As a science fiction writer, I find examining science’s current stance on futuristic ideas, such as time travel, warp drives, and other possible technological advances to be fascinating and insightful. This book by Allen Everett and Thomas Roman takes the reader on an incredibly thorough examination of the science of time travel, the paradoxes of time travel, wormholes, and warp drives.
The book starts with the basics: special and general relativity, and it spends quite four chapters examining these topics because it’s important for understanding the following chapters, which will dig into the questions of time travel, wormholes, warp drives, and paradoxes in depth. They do use some math — most of it placed in appendices for readers who enjoy examining mathematical proofs — but it’s there to illustrate and enhance their points, and they do an excellent job of explaining each of the terms in the mathematical formulas. Perhaps the most important point to take away from these preliminary discussions is the idea of the light cone, which is used extensively in the following arguments concerning time travel and warp drives. It’s a method of graphing reference frames and the worldline of the object you’re studying (such as the a spacecraft). It will prove exceptionally helpful in understanding the discussions about time travel and wormholes.
The diagrams provided in each of the chapters are clear and generally easy to understand with a close reading of the text. The most difficult chapters will probably be the last three before the Epilogue, which explore the quantum mechanics side of the discussion. It’s important to note that the book shows, quite well in fact, that for general relativity, there isn’t much restricting the possibility of time travel and warp drives. However, once you add quantum mechanics to the mix, the restrictions prove numerous. Another important point is that negative energy is necessary for the creation of a warp drive and/or time machine, but how to actually find a feasible way to harness negative energy? The book seeks to answer that question in the latter chapters and does its best to examine all the possible routes that current scientific research has examined, and possible ways it could be built and if it can be achievable at all.
Although the final conclusions in the book are not promising as to whether warp drives, wormholes, and time traveling machines can ever be constructed, it’s important to note — as the authors do — that these conclusions are based upon the current scientific evidence and theories. It is quite possible that other theories will arise that may showcase a way to circumvent the current restrictions the theory of quantum mechanics puts on these possibilities. For example, there is not yet a solid theory for quantum gravity, and it is possible that such a theory could shed more light on this topic and possibly offer a way to circumvent the current restrictions imposed by our current understanding of the universe. It’s also important to note that any new theory has to take into account experimental evidence, necessary to prove its validity, and that the current theories of quantum mechanics, general relativity, and special relativity as well as Newtonian classical physics all still are valid in their respective regions (each govern a different subset of the universe). As an example of what I mean: general relativity describes gravity and how objects react in gravity fields more accurately than Newtonian physics, and special relativity describes how objects act and how time acts at speeds close to the speed of light, but at speeds much, much less than light, Newtonian physics works just as well and for that region (of speeds much, much slower than light), special relativity equations can simplify into Newtonian equations. Each govern a slightly different region of the scales of spacetime, and so would still be valid in those regions even if we develop a more complete theory for all of physics.
That is probably the hardest part about speculation involving future technologies. We have current theories that work extremely well at predicting real life phenomenon in their current realms, but it’s not a complete picture. We still have not found a way to explain gravity on the quantum scale, and there is still some fascinating finds in our universe that have no theoretical explanation as of yet. For example, we have experimental evidence that there is something causing the accelerated expansion of the universe which has been experimentally verified numerous times, but we have no idea what it is, and hence gave it the name “dark energy” for the lack of any better descriptor. It’s possible that once we learn what exactly dark energy is, we may be able to find a way to utilize it to find a way to create a warp drive, wormhole, or other superliminial travel. There is still a lot more for us to discover and understand before we can reach a definitive conclusion as to whether these exotic and science fiction styles of travel are even possible. The book, in turn, does a great job of exploring some of these more speculating ideas as well as ideas grounded in the already known theories of physics.
Overall, the book does a wonderful job of explaining and showing the physics of these science fiction concepts, and how plausible they are with our current knowledge of the universe. It’s well worth the read for any science fiction fan and writer, and I highly, highly recommend it to those interested in such topics. The science is sound and thorough and well explained for a lay person. You don’t need a physics degree to understand it, nor need to have taken physics before in any high school or college class. Some may find the book a bit difficult to understand if your math skills are poor, but the conceptual discussion of the topics is well-rounded and thorough, so it’s really just the difficulty in wrapping one’s mind around some of the bizarre aspects of nature.