Physics of the Impossible
When evaluating a collection of potential future technologies, of course it will be much more likely for us to be able to develop some technologies than others. In Physics of the Impossible, Michio Kaku categorizes the different currently impossible tech that he discusses into three main classifications. Class I impossibilities are those technologies that do not violate any known physical laws. This category includes most of the tech that's explored in the book: force fields, invisibility, phasers and death stars, teleportation, telepathy, psychokinesis, robots, extraterrestrials, starships, and antimatter (not that it exists, because we know it does, but that we can harness its use in large quantities). These technologies are not necessarily in order of most to least possible. For example, it is likely that robots are more possible than teleportation, for reasonable definitions of each.
Class II impossibilities are those technologies that lie at the edge of the physics we know of, and so could turn out to be possible if the physics at the edge of our current knowledge turns out to work in a certain way. There are just three items in this category: faster than light travel, time travel, and parallel universes. They are all closely related to what happens around black holes and whether or not wormholes actually exist or could be constructed.
Class III impossibilities are those technologies that violate known laws of physics, so to be at all possible we would have to discover ways in which known physics is wrong. The two impossibilities in this category are perpetual motion machines and precognition. For these technologies to be possible, we would need to find conditions under which the conservation of energy or the laws of quantum mechanics did not hold, and thus, they are extremely unlikely to ever be possible.
I found Kaku's discussions of these wide-ranging technologies to be incredibly fascinating. He used each one to explain a different aspect of physics and cutting edge research. From special relativity to Schroedinger's Cat, it's all covered within the context of how these different fantastical technologies could be (and couldn't be) achieved. It was great fun to see what is considered possible within the boundaries of known physics, and Kaku was mostly careful to guard the possibilities with caveats where necessary. For example, when discussing the possibility of force fields:
In conclusion, force fields as commonly described in science fiction do not fit the description of the four forces of the universe. Yet it may be possible to simulate many of the properties of force fields by using a multilayered shield, consisting of plasma windows, laser curtains, carbon nanotubes, and photochromatics. But developing such a shield could be many decades, or even a century, away. And if room-temperature superconductors can be found, one might be able to use powerful magnetic fields to levitate cars and trains and soar in the air, as in science fiction movies. Given these considerations, I would classify force fields as a Class I impossibility—that is, something that is impossible by today’s technology, but possible, in modified form, within a century or so.This is not to say that such an implementation would ever be practical, but at least physics doesn't invalidate the concept out of hand. The force field chapter was one of my favorites, and it was intriguing to see what technologies already exist that reproduce some limited functionality of a science fiction type force field.
For some of these future technologies, Kaku observed that they are synthetic forms of natural processes, like a replicator, for instance:
As astounding as a replicator might be, nature has already created one. The “proof of principle” already exists. Nature can take raw materials, such as meat and vegetables, and fabricate a human being in nine months. The miracle of life is nothing but a large nanofactory capable, at the atomic level, of converting one form of matter (e.g., food) into living tissue (a baby). In order to create a nanofactory, one needs three ingredients: building materials, tools that can cut and join these materials, and a blueprint to guide the use of the tools and materials.The ingredients that he's talking about are proteins, amino acids, RNA, and DNA, but he did leave out one other necessary ingredient—energy. Maybe that's a given since the energy is extracted from the raw materials as they are simultaneously burned as fuel and used as building blocks. It's interesting to think that DNA replication is the process that we would want to model to make a replicator. We would have to figure out how to arrange atoms and molecules to make the food or other items we wanted to in a replicator in a generalized way, and we would have to figure out how to speed up the process so that it wouldn't take forever to make it. It takes 9 months to make a baby and 20+ years to make a fully matured human. Of course, the things a replicator makes are not nearly as complex, but it would still not be as useful if it took days or weeks to make dinner as if it took seconds, like in Star Trek. Plus, it'd be great if it didn't all taste like chicken.
Later on multiple previously discussed technologies are combined to explore more ideas, like interstellar travel and the colonization of the galaxy:
In principle, such self-replicating nanobot spaceships might be able to explore the entire galaxy, not just the nearby stars. Eventually there could be a sphere of trillions of these robots, multiplying exponentially as it grows in size, expanding at nearly the speed of light. The nanobots inside this expanding sphere could colonize the entire galaxy within a few hundred thousand years.He's talking about tiny spaceships made up of nanobots that can build more of themselves with raw materials from new planets that they travel to at near light speed. If such a thing were really possible, it immediately brings up multiple deep questions. If other advanced civilizations exist in the galaxy and near-light-speed self-replicating nanobot spaceships can be built, then why haven't we already seen them? Does that mean we are at the forefront of advanced civilizations, give or take a few hundred thousand years of travel time? Does it mean that technologically advanced civilizations, or even intelligent lifeforms, are so rare that we are the only one in the galaxy? Does it mean that near light speed travel or interstellar spaceships are actually impossible? Does it mean that advanced civilizations don't find it useful to explore the galaxy? These reasons or a host of others could explain why we have not yet seen evidence of other intelligent lifeforms, but the fact remains, we have not been visited by extraterrestrials. The real reason why would have huge implications for the future of space travel and our civilization.
