Things I learnt from Stephen Hawking
11 October 2014

tEver since I took up physics in year 11 I have had a love affair with the subject, which is odd since I went on to study an arts/law degree (but that probably had something to do with the fact that I would not have had the staying power to pour all of my energy into helping human knowledge advance towards establishing a unified theory). I still wonder where I ended up getting this book, and it had been sitting on my shelf for quite a while (probably because I was too busy listening to people tell me why I shouldn't read this book), but it wasn't until John Lennox said that it was the most unfinished book (that is people start reading it but do not have the staying power to get to the end) ever written (I'm sure there are other books that beat this book though). There are quite a few things that I have discovered while reading this book, and it is these discoveries that I wish to share with you:

1) This is not an anti-God book
tOne of the impressions that I got from certain people was that this was a book that an atheist wrote to try to argue that God does not exist, in much the same way that Richard Dawkins does in his books. However, that statement could not be further from the truth. In fact, throughout the book the question of the existence of God perpetually hangs in the background. Granted, Hawkings does suggest that if the concept of a infinite bounded universe (don't ask) turns out to be true then it would undermine God's existence, however he does not actually say that this may be the case. In fact his final sentence in this book is that the reason we study physics and try to find a unified theory is because we, as a race, seek to understand the mind of God.

2) Stephen Hawkings is actually a really good writer
tThis probably goes without saying, especially since the cover of my book says that it is a 'record breaking best seller'. While he is involved in some very serious and complicated research he is able to write in a way that many of us who have probably studied physics up to a year twelve level (that is the end of High school) can understand. Okay, I probably have an advantage over most other people since my Dad is a theoretical physicist that we have regular conversations about some of these high level concepts (such as by having any more than three dimensions would cause the orbits of the planets to collapse), but I still found that he was very easy to follow and he explained many of these high level concepts in a way that many of us could understand.

3) Scientists have a strange way of viewing the universe
tMany of us would be familiar with this guy:



but as it turns out, after reading this book, I have come to the conclusion that a lot of theoretical physicists seem to live in the same world that he does. Okay, they probably don't spend their time at the comic book store, or arguing whether Babylon Five is better than Star Trek (actually, one of my primary school friends is a theoretical physicist, and we did have such an argument), but they do seem to see the world in a way that we ordinary people would consider strange.

tFor instance, we see space as flat, meaning that if we look at a star, as far as we are concerned the star is in that direction. However physicists see space as being curved and that a straight line is not necessarily straight. We would see a brick wall as being a solid object and that the idea of walking through one would result in a sore nose. However physicists see it as being made up of mostly space, and the only reason we can't walk through it is because the nuclear forces (forces that exist inside an atom, not the force that can level an entire city) prevent us for doing so. Then there is the concept of dimensions: to us there are only three dimensions, however some scientists (and Hawking is not one of them) see that there are in fact ten, or even more, dimensions.

4) Why are so many scientists atheists
t While reading this book I could not get past about how complex this universe is and it made me wonder why it is, with the mathematical precision of the universe, and the complexity that lies therein, that so many scientists seem to argue that it all came about by chance. Even Hawking argues, using the second law of thermodynamics, that the universe cannot move from a state of disorder to a state of order – a broken plate simply cannot mend itself. However, the argument also goes that with the Big Bang Theory (not the television show) that the universe began in a state of disorder and moved to a state of order, however the laws of physics seem to suggest otherwise because what the big bang did was sent in motion a series of laws that caused the universe to come about to what we have at the moment. However, to go into details would require some intense theoretical physics, something which I have do desire to delve into at the moment.

5) Scientists assume the speed of light is a constant
tThe truth is that it is not. Okay, if light were travelling through a vacuum where there are no external forces acting upon it, then it is a constant, but that is very rarely the case. Take for instance this phenomena:



tThe reason light behaves thus is because when it hits the prism it SLOWS DOWN, and when it slows down it refracts. Thus my point is proven, the speed of light is only a constant when there are no external forces acting upon it.

tSo, what external forces may act upon light in space. Well, first of all there are black holes. When light hits a black hole the force of gravity is so strong that it will actually prevent light from escaping. Thus, gravity is a force that effects light and slows it down. Then there is the concept of dark matter, which are clouds of matter that do not emit light and float between the star systems. Okay, we know very little about the stuff (and it is also a theory, so it has not been proven) but my hypothesis is that if this stuff exists then would it not have an effect upon light, namely by slowing it down, which means that there is a possibility that our calculations as to the distance of stars from our own Sun could actually be wrong?

