I've never been one to get real picky with the plausibility of my science fiction. Fiction is fictional. Whether or not you believe it's really possible to build a light saber, one thing you ought to know for sure is that Darth Vader isn't real. He's made up. So why shouldn't his light saber and his hyperspace-travelling fleet of starships be completely made up as well? Why would they have to be plausible? I mean we don't go around questioning whether Hades' helm of invisibility from the Greek myths is "plausible." My philosophy on this can be best summed up by the immortal words of the original Mystery Science Theater 3000 theme song (the one featuring Joel, not that other guy):
If you're wondering how he eats or sleeps
or other science facts
just say to yourself, "It's a TV show,
I should really just relax."
And yet . . . it wouldn't be science fiction without that pesky word "science" in it. Much science fiction does make predictions about the future, especially future technology. And it's both enlightening and fun to question how possible or plausible those predictions might be. Certainly many authors take this aspect of their fiction quite seriously. H.G. Wells predicted dozens of inventions that later became part of our reality, among them the tank and the credit card. Jules Verne's obscure 19th century novel Paris in the Twentieth Century predicts gas-powered automobiles, high-speed trains and the Internet. Many of his critics claimed his vision was ridiculous, impossible.
So, what could our contemporary writers and producers tell us about the future of technology and science? Could there really be a Death Star? Light sabres? Ray guns? An invisibility cloak? Warp drive? Time travel? Could we one day command "Beam me up?" and get teleported across space? Is any of this possible?
The answer to all of these questions, and most of the other ones that Michio Kaku asks in Physics of the Impossible, is "Yes." (It would be a pretty crappy book if it were "No.") None of these acheivements will be easy, and while scientists are close to realizing some of them, the complexities involved in acheiving others may prove to be insurmountable. But what is important to Kaku is that none of them violates the laws of physics as we currently understand them.
Kaku divides the "impossibilities" he discusses into three classes. Class I impossibilities are those which he believes will be achieved sometime in the next 10-300 years. Class II impossibilities are those which may not be acheivable for many thousands of years (if we continue on the technological path we are currently on). And Class III impossibilities are those which are really truly impossible, unless we discover that physics doesn't work the way physicists currently think it does.
It's surprising at times which common science fiction ideas fall into each category. Teleportation, for instance, would seem to be an extremely long way off, and the type that's practiced on Star Trek--transporting large, complex and even living objects like humans--may very well be. But simpler teleportation, the teleportation of individual particles and atoms has already been acheived. And Kaku predicts that the teleportation of molecules will likely be demonstrated sometime in the next several years. Who knows where that could lead?
On the other hand, I would think that handheld ray guns would be nearly acheivable now (we have laser pointers after all). But Kaku predicts that they are still a terribly far away. Today, we could build lasers powerful enough to blast holes in concrete, but the power required to generate that kind of beam equates to a nuclear power plant's worth of energy. Kaku believes that we won't soon see a palm-sized nuclear power plant.
Kaku is a prominent physicist and on issues dealing largely with physics he is at his clearest and most comprehensive. For example, he challenges one of the primary dictates of special relativity: that nothing can travel faster than the speed of light in a vacuum. He points out that in quantum theory information travels faster than light all the time. (Unfortunately it seems that only useless information has this capability.) But even for more substantial things like people and spaceships, faster-than-light travel may be possible by creating wormholes in space-time. However, the potential traveller would need to gather or produce the energy of a star in order to even crack a wormhole open.
Likewise, on invisibility Kaku has quite a bit of fascinating information to share. He describes experiments in which small objects have already been made invisible to microwave radiation, by bending the radiation around the object. Kaku thinks scientists will be able to make an object invisible to visible light of at least one color within a decade, but it will be quite some time before anyone will be able to offer Harry Potter a replacement for his prized cloak.
In areas further from his specialty, however, Kaku is sketchier. I was particularly disappointed with the section on telepathy. Kaku clearly relates both the charlatan-infested history of telepathy and the more scientific developments in "mind reading" through monitoring brain activity using MRI machines (these, unlike ray guns, may soon be hand held) and creating a vocabularly to translate thoughts into words. All this is fascinating and well-researched but Kaku movew on to something else before considering the possibility of using brain implants to either broadcast thoughts or receive broadcasts of others thoughts. (Anyone who reads widely in the genre knows such implants are staples of science fiction.)
On the subject of alien visitors Kaku is similarly uninspiring, predicting that an intelligent alien species would probably be much like us, with eyes on the front of its head to provide stereoscopic vision and evolving from a species with predatory tendencies, rather than from herbivores. This all makes sense, but relies on the rather large assumption that life (and more importantly, intelligence) on other planets would evolve similarly to life on Earth. Why for instance, would an alien even have a head or eyes, if something else proved more adpative to its particular other-worldly environment? Would alien species even be so easily divided into plants and animals? Would the classification of herbivores and carnivores even make sense on another planet? Kaku doesn't go there.
Kaku situates each impossibility firmly in both the history of science and contemporary culture, citing past scientific research and discussion as well as myths, legends, psuedo-science, films, novels and television. While his knowledge is broad and ranges from Greek mythology to the Back to the Future series of movies, he does rely prehaps a bit too heavily on Star Trek references. Even more discouraging is that he's one of those Kirk/Spock guys who apparently never moved on from the original series.
Kaku's real agenda though, hidden in plain sight, isn't to talk about what's possible or impossible in science fiction; it's to introduce the reader to both the ideas and people behind the work being done in contemporary physics. And as such he provides a pretty good primer, introducing the reader to the priniciples of special and general relativity, quantum mechanics, the search for a Theory of Everything and strange new worlds of superstring and M theory. Wherever this hidden agenda emerges, Kaku veers off in pursuit of it, often leaving behind the impossible techonology he is discussing. This habit is entirely forgiveable, as he always wanders only into more fascinating territory, following the word "impossible" wherever it may lead.
For an interesting interview with the author see: http://www.hanselman.com/blog/HanselminutesPodcast101DrMichioKakuOnThePhysicsOfTheImpossible.aspx
For a video featuring the author discussing time travel: