The Elegant Universe 78
| 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
- Tied Up with String
- Part II: The Dilemma of Space, Time, and the Quanta
- Space, Time, and the Eye of the Beholder
- Of Warps and Ripples
- Microscopic Weirdness
- The need for a New Theory: General Relativity vs. Quantum Mechanics
- Part III: The Cosmic Symphony
- Nothing but Music: The Essentials of Superstring Theory
- The "Super" in Superstrings
- More Dimensions Than Meet the Eye
- The Smoking Gun: Experimental Signatures
- Part IV: String Theory and the Fabic of Spacetime
- Quanutm Geometry
- Tearing the Fabic of Space
- Beyond Strings: In Search of M-Theory
- Black Holes: A String/M-Theory Perspective
- Reflections on Cosmology
- Part V: Unification in the Twenty-First Century
- Prospects
- Notes
- Glossary of Scientific Terms
- References and Suggestions for Further Reading
- Index
Professional recommendation... (Score:1)
Greene is cute! (Score:1)
universe (Score:1)
can I preorder "String Theory In A Nutshell"? (Score:1)
Re:Where to start...? (Score:1)
jason
Wow... (Score:1)
Re:Evidence? (Score:1)
-- Bob
Re:Gravitational lensing. (Score:1)
I sorted out my confusion on this FAQ web site. [newtonphysics.on.ca]
Re:A thought (Score:1)
No, if gravity is instantaneous it means its effect is felt by all particles simultaneously regardless of distance from the source. There's still some argument over whether all particles are influenced by gravity; I seem to remember recently that there is talk of the gravitational lens effect (ie light being affected by gravity) being disproved.
Re:Questionable FAQ. (Score:1)
Re:Evidence? (Score:1)
Re:A thought (Score:1)
i must be hungry...
Re:Excellent Book (Score:1)
"Of course" (Score:1)
I think you should substitute the word "probably" for "of course". Not because scientists aren't clever enough to reconcile the two (although that may turn out to be the case) but because they may simple BE both true AND irreconcilable.
How can that be? Some of you may be familiar with the analogy of 20 Questions. In 20 Questions, someone thinks of an item and the player(s) ask yes/no questions to determine the item.
There is a variant of 20 questions, though, where the person who is supposed to be thinking of an item, only PRETENDS to. He then answers the players unsuspecting questions in such a way as to meet only one condition: his answers must be self-consistent. Sometimes the answerer follows some algorithm for deciding whether to say "yes" or "no" such as checking for a vowel or consonant at the end of the question.
For example, I pretend to think of an item. You ask "Is it bigger than a breadbox?" X is consonant so I say "no". You ask "Is it blue", which ends with a vowel so I say yes. You ask "does it use a mushroom for a house", another vowel, I say yes. You ask "is it a smurf", consonant, no. At this point you would be confused and I would be chuckling.
What if nature is playing this game? What if attributes and values literally don't exist until we ask about them the first time? Like the bafflement above, quantum weirdness may be the only resolution between Newtonian physics and electromagnetic theory.
All of the above is not original to me. It also still allows the "of course" in the original statement" because nature is still required to be self-consistent, like our 20 Questions Answerer. But why have such a requirement? Or what if the requirement can't be met? For instance, what if your questions had told you that I was thinking of a blue creature, 3 apples high, lives in a forest, chased by Azrael, etc but it was NOT a smurf? What if the collision between relativity and QM end up the same way?
Science generally assumes that there is a reality "out there" that it is describing. But note that this is an assumption only. Any philosophy student can tell you that it's impossible to prove there is an objective reality, but if relativity and QM turn out to be both true AND contradictory, we could end up disproving an objective reality.
--
Wanna hook MAPI clients to your Tru64/AIX/Linux server?
Superb book (Score:1)
Greene covers many similar topics of the other two books, but his style of writing is very accessible to the non-expert reader (like me!). I found the descriptions of very abstract ideas to be very intuitive (or at least as intuitive as the bizarreness of modern physics can be). His thought experiment describing the relativistic effects of a spinning disc was a real epiphany for me and I spent several evening just pondering that one small part.
It's also really nice to read a good book that is still very current. I'm sure in another few years, another good author (or perhaps Greene himself) will need to catch us all up, but for now I feel very enlightened on the state-of-the-art.
