The Elegant Universe

Unstoppable reader Jason Bennett has penned another review, this time of Brian Greene's The Elegant Universe -- proof that it's good to venture beyond the O'Reilly section of the store, at least the few feet to the Current Science area.

The Elegant Universe author Brian Greene pages 448 publisher Norton rating 9/10 reviewer Jason Bennett ISBN 0-965-088806 summary An excellent, down-to-earth account of the development of string theory and the search for The Theory of Everything.

Background

Greetings, all. This book is yet another departure from my standard software theme, but a fascinating one nonetheless. Ever since the discovery of relativity and quantum mechanics, the everyday world and the world as described by science have diverged. We have no frame of reference for time running at a different rate, nor for particles jumping through solid objects. Yet it is these very discoveries which have driven physics (and technology) for the past fifty years. Even worse, scientists have been unable to reconcile these difficult-to- understand theories with one another. Today, though, there are solutions in sight. String theory promises to revolutionize science once again by uniting the theory of the big (relativity) with the theory of the small (quantum mechanics), and now that they understand these theories better, scientists can explain to the rest of us how our world truly works. Michio Kaku did an excellent job with his Hyperspace five years ago, and now Brian Greene gives us a different and updated perspective. Although this book is not written for everyone, it is directed at anyone with a decent science background (high school physics), and a desire to learn more about how our reality works.

The Scenario

As the saying goes, let's start at the beginning. Science has recently (where recently = 100 years, recent in historical terms) faced down three major conflicts in its world view. The first, the conflict of Newton's theory of motion versus Maxwell's law of electromagnetism over whether a light wave can be outrun, was resolved by special relativity (Newton lost). The second conflict, and one initiated by the discovery of special relativity, was whether gravity can be transmitted instantaneously across distances. (Special relativity, of course, states that nothing can be transmitted instantaneously). From this conflict was born general relativity, the theory of curved space, and Newton lost again (although, to be fair to Newton, he was correct as much as he could have been). The third conflict, caused by the implications of general relativity (anyone see a pattern?), was and is between general relativity and quantum mechanics. Simply put, the theory that describes the big and the theory that describes the small do not make sense together. Therefore, either one is correct, or the atoms that make you up behave differently than the planet upon which you stand. The answer to this conflict may very well be string theory.

After a quick introduction to these conflicts, and the place of string theory in the modern framework of physics, Greene takes us on a looping yet fascinating tour through special and general relativity, quantum mechanics, and the details of the conflict between them. This foundation for his description of string theory is quite helpful in bringing the book down to the level that most people can understand (especially liberal arts grads :-). In the process, Greene shows how the weirdness and unpredictability of quantum mechanics is simply unreconcilable with relativity, given our current formulation of both theories.

Of course, such a state cannot continue forever. Enter string theory. String theory basically states that the universe is fundamentally made up of oscillating loops of "string", and it is those oscillations which determine the nature and makeup of the universe. String theory also postulates that the universe is composed of several rolled-up dimensions, influencing the vibrations of the strings, and thus the makeup of our universe.

Without going into detail (that's the author's job), string theory has gathered a lot of evidence and momentum in the past years, and what I have sketched is only a 5-minute sound bite. There's plenty more detail of both the theory and its implications in the later sections. Greene closes by explaining where physics and string theory are headed, and pronounces his hope that soon we will be able to hold in our hands a fundamental explanation of the universe (the Theory of Everything [TOE], the Holy Grail of physics).

What's Bad?

Not too much. I found some of the later chapters to drag somewhat, delving into mathematics that I neither wanted nor needed. The chapter on black holes, especially, held great promise, but tended to drag at times, on a subject that I consider horribly fascinating.

What's Good?

In a sentence, this book makes modern physics accessible. I dare say any Slashdot reader could readily read and enjoy the material, with only a little stretching here and there. It is important that we as a people know more about how our world works, and this book is a solid step in that direction. Just as Hyperspace was a bestseller, I hope TEU can acquaint more people with these fascinating and fundamental developments of science.

So What's In It For Me?

Very simply, a better understanding of how our world works, and little pain in getting there. There's something to be said for enjoying physics!

Purchase this at ThinkGeek.

Table of Contents

• Preface
• Part I: The Edge of Knowledge
  1. Tied Up with String
• Part II: The Dilemma of Space, Time, and the Quanta
  1. Space, Time, and the Eye of the Beholder
  2. Of Warps and Ripples
  3. Microscopic Weirdness
  4. The need for a New Theory: General Relativity vs. Quantum Mechanics
• Part III: The Cosmic Symphony
  1. Nothing but Music: The Essentials of Superstring Theory
  2. The "Super" in Superstrings
  3. More Dimensions Than Meet the Eye
  4. The Smoking Gun: Experimental Signatures
• Part IV: String Theory and the Fabic of Spacetime
  1. Quanutm Geometry
  2. Tearing the Fabic of Space
  3. Beyond Strings: In Search of M-Theory
  4. Black Holes: A String/M-Theory Perspective
  5. Reflections on Cosmology
• Part V: Unification in the Twenty-First Century
  1. Prospects
• Notes
• Glossary of Scientific Terms
• References and Suggestions for Further Reading
• Index

Comments

Questionable FAQ.

