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Just Six Numbers: The Deep Forces That Shape the Universe

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How did a single "genesis event" create billions of galaxies, black holes, stars and planets? How did atoms assemble -- here on earth, and perhaps on other worlds -- into living beings intricate enough to ponder their origins? What fundamental laws govern our universe?This book describes new discoveries and offers remarkable insights into these fundamental questions. There are deep connections between stars and atoms, between the cosmos and the microworld. Just six numbers, imprinted in the "big bang," determine the essential features of our entire physical world. Moreover, cosmic evolution is astonishingly sensitive to the values of these numbers. If any one of them were "untuned," there could be no stars and no life. This realization offers a radically new perspective on our universe, our place in it, and the nature of physical laws.

208 pages, Paperback

First published January 1, 1999

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About the author

Martin J. Rees

70 books270 followers
Martin John Rees, Baron Rees of Ludlow, OM, PRS (born June 23, 1942 in York) is an English cosmologist and astrophysicist. He has been Astronomer Royal since 1995, and Master of Trinity College, Cambridge since 2004. He became President of the Royal Society on December 1, 2005.

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5 stars
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96 (1%)
Displaying 1 - 30 of 207 reviews
Profile Image for Manny.
Author 29 books13.5k followers
September 27, 2018
[Original review, November 2008]

This book blew me away... I hadn't been paying attention, and had missed a scientific revolution that had happened right under my nose! To cut to the chase: either someone created the Universe expressly to make it suitable for living beings, or there are lots of universes, and we just happen to be in one of the rare ones that support life. Right now, there don't seem to be many other serious alternatives.

If you have trouble believing this, get Rees's excellent book. It will change the way you think about things.

[Postscript, December 2008]

I was just looking at Trevor's review, and thought I would update my own. Here are a couple more thoughts. First, much as I hate saying it, the creationists have a stronger position now than they've had for the last 300 years. There's something really odd about the way the physical constants are so finely tuned. Some of them need to be correct to multiple decimal places. Of course, when I say "creationists", I don't mean people who claim the world was made 10,000 years ago. I mean the faction who agree that most of science is correct, but want some Creator to have started the whole thing off.

I don't see that it's a real counter-argument that God wouldn't have anything to do for the next 13 billion years. Maybe time passes very differently for Him. Maybe He isn't really at all interested in what we're up to, and is only omnipotent and omniscient in a narrow technical sense. Suppose, as an extreme example, that our whole universe was a simulation that some student had set up as a term project in the university's quantum computer. We see 13 billion years, but from His point of view He is running us over the weekend. He's an ordinary 19 year old, He's only doing it to pass Cosmology 101, and He even copied the critical parameter settings from a friend as some students do. I don't actually see why it's inconsistent with the observed data! There could be a short story in this.

I'm sorry if religious people find the above horribly blasphemous. All I'm saying is: one explanation of the facts is that the universe was created, but we can deduce nothing at all from that about the nature of the Creator.

[Postscript, August 2012]

I have read a good deal more cosmology since I first came across Just Six Numbers in 2006, and thought I would re-read it to see what difference this had made. I'm pleased to say that the book still comes across a fine piece of work, and if you want to get a quick introduction to cosmology I strongly recommend it. The writing is excellent.

It was published in 1999. Rees made some predictions about what might happen over the next ten years. I was interested to see how they had worked out:

Prediction 1. Mainly thanks to the upcoming WMAP satellite, we would have much better values for Ω, Λ and Q (roughly, the extent to which space is curved, the strength of Dark Energy, and the graininess of the universe). Ω would probably turn out to be 1 (flat space), and Q would be about 10^-5.

This definitely came out as he said it would. If anything, we understand the large-scale structure of the universe better than we expected.

Prediction 2. We would know what "dark matter" is made of.

Alas, we still don't. I am not even sure if we are significantly closer to finding out.

Prediction 3. We would have a solid "Theory of Everything" which unified the four forces of nature, and which would probably be based on superstring theory.

This has also failed to happen - though we have at least confirmed that the Higgs particle exists, which makes his scenarios for the very early universe a little less speculative.

[Postscript, September 2018]

And another update:

Prediction 1. Mainly thanks to the upcoming WMAP satellite, we would have much better values for Ω, Λ and Q (roughly, the extent to which space is curved, the strength of Dark Energy, and the graininess of the universe). Ω would probably turn out to be 1 (flat space), and Q would be about 10^-5.

This has all worked out 100%.

Prediction 2. We would know what "dark matter" is made of.

We still don't know. Experiments to try and detect hypothetical dark matter particles have not produced any conclusive results. There is a decent summary of the situation as of early 2014 in the second half of Freese's The Cosmic Cocktail , but none of the optimistic predictions there have been fulfilled.

One interesting new idea has turned up following the 2016 LIGO gravitational wave results: it's just about possible that the dark matter could consist of large primordial black holes, of the kind found by LIGO. But this idea isn't very popular.

Prediction 3. We would have a solid "Theory of Everything" which unified the four forces of nature, and which would probably be based on superstring theory.

Superstring theory is not doing well. The predicted supersymmetric partners have failed to show up at the LHC. While they haven't been completely excluded by experiment, most people are now assuming that they aren't there.

Loop Quantum Gravity has however become considerably more respectable. There's a good summary of that in Rovelli's Reality is Not What It Seems .
Profile Image for Trevor.
1,283 reviews21.5k followers
February 5, 2008
Rees is an interesting man - I went to a lecture by him years ago where he explained his theory of the six numbers. Essentially he says that if you were to change a few numbers - the force of gravity, say, or the electric charge - the universe would be completely different. It is interesting that the universe seems to be pretty nicely set up for life to evolve and even little changes in these fundamental numbers would make life as we know it impossible.

I always have problems with this sort of argument. My main problem is that we are clearly here. My next problem is that the religious immediately take talk like this as some sort of confirmation that god was the setter of these constants. It never seems to strike them that if this is the only role their god has, god pity him. If his entire involvement with the universe is turning a few dials thirteen billion years ago and then waiting around - I can only hope he had a few good books to read as all this universe stuff played out.

The point that Rees makes that is very interesting is that there are two answers to the question - why those numbers and not others? One is, "Well, that's just the way it is." Which is pretty unsatisfying. We want more than 'because' as an answer.

Another answer to why those numbers and not others is that there must be some more fundamental necessity for these numbers to be the numbers in which the universe is 'constructed' - that these numbers 'need' to be these numbers for reasons we don't yet understand.

I hope he is right here - that there is a deeper reason we are able to grasp and understand that is just out of reach of us at present. But we have no reason to believe this is the case and that all of these numbers just happened to be the way they are by chance.
Profile Image for Riku Sayuj.
653 reviews6,942 followers
March 15, 2015
Cosmology 101

[Strictly for Cosmology amateurs]

Syllabus as follows:

- Read Rees' book thoroughly.
- Write an essay in appreciation that elucidates the crucial importance of physical constants.
- Submit three reports on the current state of understanding and how they have evolved in any of the major constants touched upon in the book
- Bonus assignment: Search out one popular science book that has managed to cover in 100s of pages what Rees covers with lucidity in a few scores.
- Extra Bonus Assignment: Pop over and read Prof. Manny's and Trevor's goodreads pieces and present your thoughts concisely (in less than 100 words) as comments. If either of them considers your comment intelligent enough to reply to, you can be sure of an A.