Re:Superb book (Score:1)
spatial anomalies detected relative to my universe (Score:1)
few feet? most bookstores i know of don't have computing topics near science topics.
A bookstore based on the dewey decimal system, incidentally, would likely have them far apart (computing - hmm, the Q hierarchy sounds like it belongs in st:tng :)
Re:can I preorder "String Theory In A Nutshell"? (Score:1)
Re:Excellent Book (Score:1)
I've ever seen. Time dilation makes sense now!
Re:Evidence?--nope! (Score:1)
Better than "Hyperspace" (Score:1)
In particular, I found this a very balanced account. He's honest about what questions string theory has potentially found answers for, against the background of the assumptions that have been involved along the way. And, unlike some other popular string-theory books, the case is rather more complete and compelling than "It all looks nice in 10 dimensions (so let's use 10 dimensions)."
What's more, it's all understandable. Some of the concepts are (like much of quantum mechanics) a challenge to the intuition, but there's really nothing in the book that isn't made clear by careful explanation and qualified use of analogy.
Re:Evidence? (Score:1)
Re:Evidence? (Score:1)
Re:3/5 bad (Score:1)
PS on paper you will be projecting 4 to 2 dimensions which makes it even harder to abstract at first.
Algebraic Topology (Score:1)
Re:Evidence? (Score:1)
Sadly physics doesn't. It is a common misconception that if the word "theory" is used to describe something then it has no experimental support and is not very well established.
An obvious counter example would be Special Relativity, which is frequently referred to as "The Theory of Relativity."
What typically distinguishes theories from laws is time rather than evidence and support. It simply takes time for a well established theory to be referred to as a law.
Re:Evidence? (Score:1)
see Brian Greene speak... (Score:1)
Nitpicking (Score:1)
Sorry ;-) A GUT is generally used to describe the theory in which the strong and electroweak forces are unified rather than all four. Predictions like proton decay have come from current GUT models, but they don't seem to work very well.
The weak nuclear force doesn't do anything else apart from cause radiative decay. The least interested force IMHO.
Re:Evidence? (Score:1)
Re:Evidence? (Score:1)
Actually you mean the string hypothesis. A "Theory" is a hypothesis that has evidence to back it up, however it is not absolute, i.e it is possible to disprove. A theorey does not necisarily have to have no evidence against it to still be called a theory, the theory of gravity being the most obvious example. Under certain relatavistic conditions, the theory of gravity as defined by newton breaks down completely. Also, to distinguish a theory from a law, a law is gaurenteed to work in all possible situations. Gravity is just a good idea, its not the law, nothing gaurentees that if you jump off a 20 story building youll fall down, however if you dont fall down, give me a call.
A hypothesis is an explanation for phenomena that has no evidence either supporting or negating it. I would beg to argue that string theory is a theory and not a hypothesis, if only because it works so well to explain the way things are. String theory is like a black box, you throw in numbers, and out come exactly the numbers you see by expirament. Unfortuneately we cant tell whats in the box through experiment, yet.
Agreed! (Score:1)
# human firmware exploit
# Word will insert into your optic buffer
# without bounds checking
Re:Evidence? (Score:1)
So - you are suggesting that Congress decides reality? Are you sure you want the Christian Coalition to define facts?
Anyhow, lots of laws have been accepted as laws, and then proven wrong. Let's be humble enough to realize that our theories are approximations of reality. If they stand for four hundred years, we might consider them roughly complete.
Re:Evidence? (Score:1)
If it's not inconsistent with the models we already have and (ideally) if we can use it to make predictions that we can test (and that turn out to be true), then we will start to gather evidence for it.
I think the nature of the field is one that couldn't allow direct empirical confirmation but, as was the case with General Relativity, the theory could be confirmed through seemingly unrelated methods (it was a subtle variation in Mercury's orbit around 1928 that put the first nail in Newtonian Gravitation's coffin).
Re:Evidence? (Score:1)
Re:Evidence? (Score:1)
Science...Why hast thou turned on me so? (Score:1)
As quantum mechanics probes down to the sub atomic level I can't help but feel like physicists are merely creating conventions for the phenomena that they cannot theoretically explain. I think that this is one of the main differences between classical and modern physics. Classical physics discovered the physical laws that govern our universe while modern physics speculates a reality that fits absurdly abstract mathematical models, which is the feeling that the book left me with.
