Picked this one up in preparation for an event with Brian Greene. Written over 15 years ago, it is missing the latest developments and consensus, which seems to be that the original vision for String Theory (ST) as a TOE didn’t pan out, yet it is still the only TOE we got. It's a bitch we can’t test it, and a shame we can’t find the shape of the Calabi-Yau manifold that corresponds to reality that we live in, but otherwise ST is quite beautiful indeed.

On the plus side - ideas from ST are now firmly embedded into quantum field theories, condensed matter physics, and cosmology. Also, in select areas, but in an unprecedented fashion, ST forged away ahead of mathematics by providing the intuitions that weren’t available to the latter.

Anyway, back to the book - regardless of where we are today, Greene gives a nice intro into the historiography and basic tenets of ST, and provides a nice expose on the challenges that any TOE would have to grapple with sooner or later. Rest are notes to self.

Starts off with Einstein’s resolution to Maxwell-Newton incompatibility (via special relativity), and then Newton’s gravity as force-at-distance paradox (general relativity); frames ST as an attempt to resolve GTR and QM.

Brief, fairly conventional overview of SR/GTR and QM. Nice stories of how SR logically falls out of fully appreciating the absoluteness of c, and similarly how QM falls out of fully accepting implications of h (Planck’s constant) . Feynman sum-over-history interpretation is rarely covered, so that was cool.

Unification attempts. Must explain all 4 fundamental forces at quantum level. Quantum Field Theory(s) do it for 3. Issues with G: Schrodinger’s equation blows up at sub-Planck level, Heisenberg’s “borrowing of energy” resulting in “constant creation and destruction” is a real nuisance, and zero-gravity flat space is no longer flat due to quantum foam.

Enter ST. Standard Model’s zero-dimension point particles blow up math with zero distances and infinite energies at the limit. But Strings are 1-dimensional, and end up quantizing size with a minimum non-zero value, and so quantum foam is masked. Now zero-g space is actually flat, ‘cause smallest building block (1D string) is too coarse. QM and GTR play nicely together.

Crap, infinities are avoided, but you still get probabilities going negative in Schrodinger’s equation… Not to worry – add 6 curved dimensions to spacetime and you are home free! But where is “home” in the 10D Calabi-Yau landscape of possibilities??

Btw, “String Theory”’s full name is Superstring Theory with “super” for supersymmetry. Quite nifty with particles, antiparticles and spin symmetries.

But it gets even better with symmetry, you see – with ST when you collapse something you don’t shrink to zero (minimum size constraint), but you go through the minimum and blow it out on the other side. And so you got “mirror symmetry” Calabi-Yau manifolds – geometrically different, yet physics-wise equivalent.

And boy, ST gets a lot of mileage out of minimum size and mirror symmetry – seems like whenever there is an issue, just transform it into a different geometric space where it is easier to solve. And if math blows up, dig up that minimum size constraint and avoid that pesky singularity.

For example, in the 90s there were 5 legitimate and different formulations of ST (“Type I”, “Heterotic” etc.), a tad hard to maintain a straight face when you are shooting for an ultimate TOE… But in ’95 Edward Witten himself unifies them all into M-theory, by throwing in another (11th!) dimension and demonstrating the equivalence of the 5 ST theories. Not to be complacent he even throws in a bonus 6th one - 11D supergravity!

Now let's launch ST into outer space and see what sticks. Black Hole as elementary particle? No problem, ST got you covered via Calabi-Yau equivalence. Hawking radiation and black hole entropy? ST jumps in with black hole thermodynamics. And now, for the encore - what happens when black hole swallows Schrodinger’s wave function!? Is information lost? Not sure about ST, but I distinctly hear Claude Shannon’s muffled moan coming from his grave… Curtain falls.

“The Elegant Universe” gives an introduction to string theory. It starts by talking about quantum physics and Einstein’s relativity moving on to explain what the principles of string theory are and how it fits between the previous two.

