The Elegant Universe: Superstrings, Hidden Dimensions, and the Quest for the Ultimate Theory by Brian Greene

The Elegant Universe: Superstrings, Hidden Dimensions, and the Quest for the Ultimate Theory Reviews

• 
  Manny

  [Original review, written December 2008]
  
  When I read this book, I remember thinking it was pretty interesting, but I am surprised how few insights I have retained... to be honest, hardly any. Smolin's
  The Trouble with Physics, which I read much more recently, suggests that string theory is in big trouble, and right now I am more tempted to side with Smolin.
  
  There's this old Nasrudin story, where he's somehow ended up as judge in a court case. The D.A. really makes a good case, and Nasrudin can't restrain himself. "Yes, you're right!" he shouts. Then the defense lawyer gets up and makes his pitch, and Nasrudin is equally impressed. "Yes, you're right!" he shouts again. The court recorder clears his throat and leans over towards Nasrudin. "Your honor," he says respectfully, "they can't both be right!". Nasrudin shakes his head. "Yes, you're right!" he agrees.
  
  Well, between Greene and Smolin I feel a bit like Nasrudin, but luckily I am not the judge here. Am I just agreeing with Smolin because I heard him most recently? Maybe. But trying to correct for that, I still think that there is a reason why Smolin seems more convincing and memorable, and why very little of what Greene says has stuck. String theory has become so divorced from experimental reality that it rarely if ever gives you that feeling you get from good science, of suddenly grasping a real physical phenomenon that you have known about for a while, but not understood.
  
  I guess the example that makes me least happy is supersymmetry, according to which every particle has a supersymmetric partner. Compare this with the discovery of the periodic table in the late 19th century, or the development of the Standard Theory in the 60s and 70s. There, insightful people gradually realized that objects (atoms in the first case, subatomic particles in the second) were related in a complicated pattern. Most of the time the pattern fit, but there were a few holes, and they were later able to find the things (new elements, new particles) that filled in the holes! I was astonished to read that there is not one single particle which has a known supersymmetric partner - so far, it's all hypothesis, and perhaps none of these "selectrons", "photinos" etc actually exist. I'm not saying that this means supersymmetry is wrong; I'm just saying it means I don't find it exciting.
  
  Maybe next year they will get the LHC working, discover a whole slew of supersymmetric partners (even one would be a lot), and put string theory on a proper experimental footing. If that happens, I'm sure I'll go back to reading books on this subject; I won't be able to stop myself. But until then, well, it may be beautiful math, but I feel no emotional connection to it. I'd love to hear from people who disagree, and can explain to me just what it is I'm missing out on.
  __________________________________
  
  [Update, May 2011]
  
  We had another particle physicist over for dinner last night. He'd come mainly to play chess, but when I found out that he was involved in looking for supersymmetric particles I took the opportunity to ask how it was going. Well: assuming he's to be trusted, and he sounded pretty knowledgeable on the subject, we should know pretty soon. The LHC is now up to high enough energies. They're collecting data. If supersymmetric particles exist, there is every reason to suppose that we'll have clear evidence of them within a year or two.
  
  I wondered what would happen if they didn't find any supersymmetric particles? Would the theoreticians just retreat into saying that they needed a more powerful collider? Not so, said my informant; if the particles can't be found at the current range of energies, the predictions were wrong. Sounds like we're finally getting a straight up-or-down vote.
  
  String theory, you can run but you can't hide!
  __________________________________
  
  [Update, September 2011]
  
  I knew it was too good to be true. We had yet another particle physicist over, whose PhD topic had been something to do with searching for a supersymmetric quark. I asked her if it really was the case that we'd soon know if supersymmetric particles existed.
  
  Alas, it turns out that, although the energies they're now reaching in the LHC are indeed sufficient to find supersymmetric particle according to the mainstream versions of string theory, there are other versions which predict higher energies - energies which are outside the LHC's range.
  
  "Of course," she added, "the mainstream version is the one that contains the original motivation for supersymmetry. If they retreat to one of the other versions, then most of the rationale disappears. But people have a lot riding on string theory."
  
  "That's terrible!" I said indignantly. She just shrugged her shoulders.
  __________________________________
  
  [Update, May 2015]
  
  Browsing the physics section at the South Australian State Library earlier this week, I picked up a copy of Becker, Becker and Schwarz's
  String Theory and M-Theory (2007). The introduction says clearly that supersymmetry is essential to string theory/M-theory, and moreover that the LHC should be able to reach high enough energies to produce supersymmetric particles, if they do in fact exist. Consulting Google Scholar, my impression is that the book is highly respected: I see 661 citations.
  
  Eight years later, no supersymmetric particles have been observed. But no doubt string theorists have an explanation for this inconvenient fact.
  __________________________________
  
  [Update, Dec 2015]
  
  Hey, if you think I'm being mean to those poor string theorists, just look at what Randall Munroe said the other day!
  
  
  __________________________________
  
  [Update, August 2017]
  
  It struck me today that the people who are criticising CERN for spending so much money finding the Higgs boson are wrong on at least two counts. First, $13B isn't actually such a large price tag for making a fundamental discovery about the laws of the universe, the truth of which is obvious only in retrospect; many physicists were unsure that the Higgs existed. Second, and perhaps even more importantly, there's the dog that didn't bark in the night. Many physicists were also expecting to find supersymmetric particles, but none have been detected. This greatly weakens the plausibility of string theory and shifts attention to competing theories for unifying quantum mechanics and gravity, of which by far the most attractive is Loop Quantum Gravity.
  
  Speaking as someone who used to work for NASA and was involved with the International Space Station project ($150B and counting), I would say CERN has given the taxpayer value for money and then some. It's a pity that all research funding isn't allocated in such a responsible manner.
  __________________________________
  
  [Update, March 2018]
  
  On pages 368-9 of Leonard Susskind's 2008 book The Black Hole War, I find the following passage:

  ... there is a whole collection of particles whose existence is only conjectural, but a lot of physicists (including me) think they may exist*. For reasons that are not important to us here, these hypothetical particles are called superpartners.
  
  * We will know within a few years, when the European accelerator called the LHC (Large Hadron Collider) starts operating.

  Well, there it is again. Susskind, one of the foremost proponents of string theory and a world-renowned expert on fundamental physics in general, said ten years ago that the LHC would soon find the superpartners/supersymmetric particles if they were there. It hasn't found them. Ergo...
  
• 
  Mohammed-Makram

  
  
  
  
  
  عندما سقطت التفاحة التوراتية سقطنا معها إلى هذا العالم و من ثم أصبح لزاما علينا أن نفهمه أو على الأقل نفهم كيف نعيش فيه. و عندما سقطت تفاحة نيوتن ظن العلماء أننا فهمنا أخيرا برغم مقولة نيوتن بأنه كشخص يلعب بالأصداف على شاطئ المحيط بدون أن يجرؤ حتى على النزول و معرفة ما فيه ناهيك عما وراءه.
  
  فسر القانون العام للجاذبية حركة الكون و وضع لنا أول تصور غير اسطورى أو دينى للعالم من حولنا و ظل صالحا لكل الأحوال ما يربو على الثلاثة قرون إلى أن جاء اينشتين و لكن هذه المرة بدون تفاح بنظرية يصعب تذوقها و هضمها اضافت الزمان إلى المكان و اصبح لدينا أربعة أبعاد سماها الزمكان في نظرية النسبية الشهيرة التي أعادت بلورة تصورنا للكون الكبير.
  
  في ذلك الوقت قادت الصدفة ألمانى أخر هو ماكس بلانك إلى اكتشاف نظرية الكم التي تكون النظرية النسبية بجوارها سهلة لا غموض فيها فقد قال علماء الفيزياء ان من يقول لك أنه يفهم نظرية الكم بصورة كاملة فلا تصدقه.
  
  عند ذلك عكف اينشتين على الوصول إلى نظرية كبرى تشرح كل القوى الموجودة في الطبيعة بنظرية واحدة شاملة و لكن لماذا؟
  
  ببساطة كانت النسبية تتعامل مع الجاذبية و حركة الأجرام السماوية و الأجسام الضخمة المتباعدة بكفاءة عالية جدا بصورة لا تقبل الشك بينما تنهار تماما عند دراسة بنية الذرة و الأجسام الدقيقة و بالعكس منها نظرية الكم التي تنجح بامتياز عند دراسة الذرة و تفشل في تفسير حركة الأجسام الضخمة المتباعدة.
  