Re:Evidence? (Score:1)
Excellent Book (Score:1)
This is probably the best book currently in print for the intelligent layman. I consider myself to understand more than the average schmoe about QM & relativity, and even those portions of the book were good enough to hold my interest.
If, for whatever reason, you want to understand more of relativity, QM, and string theory, pick this book up. I read the book about two months ago, and literally, could not put it down. I still find myself thinking about it, even two months later.
A great book! (Score:1)
I have this book - it turned out to be a nice read. Most of the chapter notes also point out other sources of information that can be used for the reader who wants to dive in deeper.
I also agree the later chapters tended to drag a bit here and there - probably too much math for the average reader.
I also strongly urge anyone that has a chance to see the author give a lecture to do so - he has toured the country giving short talks on this book and the talks are very entertaining (at one point using a 'string' quartet to make a point).
Good deal.... (Score:1)
carlos
Another Carl Sagan? (Score:1)
I concur. (Score:1)
It spends a few chapters entertainingly acquanting you with quantum mechanics and all that, then gives you all the superstring theory stuff you know you want.
Re:"Of course" (Score:1)
Anyway, this "irreconciliable _and_ true" post brought back shades of Everett / Many Worlds / Schrodinger's Cat / etc. I haven't read any of _that_ stuff in a while, either.
Regards, John
More on Black Holes (Score:1)
Thorne is one of the physicists responsible for our current understanding of black holes. Here, he presents the history of the deveopment of black holes. There is little math, mostly in supplemental sections. The book details black holes up to circa 1992.
More info... (Score:1)
Re:Evidence? (Score:1)
I purchased this book on a whim when it first came out in hardcover, enjoyed it throuroughly, and have recommended it to several friends.
String Theory and GUT (Score:1)
I have a friend who read the book and recommended it to me. Both he and I are physics majors; I don't think he minded the math!
(the Theory of Everything [TOE], the Holy Grail of physics)
What is better known is GUT (Grand Unified Theory) which hopes to explain all four fundemental forces of the universe as one entity, that separated at the origin of the universe. It doesn't suprise some that Quantum Mechanics and General Reletivity don't coalese (sp?).
FYI, the four forces of the universe are (from strongest to weakest):
Physics has managed to combine the Weak Nuclear force and Electro-Magnitism to form: Electro-Weak force (gotta love these names). Quantum Mechanics has also helped explain how the Strong and Electro-Weak work together. However, Gravity remains elusive. General Reletivity is gravity, so the combination of the two (possible with string theory) is what excites physicists who are looking for GUT.
PS This is to the best of my knowledge what the some of the ideas is modern theoretical physics are. If you know better, please correct me.
Re:Evidence? (Score:1)
Where to start...? (Score:1)
So, now that you know where I'm coming from, where would a good place be to start learning more? I'm not looking to get a degree in physics, but it is something I'm curious about. So what are some good books (preferably something a library would have) or websites that would start explaining things like the theory of relativity, black holes, etc. etc.
TIA.
Good Book... (Score:1)
Universe? (Score:1)
Re:Universe? (Score:1)
Romans 1:18 For the wrath of God is revealed from heaven against all ungodliness and unrighteousness of men, who hold the truth in unrighteousness;
Romans 1:19 Because that which may be known of God is manifest in them; for God hath shewed it unto them.
Romans 1:20 For the invisible things of him from the creation of the world are clearly seen, being understood by the things that are made, even his eternal power and Godhead; so that they are without excuse:
Romans 1:21 Because that, when they knew God, they glorified him not as God, neither were thankful; but became vain in their imaginations, and their foolish heart was darkened.
Romans 1:22 Professing themselves to be wise, they became fools,
Romans 1:23 And changed the glory of the uncorruptible God into an image made like to corruptible man, and to birds, and fourfooted beasts, and creeping things.
Romans 1:24 Wherefore God also gave them up to uncleanness through the lusts of their own hearts, to dishonour their own bodies between themselves:
Romans 1:25 Who changed the truth of God into a lie, and worshipped and served the creature more than the Creator, who is blessed for ever. Amen.
I rest my case.