Every once in a while, Kaku got a little careless with phrasing, like in this aside when discussing dark energy:
(This dark energy is so colossal that it is pushing the galaxies away from each other, and may eventually rip the universe apart in a Big Freeze.)The Big Freeze is an entirely different scenario than The Big Rip. In The Big Freeze, the universe continues to expand forever, eventually star formation stops, galaxies disassociate, black holes evaporate, and there's nothing left but the rare dwarf star remnant or rogue planet floating in the vast emptiness of space. The Big Rip happens if dark energy actually increases over time (which it doesn't appear to be doing) until galaxies, solar systems, planets, and on down to all matter is pulled apart by the force of dark energy overcoming first gravity, then electromagnetism, and finally the strong nuclear force on the smallest scales.
These little missteps didn't affect the book much, though. Kaku is an excellent, engaging writer. Every time I'd reach the end of a chapter, I'd want to continue on to the next one to see what he'd come up with for the next fantastical technology. Overall, it was exceptionally entertaining, and I ended up learning a lot about what's already possible, what may be possible in the future, and what's simply science fiction that's fun to watch in the movies.
The Physics of Star Trek
In this book, Lawrence M. Krauss goes on a tour of physics taught through the lens of Star Trek, pointing out where the shows tripped up and where they amazingly got thing right along the way. The Star Trek writers seemed almost prescient in their terminology and descriptions of certain phenomena, and it was fascinating to see how the shows and movies stacked up to real-life physics.
Krauss spent a lot of time discussing warp speed and interstellar travel, and of all the impossible technologies in Star Trek, this one seemed like one of the most improbable, other than teleportation. The immense distances involved in space travel are simply astonishing, and it's hard to comprehend how incredibly far away even the closest stars are:
It would take rockets, at their present rate of speed, more than 10,000 years to travel from here to Alpha Centauri. At warp 9, which is about 1500 times the speed of light, it would take about 6 hours to traverse 1 light-year.So even at warp 9 it would take more than a day to reach even the closest star, and the galaxy is 100,000 light years across! This is just considering the time, too. When we take into account the energy required for interstellar travel, it's even more astounding:
In the first place, we have clearly seen how daunting interstellar space travel would be. Energy expenditures beyond our current wildest dreams would be needed—warp drive or no warp drive. Recall that to power a rocket by propulsion using matter-antimatter engines at something like 3/4 the speed of light for a 10-year round-trip voyage to just the nearest star would require an energy release that could fulfill the entire current power needs in the United States for more than 100,000 years! This is dwarfed by the power that would be required to actually warp space. Moreover, to have a fair chance of finding life, one would probably want to be able to sample at least several thousand stars. I’m afraid that even at the speed of light this couldn’t be done anytime in the next millennium.Star Trek needs those self-replicating nanobot spaceships badly. It's incredible to think of how far we are away from actual interstellar travel, if it's even possible at all. The numbers that get thrown around for feasible spaceships are just ludicrous. Reading this stuff gives me a much greater appreciation for how magical the Star Trek technology actually is as represented in the shows.
The same kind of astonishment comes into play with the other major impossible technology of Star Trek, teleportation:
building a transporter would require us to heat up matter to a temperature a million times the temperature at the center of the Sun, expend more energy in a single machine than all of humanity presently uses, build telescopes larger than the size of the Earth, improve present computers by a factor of 1000 billion billion, and avoid the laws of quantum mechanics.Man, if it wasn't for that last one, we might just be able to do it, right? Right!? Of all the technologies in Star Trek, the teleporter is probably the most inspiring. To be able to transport yourself from one place to another instantly would be so incredibly awesome. It is also so incredibly never going to happen. But at least we can still dream. And it's fun to watch Captain Kirk get beamed out of daunting situations against impossible odds.
Every once in a while Krauss muddled up his explanations as well. For instance, when he was describing the effects of dark energy (it's always dark energy, isn't it?), he said, "Objects on opposite sides of the observable universe are flying apart at almost the speed of light." They're actually flying apart much faster than the speed of light. How can this be possible, when nothing can travel faster than the speed of light (unless you've got a warp engine, of course)? It's because it's not the galaxies themselves that are traveling at this speed, but all of the space between them is actually expanding at a constant rate that adds up over distance. There is so much space between galaxies on opposite ends of the observable universe, that when the expansion rate is accumulated over that vast distance, it's much greater than the speed of light. Space itself is expanding everywhere, so galaxies that aren't bound together by gravity are spreading apart as the space expands, not moving apart through space.
Like with Physics of the Impossible, these minor inaccuracies didn't take away from the book much. It was another engrossing, fascinating read. If you're at all into Star Trek and want to learn more about how fantastic the technologies are that it showcases, then this is an excellent book to feed your trekkie appetite. Even if you're not a huge fan, but love physics, this is an exceptionally enjoyable book.
Most of the technologies discussed in Physics of the Impossible and The Physics of Star Trek are simply not possible today, and may never be possible as they are portrayed in Star Trek and other SciFi movies. That doesn't mean we can't enjoy the places our imagination takes us when we watch them, and it's incredibly fun to think about whether or not warp speed, death stars, teleportation, or light sabers are even physically possible. We can learn a lot about physics from asking why these technologies are or aren't possible, and Kaku and Krauss both do a great job exploring that question to teach us what physics currently has to say on the subject. They may have quite a bit of overlap, but the repetition is not at all tedious. If you're curious, either book is a great read. Heck, why not read them both?