Relevant Links:
1. Prof. Manny's piece
2. Prof. Trevor's piece
Profile Image for WarpDrive.
272 reviews386 followers
October 23, 2015

This four-star rating is actually a compromise between the intrinsic value and merits of this book (5 star) and how much I personally enjoyed reading it (3 star).
This is a cute, very readable and superbly well written introductory book at beginners level. A fine example of popular science book, encapsulating several interesting concepts in just a little over 170 pages, with little oversimplification.
Had I come across this book 15 years ago, I would have appreciated it immensely more. Reading it now, unfortunately it did not give me much, to be honest - but this is no fault of the book per se.
It must also be said that some parts are a little dated (unavoidably so, considering the significant progress since the book was published), but it is still a very pleasurable, light read with many interesting insights.
Highly recommended as a easy, very readable introductory book, to anybody interested in the phenomenon of the apparent "fine tuning" of some of the major physical/cosmological "constants" that allowed for the development of complexity (and ultimately life) in the Universe.
Profile Image for Maru Kun.
215 reviews475 followers
August 15, 2016
After we've had a few drinks my fundamentalist friends will often bring the talk round to The Creation just to have some fun at my expense.

They laugh at my belief in a "big bang", make ribald jokes about my "sudden, enormous inflation" and tell me I don't have much energy at all these days let alone any "dark energy". I've only myself to blame for not keeping up with the latest in cosmology. I tend to end up mumbling something about micro-wave background radiation before heading off quickly to the bar to order the next round.

Well, rounds aren't cheap anymore, so I thought I should do something to remedy the situation. This book is a great help to anyone wanting to bring some modern cosmology into the metaphysical discussions that inevitably crop up on pub night and I've written this review to help me crib a few points.

Thanks to the excellent explanation in this book I could get together a summary of key parameters underlying the whole of material existence which I can take a look at in the pub toilets on my iphone next time we're out drinking. My knowledge of the first few nano-seconds at the birth of the universe should be enough to blow their Ark out of the water. Drinks on the faithful for a change!

N - the relative strength of the force of gravity compared to the electrostatic forces of attraction or repulsion, with the force of gravity being about ten to the thirty-sixth power weaker. If gravity was much stronger galaxies would form more quickly and be more dense resulting in greater difficulty forming stable planetary systems; stellar lifetimes would be shorter, potentially not allowing sufficient time to evolve complex biological molecules.

e - nuclear efficiency - the percentage of mass of a helium atom compared to the mass of its separate parts (i.e. two protons and neutrons). e is a measure of the amount of the energy generated from fusion into helium given Einstein's well known formula. If e were too low, deuterium - an important intermediate in helium fusion - would not form. If e were too high then protons could join directly without neutrons and in such quantity that little hydrogen would be available to form stars and then through stellar evolution for the formation of other elements required for evolution of biological molecules.

Omega - the ratio of actual matter in the universe to the critical amount of matter to balance expansion of the universe with contraction due to gravity. If omega is less than one the universe will continue expanding indefinitely and too rapidly to allow galaxy and star formation and hence development of life; more than one and the universe will ultimately begin to contract, again too fast for stellar evolution and hence life to develop.

The rate of expansion suggests strongly that omega was either very close to one at the time of the big bang (i.e. differing from one by one part in ten to the fifteenth) or raises the question as to whether there is some theoretical reason that omega should have been one at the time of the big bang.

Observable matter in the universe suggests omega is well below one, leading to the search for "dark matter". But what is "dark matter"? Candidate matter includes "brown dwarf" stars, mini-black holes or some type of as yet unknown particle. As an aside anti-matter seems relatively unlikely to be a candidate for dark matter: an asymmetry was found in the rate of decay of the k particle which implies that if a similar asymmetry exists in the strong nuclear force there may have been a surplus of matter after quark vs anti-quark annihilation during the early stage of the big bang. In fact the ratio of photons to protons observed in the universe is not inconsistent with the magnitude of this asymmetry.

Lambda - Einstein's famous cosmological constant reborn - the constant introduced into Einstein's equations at which "cosmic repulsion" exactly balanced gravity and would reflect the net effect of energy within empty space. There is strong but not overwhelming evidence for lambda being low but non zero. If lambda was too large repulsion would have overwhelmed gravity in early stages of the universe, again preventing galaxy and star evolution and the formation of life.

Q - a measure of how tightly matter is bound in clusters of galaxies rather than being evenly spread, measured as the ratio of the energy required to disperse matter over the rest mass energy of the matter concerned (i.e. mass times the speed of light squared energy). Q is low (10e-5) implying a relatively homogeneous universe. However if Q was too low the gravitational force required to form aggregates of stars and galaxies would not be strong enough to overcome repulsive forces of radiation. Conversely if too high then matter would aggregate in forms that would not be able to sustain life - perhaps vast black holes that would emit gamma radiation as they grow larger.

D - the number of dimensions, being four - three spatial dimensions and one time dimension. With three spatial dimensions forces of gravity and electro-magnetic forces will follow an inverse square law - as you double the distance the force will drop by a quarter. Mathematically speaking planetary orbits are stable under an inverse square law; a slight change in speed will bring about a correspondingly slight change in orbit. However under an inverse cube (or higher) law orbits would not be stable; if your orbit was slowed down or sped up from an asteroid collision the changes are you would spiral down into the sun or off to outer space. How fascinating.
Profile Image for عمر الحمادي.
Author 6 books597 followers
October 12, 2017
كتاب مذهل وممتع جداً يأخذك في رحلة شيقة في ماضي وحاضر ومستقبل هذا الكون، لا تقرأ هذا الكتاب إذا لم تكن مستعداً ذهنياً لفهم قوانين الرياضيات والفيزياء وإعادة قراءة الجملة عشر مرات حتى تفهم معنى كلام المؤلف.

ستموت شمسنا في غضون ٥ مليارات سنه ومعها الأرض، وستتجه نحو مجرة "أندروميدا" لترتطم معها ومن ورائها كل مجرة درب التبانة، تلك التكهنات بعيدة الأمد موثوقة لاعتمادها على مُسلمة عمل قواعد الفيزياء خلال الخمسة مليارات عام القادمة كما كانت كذلك منذ ٥-١٠ مليارات سنة، سيتوسع الكون إلى الأبد لكن لن تكون هناك حياة، ولن تستطيع النجوم والمجرات سحب بعضها البعض من خلال الجاذبية ومن ثم التكثف، على التوسع أن لا يكون بطيئاً جداً وإلا سيتقلص الكون على نفسه من جديد وبسرعة كبيرة أثناء الانسحاق الكبير.

يتحدث الدكتور مارتن ريس عن ستة أرقام كونية تحدد كيف يتطور الكون:

١- N: القوى الكهربية التي تربط الذرات ببعضها مقسومة على قوى التجاذب بين الذرات، لو نقصت أصفاراً قليلة لما استطاع الكون أن ينمو إلى حجم أكبر من الحشرة ولكان عمره قصيراً.