Ugh. Now my brain hurts. (Score:1)
Good. So maybe I can ask you a question, and while it's fully probable that you won't know the answers, you'll at least know where to find them and how to distill the technical aspects to a level that we Slashdorks can understand. :)
Gravity -jump and find out; currently scientists are looking for gravity waves, using a VERY large (2+ mile) interferometer with lasers to measure the wave)However, Gravity remains elusive. General Reletivity is gravity, so the combination of the two (possible with string theory) is what excites physicists who are looking for GUT.
I think I share the same fascination with the fundamental forces of nature as the rest of us here; in fact, I had done an internship at a nuclear research facility during my younger days. But, while I have a good instinctive and practical knowledge, I have no hope whatsoever of understanding the theoretical math, so I ask that you go gently with me. I also understand, like I indicated above, that this is not your physics specialty.
In a nutshell, Cole's Notes edition, how does gravity work, according to science's current understanding?
I mean, so far as I can tell, we have a pretty reasonable understanding, at least of how to harness, the other three of the fundamental forces.
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.
We're pretty capable of controlling electricity and magnetism; this forum wouldn't be available for me to ask this question if it weren't.
Weak Nuclear -primarily responcible for radiation. I am not to sure what else Weak Nuclear does -(someone wish to elaborate?)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?
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.
So, finally, we come to gravity. And, even so, to what I must imagine to be a fairly close relative, magnetism.
We can view magnetic lines of force, it's safe to say that with the right technology, we'll probably be able to do it with gravity, too. But I have a problem conceptualizing the way this can overcome inertia.
It's all well and good to say that we can see the lines of force, but what are the lines of force? What are these invisible strings that pass, without sensation, through my hand and down to the center of the earth as they hold the quarter that is resting in my palm?
Obviously, they're a form of energy, since the application of these forces can overcome inertia.
If I place a screw on my desk and suspend a magnet above it, the screw will remain planted on the desk by gravity until the force of the magnetic field is increased to the point of overcoming gravity.
As the magnet approaches the screw, if I measure the weight of the magnet, it will appear to increase as more of the screw's weight is shifted from the desk to the suspended magnet. Note, of course, that the magnet's mass has not changed.
Once the threshold has been exceeded, the mass of the screw will be entirely supported by the magnetic field and it will overcome inertia to jump free of gravity and stick to the magnet.
Now, that's kinetic energy, caused by the magnetic field. Where is that energy coming from? Is it there because of the energy required to place the screw near the magnet? Or is it coming from inside the magnet, suggesting that magnetic force - and probably gravity, since they're quite probably very closely related - is actually coming from within the atoms of magnetized ferrous metals?
Now, magnetism is a lot more clear in this respect than gravity. If I hold the screw and drop it to the ground, I'm just releasing the potential energy that I incurred as I picked it up off the ground. But I would suggest that the same thing holds true as NASA used gravity to slingshot Voyageur out to past Jupiter - Voyageur has never accumulated potential energy by being removed from the surface of Mars or Jupiter, and yet it's still able to acquire kinetic energy from them.
If this were the case, since you don't get something for nothing, isn't it possible that there's some decay of matter occuring, which might be quantified by Einstein's famous E=mc^2? This would suggest that magnets, and possibly all matter, since all matter is a source of gravity, is "decaying" constantly and spontaneously into energy. Granted, given the numbers involved and the quantities of kinetic energy released, very slowly. But does this mean that all matter (magnetized ferrous products in particular, since they're affected by both forces) is gradually losing mass?
Or am I way off?
Finally, if the magnetic energy, as I suggested, exists and can be turned on and off (aligning domains within ferrous materials by rubbing them with a magnet - or by countering that in a number of ways), is it not somehow possible that one day, we can control gravity, turning it on and off with the same relative ease?
(That's a little hope for the future. I mean, I think we'd *all* like to be able to levitate. It'd be a great party trick.)
Re:Evidence? (Score:1)
Exactly... (Score:1)
Re:Ugh. Now my brain hurts. (Score:1)
There are other types of radiation as well that are not associated with the weak force: nuclear fission is governed by the relationship between the strong force, which tries to bind the nucleus together, and the electromagnetic force, which tries to tear the nucleus apart. Fission results in the emission of neutrons.