The book is written primarily for non-physicists who want to gain a better understanding of string theory: the author does a very good job in keeping things as simple as possible.

I can’t say I know everything about string theory now, obviously, but I reached my goal to find out what is about and why is it considered so important.

My only complaint is that, perhaps, there is a bit too much information, especially in the second half of the books, but probably readers who are more into physics that I am will welcome the extra information

I really liked this book. It wasn’t an easy read, but it was very informative and worth the effort.

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 بال��لم 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.

على 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

Picked this back up after many many years! The first few chapters covering relativity and quantum mechanics were fairly accessible, but not sure how much I retained about string theory itself. Will have to look into where the theory had gone in the decades since this was published.

This book blew my mind countless times as I read through it, so much so that I could usually only read 10-20 pages in one sitting. I had physics in high school, watched Cosmos and tons of other programs on the universe/relativity/quantum physics etc. so I have always had an interest but not enough to have that be my profession - nor am I smart enough in that way. Books like this let you visit that world for a while and this author does a fantastic job explaining general and advanced physics, Einstein, etc with many real world examples. Trust me, your mind will be doing flip flops when he talks about time bending, space travel, etc. After he builds the foundation, he sets the stage to cover string theory which many believe will be the next great leap in figuring out why the universe exists and where is it going. Awesome read to keep your mind sharp.

Temel aldığı konular üzerine yazılmış en önemli en azından Türkçe çevirisi yapılanlar arasında en önemli eserlerden biri. Yalnız benzer bazı ünlü örneklerle karşılaştırıldığında pek çok bölümünde belli bir altyapı bekleyen bir kitap olduğunu belirtmek gerek. Captain Fantastic filminde kızlardan biri bu kitabı okuyordu diye hatırlıyorum.

[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 n  String Theory and M-Theoryn (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...

Jeigu nori perskaityti tik vieną knygą apie fiziką, tebūnie tai ši

كتاب في أغلبه عن نظرية الأوتار.. بالنسبة أجزاء كثيرة منه استعصت على فهمي، لكن يبقى كتابًا مفيدًا جدًا..

3.5

او اتفرج على السلسله اتعملت 2003
الجزء الاول
http://www.youtube.com/watch?v=UV_X2B...

الجزء التانى
http://www.youtube.com/watch?v=k9giLn...

الجزء التالت
http://www.youtube.com/watch?v=36tGKr...

I was given this book as a gift. I typically don't go for the sort of fluffy stuff you'd find in the "Science" section at Barnes & Noble, which I figured this would be. I'm much more into mathematics than physics and have devoted most of my academic career to math shit rather than physics shit. So I was already prepared to lose my footing at some point in this book. I have a pretty good grasp on Special Relativity though so I tried to use that as a gauge for how well this dude was describing the more recent stuff beyond the point where my eyes just glazed over.
I was happy that this fella got into stuff that lost me. It worries me when I finish a book about a complex or abstract thing and it's not a struggle to understand the material. I wonder whether the writer is just that good or that bad.
What I found about this dude is that his wanting to illustrate everything with a metaphor or an analogy wound up confusing the stuff more. I mean, some were cool and I think I gleaned something of the rough shape of an idea. There were other spots where he used 3-4 different metaphors to get across an idea that was already pretty damn abstract. I think at those spots I'd have preferred more elaboration in the form of the notes in the back for "the expert reader" or for "the mathematically inclined".
I basically read this as a starting point. I kept a book for notes as I read and now I have a bunch of pages of leads for further investigation.
On a superficial level, I liked this guy's writing style. And the book was somewhat enjoyable while discussing bananas shit. I think there was a chapter or 2 where my reading was as productive as staring at the floor. All in all I don't know who I'd recommend this to. I'm part of a math club and no one there would take it off my hands when I was done because they don't like "rock star physicists" who write fluffy science books. But at the same time I can't give it to my mom because it does get into stuff within the first page that would lose her.
I'm not sure if all this explains why I gave it 3 stars, but I felt the need to be lengthy.