21 October 2015 is marked in the diaries of science fiction geeks of the 80s the world over.
It marks the day which Doc Brown and Marty McFly travelled to in the 1989 film Back to the Future Part 2.
During the first half of the movie, a vision of what California would look like in 2015 was portrayed.
It offered portable fusion reactors that power flying cars, and hoverboards ridden on by kids.
While the clean energy and hover technology of Back to the Future 2 did not become a reality, there are wonderful inventions which the film failed to predict, and which we take for granted.
Ubiquitous cellular coverage
In the 2015 of Back to the Future 2, fixed-line telecommunications were the way people communicated.
Our reality is very different, with mobile wireless technology stretching to some of South Africa’s remotest places and more people communicating via cellular towers than fixed-line phones or Internet connections.
Instead of communicating through the patchwork quilt of vendor and technology-neutral interconnected networks we know as the Internet, people in Back to the Future were stuck on proprietary networks.
While they do have video calling, this seems to be a service offered by US telco AT&T.
Thanks to the Internet we have e-mail, instant messaging, and a smörgåsbord of IP-based voice and video-calling services to choose from.
Combine widespread cellular coverage and the Internet, and you get the smartphone.
People in Back to the Future had some innovative technology, in the form of smart glasses and voice recognition with natural language processing.
However, where our smartphones are portable computers, the smart glasses in Back to the Future must be connected to something else – either the car, or a house system.
Computer graphics are incredible
Back to the Future had fairly unambitious predictions of the kind of graphics quality modern computers would be able to achieve.
While holographic technology may not be cost effective enough to be used in the way depicted in the film, 3D designers today can certainly produce a much more realistic-looking shark.
Bonus round: tech inspired by Back to the Future Part 2
Back to the Future fans may not have received their flying car, self-adjusting and self-drying clothing, hoverboards, or Mr. Fusion, but the film has inspired companies to build some of the tech we dreamed of in the late 80s.
Earlier in 2015, Nike promised shoes with “power laces” as depicted in the film. It showed off designs which looked like those in the movie, and dubbed it MAG.
Hoverboards are another film fantasy companies have tried to make a reality, with Lexus and the Kickstarter-funded Arx Pax building their own versions.
However, real hoverboards can’t just levitate off any surface and will need special skate parks to work.