  وجد علماء الفيزياء أنفسهم أمام نظريتان كلاهما صحيح في مجاله خاطئ في الناحية الأخرى و من هنا بدأ الجهاد الأعظم في تاريخ الفيزياء و الذى مات اينشتين قبل ان يتوصل فيه لأى نتيجة.
  
  يتكون هذا الكون من عناصر كالمعادن و الغازات و غيرها و يتكون كل منها من ذرات و تتكون الذرة من نواة و الكترونات و تتكون نواة الذرة من بروتونات و نيوترونات و تتكون كل منهما من كواركات.
  
  
  
  
  إذا فما لدينا هو الكترونات و كواركات و بعض الجسيمات الأخرى متناهية الصغر مختلفة الوظائف كالفوتونات و الميزونات و البوزيترونات و الأجسام المضادة و غيرها من المسميات الفيزيائية لجسيمات لم يرها أحد و انما رأينا تأثيرها و أمكننا هذه من دراسة سلوكها و صفاتها.
  
  
  
  
  نظرية الأوتار توصلت في النهاية إلى أن كل تلك الجسيمات تتكون من شيء واحد هو الوتر أو الخيط و هو شيء أشبه بالحلقات المطاطية التي نستخدمها في حزم النقود و يكون مغلق الطرفين أو مفتوحهما و تبعا لتذبذب كل وتر يتحدد طوله الموجى و سعته الموجية و بالتالى طاقته و كتلته فيصير هذا الكترون و هذا كوارك و هذا جرافيتون و ذلك ميزون و هكذا.
  
  
  
  
  إذاً حولت النظرية العالم لسيمفونية من العزف الجماعى لترليونات الترليونات من الأوتار في كل سنتيمتر من الكون و لم تكتف بذلك بل أضافت إلى الأبعاد المعروفة سبعة أبعاد جديدة ليصبح لدينا إحدى عشر بعدا منها بعد زمنى واحد و عشرة أبعاد للمكان.
  
  فسرت نظرية الأوتار حركة الأجسام سواء كانت متناهية الصغر متقاربة جدا كالكواركات و الفوتونات أو ضخمة جدا متباعدة كالمجرات.
  
  
  
  
  كل الشواهد تؤكد صحة النظرية و لكن من الناحية الرياضياتية أما من الناحية العملية فلم يتأكد نجاها إلا منذ حوالى سبعة سنوات عندما حصل أحد العلماء على جائزة نوبل في الفيزياء بعد رصده للجرافيتون الذى تنبأت النظرية بخواصه بدقة قبل ذلك بسنوات. أما حين صدور الكتاب فلم تكن النظرية قد تأكدت بعد.
  
  طالت المراجعة و وصلت لحد الملل و ما زال في الكتاب الكثير و الكثير و كذلك في الفيلم الوثائقى بأجزاءه الثلاثة الذى سيسهل عليك هضم الكثير مما ذكر في هذا الكتاب القيم.
  
  سأكتفى بهذا القدر لأترككم مع الوثائقى و الكتاب في تلك الرحلة الممتعة.
  
  نقطة أخيرة:
  
  هل نظرية الأوتار دليل على وجود خالق أم دليل على عدم وجوده؟
  
  في الحقيقة لا نظرية الأوتار و لا غيرها لهم علاقة بالتدليل على وجود الخالق من عدمه فهى قضية ايمانية لا تخضع أصلا لسلطان العقل و لا علاقة لها بالعلم أو الفلسفة و انما هي محض ايمان و تسليم قلبى روحى و لنفصل دائما بين طريق العلم و طريق الدين ان كنا نبغى التقدم في المسارين و الا فإن أحدهما سيلتهم الأخر و في النهاية ستكون أنت الخاسر.
  
  ع��ى الهامش:
  
  الضوء ليس له عمر فالوقت لا يمر عند الوصول إلى سرعة الضوء فالفوتون الذى انطلق في الإنفجار الكبير عمره هو نفس لم يتغير حتى الأن
  
  تمسك الكتلة بالفضاء المكتن لتخبره كيف يتحدب بينما يمسك الفضاء المكان بالكتلة ليخبرها كيف تتحرك
  
  تحديد مكان الجسيم تبعا لنظرية الكم يخضع لقاعدة عدم اليقين و حينها يبدو لك أن الجسيم يستعصى على التحديد و قد تظن انه انتشر في المكان كله فكل الاحتمالات جائزة
  
  
  
  
  عندما اكتشف هايزنبرج مبدأ عدم اليقين استدارت الفيزياء بحده إلى اتجاه لم ترجع عنه أبدا فالاحتمالات و وظائف الموجة و التداخل و الكمات تتضمن وسائل راديكالية جديدة لإدراك الواقع. و اختفى مفهوم الحقيقة المطلقة و يا أبيض يا اسود اللون الرمادى ده انا محبوش و فجأة أصبح كل شيء رماديا.
  
  
  
  و يبدو الأمر و كأن الفوتون ليس هو الناقل للقوة بذاته و لكنه ينقل رسالة إلى المتلقى عن الكيفية التي عليه أن يتجاوب بها مع القوى المؤثرة فالبنسبة للجسيمات متشابهة الشحنة فإن الفوتون يحمل رسالة "تفرقو" و بالنسبة للجسيمات مختلفة الشحنة فإنه يحمل رسالة "تجمعوا"
  أحيانا أتصور أن الكون كله خاضع لشفرة موحدة هي أون أوف أو واحد صفر تفرقوا تجمعوا شيء واحد و عكسه. شفرة بسيطة و لكنها تطغى على كل شيء بداية من القوى الطبيعية و حتى لغات البرمجة الحديثة حتى التقسيمة الرئيسية للموجودات تحصرها بين المادة و الطاقة و كل منهما قابل للتحول للآخر و من االموت تأتى الحياة و من العدم أتى الوجود من قبل بسر كلمة كن.
  
  الطول الموجى و السعة الموجية يحددان كتلة الجسيم و طاقته و بالتالى شكله و وظيفته و سلوكه في الكون.
  
  يؤكد مبدأ عدم اليقين أنه لا شيء في حالة سكون تام فكل الأجسام تعانى من الهياج الكمى و ينطبق ذلك أيضا على الأوتار و كل في فلك يسبحون.
  
  الفيزيايون هم الأنبياء الجدد اللذين يحللون اشارات الله و وحيه الذى يأتيهم على هيئة نظريات يبسطونها و يمررونها الى الشعوب
  
  الكون باق و يتمدد.
  
  الوثائقيات:
  
  الأول
  
  https://youtu.be/q1rVGQ7911k
  الثانى
  
  https://youtu.be/FA1fpiEgRt0
  الثالث
  
  https://youtu.be/W-36A4ELHDY
  
  كلها مترجمة للعربية و على ثلاث قنوات مختلفة
  من تهمه مشاهدتها فلينته منها سريعا لتكرار ازالتها من يوتيوب لحماية حقوق الملكية
• 
  Marvin

  
  
  
  Do I understand string theory? Not sure.
  
  Do I understand M theory? A little bit but don't ask for any algebraic reasoning.
  
  Do I know exactly what a Calabi-Yau is? Not really but I think they look a little like the hair balls from my cat.
  
  This is the second time I've equated quantum physics and all its detours to a hair-ball. That's because I can study a hair ball and still have no idea what it is for and why they exist. String Theory and the elusive TOE is in the same category. I could go on my entire life not knowing about them but now that I do, I need to know why. Newton, Einstein, Feynman, Hawking, and my cat can't all be right. Or can they?
  
  That is essentially the dilemma of string theory and the book. Greene does a great job of putting everything in layman's term but there is a point which he must exceed the intellectual ionosphere and soar into the incalculable. I really like this type of book. The challenge is the fun. But rest assured when the scientists get their act together and write an Idiot's guide to The Unified Theory Of Everything, I'll be the first in line.
  
  P. S. Hair balls and string theories have something else in common. Once you tore one apart, you can never get your hands clean.
  
