This book covers most of the basics of Physics theory. Relativity, quantum physics and then string theory. As the authors specialty is string theory about 50% of the book is dedicated to this subject. I admit that there were some concepts that I had a hard time understanding as there is no easy way to make the subject relateable to everyday experiences. Almost all of string theory is math driven and all the discoveries are just the relationships and solutions to incredibly complex math formulas. Even then, many of the ideas come down to interpreting results that are just approximations of the final solutions. Even our most powerful computers are unable to solve these equations completely. For me that's where string theory loses some of it's credibility. With such complex math it's manipulating the numbers until you get the answer you want.

As this book was written in 1999 it's inevitably a bit out of date. This was before the existence of the LHC at CERN and some of the experiments in the last decade may have shed more light and indirectly confirmed some string theory concepts. In particular the existence of the superheavy Higgs boson would be evidence of symmetry predicted by string theory.

A decent book but only for people really interested in the subject. It's hard going at times so be prepared to read some sections more than once.

I read (well, listened to) this book twice and I still don't understand string theory. What gives?!

Ok, in all seriousness, this is an enjoyable book to read, but you're not going to come out of it understanding much about string theory. It's just too complicated, which is one of its serious flaws. I have really liked all of Brian Greene's books, but the more I read the less inclined I am to believe in string theory. Maybe if I had read this before Not Even Wrong: The Failure of String Theory and the Search for Unity in Physical Law by Peter Holt or The Trouble with Physics: The Rise of String Theory, the Fall of a Science and What Comes Next by Lee Smolin, but those two books really do a good job of refuting this one.

Brian Greene had put all his efforts to write this book as much simple as he can and he succeeded to do so.The way he describes the technical terms in this book with such a great simplicity is really very appreciating.Several examples are also taken into account to profoundly explain some of the subtle concepts in this book.It takes us back to Relativity and then to Quantum Mechanics before proceeding to String Theory.It is hard to tell whether I believe in String Theory or not. There are ample evidences that proves this theory to be correct.but this theory is still in its premature form and due to its complexity, its hard to prove it experimentally.I learn many new things in this book and even made a notebook to prepare notes regarding the theory.I believe that time is not far enough when our physicist can finally prove whether The String Theory is really an Ultimate Theory of Universe or not.

Dr. Greene, unfortunately, imagines himself to be a much better writer and expositor than he actually is. Far too much time is wasted on silly examples to explain his points; so much that the analogies not only break down but become absurd. These concepts are not very difficult. Dr. Greene fairly well crosses the line into talking down instead of explaining things.

However, this book has some rather well laid out charts and diagrams and other visual aids. Importantly these come with a gracious degree of explanation. It almost makes up for the long-windedness.

The universe & Dr. Greene's charts are elegant; Dr. Greene's writing is not.

Disclaimer: I am not a physicist. I have a MSc in environmental sciences which is 20 years out of date.

Brian Greene describes elegantly special and general relativity as well as important aspects of quantum physics in the first third of his book. It is worth its money for these first few chapters.

Unfortunately, his writing about the five string theories and their meta-theory called M-theory is almost unreadable and loses its focus very rapidly. Brian Greene seems to be so intimately and unconditionally in love with string theories that there remains no hope for an objective assessment of their ability to stand up as a collection of scientific theories. As far as I understand, none of the string theories makes falsifiable predictions or suggests doable experiments compatible with today's technology.

Greene admits by his own writing that string theories have not delivered what they have been invented for, in spite of intense research for more than 15 years (the book was written in the 90s'):
- the seemingly arbitrary values of the standard model masses and force charges have not been explained
- the number of possible implementations of the theories is so big that any specific real world observation can be explained by at least some of the myriad of possible solutions these thought models allow.

In spite of these facts, the reader is invited to believe that string theories are the only way forward for physics in the 21st century. The main arguments I have retained are as follows: string theories are beautifully elegant. Hence, they must be true in some important and overarching way. And if the most clever mathematicians and physicists believe this, the not so gifted have no choice than to support their view.

Well, I disagree.

This is as clear as I think a book like this could be. That said, I got through maybe a third of it; I gave it my best college try.

I don't know how well these theories hold up--like did any recent discovery at CERN refute anything from the book? Psh beats me.