٢- E: يحدد متانة ارتباط الأنوية ببعضها ويتحكم في كيفية تحويل النجوم للهيدروجين إلى باقي ذرات الجدول الدوري، لو قلت أو زادت قيمته قليلاً لما وجد هذا الكون، فلم يحتج الخالق إلى خلق ٩٢ نوعاً مختلفاً من العناصر، فالحلقة الأولى في سلسلة تكون العناصر هو تحول الهيدروحين إلى هيليوم، فلو زادت E لما بقي هيدروجين ليوفر وقوداً في النجوم العادية ولما بقي هيدروجين ليكون الماء، وإذا قلت E لقل عدد الذرات المستقرة عن ٩٢ عنصراً ليقود ذلك إلى وجود كيمياء فقيرة.

٣- أوميغا: يقيس كمية المادة في الكون من مجرات وغازات منتشرة ومادة مظلمة، لو كانت قيمتها أعلى لانهار الكوكب من زمن بعيد، إن سرعتها التمدد الأولي تبدو مضبوطة بعناية.

٤- لمدا: الجاذبية الكونية المضادة التي تتحكم في تمدد كوننا، لو كانت قيمتها كبيرة لأوقف تأثيرها تكون المجرات والنجوم ولتعطل التطور الكوني قبل أن يبدأ.

٥- Q: النسبة بين طاقتين أساسيتين، لو كانت أصغر لخمل الكون وصار خالياً، ولو كبُرت النسبة لخرب الكون وصار عاصفاً ولسادت الثقوب السوداء الهائلة ولما تمكن نظام شمسي من البقاء حياً.

٦- D: الأبعاد الفراغية في هذا العالم، لو قلت أو زادت لما وجد هذا الكون.

إن التحدي الكامن في توضيح كيف جمعت الذرات نفسها على سطح الأرض لتشكل كائنات حية معقدة بما يكفي لتتفكر في منشئها لهو أكثر تحد مخيف في علم الكون، وإذا لم يتقبل المرء حجة العناية الإلهية للكون فهناك وجهة نظر تخمينية يدعو إليها المؤلف وهي كون انفجارنا الكبير قد لا يكون الوحيد فنحن قد نكون ذرة واحدة مختارة من أكوان متعددة لانهائية، يرى المؤلف أن نظرية الأكوان المتعددة تدخل بجدارة ضمن نطاق العلم رغم كونها غير مؤكدة حالياً، وتظل هذه النظرية ونظرية تفسير الكون المبكر من تحديات القرن المقبل.
Profile Image for Zork.
24 reviews4 followers
August 2, 2008
I don't hold much respect for "fine-tuning" arguments in relation to cosmology, but the book was a gift, so I felt obligated to give it a try. Also, if one wants to be knowledgeable about this kind of thing, one has to read more than just the stuff that supports one's own ideas.

In his attempt to be accessible to the public, the author does what I consider to be a lot of hand-waving and emphatic gestures rather than actually explaining anything. He also fails at what I think is a basic level of imagination: when he says stuff about how a fundamental number, if it had a different value, would preclude the emergence of life, he's assuming that no other kind of life could exist.

There is some good basic information about cosmology in here, especially with regard to the fundamental forces, but readers would be better off with one of Stephen Hawking's books (A Brief History of Time or The Universe in a Nutshell) if they're looking to actually learn something.
Profile Image for أحمد دعدوش.
Author 10 books2,650 followers
February 16, 2019
ليس بالكتاب السهل لكنه مفهوم وقريب من غير المختصين.
في النهاية لا ينتصر للإيمان بالخالق ويترك الباب مفتوحا أمام فكرة الأكوان المتعددة بل يحاول دعمها، لذا يبدو المؤلف لا أدريا.
Profile Image for Jose Moa.
519 reviews65 followers
December 21, 2018
A book about cosmology but mainly about anthropic cosmolgical principle,weak and strong,the book develops the importance of fine tuning of six,mainly of cosmic significance ,numbers.
This numbers are:
N the relation between the strenht of electrical with regard to the gavitational forcé.

Epsilon the los of mass or energetic efficiency in the nuclear fussion of protons.

Omega the mass density of our universe.

Lamda the value of cosmic repulsion that acelerates the universe expansión.

Q the ripples or asimetries imprinted in the Big-Bang.

D the number of spatial dimensions 3 of our universe.

The very precise fine tuning of the values of this numbers play a fundamental role in make a universe where complex long lived structures between them the life and inteligent life can exist.

In Font of this fact one can take two positions:
First ,to think that this is not a chance instead it is the fruit of a inteligent design,this the anthropic cosmological principle strong versión.
Second,following the latest ,yet speculative,theories of cosmic inflaction there are infinite inflactionary bubbles generating each one a different universe ,each one with differen phisical laws and constants and the universe we live is so because we are here to see it,this the weak versión of the anthropic cosmological principle.
With regard to all this I Will type two textual paragraphs that I think are important in the philosofy of the book.
"If evolution were rerun,the outcome would be different.Nothing seems to pre-ordain the emergence of inteligence;indeed some leading evolutionists believe that,even if simple life were widespread in the cosmos,inteligence could be exceedingly rare."

"Theorists may,some day,be able to write down fundamental equations governing physical reality.But physics can never explain what breathes fire into the equations,and actualices them in a real cosmos.The fundamental question of "Why is there something rather tan nothing?" remains the province of phylosofers.And even they may be wiser to respond,with Ludwig Wittgenstein,that"whereof one cannot speak,one must be silent.""

I now Will dare to make a ,personal surely fool ,reckoning about the limits of human attempt of answer the ultimate ask of Martin Rees.given that every thought or chain of thougths is a physical state or sucession of physical states of our brain and by that constrined to the basic physical laws of our cosmos it must be a autorefference problem,a sort of Godels theorem that prevents the explanation of the laws inside the laws or the game from inside the game,if so the ultimate ask will be ever unanswered and out of the human ,or other inteligent being inside the universe, reach.