• 
  Alisha Bruton

  I left Christianity a few years ago and swore off religion altogether; however, after reading this book, string theory has become tantamount to religion in my life. Brian Greene writes beautifully about particles, planets, and the origins of our universe as we know it today. It is a heavy book- I don't recommend it for anyone who wants a quick, easy read. It took me almost two months to get through, but I learned a tremendous amount and came away in complete awe of the world and the forces at work in it today. Since Green wrote his book string theory has come under intense scrutiny; despite this, I would still support this book on the basis that it is gorgeously written, based in fact (many of the experiments and proofs were done by Greene himself), and incredibly informative. A vertible Bible of where we came from, where we're going and the incredibly complex way things function in this glorious universe of ours.
• 
  Riku Sayuj

  To think I put all that effort to understand a discredited theory...
• 
  Daniel Clausen

  For most of my life, physics and the general sciences have seemed beyond me. At the same time, I've been lucky enough in high school and university to have instructors who are willing to let me "give science a try" in a not threatening way. This book is one such attempt to allow ordinary people to give science a try. In this book, you'll get a crash course in physics as an evolving subject, from the theory of gravity, to special relativity, to general relativity, to quantum mechanics, to string theory, you'll be taken on a fantastic journey into the heart of science. A word of warning, though, one of my geeky friends told me that "String Theory" is now a passing fad. That might put you off the book. I still felt like there was a lot of value in reading this book simply as a mental challenge. The book was challenging to read, even if it is supposed to be dumbed down physics.
  
  
  
• 
  Stephen

  4.0 to 4.5 stars. There is a great quote to the effect that "if you can't explain a subject in non-technical terms so that a lay person can understand it than you haven't really mastered the subject yourself." On that basis, it is clear that
  Brian Greene has DEFINITELY mastered the subject of general relatively, quantum dynanmics and string theory (at least to the extent present technology allows). For such a complicated and often "non intuitive" subject, Greene does an excellent job of laying out in understandable terms: (1) the evolution of special relativity into general relativity; (2) the basics of quantum dynamics; (3) the fundamental conflict between general relativity and quantum dynamics; and (4) the amazing development of string theory and (5) the prospects for string theory to be able to resolve the conflcit between general relativity and quantum mechanics and come up with a Unified Theory of Everything (the fabled TOE).
  
  Now even with Greene's fantastic explanations, once we got beyond the basics of string theory and onto such concepts as 10 "spatial" dimensions, mirror symmetry and Calabi-Yau manifolds, there were times when the subject matter was just difficult to grasp on an intuitive level. However, Greene was quick to point out that the reader (i.e., me) was not alone in that confusion and it did not prevent me from walking away with a much better understanding of these difficult topics. It also made me interested in learning more. HIGHLY RECOMMENDED!!
• 
  aPriL does feral sometimes

  ‘The Elegant Universe’ by Brian Greene is a general introduction to cosmology and string theory. It is a beautifully written book! However, it is not for beginners. I think some classes in physics or cosmology, or a long-time subscription to a magazine like New Scientist or Science News would be a necessary educational background before reading this book. Or a genius-level understanding of mathematics. So. As far as I can tell, the book is a five-star read in clarity and expert knowledge.
  
  From Wikipedia, I learned Greene is a genuine scientist. He attended Harvard and got his Ph.D. at Oxford. Greene joined the physics faculty at Cornell in 1990 and was appointed to a full professorship in 1995. He joined the staff of Columbia University as a full professor. At Columbia, Greene is co-director of the university's Institute for Strings, Cosmology, and Astroparticle Physics (ISCAP) and is leading a research program applying superstring theory to cosmological questions. With co-investigators David Albert and Maulik Parikh he is a FQXi large-grant awardee for his project entitled "Arrow of Time in the Quantum Universe.
  
  Greene does an amazing job of condensing a hundred years of cosmological science and physics into a few chapters. He describes in the first six chapters the most cogent and clear explanation of Einstein’s Special Relativity and General Relativity theories I have ever read. He also links past discoveries about electricity, magnetism, and gravity insofar as how such discoveries led to Einstein’s theories. These past discoveries about gravity and electricity also led to what were concurrent studies in Einstein’s lifetime by other scientists on quantum mechanics. Greene leads readers, gently, into how scientific experiments on quantum particles, especially photons and electrons, led to discoveries about the structures of atoms. These explorations have added hints about further mysteries yet to know surrounding the beginning and current state of the universe.
  
  Around chapter five, Greene begins discussing string theories in depth. At first, I could follow. Clearly mathematics is the main source behind string theories (and physics), making real-world descriptions difficult. Green makes a heroic effort at avoiding direct mention of the maths (except in the Notes section at the back of the book). He includes drawings and word-picture analogies (using vivid visuals such as walnuts and donuts and trampolines and beach balls and floating astronauts moving about in space), to illustrate the theoretical conclusions derived from the mathematical view of the universe. I understand the necessity of alternative visual examples - how do you describe and show visually the concept of Time, or show how a Planck length of strings affects an invisible, to us, dimension’s dimensions!
  
  
  Frankly, my history/literature brain burned out. This is an example of what killed neurons in my head:
  
  “The particular calculation we were performing amounts, roughly speaking, to determining the mass of a certain particle species — a specific vibrational pattern of a string — when moving through a universe whose Calabi-Yau component we had spent all fall identifying. We hoped, in line with the strategy discussed earlier, that this mass would agree identically with a similar calculation done on the Calabi-Yau shape emerging from the space-tearing flop transition. The latter was the relatively easy calculation and we had completed it weeks before; the answer turned out to be 3, in the particular units we were using. Since we were now doing the purported mirror calculation numerically on a computer, we expected to get something extremely close to but not exactly 3, something like 3.000001 or 2.999999, with the tiny difference from rounding errors.” Page 277
  
  
  Wtf does 3 mean to Greene? Confirmation of space-tearing flop transitions by a mirror mathematical version of normal physics mathematics, which proved part of the physics of string theory.
  
  Got it?
  
  
  Or this:
  
  “Two related notions underlie these observable consequences; we will explain each in turn. First, as we have discussed, Strominger’s initial breakthrough was his realization that a three-dimensional sphere inside a Calabi-Yau space can collapse without an ensuing disaster, because a three-brane wrapped around it provides a perfect protective shield. But what does such a wrapped-brane configuration look like? The answer comes from Horowitz and Strominger, which showed that to persons such as ourselves who are directly cognizant only of the three extended spatial dimensions, the three-brane “”smeared”” around the three-dimensional sphere will set up a gravitational field that looks like a black hole. This is not obvious and becomes clear only from a detailed study of the equations governing the branes. Again, it’s hard to draw such higher-dimensional configurations accurately on a page, but figure 13.4 conveys the rough idea with a lower-dimensional analogy involving two-dimensional spheres.....Moreover, in Strominger’s 1995 breakthrough paper, he argued that the mass of the three-brane— the mass of a black hole, that is—is proportional to the volume of the three-dimensional sphere it wraps: The bigger the volume of the sphere, the bigger the three-brane must be in order to wrap around it, and the more massive it becomes. Similarly, the smaller the volume of the sphere, the smaller the mass of the three-brane that wraps it. As this sphere collapses, then, the three-brane that wraps around the sphere, which is perceived as a black hole, appears to become ever lighter. When the three-dimensional sphere has collapsed to a pinched point, the corresponding black hole—brace yourself—is massless.” Page 330
  
  My brain vibrated feebly, then flopped, and collapsed into a massless black hole, gentle reader.
  
  Also: Perturbation Theory, Duality, Quantum chromodynamics, Symmetry, Spins, Supergravity, M-Theory, primordial nucleosynthesis, curled up dimensions (from nine to eleven - they don’t know how many exactly since the math is giving various answers to the question of multiverses, depending on the equation), Entropy, the Big Bang, the fabric of Space/Time, and my favorites, the uncertainty principle, spatial topology and reciprocals - not.
  
  None of this is visible to the naked eye, gentle reader, and some of it not to the naked brain in any kind of brane. My bosons are weak, gentle reader, weak, by my gauge. The forces of my framework have been mechanically perturbed into a mass universe of simplified confusion. I am a flatland of one-dimensional fundamentals when it comes to ‘ordinary’ physics, much less possessing a particle of understanding the speculative kind of physics like string theories!
  