Alpha particles are emitted directly from the nucleus -- alpha particles are two neutrons and two protons bound together (essentially a doubly-ionized helium atom). Finally, there are gamma rays and x-rays. Gamma rays and x-rays are the same thing, namely high-energy photons. The difference is in the definitions: gamma rays are the result of some sort of nuclear transformation (rearrangement of the nucleons in the nucleus, or the nuclear capture of an electron, for example), while x-rays are the result of an electron (atomic) tranformation, such as a valence electron changing energy states.
Re:Superb book (Score:1)
If you REALLY want to learn about gravity and general relativity, read the book Kip Thorne co-wrote with John Wheeler and Charles Misner, "Gravitaion". That'll keep you busy for a few days...
Re:Evidence? (Score:1)
first, as the nobel laureate physicist steven weinberg eloquently argues in his "dreams of a final theory," theoreticians are often guided more by their aesthetic senses than parsimony, and choose complex but beautiful theories over simpler, but sterile ones. check out this book if you are at all interested in the art of scientific theorizing -- it's really quite underrated.
second, there seem to be no good arguments that choosing simple theories over complex ones actually leads to the selection of truer theories over their more-false alternatives. the philosopher james mcallister's "beauty and revolution in science" covers this ground.
Re:Evidence? (Score:2)
Not to start an epistemiological debate, but I wonder how you define "right" and "wrong" in the context of contemporary science?
I try not to :-) I don't think it's possible to prove a scientific theory (yet, anyway) but thinking about it, I would (for example) consider Einstein's theory as more correct, more "right", than Newton's...even though, in Newton's time, Occam's razor would have led me to support Newton.
Heh...I'm not even sure if that's what you were asking; I looked to my .sig for guidence and now my head hurts...
dylan_-
--
Re:Evidence? (Score:2)
Is there any evidence for string theory?
Well, according to the book (read it and enjoyed it), the problem is trying to find something to predict that could be tested.....the strings are so small that it's very difficult to show that they aren't points. As far as Occam's razor goes, string appears to be the more elegant theory, but the new theory tends to have the burden of proof....anyway, all Occam's razor is is a rough guide on what to work with...it doesn't actually have anything to do with what's "right" or "wrong"...
dylan_-
--
Re:Evidence? (Score:2)
As to the argument about Occam's Razor, frankly you're right. If String/M-theory can't explain what we want it to, or if there is a simpler theory that explains the same things, then string theory will fall to this other theory. But at the present time there is no other theory that holds half the promise of string theory. General Relativity can't explain Quantum Mechanics, and Quantum Field Theory, which is so good for electromagnetism, the weak force, and the strong force, can almost certainly not explain gravity. (and has some unsatisfactory properties for other reasons - like 30-odd "arbitrary" parameters. We'd like to know why these 30-odd parameters have the values they do)
String theory is promising because it has a very large space of possible configurations. In other words, there are billions of ways you can tune all the parameters in string theory to end up with different "universes". Many of the he generic properties of these universes have already been verified to correspond to our own. In some sense "solving" string theory will someday be a game of trying out all the possible permutations of configurations, and finding one that works. But for now we also need to concentrate on understanding the fundamentals of it.
It is important to note that General Relativity, and Quantum Field Theory must be derivable out of string theory for it to be a viable theory. (This is generically how physics works) People have been deriving QFT's and GR out of various string theories for a long time, so it can be done. It's just a matter of finding the right string theory, from which we can derive the electroweak QFT, GR, and the masses of all the particles that we see.
--Bob
Gravitational lensing. (Score:2)
That would be quite a trick. If I remember correctly, one of the measurements used to support relativity was of gravitational lensing of starlight by the sun (mask out the disc and take careful measurements of the apparent positions of stars next to it).
Gravitational lensing studies are also being performed to measure the mass of distant galaxies (by looking at multiple images of even more distant galaxies). If gravitational lensing didn't exist, it would have been noticed in a big way by these studies.
As far as anyone's been able to determine, photons are constrained to follow the geometry of spacetime like everything else. Can you give a citation for the articles that you refer to that propose otherwise?
Re:Evidence? (Score:2)
Don't hold your breath. It's not the sort of subject where empirical evidence is easily available. Nowadays string theory has evolved into m-theory, which basically adds another dimension to our already burgeoning universe. Check out here [cam.ac.uk]
Re:Evidence? (Score:2)
Not to start an epistemiological debate, but I wonder how you define "right" and "wrong" in the context of contemporary science? Specifically, how can you tell if whether science theory is "right"? Is is possible to *prove* a science theory?