A recomended book for all that would like to take a clear concise introduction to cosmology and its implications.
Profile Image for Hessam Ghaeminejad.
134 reviews12 followers
November 25, 2020
چرا هستیم به جای آنکه نباشیم؟
یکی از پرسش‌های اساسی فلسفه است .
اگر این سوال رو بسط بدهیم درواقع تمامی علوم با همچین سوالی روبرو خواهند شد، مثلا چرا حیات وجود دارد، چرا بیگ بنگ اتفاق افتاد و چرا انسان موجودی اجتماعی است و غیره. این سوالات پایه، شاید هیچ‌گاه پاسخی مناسب پیدا نکنند اما لرد مارتین ریس، استرولوجیست و منجم سلطنتی با این کتاب به ما میگوید که بعد از بیگ بنگ و قبل از آغاز حیات چه اتفاقی افتاده است تا شما بتوانید به این سوالات فکر کنید
شش عدد کتابی فیزیکی در حوزه عمومی است وحداقل پیش نیاز آن برای فهم بهتر، فیزیک دبیرستان است. جان کلام کتاب درباره تعادل میان شش عددی می‌باشد که باعث پدید آمدن کیهان به شکلی که ما می‌شناسیم شده‌است. درواقع اگر هر کدام از این اعداد کمتر یا زیادتر بود این کیهان به شکل دیگری شکل می‌گرفت.
عدد اول اپسیلون ،است که معرف نسبت هیدروژن تبدیل شده به هلیم در انفجار بزرگ میباشد
عدد دوم عدد N است که بیانگر نسبت نیروی الکتریکی به نیروی جاذبه است
عدد سوم عدد امگا یا چگالی نسبی جهان، با این عدد و عدد بعدی مشخص میشود که چرا کیهان درحال گسترش است
عدد چهارم عدد لاندا نیروی پادگرانش کیهانی، کاربرد این عدد در این است که کیهان به سرعت انبساط پیدا نکند یا خیلی سریع از هم نپاشد
عدد پنجم عدد Q این عدد نسبت دو نیروی بنیادی آغازین بیگ بنگ هست که اگر ازمقدار 0.00001 بیشتر می بود با جهانی پر از سیاهچاله و اگر کمتر بود با جهانی مرده که در آن ستا��ه یا کهکشانی شکل نمیگرفت روبرو بودیم
آخرین عدد، که ساده ترین عدد از نظر مفهوم اما سخت ترین آنها از نظر درک است عدد D یا بُعد است
همه‌ی ما با جهان سه بعدی آشنا هستیم ، حالا اگه جهان تک بعدی بود چطور؟ در واقع هیچ اتفاقی نمی افتاد چون ذرات برهم هیچ واکنشی نشان نمیدادند و ‌چون بعد بالاتری نیست به راحتی از هم عبور میکردند (حتی نمیشه گفت از درون هم چون درون هم ندارند) ، برای جهان دو بعدی یه میز رو در نظر بگیرید که موجوداتی سطحی روی آن در حال تنازع برای بقا هستند. خب در آخر قوی ترین موجود ناچار است انتهای خود(دم اگه داشته باشه) را به عنوان غذا بخورد ( مانند مار اوروبروس یا دمب خوار) و خب نهایتا حیات هم به پایان خودش می رسید، اما حیات و جهان در سه بعد امکان گسترش و پچیده شدن را دارد، مثلا اتم ها مولکول های پیچیده تر را میسازند یا مجموع ستارگان کهکشان ها یا خوشه های کهکشانی را تشکیل می‌دهند.
در آخر هر چند نظریه جهان های چند بعدی مانند نظریه M وجود دارد، اما مارتین ریس به توضیح تنها کیهانی که ما می‌شناسیم می پردازد نه جهان‌های ناشناخته.
اوج کار پروفسور مارتین ریس نه معرفی و تبیین این اعداد،بلکه به عنوان یک بی‌خدا (آتئیست) بیان این موضوع است که برای دستیابی به این نظم دقیق جهان نیازمند به یک خالق دانا نیستیم بلکه به بینهایت بیگ بنگ با زایش جهان‌هایی با ماهیت‌های گوناگون نیاز داریم تا به این خط باریک حیات دست پیدا کنیم.

Profile Image for Cassandra Kay Silva.
704 reviews278 followers
August 19, 2011
I gobbled this one up in a heartbeat. Brilliant, wonderful, insightful. I loved it. I plan on reading it again before taking it back to the library. Maybe I will get a copy for the house too. I don't have anything to add to what the author said. Bravo and thank you for letting the reader make his own conclusion or choose not to make any at that point. I was worried there for a bit that he was going to pounce an agenda on me. Nope. It looks like the author is just genuinely interested in as he calls them the "Deep Forces That Shape the Universe" and dang it I am too. I am very interested and was very pleased with this presentation. This is a book that will be deliciously satisfying but leave you pondering and doing a lot of internal dialogue on the matter. Its worth having this discussion with yourself and I feel the author has done just that and let you in on his musings. I will absolutely be picking up another one by Rees, I was very pleased.
Profile Image for Mohamed al-Jamri.
174 reviews112 followers
February 21, 2016
This book might be short, but it is full of information that are presented in an easy-to-understand style. Unlike many of popular science books, this one is to the point and there are very few diversions. The main thesis is one of the greatest discoveries in physics that was made in the 1970s and 1980s; it tells us that there are these six numbers, which are extremely fine-tuned and what would happen if any of them is only slightly modified.

What makes this book more interesting is the fact that the author is an atheist, yet as a leading astronomer he is telling us about the scientific foundations of the fine-tuning case that is used by theists as evidence for the existence of god. Fine-tunning is according to prominent atheist (and anti-theist) Chritopher Hitchens the only serious argument for existence of God and Jerry Coyne called it the new Natural Theology. It should be noted that the author keeps good relations with the religious; he won The Templeton Prize in 2011 which is given to those that have "made an exceptional contribution to affirming life's spiritual dimension". Richard Dawkins called him a "compliant quisling" (i.e. a collaborator with the enemy) for accepting that prize.

The author takes us through inspirational observations of the universe. How did life emerge and develop? Is there life elsewhere? How big can living things grow to? What are the four powers of nature and how are they fine tuned? What is gravity, neutrino stars and black holes? How did elements and galaxies form? Why are carbon and nitrogen abundant in Earth while gold and uranium rare? What are the nuclear forces and how are they fine tuned? Is the universe expanding? What is the evidence for the Big Bang? What is Dark Matter, Anti-matter and Neutrinos? What is Dark Energy? What is the story of Einstein's cosmological constant? What is time? What is the inflation theory and superstring theory?

For fine-tunig, the author offers two options, chance or design. But then he adds that there is a third option which is the multiverse, which the author subscribes to despite calling it speculative and "a hunch". The author is optimistic that further advancements in science will strengthen our understanding of the multiverse. After reading Max Tegmarks Our Mathematical Universe, I can say that I'm half way convinced about the multiverse.

A recurring point in many popular science physics book that I'm repeatedly seeing and is included in this book is the fact that since the universe is flat its total energy is zero. And since gravity is a negative energy, the total cost to create the universe is zero. This is tackled in more detail in Laurence Kruass's A Universe from Nothing.

The book was published in 1999 and so some of the information in it is slightly outdated. This shows how science has progressed in the last 17 years. For example he says that the age of the universe is between 12 and 13 billion years and that we don't know the deceleration and acceleration of its expansion since its creation. We now know that the universe is 13.72 billion years old and that its expansion was decelerating in the first 7 billion years before changing to accelerating due to the increasing power of Dark Energy.

So in overall in an amazing book that is thought provoking about one of the deepest questions. It might feel a bit dry for those not used to reading science books, but the journey is well worth it.
Profile Image for Raed.
244 reviews54 followers
November 26, 2021
N : 10.....0 (36 zero) This number measures the strength of the electrical forces that hold atoms together, divided by the force of gravity between them , Only a short-lived micro universe could exist if N had a few fewer zeros: no animals could grow larger than insects, and there would be no time for biological evolution.

O: whose value is 0.007 , specifies the strength with which atomic nuclei link together and how all of Earth's atoms are formed. Its value determines how the Sun's power is distributed and, more importantly, how stars convert hydrogen into all of the periodic table's atoms.