  
  There is a Notes section which supposedly is in English, not that I could tell - a native English speaker - and an Index. Thankfully, there is a glossary of scientific terms, of which its pages I wore down to a Planck’s constant. However, maybe too many donuts (whether torus or spherical) and not enough broccoli in my life has annihilated the necessary electrons I needed to shine like an energetic photon. I am clearly reduced in mental energy to the lower spectrums, like ancient photonic microwaves spread out in a vast void of background noise, barely distinguished.
  
  *sigh*
  
  
  I found this, gentle reader - a PBS NOVA show about Brian’s Greene’s book. It’s easier.
  
  
  https://www.pbs.org/wgbh/nova/video/t...
• 
  يونس عمارة

  لنقل ان الفيزياء تنقسم الى نظريات .
  فيزياء كلاسيكة ، فيزياء حديثة .
  الفيزياء الكلاسيكة تفسر الكون على اساس معادلات نيوتن وهي صادقة لحد كبير في التنبوءات ومازالت تستعمل وتدرس في المدارس لحد الآن.
  الحديثة تنقسم الى عدة اقسام : نظرية النسبية العامة والخاصة . نظرية الكم ، نظرية الاوتار الفائقة التي ادعت انها جمعت كل النظريات السابقة ..هناك ايضا سيناريوهات اخرى منها نظرية –ام و عدة اقتراحات اخرى تسمى بنظريات كل شيء ..
  ان رأيت ان الامر صعب –كما ظهر لي من قبل – فاقرا كتاب (الكون الانيق ) لبرايان غرين ويكفيك ذلك لكي تفهم كل هاته المصطلحات حتى لو كانت ثقافتك الفيزيائية عادية ، ان كنت تريد الفهم حقا فزد اطلع على سيتفن هونكينغ في' الكون في قشرة جوز' .وكتاب من الذرة للكوارك ..والمنظمة العربية للترجمة باشراف الدكتور جابر عصفور فعلت خيرا باخراج كل هاته الروائع بصفة ممتازة جدا ..
  
  الكون الانيق كتاب ممتاز جدا لدرجة كبيرة ولو كانت لي القدرة لجعلت كل الذين يدرسون الفيزياء يقرئونه اجباريا بدل الكتب البيداغوجية التافهة التي توزع عليهم ..لقد قال (هل وجود الجسيمة الأولية نهاية الطريق ؟ ابدا، انها بداية الطريق –الطويل – نحو بناء نظرية كل شيء).
  انا اعتقد ان كل الفيزيائيين الذين مارسوا معادلات الكم و مجال هيغز والنموذج المعياري للجسميات والنسبية ونظرية الاوتار الفائقة وطول بلانك ومعادلات شرونديجر .. مؤمنون بالله في اعماق انفسهم ..
  انه كون باهر لدرجة لا تصدق انه رائع ومدهش ومميز وليس عشوائيا .. ممتعا مسليا ممتازا غامضا مليئا بالاسرار مشوق مثير وكل الصفات الرائعة التي تجعلك متحمساً ..لذا لا غرابة في ان سمى كتابه (الكون الانيق (..انه ببساطة كذلك ..
  
  
  من مقال لي : بوزون هيغز : الرابط للمقال الكامل هنا :
  
  http://goo.gl/X3OGJf
  
• 
  Rob

  AN INTRODUCTION BY WAY OF HYPERBOLIC SENTIMENT: The Elegant Universe is "The Bible" of superstring theory[*:].
  
  I close the covers of The Elegant Universe with powerfully mixed feelings. On the one hand, Brian Greene gives us a lucidly-written layman's-terms explanation for high-concept modern physics, providing an excellent survey of 20th century science and painting a vivid picture of a promising strategy for reconciling the discrepancies in the otherwise dominant theories. On the other hand, about half-way through the text, it devolves into (what feels like) a navel-gazing vanity project that fails to connect that promising strategy with the target audience (i.e., the layman that actually gives a damn about modern science).
  
  To be clear: the first third of the book is a remarkable accomplishment. Brian Greene is a cogent writer with a wonderful pedagogical streak that is able to produce a clear image of some otherwise hard-to-decipher concepts in modern physics. Because of The Elegant Universe, I feel like I now have a fairly good understanding of the core concepts underlying Einstein's theories of special and general relativity, and quantum mechanics (e.g., Heisenberg's Uncertainty Principle). Greene is also able to give a decent explanation regarding how these theories break down when you try to "merge" them (e.g., like when you come up with "infinite energy" and/or "infinite mass" and/or "infinite probabilities" through calculations of black holes or the Big Bang).
  
  This first third of the book is very accessible, very enjoyable, and very informative. Engaging, fascinating, and extremely powerful.
  
  Somewhere during that potent 130-150 pages, Greene remarks (something to the effect of): You cannot be said to fully understand something until you can explain both its system and significance to a complete stranger. (Not a quote, but I'm sure you know what I'm getting at...)
  
  And with that statement does Dr. Greene undermine the remaining two-thirds of the book. After introducing string theory, after explaining that it is a strategy with the potential to marry relativity and quantum mechanics, after getting you (the lay-reader) excited that you too will have some insight into the critical significance that is superstring theory — he glosses over some math (which doesn't really feel like physics after that first 120 pages) and more/less asks you to "bear with me here, trust me..." EXAMPLE: after introducing the concept of strings, the text rushes into a discussion of 6-dimensional "curled up"
  Calabi-Yau manifolds without really giving a good way of visualizing that whole mess[†:]. EXAMPLE: after 2 or 3 chapters about string theory where Greene is introducing it and discussing how it might reconcile relativity and quantum mechanics, he starts to segue into reconciling aspects of string theory with itself — looping back (like its own subject strings) on itself in a perverse recursion full of mathematical adjustments and jargon. EXAMPLE: in the midst of discussing how this New Science, and where you expect it to loop back on the promised explanations for the Old Science, Greene veers off into a series of anecdotes about "this one time at Harvard..." and/or "once at Princeton we stayed up all night and..." — which really just seemed a little gratuitous.
  
  By the time I realized what was happening, my attitude was already tainted. Perhaps I could have extracted more of the science if my cynicism hadn't kicked in so virulently and so early on in the reading. Perhaps spending more time with the end-notes will prove fruitful. Or perhaps on a future, subsequent follow-up reading I will discover that I was right the first time and we have 150 or so pages of incredible science writing and the remainder is chintzy vanity project[‡:].
  
  RATED FOR HYPE: ★★★★★
  RATED FOR STYLE: ★★★☆☆
  RATED FOR SCIENCE: ★★☆☆☆
  
  
  
  ---
  [*:] Let's hear it for faith-based science?
  
  [†:] This is partly me being overly critical of Greene's (in my opinion) cavalier treatment of the Calabi-Yau concepts immediately following their introduction. There are some end-notes and citations for further reading, and he does attempt to dedicate some space in the main text to the idea — but his "dumbing down" of the Calabi-Yau manifolds to the "ant in the garden hose" analogy just doesn't really address it with sufficient vigor. Not after the incredible work he did in the earlier chapters re explaining relativity and quantum mechanics. I suppose I may have been more satisfied with something along the lines of "you have your time dimension, your three 'regular' space dimensions, and then these other six are really dedicated to providing reference points to describing the shape and vibration of the string IN THE THREE DIMENSIONS YOU ARE ALREADY FAMILIAR WITH" — but no such explanation was there. If that's even really what he might have meant.
  
  [‡:] Which I mean in the nicest possible way...? To be fair, Greene leaves plenty of room throughout the text to permit himself (and his colleagues studying superstring theory) to be "wrong". It reminds me of when Robert Wright hedges his bets in
  The Moral Animal, saying that the evolutionary psychology approach (as championed by himself, Richard Dawkins, E.O. Wilson, Robert Trivers, and others) is a strong one that explains a whole lot but you better be careful before you go painting too broad of a stroke with those kinds of theories... Greene seems to do similar hedging, admitting that aspects of superstring theory seem tenuous (esp. when you consider how many "adjustments" they perform while "fine-tuning" a given aspect of the theory(s)) and that they (as scientists) are wise to temper their enthusiasm, to not lose sight of goals like "experimental verification". But then there's Greene's enthusiasm — which can easily electrify the reader but also just as easily undermine all of that careful hedging.
• 
  Elyse Walters

  My local book club picked this book for our non-fiction month. I've been a part of this group- the largest-best Bay Area Book club!!!!
  