[Christopher Thomas]

I sorted out my confusion on this FAQ web site.

I made it a few pages down the FAQ, and I'm afraid I have to say that it's one of the worst that I've ever seen. The author's argument seems to amount to "Well, you can describe the universe mathematically using four dimensions, but because I only see three of them this is purely bunk.".

At this point, I stopped reading.

In point of fact, if you want to see the effects of space being four-dimensional, you need only look at two reference that are moving quickly with respect to each other. The time and space directions measured by observers in each frame are different - this is the Lorentz transform (if I remember the term correctly). Space in one frame corresponds to a skewed space-and-time axis in another frame.

This has been verified experimentally by very careful measurements of atomic clocks moving at different speeds with respect to each other. A more dramatic illustration is measuring the decay times of unstable particles moving at different speeds. As they approach the speed of light, the lifetime as measured by the observer gets longer. This is called "time dilation", and is one of many effects caused by the "time" and "space" axes not being the same for observers moving with respect to each other.

You can find a very good FAQ on relativity here:
http://math.ucr.edu/home/baez /physics/relativity.html

This links to a FAQ on general physics, and many other FAQs that may be of interest.

Evidence?

[Kaa]

Is there any evidence for string theory? I was under the impression that this is somewhat-elegant-but-not-great-friends-with-Occams 's-razor theory which is a long, long way from getting any empirical support. Yet this review mentions accumulating evidence for the sting theory. Did I miss something? (and no, accumulating papers and preprints are not evidence).

Kaa

Re:Ugh. Now my brain hurts.

[Upsilon]

That's a long post, but I think I may be able to help ;-)

In a nutshell, Cole's Notes edition, how does gravity work, according to science's current understanding?

That's an incredibly vague question. General Relativity describes gravity as being a property of the curvature of spacetime. Wherever there is a mass, it will "bend" spacetime around it and cause the effects of gravity. This interpretation works very well and is consistent with all experimental data, but it still leaves out some questions. What is spacetime? How does gravity bend it? And so on.

Quantum mechanics takes a different approach. It says that all the fundamental forces (strong nuclear, weak nuclear, electromagnetic, and gravity) are caused by the exchange of particles, and this of course includes gravity. The strong nuclear force is caused by the exchange of gluons, the weak nuclear force is caused by the exchange of W+, W-, and Z bosons, the electromagnetic force is caused by the exchange of photons, and gravity is supposed to be caused by the exchange of gravitons. Notice I say "supposed", because there is currently no direct evidence whatsoever for the existence of the graviton. Just about every modern physicist believes it must exist simply because all the other forces are caused by the exchange of particles. If gravity somehow operated by a different method it would pretty much ruin any chance of coming up with a TOE

We are capable of creating and breaking nuclear bonds, both in (un)controlled fission and uncontrolled fusion. We're pretty capable of transmuting elements from one to another; U-238 into Am-241 for smoke detectors, etc., even if these transmuted elements are just by-products of other processes. Is it gravity or is it gluons that hold together the protons in a nucleus despite their repellant similar charges? (Especially fascinating in some isotopes of helium and lithium that lack neutrons.) Even if we don't know, we have some control over the makeup of an atom.

First of all, it is definately gluons, or rather the strong nuclear force which is caused by the exchange of gluons among so-called "colored" particles (That has nothing to do with what most people think of as "color". Don't worry about it for now.), which cause the nucleus of the atom to be held together. The effect of gravity is incredibly weak when compared to the electromagnetic force and it could not possibly hold a nucleus together. The electromagnetic force, on the other hand, is rather weak when compared to the strong nuclear force.

Anyway, that's besides the point. You're talking about our "control" over the fundamental forces. But what does it mean to "control" a force? You use nuclear fission as an example, but all we do there is take some radioactive material, stick it all together, and let nature run its course. Is that really "controlling" it? Can I say that I am "controlling" gravity when I ride a rollercoaster? Just something to think about...

I'm not sure what this means, either. Fission and fusion relate to changes to the makeup of the nucleus; the net number of protons in the nucleus will change the number of electrons required to achieve equilibrium and therefore will affect the chemical properties of the element. Is it possible that weak nuclear refers to chemical properties brought on by the number of electrons required for equilibrium and therefore determines which other elements will chemically react with this element? Or is weak nuclear referring to things like photon emissions as electrons drop shells?