The cosmic number Ω (omega) : quantifies the amount of matter in our universe, including galaxies, diffuse gas, and dark matter, it also tells us how important gravity and expansion energy are in the cosmos.

fourth number, λ (lambda): was the biggest scientific news of 1998. An unsuspected new force a cosmic antigravity controls the expansion of our universe

Q: which represents the ratio of two fundamental energies and is about 1/100,000 in value. If Q were even smaller, the universe would be inert and structureless; if Q were much larger, it would be a violent place

D : It is the number of spatial dimensions in our world

⭐⭐ because this is just a classic science book

Profile Image for Bettie.
9,988 reviews15 followers
March 6, 2014
Just six numbers, written and narrated by the author (k drive)

science (multiple universe theory, super strings)

Martin Rees has been Astronomer Royal since 1995.

You can't get away from the black and white of the situation, manouvered or evolved. You will find that there is no point in discussing this with anyone. Everyone believes, in the depths of their very being, one way or the other...

tweaked or not tweaked

You could not hope to convert by discussion so why bother trying. I am the one who crawls out of the Chinese Coal Mine every morning at 5a,m to cook the porridge oats; I get to watch the independent eruptions occuring within the one closed system of the saucepan and so have no problem at all with envisioning the parallel universe scenario - it is nothing but beautiful and natural and right. No tweaking needed.

*Anyone falling into a blackhole encounters the end of time* and I love the term spaghettification.

Profile Image for Saleh MoonWalker.
1,801 reviews269 followers
June 22, 2017
کتاب فیزیکی خوندنی ای برای عموم. نگاهی کلی به شش عنصر اصلی که این جهان رو محل مناسبی برای زیستن میکنه، میندازه. خواندنش ساده س و مقدار استفاده ش از فیزیک تقریبا کمه که باعث شده این کتاب برای عموم مناسب باشه و دید کلی ای راجع به این موضوع بهشون بده. حجمش کمه و خیلی سریع هم به پایان میرسه.

If one had to summarize, in just one sentence, 'What's been happening since the Big Bang?', the best answer might be to take a deep breath and say: 'Ever since the beginning, gravity has been moulding cosmic structures and enhancing temperature contrasts, a prerequisite for the emergence of the complexity that lies around us ten billion years later, and of which we are part.
Profile Image for Gendou.
581 reviews255 followers
January 25, 2010
A terse survey of cosmology. Covers a wide breadth without going into satisfactory depth.
For example, the author sometimes mentions only one of several interesting points of view.
Still, a fine read, especially valuable to the novice, but not boring to the expert.

Embarrassingly, the author predicts the discovery of dark matter particles by 2005.
Profile Image for Jonathan.
913 reviews940 followers
April 4, 2020
My gut? After reading this and the books on the big issues at the heart of quantum physics, it seems likely that something key is missing from our theories. Maybe some physicist trapped in covid lockdown will have a flash of boredom-triggered-brilliance and solve it...
Profile Image for Jimmy Ele.
233 reviews86 followers
June 25, 2017
3.5 stars. I appreciate it for familiarizing me with these 6 important numbers. However, the reason for the loss of 1.5 stars was due to the book's seeming lack of inspiration. There doesn't seem to be any excitement throughout. Very bland at times for such an interesting topic.
Profile Image for Sajjad thaier.
204 reviews104 followers
May 8, 2017
هل هذا الضبط مجرد حقيقة عمياء غشوم ؟ أو مجرد صدفة ؟أم هو رزق من خالق كريم ؟
يناقش الكتاب ستة من الثوابت الكونية التي أن تغيرت ولو لمقدار طفيف فهذا سيؤدي الى تبعات تؤدي الى عدم تشكل الحياة او الكون في بعض الحالات .
وهذه الثوابت الست بأختصار هي :
1-N وهو رقم كبير جدا قدره واحد متبوعا ب36 صفر وهو يمثل النسبة بين القوة الكهرومغناطيسية والجاذبية لو كان هذا الرقم اقل بقليل ستصبح الجاذبية اقوى مرات عديدة ولن تنشأ اي كائنات ما عدا الحشرات الصغيرة .
2-E وهو رقم قيمته 0.007 وهو المسؤول عن ارتباط الانوية ببعضها البعض . ولو تغير قليل لما تكونت اي عناصر دا��ل الشموس من الاندماجات النووية .
3- (اوميغا ) وهي المسؤولة عن كثافة المادة في الكون فلو كانت عالية ولو بقليل ستنجذب كل المجرات نحو بعضها البعض وستفني بعضها البعض ولو كانت اقل لتوسع الكون بسرعة من دون منح فرصة للمجرات وحتى الشموس من التكون .
4-(لمدا) وهو الرقم المسؤول عن توسع الكون بهذه السرعة المحددة
5-Q وهو يصف التارجحات الجذبوية في بداية الكون والتي كان لها التأثير الكبير على كوننا المنظر وقيمتها هي 1/1000000.
6-Dوهو عدد الابعاد فنحن نعيش في كون ثلاثي الابعاد بالاضافة لبعد الزمن وهذا العدد من الابعاد هو بالضبط المناسب للحياة اذا لا يمكن تكون حياة في بعدين او اربعة ابعاد.

الكتاب يطرح العديد من الاسئلة الفلسفية المهمة مثل هل يمكن تولد شيء من لا شيء وهل للكون من صانع ام هي صدفة او اكوان متعددة والكاتب يميل للاختيار الاخير . الكتاب ممتع وبسيط لمن يريد التعرف على الكون الذي يعيش عليه .

ما يعيب الكتاب ان بعض المفاهيم قد استحدثت وكثير من الحقائق قد كشفت منذ كتابته سنة 1999 .والترجمة لم تكن جيدة جدا بل حوت الكثير من الاخطاء وهذا عكس ما توقعته لاني توقعت ان ترجمة براهين ستكون قوية لكن خفت ان يحرفوا كلام الكاتب ليثبتوا وجهة نظرهم لكن على العكس التزموا بكلام الكاتب الحرفي ولم يغيروه ولكن الترجمة كانت سيئة.
Profile Image for Tom Adams.
13 reviews7 followers
February 24, 2012
Martin Rees is the Astronomer Royal of Great Britain (since 1995) and is a skilled writer on matters astronomical for the general public. In this book he describes six numerical constants that lie at the heart of knowledge about the universe at the turn of the millennium (the book was published in 1999). His subjects range from fundamental particle forces to the mysterious "dark energy" as represented by lambda, the force believed responsible for the accelerating expansion of the universe. At only 160 or so pages, this book is necessarily short on detail, but Rees presents a very readable introduction to some fascinating science.
Profile Image for Moataz.
53 reviews9 followers
July 5, 2014
I never rate a book before finishing it, but this one is an exception.
Profile Image for Alfaniel Aldavan.
49 reviews32 followers
October 9, 2013

Six numbers: if any was altered in a very small degree, the universe would not have permitted life to develop.
For example, if gravity wasn't exactly this weak comparing to other forces in the atom, but not weaker, the universe either would have collapsed right after Big Bang, or would have expanded so fast that no stars, galaxies, planetary systems could've formed.
Thus, no potential for life.

