sometimes help refine a later one and inspire an entire industry.

Consider Apple's Newton, an early version of the hand-held personal digital assistant, or PDA. The device failed to excite consumers, in part, because one of its main features didn't work as marketed. Besides permitting users to store contacts and manage their calendars, the Newton was supposed to allow people to write on the pocket-sized screen and then convert their handwriting into legible text. It didn't.

But the Newton served as a sort-of proof-of-concept for handheld organizers and paved the way for Palm's Pilot, the first commercially successful PDA.

Now, the functionality of PDAs, along with that of music players and cell phones, is wrapped up in Apple's iPhone.

Kenneth Simons, an economics professor at Rensselaer Polytechnic Institute, says few ideas are completely worthless. Minor ideas and even seemingly useless ones can prove their value with time.

Technological change, Simons said, "often works in funny and unexpected ways."

Consider the pneumatic, or air-inflated, tire. Created in 1846 when folks got around via horse-and-buggy, the tires looked like a wasteful novelty. Then bicycles, a relatively new technology at the time, started to catch on and the invention looked genius.

So maybe all those flops were a good thing, spurring a cycle of innovation that has exploded since "Back to the Future, Part 2" with its flying cars hit screens 26 years ago. While flying cars aren't on the drawing board, a convergence of battery technology and software is changing the way we drive.

"In the next 6 or 8 weeks, I'm getting the next Tesla Model X that is going to drive itself on freeways," said Vivek Wadhwa, a vice president at Singularity University, referring to the latest version of the company's electric car. "Fifteen years from now, we'll ban humans from driving on roads because they're dangerous."