First off, everything you talked about is dealing with the electromagnetic force. The weak nuclear force is a strange force. It's not really responsible for a "force" in the sense of what we normally think of as a force. What it is responsible for is various processes which occur in the nucleus of an atom. The classic example is beta decay. Before I begin I should note that I may have the neutron and the proton reversed, as I can never remember which is udd and which is uud. What happens in beta decay is that a down quark inside a neutron changes to a up quark, converting the neutron (which consists of an up quark and two down quarks, udd) into a proton (uud). In the process, an electron and an anti-electron neutrino are released. The weak force is what is responsible for this process. The quark actually changes by emitting a W- boson, which immediately decays into the electron and the anti-electron neutrino. This is not the only process which the weak nuclear force is responsible for, but it is the only one I can come up with off the top of my head.

The emissions of radiation I see as being caused by the stronger nuclear forces. As the nucleus gets larger (and gets seeded with neutrons in the right ratios), it becomes more unstable, more likely to break the ?gravity? or ?gluonic? bonds that attach the similarily-charged protons which indirectly control the chemical properties. Net effect: fission occurs, energy is released. Alpha particles are just positive helium ions, beta particles are just electrons (that get shot from the positive nucleus, go figure) and gamma rays are photons of energy released as an infinitesimally small quantity of matter in the nucleus is converted to energy. So, since nuclear radiation is occuring very much as a factor of the strong bonds that hold a nucleus together, is radiation really a part of the weaker nuclear bonds? I must be missing something; I fail to understand.

You're actually pretty close to the mark with the radiation thing. It so happens that as the nucleus of an atom becomes larger and larger the strong nuclear force has difficulty holding it together and the nucleus become unstable. I do not remember the exact reason why this is so, but I believe it has something to do with the short-range nature of the nuclear forces (unlike electromagnetism and gravity, which continue on theoretically forever growing closer and closer to zero as distance increases, the nuclear forces actually have a "range", which is why their effects are limited to the nucleus of an atom), however don't quote me on that. Alpha particles are basically just pieces of a nucleus that get spit out, they're not that interesting ;-) . I talked about beta decay when I discussed the weak force. I should note something about Gamma particles however. Basically, what happens with a Gamma particle is that a neutron or a proton in the nucleus of an atom becomes "excited", similar to how electrons circling the nucleus become "excited" all the time. However, the neutron of the proton are controlled primarily by the strong nuclear force, which is a great deal stronger than the electromagnetic force, and so it takes significantly more energy to exicte them than it takes to excite an electron. Generally, the excitement of a neutron or a proton is caused by some other nuclear interaction (Alpha or Beta decay, being hit by a free neutron, colliding with another nucleus [fusion]) because that is the only way to get enough energy to excite a proton or neutron. When the proton or neutron returns to its previous "energy level" (we don't normally think of protons and neutrons as having energy levels, but really they do) it releases a photon, only this photon has far more energy than any photon released in normal chemical processes.

I really don't understand what you are asking in the last part of your paragraph there. Radiation can be caused by the strong nuclear or weak nuclear forces, as discussed above. It all depends on the type of radiation really.

Anyway, I'd love to continue this discussion with gravity (which I know is what you were asking about in the first place), but I've spent too much time talking already and I think my boss will be upset if I don't actually do some work today. Oh well, I hope I've cleared some things up.

Black hole entropy proof

[spiralx]

Well, it's not really proof of superstring theory as such, but superstring theory has been used to proof Bernstein's (?) hypothosis that the surface area of a black hole is proportional to its entropy, which had resisted proof by other methods for 30 years. There's more about the proof in the book, which is well worth a read.

So no, nothing definite, but that's one of the goals of superstring theorists - to look for low-energy consequences of the theory that can be tested within the forseeable future. Until then, the theory is in an experimental limbo, but it does seem too good not to be true. But that is purely my opinion, and some quite famous physicists would disagree :)

I think a better book..

[Rombuu]

Covering the same subject matter, but somewhat more accessable for the layman is The Whole Shebang : A State-Of-The-Universe(s) Report

I've read both, and enjoyed The Whole Shebang quite a bit more, and they really do cover largely the same material, even if The Whole Shebang is maybe 2 years older... it includes quite a bit more cosmological material as well.

Its available from amazon here

Newton not wrong, just limited

[ballestra]

In fairness to Newton, after your multiple references that he "lost", Quantum Mechanics doesn't disprove Newtonian Physics, it just places it at a differnt level of abstraction. Outside of pure mathematical abstraction, all science is made of theories which model the workings of the universe to the best degree of accuracy and measurement that exists. Someday, physicists will probably unlock the secrets of the sub-sub-sub-atomic particles and declare that quantum physics of the 20th century was a primitive approximation for how things really work. In our current frame of reference, our present theories hold up. In Newton's frame of reference, his theories also hold up.

You can argue that theoretically, Newtonian physics can't fully explain the physics of a 90mph pitch of a baseball, but if you try to pull out transformations to take relativity into account, your corrections will be many orders of magnitude too small to affect a significant digit. Newton deserves the same respect we give Einstein, who may someday be just as "wrong".

"What I cannot create, I do not understand."