Writing and readability
Rees makes his case of fine tuning with regard to life very convincing. The book is written for the lay reader, and it's decidedly a must-read for anyone interested in cosmology, astronomy, physics. It's rare that I find books for popularizing science that don't have the faults of being clumsy written or assuming a much higher level of knowledge that they're advertised for. To bring science down to earth is no easy enterprise, and Rees, reputable cosmologist, succeeds amazingly.
The book makes many comparisons of the numbers and ratios it speaks of, with every day examples, or it creates elocvently frame by frame images, to convey just how precise (small or big) the numbers are. This is done so well that it leaves you feeling you now really - really - know more, understand the universe better, and estimate the extreme unlikeliness of our universe to turn out just right for life.

The writing style does wonders to convey to the reader a powerful case for the fine tuning of each number.

However, the thesis doesn't stand up to basic philosophical/logical objections.
Rees compares what would happen if each number varies, assuming everything else is equal. One at a time. And concludes from it, that they're extremely fine-tuned. However, what would happen if you vary two numbers at a time? How about three? How about varying relations between one of these numbers and the other elements, which Rees combines with it (according to laws of physics of our universe) to yield his results of dead universes?

Varying one at a time is not a throughout investigation. I can't conclude from it *anything*.

Example. Let us say we have six integer numbers, and their sum is 1000. Let us say that a "life-permitting sum" is in the range 999 and 1001.
If I vary one of the numbers, with 1 (plus or minus 1), I still get about 1000. If I vary that number with 2 (plus or minus 2), I no longer get my goal sum. If I vary it more, the sum will never be in the goal range. I had only two permitted variations.
But, if I vary 2 numbers at a time, I can obviously "succeed" with significantly more variations. If I vary 3 numbers at a time, ever more.
If I also accept that the "law" can be changed (the function may be a sum, or a product, or an exponential function, etc), I can have way more winning combinations.
I may have more failures than successes, true, but I have a bigger pool of wins, meaning the numbers themselves are not "just about right".

Rees' fine-tuning thesis assumes varying one number at a time, which is only a slice of the research to get a whole range of (potentially) life-permitting universes. After it limits itself this way, it asks for an explanation for such an improbable event of each number being exactly right.
I'll say it's not a defensible position, from a logical-philosophical perspective.

Rees' possible answers to his question are the multiverse theory and the creationist hypothesis, with a nod in the direction of a possible unified theory that will eventually explain why these numbers had to be as they are. Since I don't think the question was entirely correct to begin with, I don't feel compelled to jump to his conclusions yet.

Critique of the critique
When I read the book, I was left with the question: is fine-tuning, in the current mainstream physics and cosmology, assuming variation of one number at a time, and drawing conclusions from only it?
I don't know, I'm no physicist, and while I feel I learned from this book (and it's Cosmology 101!), I will say that the reasoning itself at the basis of the argument is flawed. However, it seems I received my answer, from another direction.

This week, in the discussion on Manny's review of The Fallacy of Fine-Tuning, he quotes another cosmologist, Barnes, a supporter of fine-tuning theories. With this occasion (with this occasion I read Rees' book as well), I read more of Barnes' blog and articles, and I came upon this:

This gives me my answer, in no uncertain terms:
There is an objection to fine-tuning that goes like this: all the fine-tuning cases involve varying one variable only, keeping all other variables fixed at their value in our universe, and then calculating the life-permitting range on that one variable. But, if you let more than one variable vary at a time, there turns out to be a range of life-permitting universes. So the universe is not fine-tuned for life.

This is a myth. The claim quoted by our questioner is totally wrong. The vast majority of fine-tuning/anthropic papers, from the very earliest papers in the 70′s until today, vary many parameters.

Also, further down the page, Barnes refers to this book:
This myth may have started because, when fine-tuning is presented to lay audiences, it is often illustrated using one-parameter limits. Martin Rees, for example, does this in his excellent book “Just Six Numbers“. Rees knows that the limits involve more than one parameter – he derived many of those limits. But equation (1) above would be far too intimidating in a popular level book.

Indeed, I got my answer, spot on! The equation noted is above my (undergrad and forgotten) math level. However, the question I had while I was reading Rees' book had to do with internal logic of his thesis.

The road ahead
Which raises another question: what is then, the actual thesis/question of fine-tuning literature today?

According to Barnes, the only constraint in varying parameters to get possible universes, is for these universes to be logically possible. (non-contradictory)

That's a bold claim, if I ever saw one. And I mean bold. Particularly surprising when Barnes explicitly states that an universe is defined by (initial conditions, constants, laws of physics), and, according to him, *all three* are fair game, for the variance experiment, including laws of physics. I should add though, the claim strikes me as methodologically correct, because what else is there to assume about the possible universes? We can't necessarily assume they obey the physical laws that may have been set from the initial conditions (which we vary!) of our Big Bang for our universe. But the magnitude of the task, even if there are mathematical tools to make it more reasonable, leaves me in a combination of awe and disbelief.

Once she chose their universe(s) to examine, the fine-tuning-interested cosmologist then solves the equations for those possible universes. If the universe is not self-consistent, then it's trashed. Then estimate the probability for the universe under examination (actually class of universes) to be life-permitting.
The purpose: estimate the probability of life-permitting universes in the set of possible universes.

This is my current understanding of Barnes' paper and blog, and with them, a certain direction on fine-tuning today. I'd have more to say about those logically possible only universes (!), but I guess I'd better wrap up this review and read more.

Rees doesn't claim for his book to have another purpose than it does: to make general readership understand better a slice of one of the problems of cosmology today. He succeeds very well, perhaps too well. Apparently, we, lay readers, might get easily from it a too limited but powerful impression about the sides of the controversy of fine-tuning. :)
Luckily, the same is not the case on physics and cosmology. Controversies aside, I think this 101 in cosmology is one of the best written books popularizing science. Very recommended, and easy to read.

Creative Commons License
This work by Alfaniel is licensed under a Creative Commons Attribution-ShareAlike 3.0 Unported License.
Profile Image for Brie.
317 reviews16 followers
February 9, 2012
Meh. That about sums up my feelings on this book.

When I finally got my hands on this book I was so excited. I expected to be blown away by the 6 numbers and the perfection to which they were tuned to allow life to emerge in our universe. Instead I was bored at times, and definitely not blown away. There is a show on the History channel called 'The Universe', which at times is over the top, but in this case they have done a better job of getting the point across then Rees has. This book is basically the same as Rees' book Our Cosmic Habitat, just presented slightly differently. I wasn't all that impressed with that book either, so perhaps I am just not a Rees fan.

Anyway, on to the facts. Here is an excerpt from the first chapter explaining the 6 numbers and their meanings:

1. N=1,000,000,000,000,000,000,000,000,000,000,000,000. It measures the strength of the electrical forces that hold atoms together, divided by the force of gravity between them. If N had a few less zeros, only a short-lived miniature universe could exist, thus not allowing enough time for evolution.