  In the 5 years I been part of this group, I can't remember a more challenging book to fully understand. The superstring theory is 'taught' by Brian Green' for those of us with maybe a basic Physics level one course. I can't imagine understanding anything, without having had at least some High School or College physics. This book is not for everyone, yet it's Top Notch ....
  
  If you have a strong desire to read about The fundamental laws of the universe, how they are structured, then by all means, give this book a shot. I took soooo many notes, and I've still a dozen questions, yet the author does do an excellent job in explaining the new advances of the cosmos that have come to light during this last decade. The author explained over and over... So the lay person may understand that we must merge general relativity and quantum mechanics--and make use of string theory. It's the 'teaching' of the ways string theory appears which begins to get more challenging to comprehend. I've done my best... Yet hoping others in my book club might be able to fill in some holes which went way over my head.
• 
  Szplug

  Greene's eminently readable attempt to explain the possibilities for string/superstrings to provide the linchpin for the long-awaited-and-desired merger of gravity with the two nuclear and electromagnetic forces into a Grand United Theory. Frankly, the entire idea of rolled up dimensions—of a universe containing perhaps ten, twelve, eighteen dimensions, of which we are only capable of perceiving four—is suitably mind-blowing and humbling at the same time; and although Greene's low-culture themed analogies that frequently pop-up to help elucidate the complex concepts he is trying to convey may irritate at times, he does a bang-up job in making it understandable without blotting the outlines in thick physiquese or mathematics. Surfer-Dude physicist Garrett Lisi submitted an
  Exceptionally Simple Theory of Everything based upon the stunningly beautiful symmetry of Lie Groups as an alternative to String Theory a couple of years after the publication of Greene's follow-up
  The Fabric of the Cosmos; it will be interesting to see how Lisi's proposal affects the future of string/superstring theory as the most likely path towards that elusive group-wedding of the four forces. I believe that several physicists have now concluded that Lisi's theory doesn't hold up, but I'm intrigued by the rumblings I've encountered by others who consider string theory to be a corridor that is proving of a confining narrowness, one that has consumed a disproportionate amount of the energy from some of the top minds in this field in pursuit of a theory that more and more appears irreconcilably inelegant and complex for the unifying end that it is meant to achieve. I have some potentially stunning books on the shelf awaiting my attention—in particular, Lisa Randall's
  Warped Passages, Michio Kaku's
  Hyperspace, Michael Fayer's
  Absolutely Small, and Lee Smolin's
  The Trouble With Physics—all of which I have unfortunately neglected for some time now, but are ripe with the promise of immense rewards to the mind when their contents are finally consumed.
  
  Personally, one of the most stimulating moments in the The Elegant Universe was Greene's articulation of how we, as humans, are travelling through time at the speed of light; thus tickling my brain with the thought that light—immune to the mundane effects of forward-marching time—is a bridge towards an omnipotent godhead. If light is moving at the speed of light through space—not time—is it possible that its entire permutation from Big Bang through to Cosmic Deflation would be accessible in a single given moment of time, i.e, if some manner of consciousness—not necessarily as we conceive of it—was to exist at that level of configuration, would the entirety of past, present, and future—the ticking tenure that provides the structural frame for the playing out of human existence—be available? At temporal lightspeed, can any photon wave/particle duality be positionally known within Space-Time as it cannot to our Time-delimited minds? Would access to this particular modular level of existence—as alien as it may be to comprehend—be the beginnings of omniscience and the hierarchical understanding of how the universe plays out/was meant to play out/will play out? As an object approaches the speed of light, its mass becomes infinite—would the same exponential assault waylay ever-present light as it approaches the speed of time? Would fulgent awareness become infinitely sluggish or limited as it neared this clock-marked barrier? From the—for lack of a better word—point of view of Lightspeed, would there exist differing quantum pathways that wend throughout the four perceivable dimensions, and from a high enough level, will they appear identical at select points of chronological evolution? Thanks Brian, for zapping me like you did into further confused wonder.
• 
  Ana

  Physics books. Can I understand them properly? No. Am I still absolutely fascinated by them? Yes. String Theory. Do I understand it properly? Hell no. Am I fascinated by it? To the last detail.
• 
  Stuart

  The Elegant Universe: Superstrings, Hidden Dimensions, and the Quest for the Ultimate Theory
  If you’ve heard of string theory, and know it’s not about tying shoelaces, then you probably know about Newtonian and Einsteinian physics, especially that which pertains to gravity, special relativity, and general relativity. You’ve probably heard of quantum physics as well, which studies the microscopic interactions of particles. But you might not know that general relativity (which explains the behaviour of massive objects in the universe) and quantum physics (which describe particle behaviour in great detail), are two ways of explaining physical phenomena that do not mesh well and cannot explain the origin of the gravitational force, the fourth element of the Standard Model of Physics, the other three being the strong nuclear force, weak nuclear force, and electromagnetic force. This is where string theory was born, and despite it being extremely heavy on theory and very difficult to be tested at the experimental level, there has been a great deal discovered in particle physics, including the Higg’s boson (or “God particle) that was experimentally confirmed on 4 July 2012 using the Large Hadron Collider at CERN in Bern, Switzerland, which was depicted in very well in the 2013 documentary Particle Fever.
  
  String Theory is truly a mind-boggling and reality-bending collection of scientific theories attempting to bridge the gap between relativity, quantum physics, and gravitation. It’s not a single theory, and is still in its early developmental stage, and is immensely difficult to understand both conceptually and to formulate given the incredible complexity of the high-level mathematical constructs needed to model it. So if you are a layman or science enthusiast without a background in particle physics or advanced mathematics, you can be certain you will probably never really understand the underlying details, but Brian Greene, who is one of String Theory’s biggest proponents, has attempted to write a book to explain these highly speculative ideas in a book for non-scientists.
  
  Given the inherent difficulty in explaining such impossibly bizarre concepts without any complex equations, he does his level best by providing a large number of analogies to make the conceptualizing a bit easier, but even then you are likely to finish the book thinking, “Yes, I do understand a bit more than before, but much of that still went totally over my head.” So when judging books like this, it’s not really fair to say “Hey, I still don’t get String Theory, so Brian Greene did a bad job in his book.” Far from it, I’d say he tried very hard to convey all the key concepts, so I give him props for that. I understand his mother found the book impossible to understand and gave up, which prompted him to write a second, easier-to-understand version called The Fabric of the Cosmos (2003). Too late, as I started with The Elegant Universe (1999), but it wasn’t so bad.
  
  The book is so packed with mind-expanding concepts that it’s impossible to summarize, other than to list some of them here, borrowed from the very helpful SparkNotes website:
  
  Antimatter - Matter with the same gravitational properties as regular matter, but with an opposite electric charge and opposite nuclear force charges.
  
  Antiparticle - A particle of antimatter.
  
  Big Bang - The widely accepted theory concerning the origin of the universe. The big bang theory posits that the universe evolved approximately 10 to 15 billion years ago from the explosion of an incredibly dense, hot substance that was contained at one point. The universe has been expanding since the first fraction of a second after the big bang occurred.
  
  Big Crunch - The term referring to what some physicists believe will happen when the expanding universe stops and implodes. When the big crunch occurs, according to the theory, all space and matter will collapse together.
  
  Black Hole - A region of space formed when a giant star collapses and all of its mass compresses to a single point, forming a gravitational field so overpowering that it traps anything that comes close to it, including light.
  
  Boson - A pattern of string vibration with an amount of spin measurable in whole numbers. A boson is most often a messenger particle.
  
  Bosonic String Theory - The first version of string theory. Bosonic string theory, which dealt with string’s vibrational patterns, emerged in the 1970s. This version was later revised and replaced by supersymmetrical string theory.
  
  Calabi-Yau Shape/Space - A theoretical configuration that many physicists believe might contain the additional dimension string theory requires. Many thousands of such possible configurations exist, but string theory has yet to verify the correct one.
  
  Electromagnetism/Electromagnetic Force - One of the four fundamental forces, along with gravity, the strong force, and the weak force. Electromagnetism determines all types of electromagnetic radiation, including light, X-rays, and radio waves.
  
  Electroweak Theory - A relativistic quantum field theory that describes the weak force and the electromagnetic force within a single framework.
  
  Elegance - To Greene, string theory defines elegance because it is extremely simple, but it may explain every event in the universe.
  