Kaa
Re: (Score:2)
I found the book weak (Score:2)
I have some familiarity with relativistic phsyics, having read Einstein's own attempt at popular science, "Relativity", and quantum physics from "The Dancing Wu Li Masters" Contrasting these works with "The Elegant Universe", I found that Greene never hit the right stride for a book that purports to make complex scientific topics clear.
Crucial issues that lead to the birth of quantum physics like the ultraviolet catastrophe and the photoelectric effect are given a shallow treatment that barely suffices to convey why turn-of-the-century was in such turmoil. Greene even manages to make the famous double slit experiment seem irrelevant and confusing. I felt that if I had studied these topics in college, I would not have comprehende why Greene chose these topics for inclusion in his book.
On the relativistic front, well, Greene completely eschews equations in that section, which was a mistake. Without the dilation equations, the reader gets no sense of *why* things stretch and slow down as they approach the speed of light. You only have to take Einstein's word on it.
Having seen how his coverage of these two topics was lacking, I am suspicious that the discussion of string theory (the reason the book was written) is probably equally weak. Having read the book, I doubt I could speak intelligently about those topics, as I sometimes can do with quantum physics and relativity, having had only the minimum of study described above.
If you enjoy reading about science rather than actually understanding science, this book may be for you. All others I advise to pick up a college freshmen physics text - you'll find it far more gratifying.
-konstant
Yes! We are all individuals! I'm not!
Greene, not only smart, but a good teacher too (Score:2)
Re:I think a better book.. (Score:2)
Though older than TEU, it only lacks proof of the sixth quark. Otherwise, it matches TEU in a understanding and insight.
However, easily its main selling point is Lederman's status as an experimental physicist. Unlike "The Elegant Universe" and "A Brief History of Time" (by Stephen Hawking, also a phenomenal book, though even more focused on the layman), "The God Particle" thoroughly examines what we know in physics, not just what we suspect, and does so in an amazingly entertaining way, yet without pandering to the lowest common denominator. You may feel inclined to skip the first couple chapters that deal with the development of classical physics (which each of these books do exhaustively). "Schroedinger's Cat" and "Schroedinger's Kittens" are both excellent books that cover quantum mechanics very concisely, and are a nice alternative to the complete anthology presented in "The Elegant Universe."
I have read all of the books I've mentioned here, but IANAPMY (I am not a physics major, yet), so I don't vouch that they are completely current in the realm of theoretical physics today. They are all thoroughly enjoyable, entertaining (no kidding, laugh out loud) and educational, and I highly recomment them.
Just ignore the sig, it's not supposed to be flaimbait.
Re:A great book! (Score:2)
When they reviewed the Linux Source Code Commentary book, nobody said, "There's too much code in this book." Mathematics is the fundamental code of the universe, and IMHO there can never be too much of a reference to it. I am a big Linux fan, but the Math code that controls the universe is 10^6 times more elegant and beautiful.
Some good Math references...
Lang, Algebra
Gleick, Chaos
Arnold, Mathematical Methods of Classical Mechanics
Churchill and Brown, Complex Variables and Applications
Andrews, Number Theory
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Re:Evidence? (Score:2)
Thad
Re:Evidence? (Score:2)
The upgrades to the Tevatron at Fermilab, and the completion of the Large Hadron Collider at CERN in 2006 will provide energy scales large enough to create and observe superpartners. (And perhaps the Higgs boson, if you're familiar with the Standard Model). On the horizon after that are are the Very LHC, or a giant linear accelerator -- then, and only then, are we going to get even close to start solving mysteries like this empiracally.
Bear in mind though, that Maxwells equations (and even Newton's) equations went unsupported for years (even almost a century) before they were widely accepted. Most of modern particle physics is young by comparision, and the energy barriers are much greater, so its not surprising there is no evidence so far.
Questionable FAQ. (Score:3)
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
This links to a FAQ on general physics, and many other FAQs that may be of interest.
Evidence? (Score:3)
Kaa
Re:Ugh. Now my brain hurts. (Score:3)
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 (Score:3)
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.. (Score:4)
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 [amazon.com]
Newton not wrong, just limited (Score:4)
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."