2. Є=0.007. It defines how atomic nuclei bind together and how atoms are made. Its value controls the power from the Sun and, more sensitively, how stars transmute hydrogen into all the atoms of the periodic table. If Є were 0.006 or 0.008, we could not exist.

3. Ω (omega) is the amount of material in our universe – galaxies, gas, and ‘dark matter’. If this were too high relative to a particular ‘critical’ value, the universe would have collapsed long ago; had it been too low, no galaxies of stars would have formed.

4. λ (lambda) controls the expansion of our universe, even though it has no discernible effect on scales less than a billion light-years. Fortunately for us λ is very small. Otherwise its effect would have stopped galaxies and stars from forming, and cosmic evolution would have been stifled before it could even begin.

5. The fabric of our universe depends on one number, Q, which represents the ratio of two fundamental energies and is about 1/100,000 in value. If Q were smaller, the universe would be inert and structureless; if Q were larger, it would be a violent place, where no stars or solar systems could survive, dominated by vast black holes.

6. The number of spatial dimensions in our world, D, equals three. Life couldn’t exist if D were two or four. Time is a fourth dimension, but distinctly different from the others in that it has a built-in arrow: we ‘move’ only towards the future.

Unfortunately, I wouldn't recommend this book. There was just no excitement or spark, and I really couldn't wait to be finished with it.
Profile Image for Modather Abozaid.
36 reviews13 followers
August 9, 2019
انا انتهيت من قراءة الكتاب ده من عدة أيام وحقيقة من قتها كل ما افتكر خاتمة الكتاب وتعليق الكاتب برغم كلامه طوال فصول الكتاب لا أرى تعليق أفضل من قوله تعالى في سورة الجاثية الأيات ٢٣-٢٧:
{أَفَرَءَيۡتَ مَنِ ٱتَّخَذَ إِلَٰهَهُۥ هَوَىٰهُ وَأَضَلَّهُ ٱللَّهُ عَلَىٰ عِلۡمٖ وَخَتَمَ عَلَىٰ سَمۡعِهِۦ وَقَلۡبِهِۦ وَجَعَلَ عَلَىٰ بَصَرِهِۦ غِشَٰوَةٗ فَمَن يَهۡدِيهِ مِنۢ بَعۡدِ ٱللَّهِۚ أَفَلَا تَذَكَّرُونَ

(Sahih International)
Have you seen he who has taken as his god his [own] desire, and Allah has sent him astray due to knowledge and has set a seal upon his hearing and his heart and put over his vision a veil? So who will guide him after Allah ? Then will you not be reminded?

وَقَالُواْ مَا هِيَ إِلَّا حَيَاتُنَا ٱلدُّنۡيَا نَمُوتُ وَنَحۡيَا وَمَا يُهۡلِكُنَآ إِلَّا ٱلدَّهۡرُۚ وَمَا لَهُم بِذَٰلِكَ مِنۡ عِلۡمٍۖ إِنۡ هُمۡ إِلَّا يَظُنُّونَ

(Sahih International)
And they say, "There is not but our worldly life; we die and live, and nothing destroys us except time." And they have of that no knowledge; they are only assuming.

وَإِذَا تُتۡلَىٰ عَلَيۡهِمۡ ءَايَٰتُنَا بَيِّنَٰتٖ مَّا كَانَ حُجَّتَهُمۡ إِلَّآ أَن قَالُواْ ٱئۡتُواْ بِـَٔابَآئِنَآ إِن كُنتُمۡ صَٰدِقِينَ

(Sahih International)
And when Our verses are recited to them as clear evidences, their argument is only that they say, "Bring [back] our forefathers, if you should be truthful."

قُلِ ٱللَّهُ يُحۡيِيكُمۡ ثُمَّ يُمِيتُكُمۡ ثُمَّ يَجۡمَعُكُمۡ إِلَىٰ يَوۡمِ ٱلۡقِيَٰمَةِ لَا رَيۡبَ فِيهِ وَلَٰكِنَّ أَكۡثَرَ ٱلنَّاسِ لَا يَعۡلَمُونَ

(Sahih International)
Say, " Allah causes you to live, then causes you to die; then He will assemble you for the Day of Resurrection, about which there is no doubt, but most of the people do not know."

وَلِلَّهِ مُلۡكُ ٱلسَّمَٰوَٰتِ وَٱلۡأَرۡضِۚ وَيَوۡمَ تَقُومُ ٱلسَّاعَةُ يَوۡمَئِذٖ يَخۡسَرُ ٱلۡمُبۡطِلُونَ

(Sahih International)
And to Allah belongs the dominion of the heavens and the earth. And the Day the Hour appears - that Day the falsifiers will lose.}

نسأل الله العافيه والحمد لله على نعمة الإسلام وكفى بها نعمة.
Profile Image for Nicky.
4,138 reviews1,007 followers
October 12, 2017
This is a little out of date now, and some of the predictions are almost adorably wrong at this point — that we would understand dark matter and dark energy, and that we’d have a unified Theory of Everything explaining how all the forces we know of are tied together. But this book is still useful in explaining, in clear and simple terms, why exactly people say the universe has been “fine-tuned”. It’s not the most in-depth treatment out there, but I think it’d be very good for getting to grips with the basics.

In summary: there are several numbers underlying the universe which are constant, and they are very precisely definable down to multiple decimal places… and if you change them in any way, you make our existence as we know it impossible. There are problems with this, of course; life doesn’t have to look exactly like us to be viable, and of course we’re in a world that is perfectly tuned for us to exist. That doesn’t, in and of itself, prove anything. I know people often use it to support the idea of multiple universes, all varying slightly — but something can be made just once and be utterly unique and turn out to be perfect for something, even if you don’t make multiples.

This is, honestly, why I find physics so frightening. It’s all so terribly unlikely, and we don’t understand it, and against all this it becomes very apparent, to my mind, how small and alone and temporary each human being is.

It’s also fascinating, even for those who prefer biology as a science, like one you could probably name…