My takeaway is one the author likely didn't intend to leave with his readers: much as space and time are important within the larger universe, humans categorize their worlds within the confines of space and time...meaning, where and when. Example: a work assignment comes through my inbox referencing a document I'll need to refer to. Where precisely is the document? When must I complete this? Instructions like these are so often left out.

I'm getting married in seven days. Where must I be to marry and when must I be there? Thankfully I know that one.

Where will I be when the James Webb Space Telescope finds signs of life on a distant planet, and when will that be? Knowledge like this is unknowable, and having no ability to know where and when some things will occur or have occurred is maybe why humans are one distraught and dangerous being.

3.5 Stars out of 5 stars

For a great discussion about the history of String Theory and the current state of the field check out this video from the 2019 World Science Festival.

I’m a fan of String Theory, but I came to this book more than two decades after it is written. Because of that, one thing bugged me throughout this book. How much has actually changed in one of the most fringe areas of physics? The book starts out with a recap of basic physics (i.e. quantum vs relativity). The problem is I am familiar with all the ideas explored in this book. I've read all but  Brian Greene's newest book, Until the End of Time, before this, and that, coupled with all the other material I've consumed, made the recap feel more distracting than anything. While I am a big proponent of constantly reconsuming things, especially ideas outside your realm of expertise, this book is necessarily less well developed as everything that has come since. The sign of a good scientist and author is to learn how to communicate better with time. It isn't particularly bad, but it was easy for me to zone out.

Then we get into string theory. Even here, most of the major ideas I was familiar with. I was hoping to leave this book with a better appreciation of the finer details of the theory, but I found it was most effective at communicating the broad ideas. Then the finer details were really hard to get through and failed to make a lasting impression. I feel like this book would have been a much more positive experience if I had read it earlier in life because it would have been an excellent introduction to the field and precursor to  Brian Greene's own follow up book,  The Fabric of the Cosmos. I do think it is time I return to  Brian Greene's other novel,  The Hidden Reality, which was the first book of his I ever read; that was with very little background.

If you’re interested in learning more about this theory, I highly recommend watching the Loose Ends video I posted at the top of this post. For a brief review, string theory is a theory that the smallest things of nature are these tiny vibrating strings of energy, where the vibration of each string is what defines the type of particle it is (e.g. quarks, neutrinos, electrons, etc.). These strings can perfectly reproduce our current model of particle physics, but it comes at a cost. 1) it requires the existence of many more dimensions, and 2) it suggest all of our particles have a twin symmetric particle. Why don’t we see these other dimensions? They are small and folded in onto one another. If you have a problem with the idea of tiny dimensions, I found it helpful to remember our current 3D space used to me much much more constricted before they began to expand. They don’t say this explicitly, but my mind figures, perhaps the process of expansion only applied to the 3 dimensions we see. I wonder what Greene would say to that logic? Take it with a grain of salt. This theory is fundamentally mathematical, and we have yet to show it experimentally.


(An example visualization of how smaller dimensions may be curled up on themselves out of view from us.)

The physic's true success is in connecting Quantum Mechanics with General Relativity because the math of the two fundamentally disagree with one another (i.e. I think in particular situations like a black whole with large gravity in and very small spaces). The true beauty, as Greene suggests, is not that it necessarily needs to be a description of reality; it is that String Theory proves the two laws n  are reconcilablen. It may be that this is not necessarily the true description of our reality. Nevertheless, it shows that a connection can exist. Now is it worth believing? That’s where things get really complicated.


(A diagram from the Loose Ends video above. The math connects the two fundamental, conflicting, sides of physics. That is, general relativity and Quantum Mechanics. However, above the third row there is no experimental data confirming this.)

The theory itself, I love despite my issues with the book. It’s a fascinating concept with compelling motivations. There are many Goodreads reviewers who seem to approach string theory with a level of cynicism. Some who dismiss it because they struggle to understand it. Others who dismiss it because it breeches into the currently unknowable. However, there is a strong argument to be made about using the information we have available to best describe the nature of the universe. As we strive to improve these descriptions we can push ourselves forward in hopes that it can be improved further. That may or may not happen. The problem I have with opponents to this theory is that they seem comfortable dismissing a theory that may very well be the nature of reality simply because the physics is so difficult to constrain. Such a mindset will merely ensure that what is currently unknowable remains unknowable.