  Elementary Particle - The indivisible or “uncuttable” unit found in all matter and forces. Elementary particles are now categorized by quarks and leptons, and their antimatter counterparts.
  
  Equivalence Principle - The basic tenet of general relativity. The equivalence principle states that accelerated motion is indistinguishable from gravity. It generalizes the theory of relativity by showing that all observers, regardless of their state of motion, can say that they are at rest, provided they take the presence of a gravitational field into account.
  
  Flop Transitions - Also called topography-changing transitions. Flop transitions are the act of Calabi-Yau space ripping and repairing itself.
  
  Force Carrier Particle - A particle that transmits one of the four fundamental forces. The strong force is associated with gluon; electromagnetism with the photon; the weak force with W and Z; and graviton (which hasn’t yet been discovered) with gravity.
  
  Fundamental Force - There are four fundamental forces : electromagnetism, strong force, weak force, and gravity.
  
  General Theory Of Relativity - Albert Einstein’s formulation that gravity results from the warping of spacetime. Through this curvature, space and time communicate the gravitational force.
  
  Graviton - Physicists believe that graviton—which has not yet been proven to exist—is the particle carrier of the gravitational force.
  
  Gravity - The weakest and most mysterious of the four fundamental forces. Gravity acts over an infinite range, and gravitation describes the force of attraction between objects containing either mass or energy.
  
  M-Theory - The theory under which all five previous versions of string theory fall. The most recent synthesis of string theory ideas, M-theory predicts eleven spacetime dimensions and describes “membranes” as a fundamental element in nature.
  
  Mirror Symmetry - A precept of string theory that demonstrates how two different Calabi-Yau shapes have identical physics.
  
  Newton’s Laws Of Motion - Laws of motion based on an absolute and unchanging notion of space and time. Newton’s laws of motion were later replaced by Einstein’s theory of special relativity.
  
  Particle Accelerator - A machine that speeds up the movement of particles and then either shoots them out at a fixed target or makes them collide. Particle accelerators allow physicists to study the movement of particles in extreme conditions.
  
  Perturbation Theory - A formal framework for making approximate calculations. Perturbation theory is a linchpin of string theory in its current form. The approximate solution will be refined later as more details fall into place.
  
  Photon - The smallest bundle of light. Photons are the messenger particles of the electromagnetic force.
  
  Photoelectric Effect - The action of electrons shooting from a metallic surface when light is shone onto that surface.
  
  Planck Energy - The energy required to probe Planck-length-scale distances.
  
  Planck Length - Planck length—approximately 10–33 centimeters—is the scale at which quantum fluctuations occur. Planck length is also the size of a typical string.
  
  Planck Mass - Planck mass is roughly equal to the mass of a grain of dust, or ten billion billion times the mass of a proton.
  
  Planck’s Constant - Planck’s constant is also known (and written) as the “h-bar.” It is a fundamental component of quantum mechanics.
  
  Planck Tension - About 10 (to the 39th power) tons. Planck tension is equal to the tension of a typical string.
  
  Quanta - According to the laws of quantum mechanics, the smallest physical unit that something can be broken into. Photons are the quanta of the electromagnetic field.
  
  Quantum Field Theory - Also known as relativistic quantum field theory. Quantum field theory describes particles in terms of fields, as well as how particles can be created or annihilated, and how they scatter.
  
  Quantum Foam - Also known as spacetime foam. Quantum foam is the violent turbulence of spatial fabric at an ultramicroscopic scale. Its existence is one of the chief reasons that quantum mechanics is incompatible with general relativity.
  
  Quantum Mechanics - The framework of laws that describe matter on atomic and subatomic scales. The uncertainty principle is a pillar of quantum mechanics.
  
  Quarks - A family of elementary particles (matter or antimatter) that make up protons and neutrons. There are many types of quarks: up, charm, top, down, strange, and bottom. Quarks are acted upon by the strong force. Murray Gell-Mann named quarks after he read James Joyce’s Finnegans Wake.
  
  Special Theory Of Relativity - Einstein’s description of particle motion, which hinges on the constancy of the speed of light. The theory of relativity states that even if an observer is moving, the speed of light never changes. Distance, time, and mass, however, all depend on the observer’s relative motion.
  
  Spin - The theory that all particles have an intrinsic amount of spin in either whole- or half-integer denominations.
  
  Standard Model - A quantum model that explains three of the fundamental forces—electromagnetism, the strong force, and the weak force—but does not take gravity into consideration.
  
  String - Miniscule one-dimensional vibrating strands of energy. String theories posit that these filaments are the basis of all elementary particles. The length of a string is 10–33 cm; strings have no width.
  
  Strong Force - So called because it is the strongest of the four fundamental forces. It holds quarks together and keeps protons and neutrons in the nuclei of atoms.
  
  Superstring Theory - A theory that describes resonant strings as the most elementary units in nature.
  
  Supersymmetry - A principle of symmetry relating the properties of particles with a whole-number quantity of spin (bosons) to those with half a whole number of spin (fermions). Supersymmetry posits that all elementary matter particles have corresponding superpartner force carrier particles. No one has yet observed these theoretical superpartners, which are thought to be even larger than their counterparts.
  
  Tachyon - A particle that has a negative mass when squared. The existence of a tachyon usually indicates a problem with a theory.
  
  Topology - The study of geometric figures’ properties that exhibit ongoing transformations and are unchanged by stretching or bending.
  
  Uncertainty Principle - Heisenberg’s uncertainty principle is the crux of quantum mechanics. It proclaims that you can never know both the position and the velocity of a particle simultaneously. To isolate one, you must somehow blur the other.
  
  Unified Field Theory - A theory describing all four fundamental forces and all of matter within a single framework.
  
  Weak Force - One of the four fundamental forces. Weak force operates over a short range.
• 
  ayden

  I read this book while taking a course (for non-physics students) called Modern Physics in Perspective, which centered on string theory. I learned so, so, so much in this class & the book helped a lot. If you're reading this book unassisted, be aware that there are some very confusing sections that you'll need to read a few times. Sometimes his analogies are a bit too inane. Also, I've discovered that many physicists have an unhealthy obsession with their research pet projects- I'd advise that you ignore the sections on Calabi-Yau shapes entirely.
  
  These faults aside, The Elegant Universe is the only book about science that I have ever read from start to finish and enjoyed from start to finish. It'll blow your mind.
  
• 
  مولاي أرشيد أحمدو

  كتاب ممتع إلى أقصى الحدود
  لا يتطلب منك معرفة عميقة بالفيزياء
  بل فقط يكفي الشغف حول معرفة هذا الكون الأنيق
• 
  Jenny

  The first few chapters are fascinating as Greene recounts the history of modern physics, its departure from classical, Newtonian understanding. Then, he moves into string theory, and I found the arguments and explanations harder to follow. As Greene wrote the book just a few years after the Second Superstring Revolution, it makes sense that the arguments aren't as well-developed as those describing theories and experiments perfected and refined over the past 100 years or so. I really enjoyed the last few chapters: one on black holes, one about cosmology, and the final chapter, entitled "Prospects," in which Greene discusses the implications of string/M-theory on future thought and the possible questions string/M-theory may be able to answer.
  Overall, I really liked this book. It took me a while to get through because of the subtlety of the arguments and the density of the subject matter (no pun intended), but it was extremely informative. I also enjoyed Greene's writing style, especially the examples/metaphors/analogs he presented the reader with for help in understanding the extremely subtle topics he discusses.
  The only thing missing for me from Greene (and from Hawking and K.C. Cole) is: why did the Big Bang happen when it did, and where did the materials constituting the singularity (or the "Planck-size nugget") come from? My only problem with non-Christian, scientific accounts. The physicists never do offer a possible explanation of the origins of the origins.
  I recommend this book to anybody interested in astrophysics, to fans of Greene, and to anybody looking for a book geared towards general readers that is more updated than Hawking's A Brief History of Time but that still offers insight into points that Hawking discusses in his famous book.
• 
  Fatima Al-Quwaie

  في مزيج نادر من البصيرة العلمية، والكتابة الأنيقة كأناقة النظريات التي يناقشها، يزيل برايان جرين الغموض عن أكثر النظريات العلمية تعقيداً، والتي تسمى بنظرية "Super String Theory" أو الأوتار الفائقة وهذه النظرية تقول: إن كل الأحداث المدهشة التي تحدث في الكون هي انعكاس لمبدأ فيزيائي واحد ومظاهر لكينونة واحدة وهي خيوط متناهية الصغر من الطاقة، يبلغ حجمها واحد في المليار من المليار من حجم الذرة.  
  