Reviewed for The Bibliophibian.
Profile Image for Mansoor.
633 reviews8 followers
June 21, 2014
این کتاب یکی از نمونه های موفق در زمینه ی ترویج علم* است که به قلم یک دانشمند برجسته نوشته شده و از این لحاظ ترجمه اش می توانست مایه ی خوشنودی و راه گشا باشد.ولی ترجمه ی کتاب این امید را به باد می دهد.مترجم در موارد متعددی عقاید ایدئولوژیک اش را در قالب پاورقی به خواننده ی این کتاب علمی تحمیل می کند و یا توضیحاتی بی فایده ارایه می دهد. برای نمونه در پاورقی یک کتاب علمی به "عدل الاهی" مرتضی مطهری ارجاع می دهد و با اشاره هایی ناقص یا اشتباه به ابیاتی از سعدی و حافظ، متفنن بودنش را در آن زمینه ها نیز نشان می دهد
در صفحات آغازین کتاب، جایی که نویسنده هر دو گزینه ی "تصادف" و "تقدیر یک خالق مهربان" را برای توضیح پیدایش جهان رد می کند و موضع سومی ("تنظیم دقیق") اتخاذ می کند، مترجم عقاید نویسنده را شرم آور (!!) خوانده و با نفهمیدن موضع نویسنده، او را متهم به تناقض گویی می کند.مترجم می گوید نویسنده از انتخاب گزینه ی "خالق مهربان" شرم دارد.ولی فقط چند صفحه بعد که نویسنده در ادامه ی اتخاذ موضع سوم، جهان بینی ای "انسان بنیاد" ارایه می کند، مترجم موضع او را تایید کرده و آن را تفسیری طبیعی از یک حدیث قدسی می خواند
ولی مشکل مهم تر این است که مترجم (به خاطر هراس از عقاید نویسنده)در مواردی امانت را رعایت نکرده و ترجمه را مخدوش کرده است.معادل هایی هم که مترجم برای اصطلاحات علمی انتخاب کرده در مواردی نادقیق (مانند "تنظیم ظریف"**) و در مواردی غیر قابل استفاده (مانند "عالمین"***) است
با این اوصاف خودتان قضاوت کنید که کار این مترجم شرم آور است یا عقاید آن فیزیکدان! البته بر مترجمان متفنن و فقه پیشه ای از این دست حرجی نیست. از ناشری چون نی انتظار می رود که بر کتاب هایش نظارت کند
*Popular Science
Profile Image for Ana.
805 reviews592 followers
June 6, 2016
Science. Not much to review here, trying to understand physics is hard enough as it is.
Profile Image for Roger.
72 reviews13 followers
January 4, 2015
As its title suggests, this 1999 book by Martin Rees, the UK's Astronomer Royal, addresses six numbers that determine whether a universe can support life as we know it. The first number Rees calls N, which is the ratio of the gravitational force to the electromagnetic force and is about 10^36. He explains how, if this ratio were less, and therefore gravity was relatively stronger, stars would be much smaller and would burn much quicker. There would not be sufficient time for life to evolve.

The second number, epsilon (ε), dictates the strength of the strong nuclear force. Rees refers to ε being equal to 0.007 and this denotes the proportion of energy that is released when hydrogen fuses into helium. If this force was weaker than it is (say, 0.006), then nuclear fusion wouldn't happen; we would have stars full of hydrogen but there would be no nuclear reactions. Conversely, a stronger force (say, 0.008) would have led to protons joining with other protons shortly after the Big Bang so that there would be no hydrogen left to fuel the stars. Either way, life as we know it would not have been possible.

The third number is omega (Ω), which Rees defines as the ratio of the actual density of the universe to the critical density needed for gravity to bring cosmic expansion to a halt. If the ratio were too high, the universe would collapse in a big crunch; too low and expansion would be too fast to allow matter time to condense into stars and galaxies. Discussion of Ω led into a discourse on dark matter, which accounts for about 90% of the universe but which could be made up of entities with masses ranged from 10^–33 g (neutrinos) up to 10^39 g (heavy black holes), an uncertainty of more than seventy powers of ten. As Rees points out, our ignorance on this subject is somewhat embarrassing.

Lambda (λ) is the fourth number, which concerns whether the expansion of the universe is increasing or decreasing. In fact, λ is almost, but not exactly, zero; it is a measure of dark energy although this phrase is not used by Rees. λ was first postulated by Einstein in his General Theory of Relativity as a form of anti-gravity to achieve a static universe but he later gave up this idea when it was shown by Hubble that the universe was actually expanding. Einstein later referred to his abandonment of this concept as his "greatest blunder".

Q is the fifth number and this refers to the amplitude of the irregularities in the density of the universe shortly after the Big Bang. If the universe had been completely homogenous then there would have been no areas where gravity was slightly greater than other areas, such areas seeding the formation of stars and galaxies. Q has a value of about 10^-5 which reflects the fact that gravity within galaxies is exceedingly weak. This value is crucial; were it much smaller, or much bigger, the texture of the universe would be quite different, and less conducive to the emergence of life forms. A much smaller value of Q would stop galaxies forming, whilst if much larger it would result in super large galaxies but with black holes rather than stars.

The last of the six numbers Rees calls D which is the number of spatial dimensions. In our universe D is equal to 3 and Rees argues that if D were not equal to 3 then life would not exist.

I can't say that I really enjoyed this book and, as a consequence, it took me a long time to finish it. Undoubtedly, Rees is an expert in his field but the excitement that he must feel for his subject didn't come across to me. His account didn't grip me and it seemed to me to be rather disjointed. For example, whilst the book is concerned with six numbers, it has eleven chapters, with three of the extra five being interspersed with the six on the numbers; I found these interruptions disrupted the flow of the book. Notwithstanding these criticisms, some parts of the book were thought provoking and prompt me to read more accounts on cosmology. Essentially, it is a book about the Anthropic Principle although this is another term that the author never uses.

Aside from the discussions on the six numbers, there were some interesting observations in places. For instance, I was surprised to read that it was as early as the late 14th century that it was postulated that planetary systems were probably commonplace around other stars and that some of these planets would undoubtedly hold intelligent life. This concept was the brain child of the far-sighted Giordano Bruno but, needless to say, his views were considered heretical by the Church and for this and other "crimes" he was burnt at the stake in 1600. It was also fascinating to learn that at the time Rees wrote his book there had only been one instance where the precursor star of a super nova was known. This was in 1987 and before it exploded the star in question had been a blue one of about twenty solar masses.
Profile Image for Keith.
807 reviews31 followers
March 3, 2012
If any of six numbers were slightly altered, the universe as we know it – including ourselves – would not exist. Small changes to any one of six numbers – the strength of electrical forces, the amount of matter in the universe, antigravity, etc – and everything would be different. So how did the universe become so finely tuned to support our existence and the existence of the stars?

Was it Providence? A cosmic coincidence?

Neither, says Martin Rees. He postulates that our universe is one of many in a multiverse – a universe of universes, some dark and dead, others fiery and combustible. Among these many universes, ours just happened to have all six of these numbers tuned to the “right” settings, creating our universe – and us.

The idea of a mulitverse is growing in popularity. It was a key component of the book From Eternity to Here which I read earlier this year. For a book written in 1999, Just Six Numbers was ahead of its time.

Of course, the idea of a multiverse is sobering. In our universe, we are less than a speck of dust in a space that is vast beyond our comprehension, so enormous we are swallowed up in scales of space and time we cannot understand, and rendered completely insignificant. Now, we have astronomers speculating that our universe, as vast as it is, is just one of many – and possibly just a speck of dust in an even larger universe.

Just Six Numbers is a good, concise overview of astronomy, and though it is over ten years old, the book does not seem dated (at least from my amateur perception). It was interesting but not compelling.

Profile Image for Raj.
1,374 reviews29 followers
March 7, 2010
Subtitled The Deep Forces that Shape the Universe, this pop science book, written by the astronomer royal, discusses six cosmological constants that define the size, shape and structure of the universe.

An interesting book, but one that didn't really teach me that much that I didn't already know. The most interesting thing was the stress on how if any of these numbers were very slightly different, they would have resulted in a universe that would be unsuitable for life. Rees deliberately avoids the question of why this 'fine tuning' exists until the final chapter and even then, he remains fairly neutral on the matter just outlining the possibilities, including that of a creator.
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