The Large Hadron Collider was hoped to show indirect evidence for String Theory. The energies and technology needed to observe strings are far outside our wheelhouse, but string theorists had hoped the energy at the LHC would be enough to produce the larger by products of the theory, the symmetric particles that we have yet to observe. This did not happen. However, string theorist had already noted it may be more difficult to reach the energies needed than those achieved with the LHC. The simplest explanation as to why string theorists were unable to simply make a fixed prediction of what energies are needed to produce the predicted particles is that there are a large array of possible configurations of string theory. At one time, it was small enough to brute force the process, but we now recognize far too many solutions exist to truly test them. It is, in that way, currently unfalsifiable. Nevertheless, we are brought back to the point I made before: it is still the best way we have to describe reality.

If you are interested in this topic, you could read this book. It’s worth noting most people I see enjoyed this book much more than myself. However, there is an ample supply of more recent resources you can pursue too, or you could read the book and follow up with the most recent discussions available. Here are some of the resources I sought out. The first video I posted at the top of the blog was a fantastic discussion about the history and current state of ST hosted by  Brian Greene at the World Science Festival in 2019.

Sean Carroll did a discussion with Greene, where  Brian Greene put his bets at String Theory being a real description of reality at 50/50 shot (obviously an off the cuff comment). This was a great casual discussion. Another episode of  Sean Carroll's podcast had a more formal, string theory specific, discussion as well. Greene also discussed String Theory, black wholes and other topics with Leonard Susskind (one of the founders of String Theory) in late 2020 on the WSF YouTube channel.


Of these, if you are coming in blind, I would recommend you check out the WSF YouTube discussion first. If you’re someone more familiar with it, you may find these other resources interesting too. Lastly, there is  Brian Greene's adaption of this book on PBS which I have not watched, but I will soon.

I have copious notes where I disagreed with the author. While I understand he is probably the leading public proponent of string theory, I felt that his oversimplification lead to some really problematic axioms and it was upon these shaky foundations that he tried to map out string theory. I'm afraid I think that the Theory of Everything (or Grand Unified Theory) will be articulated in a much more coherent way if one sets aside the supposition that is string theory. This may also be an oversimplification, but the theory strikes me as designed to be mathematically expedient, so while most theories are tested to find out if the equations work, this theory has the equations designed to work in the framework before it is even tested. Not my definition of true scientific work.

It was fascinating to think of how much research has progressed, and probably just as much since this book was published. There were times in the explanation where I was lost, but the idea mentioned come back later to give a more clear explanation after.

You know when something is too incredible, too mind blowing and you’re at a loss for words? Brian Greene has the words. One of the world's leading string theorists, he eloquently shines a light on Superstrings, Hidden Dimensions, and the Quest for the Ultimate Theory. Beautifully written, even if you don’t understand everything that’s being discussed (hello, it’s me). Interesting for sure, even if questionable on the amount of hard science as much is speculation/theoretical.

This is the first book by Brian Greene that I read. The first chapters were amazing and engaging, however later chapters about string theory were very hard for me to understand and I actually didn't finish the whole book, because I could not understand what I was reading.

The author uses many metaphors to make his ideas simpler. He starts with a very easy to understand telling of history of scientific discoveries reaching to the theory of general relativity and quantum physics and the unification efforts. He maintains that string theory could be the one that finally unifies them and explain the number of particles we have and their specific masses and properties.

My understanding of special and general relativity theories was greatly enhanced after reading it here as well as that of quantum physics. However when he got the details of string theory I was completely lost and gave up on it.

Well I have finally did it, I've finished this book!

Honestly, it felt like too much work to read it, started while I was in my 2nd year Bsc Physics, finished in my 3rd.
The more I learned about quantum physics the less m-theory and string theory sounded like complete nonsense. In saying that, theory has a lot of issues and there is a reason it remains as an outsider in the mainstream physics.
Regarding the book itself, the writing is competent and the author really tries to present the subject matter in the most accessible way possible. One outstanding feature is how the references/notes are handled: a lot of either more in depth, mathematical discussions or more detailed explanations for clarity are done through that and it is one of the best use of the notes I have seen.

Not much else to say really, if you're interested in string and m-theory give this a read, you'd be surprised how much there is to it.