  ويعطي جرين في كتابه العديد من الأمثلة المستمدة من عالمنا اليومي من الحركة أثناء ركوب ألعاب الملاهي، إلى وقوف النمل على خرطوم المياه، ليفسر لنا واقعنا الجميل والغريب في آن، والذي يكشفه لنا علم الفيزياء. 
  
  والكتاب يعرض النظرية في لغة تجمع بين الدقة العلمية والاسلوب الأدبي الرفيع، يتساءل عن حدود معرفتنا بالكون، ويتناول مأزق المكان والزمان والكم، ناظراً الى الكل الكوني، باعتباره سمفونية كونية يبني من خلالها نظرية الأوتار التي قد تبدو مستعصية على غير المتخصص في الفيزياء، ولكنها قراءة تستهوي جميع من يريدون التأمل في الكون، ومن هذه الوجهة يساهم الكتاب في تدريب القارئ غير المتخصص على استيعاب المعرفة العلمية، اضافة الى ما يثيره من أسئلة جديدة لدى المتخصص.
  
  الكتاب رحلة ممتعة في عالم الفيزياء الحديثة، ويطمح لجعلنا أقرب لفهم السؤال الأبدي: كيف يعمل الكون!
• 
  Howard

  4 Stars for The Elegant Universe (audiobook) by Brian Greene read by Erik Davies. This is a great overview of string theory. Greene does good job of putting a number of theories into perspective. It can be a bit of a challenge keeping up with the science listening to the audiobook.
• 
  Daniel

  Greene can explain complicated theories better than anyone. I read the best explanation of Einstein’s general and special relativity theories. Especially when when we see an object travelling at high speed, they appear the age more slowly. But the same applies to the other side looking at us, making us age more slowly from their standpoint! This is perfectly fine unless they want to meet up, and one side accelerates to meet the other one. In this case the accelerating side will find they indeed had aged much more than the side being caught up. Had gravity bends space time itself, and we always travel at light speed; any other movement slows down time itself.
  
  Nobody really understands quantum physics, like a photon behaves like a particle when passing through one slit but when faced with double slit it interferes with itself and show wave interference patterns. Particles can appear and disappear spontaneously. Shrodinger’s cat is both dead and alive until one looks and collapses its wave function.
  
  Gravity stumps quantum physics because when quantum equations are applied to gravitons, infinite solutions appear. So string theory comes to the rescue.
  
  So strings are fundamental stuff of everything, the real Greek Atoms. They coil up in 3 big dimensions and many tiny dimensions. Unfortunately this is untestable and thus lots of maths and imagination are required. In the end, the M theory which is a master theories of all string sub-theories is proposed. 10 physical and 1 time dimension.
  
  I must say I am a but lost from that point onwards, because of lack of experimental support. To identify strings. we would need an impossibly large amount of energy so we may Never be able to prove its existence. It is tough to actual acknowledge that we may never be able to go much further in particle physics, but such is life.
  
  The best physics book I have ever read.
  
  
• 
  João Vaz

  Dear God,
  
  Will you ever allow us folks down here on Earth to come up with Einstein’s dream of a Theory of Everything (ToE)? The fact of the matter is that there are essentially two opposing theories upon which rests our knowledge of the universe: General Relativity and Quantum Mechanics. That is, the world of the large and the world of the miniscule. But whenever we try to unify them, our calculations just fall short; or better, fall large!, for we bump into infinity.
  
  Oh wait!, this book has just told me that String theorists already have! They claim that all fundamental particles are composed of tiny vibrating strings of energy whose movement gives rise to all those different particles that we know of. And in so doing, not only do these strings fit into Quantum theory, but they're also able to accurately predict the whys and wherefores of the big bulks of matter, like those of stars and galaxies! TADÃÃN!
  
  BUT, not only are there five different versions to the theory, but also, and because we are talking about excruciatingly small objects, it is impossible to test it! Not really a theory is it? (daimn!) It shamelessly enters the realm of Philosophy… Oh those naysayers! Tell me of one thing that we take for granted today that hasn’t started as Cartesian doubt! You go get them my fairy little oscillating strings, which so happen to explain black holes!
  
  But back to you old man, you never really cease to surprise me! So you’re telling me that the universe is this big cosmic symphony whose musical notes are the sounds exuded by the movement of strings? Oh you shrewd mayster!, I always knew you had a bend for drama!
  
  With my heart in your stars,
  
  J
  
• 
  ΑνναΦ

  E' un Universo liquido
  
  E' un Universo difficile, lavoro duro e destino incerto.
  Dopo Zygmut Baumann, ci voleva anche la fisica quantistica a toglierci ogni certezza, immersi in un cosmo che funziona come un mantice, si gonfia e si sgonfia (forse), e noi in mezzo, a vivere chissà, forse più vite, su più dimensioni, arrotolate come bigodini o srotolate come tappeti.
  Richard Feynman, guru della meccanica quantistica, disse “penso di poter affermare con sicurezza che nessuno capisce la meccanica quantistica”. Molto bene, a me qualcosa sembra di aver capito.
  Il bello di questo libro, molto elegante, è che è scritto così bene che ti sembra di capire tutto. Greene è bravo, conduce il lettore medio, non tecnico, mano per mano, esempi chiari e divertenti e ti fa capire. Poi, quando sei contento perché pensi di aver raggiunto il tuo scoglio su cui aggrapparti felice, in mezzo a tutte queste turbolenze quantistiche, ti spiazza dimostrandoti che non è così, del resto abbiamo capito che dobbiamo esser pronti a tutto: tutto è relativo (Einstein) e tutto è assai indeterminato (fisica quantistica).
  Forti di queste certezze incerte, colpisce il fatto che i fisici dei quanti nella visione cosmogologica arrivino a teorizzare cose postulate secoli fa dai filosofi Greci o dai corsi e ricorsi di Vico o dell'Univesro eterno e dei molti mondi di Tommaso Bruno. Forse scopriremo che la fisica coincide con la filosofia. O magari con la Metafisica. Buffo no?
• 
  Genia Lukin

  I never really got the hang of String Theory. I find it awfully weird and almost nigh-unscientific. Not being a physicist, I try not to make judgments about it, since I clearly don't understand it one bit - at least on the math level! - but I have to say that Brian Greene didn't endear it to me.
  
  I also fervently found myself wishing for the Nth time that science books were not so firmly divided between "professional, terrifying math texts" and "written for people who never figured out the Theory of Relativity". I think we need "Science for the Educated Sci-Fi Reader" or something like that. As it is, unless you're Stephen Hawking, who pretty much has the right to do anything he liked, if you're trying to explain relativity to me, again, you will put me off.
• 
  Nada Khaled

  الحقيقة ليست سوى وهم، لكنه وهم ثابت.
  هذا الكتاب رائع إلى حد يعجز معه الوصف ..
  - الفيزياء بالنسبة لى لا تمثل مجرد قرا��ة فقط أو هواية بل تمثل لى أستكشاف عوالم مجهرية وعوالم مجهولة، إذا أستطاع العقل البشرى أحتوائها كاملةً سينفجر كسوبر نوفا يملأ الجو بمعلومات مهولة خارج إطار المألوف .
  ..
  براين غرين عبقرى فى تبسيط وتوضيح المعلومات، بالرغم من أنه تحدث عن النسبية وبداية الكون ونشأته كلها فى أول كم فصل، وتناول الكتاب الفصول الباقية كلها ميكانيكا الكم، ونظرية الأوتار الفائقة، إلا أننى تكونت عندى خلفية لا بأس بها بنظرية كل شيئ ونظرية الأوتار، .. أتمنى ف المستقبل أن استطيع أن أكتب كتب فيزيائية عن الكون وتبسيطه للغاية للمبتدئين وأن أستطع أن أجعلهم يرون الجمال الذى أراه فى كل صفحة من صفحات كتب الفيزياء وخصوصا الفلكية 💜
• 
  Dan (Reader&Writer)

  I love this book! Now I admit, I’m a maths guy, but I found dipping in and out of this to be so much fun. Complex stuff presented simply, if you like maths, you’ll most likely love this too.
• 
  Julio

  Una excelente y razonablemente clara presentación de la teoría de cuerdas.
  
