Apple's Watch Ultra, with its 2000-nit digital display and GPS capabilities, is a far cry from its Revolutionary War-era self-winding forebears. What sorts of wondrous body-mounted technologies might we see another hundred years hence? In his new book, The Skeptic's Guide to the Future, Dr. Steven Novella (with assists from his brothers, Bob and Jay Novella) examines the history of wearables and the technologies that enable them to extrapolate where further advances in flexible circuitry, wireless connectivity and thermoelectric power generation might lead. Excerpted from the book The Skeptics' Guide to the Future: What Yesterday's Science and Science Fiction Tell Us About the World of Tomorrow by Dr. Steven Novella, with Bob Novella and Jay Novella. As the name implies, wearable technology is simply technology designed to be worn, so it will advance as technology in general advances.

As children growing up in the 1970s and 1980s, the brothers were obsessed with science fiction and futurism. "Our younger selves definitely imagined that by now it would be like 2001: A Space Odyssey," Novella says in Episode 526 of the Geek's Guide to the Galaxy podcast. "There's going to be permanent space stations in space, there's going to be an infrastructure between here and the moon, a lunar base. All that stuff, we took it for granted." The next few decades showed that futurism is harder than it looks.