  El autor, que hace un esfuerzo decidido en ser claro a pesar de la dificultad del tema, hace primero una presentación amplia de las dos teorías que explican nuestro universo: la teoría de la relatividad y la mecánica cuántica.
  
  La primera explica el comportamiento de los objetos macroscópicos con la gravedad como elemento central y tomando en cuenta los efectos sobre el tiempo y el espacio que ella genera. Green explica los elementos centrales de la teoría, incluyendo las características poco intuitivas (como el hecho que la masa de un cuerpo deforma el espacio y afecta el paso del tiempo o el hecho que la velocidad de un rayo de luz en el vacío es siempre la misma, incluso para dos observadores que se mueven a velocidades diferentes entre si - algo que no ocurre (o que no se detecta) con objetos que se mueven a las bajas velocidades en que vivimos) y las notables consecuencias sobre nuestra comprensión del universo.
  
  La teoría cuántica explica mas bien el comportamiento de las partículas a nivel atómico y subatómico. Si la teoría de la relatividad genera resultados poco intuitivos (pero comprensibles al fin), la teoría cuántica es tremendamente anti-intuitiva. Cómo entender por ejemplo el clásico experimento de las dos rendijas, en el que un flujo de fotones parece interferir consigo mismo, como si el mismo fotón pasara por ambas rendijas al mismo tiempo? O que una partícula se describe por medio de una función de onda que define una distribución de probabilidades del estado de esa partícula, función que colapsa y genera un "resultado" cuando la partícula es observada? (El libro no habla del entrelazamiento cuántico, otro ejemplo de lo difícil que es entender la mecánica cuántica. En efecto, el entrelazamiento implica que si uno actúa sobre un partícula que está entrelazada con otra y cambia su estado, el estado de la otra partícula cambia instantáneamente, aunque se encuentre a muchísima distancia de la primera, violando el principio de localidad). La mecánica cuántica considera que le energía se emite y absorbe en cantidades discretas (cuantos) y permite explicar la acción de las otras 3 fuerzas de la naturaleza (la electromagnética, la fuerza nuclear fuerte y la fuerza nuclear débil).
  
  Ambas teorías explican el universo en sus respectivos ámbitos de manera notablemente certera. Experimento tras experimento muestran que ambas son descripciones extraordinarias de la realidad. Sin embargo, es sorprendente que se requieran dos teorías para explicar la misma realidad. La teoría de la relatividad no puede explicar lo que ocurre en escalas subatómicas donde los efectos cuánticos dominan, ni la mecánica cuántica lo que ocurre a escalas macroscópicas y con presencia de la gravedad. Es profundamente insatisfactorio para los físicos tener dos herramientas, que funcionan tan bien, pero que son fundamentalmente incompatibles para explicar un mismo objeto: nuestro universo.
  
  Green presenta la promesa más grande para tener una teoría única que permita explicarlo todo: la teoría de cuerdas. Según lo que Green explica, la incompatibilidad entre ambas teorías (que es evidente en distancias muy pequeñas, por debajo de la distancia de Planck) resulta del hecho que la relatividad considera un universo homogéneo en toda escala. Sin embargo, en muy pequeñas escalas, los efectos cuánticos (que incluyen, por ejemplo, la creación espontánea y temporal de pares de partículas y anti-partículas que generan una ebullición intensa - una espuma cuántica - pero temporal - pues la energía prestada para crear ese par debe ser devuelta muy rápido) evitan que esa homogeneidad exista.
  
  Según la teoría de cuerdas, el universo está hecho de pequeñas cuerdas cuyos patrones de resonancia (su vibración) generan las masas de las partículas que observamos además de las cargas de las fuerzas. De todas las fuerzas. En efecto, la teoría de cuerdas permite explicar las 4 fuerzas, incluyendo así la gravedad desde el inicio! (Algunos consideran que esa es su primera predicción (o, mas bien, pos-dicción, pues ya sabíamos que la gravedad existe)). Más interesante aún, la teoría de cuerdas tiene el potencial de explicar las masas de las partículas elementales y las características de estas fuerzas, algo que la mecánica cuántica no puede hacer. En efecto, la teoría cuántica toma esos valores como datos, sin explicarlos. Eso es también notable, pues afinar los valores de la mecánica cuántica con datos exógenos suena un poco arbitrario.
  
  Lastimosamente, la teoría de cuerdas es tan compleja matemáticamente que a pesar de su potencial explicativo, los resultados no pueden aún calcularse y algunos de ellos sólo pueden aproximarse. Eso reduce el potencial de generar predicciones que puedan ser luego verificadas empíricamente. Una notable predicción, sin embargo, es que como consecuencia de la simetría del universo (y la teoría de cuerdas es super simétrica, por eso el nombre de super-cuerdas), cada partícula elemental tiene otra partícula "simétrica", pero cuya masa estimada es muchísimo más alta que toda partícula conocida u obtenida en los aceleradores actuales, lo que dificulta su validación empírica. Encontrar esas partículas super masivas en el futuro sería una prueba substancial en favor de la teoría de cuerdas.
  
  Otro elemento sorprendente es que la teoría de cuerdas requiere la existencia de 10 dimensiones (9 espaciales y una temporal). Vivimos en un universo de (aparentemente) 3 dimensiones temporales. Dónde están las otras dimensiones? Pues enrolladas sobre sí mismas de manera muy compacta y, por tanto, prácticamente indetectables para nosotros. Pero no sólo que esas dimensiones deben existir, sino que su forma precisa tiene un rol crítico en determinar la forma en que las cuerdas vibran - y por tanto, en las características de las partículas y fuerzas que esas vibraciones generan...
  
  Curiosamente, la teoría de cuerdas muestra también que no es posible para un objecto reducirse a un tamaño inferior a la distancia de Planck. Eso se debe a que la vibración de las cuerdas tiene un valor mínimo (ligado también al principio de incertidumbre), y por tanto no puede ser inferior a cierta distancia (que es mayor a la de Planck). Ese aspecto permitiría explicar por qué la teoría de cuerdas resuelve el problema de la incompatibilidad entre las dos otras teorías. En efecto, si la teoría de la relatividad pierde sentido cuando se aplica a distancias muy pequeñas (inferiores a la distancia de Planck) donde el caos cuántico impide la homogeneidad que la relatividad requiere, pero en realidad, no es posible llegar a esas distancias, esa incompatibilidad desaparece pues no hay forma nunca de llegar a esas distancias. La mecánica cuántica, por su lado, se equivoca entonces en considerar posible llegar a esas distancias.
  
  Eso permite resolver un par de aspectos que eran imposibles de explicar con las teorías existentes. Por ejemplo, que pasa en la singularidad en el centro de un agujero negro - que pareciera que podría rasgar la trama del espacio - y que pasó al inicio del Big Bang, donde se supone que todo el universo estaba concentrado en un punto de infinita masa y temperatura.
  
  Un último comentario: a falta de una teoría de cuerdas, hay en realidad cinco. De inicio, eso podría quitarle seriedad a la propuesta. Es bueno tener una teoría que explique todo, pero tener 5, sin poder elegir una, es por lo menos curioso. Sin embargo, Green explica que a mediados de la década de los 90, Edward Witten postuló que todas las 5 forman parte de una única y misma teoría. En efecto, él demostró la relación entre dos de ellas al pasar de una a otra cambiando el valor de su constante de acoplamiento. Esto es: el universo que una generaba usando una constante de acoplamiento alta (mayor a uno) era el mismo que la otra generaba con una constante de acoplamiento baja (menor a uno). No sólo eso, sino que al aumentar substancialmente el valor de esta constante, aparecía una 11 dimension (una más!) que no se había tomado en cuenta en ninguna de las 5 teorías iniciales y que provocaría que las cuerdas de repente muestren una segunda dimensión. Ya no son entonces cuerdas unidimensionales!
  
  Existiría entonces una única teoría (llamada M-theory) con 11 dimensiones que absorbe a las 5 previas - que resultan ser visiones diferentes de la misma - y que podría, esa vez sí, ser la Teoría del Todo...
  
  Será?
• 
  Marius

  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.