6) Scientists do not know as much as we think they know
tOne of the things that Hawking stresses in this book is that theories are not actually proven. A theory is an idea that has some foundation based on mathematical calculations and empirical evidence. Therein lies the problem. Much of our understanding of the universe is based upon mathematical calculations, and it appears that if an event comes about which causes this mathematical calculation to break down, they immediately set out to try to find another mathematical equation to plug the hole.

tTake light for instance. For years we believed that light acted as a wave and suddenly it was discovered that it also behaves like a particle (a particle of light is called a photon). The same goes with matter – for years we believed that they were particles when all of the sudden we discovered that they can also behave like waves. As such, our understanding of the universe suddenly breaks down (meaning that we are not necessarily made up of atoms, but have wavelike properties as well).

tMathematical equations have been very destructive in out modern world. Take the Global Financial Crisis for instance. A bunch of apparently really smart people create complex mathematical equations to determine when to buy and sell shares and how to make billions of dollars. However what these equations did not take into account was the fact that people could not simply continue to accumulate debt without having to pay it back and when people began to default on their loans enmass, the whole concept broke down and we were taken to the brink of financial armageddon.

tAnother point goes back to Ancient Greece. Here we have the theory of Democritus, namely that matter was not infinitely indivisible (the smallest piece of matter is an atom), and then the theory of Aristotle, that is that matter is infinitely divisible. Scientists preferred Democritus' theory, however they soon discovered that you could break down the atom into protons and neutrons, and you could even break them down to quarks. So, maybe Aristotle was right after all.

7) We accept their theories because our gadgets work
tIt goes without saying that their research and discoveries have lead to the computer that I am writing this on, the energy that powers our devices, and the bombs that can level entire cities. We know how to make a nuclear bomb, as well as a smart phone, so we don't question what they say, because it obviously works. However, as a friend of mine once said, it is still all based on theory, and just because something works does not necessarily mean that the theory is correct. Remember that penicillin was discovered by blind chance.

8) Nobel Prizes are simply shiny baubles that have no merit
tOkay, maybe the people that win these prizes are actually really smart, but then again, the guys who set up Long-Term Capital Management also won a Nobel prize, which proves my point.

9) Nobody really knows how gravity works
tGravity is one of those odd forces that doesn't seem to connect with any of the other forces in our universe. As Hawking points out, there are four forces that have been identified: electro-magnetic, strong nuclear, weak nuclear, and gravity. Out of those four forces (five if you divide electric and magnetic, but since electricity will create a magnetic force, they are effectively combined) only gravity stands out. This is probably why Hawking spends so much time talking about black holes because black holes are where the gravitational pull is so strong that not even light can escape from its grasp. The other thing is that gravity does not, at least in our knowledge, have an opposing force. Gravity basically sucks, and that is all it does – it doesn't repulse as the other forces can.

tIt is interesting that in some texts that I have read (maybe it is speculative science-fiction but I simply cannot remember off the top of my head) some people have suggested that gravity is actually a force from another universe that affects our universe and what it is effectively doing is sucking our universe into their universe. However, as I have said, that is incredibly speculative, and since I am not a theoretical physicist I can't really say any more on the subject.

10) The God of the Gaps is a cop-out
tThe idea of the God of the Gaps is that where there are gaps in our knowledge we simply say 'oh, God did that' and think nothing more of it. This goes back to the days of paganism (and Medieval Europe) where all of the unknown forces, such as the weather, was attributed God (or the gods) and we could not know anything beyond that fact. However I am arguing that it is a cop out. Creation scientists who resort to this argument are at best lazy and at worst dangerous. The reason I say that is that it discourages research into areas that we do not understand. Okay, we may never be able to control the weather, or predict earthquakes, but that does not mean that we should throw our hands up in the air and say 'this is too hard'.

tWhile I may be taking a swipe at creation scientists here, I would also take a swipe at the atheists who claim that there is no God. The reason I say that is because there seems to be a fear within the scientific community that suggests that we may not be able to know everything, or that our understanding of the universe may be wrong. The problem that arises is that if we throw the idea of God out of the window and claim that the universe came about by chance, then we deny the fact that we live in an incredibly ordered universe that we can learn and understand through the development of mathematical formulae. If a formulae turns out to be wrong, that does not mean that the universe will collapse in on itself – it won't – it just means that we have to go back to the drawing board and start over from scratch.

11) Why are Creation Scientists so dogmatic
tWhy is it that some members of the scientific community insist that we must take the Bible literally? The Bible is not a scientific text, and it was never meant to be a scientific text. It is a theological text that tells us how we should live with one another and how we should view God. Science exists beyond the Bible, and neither contradicts the other. Okay, granted, God has intervened in this world and done things that break the laws of science, but doesn't he have a right to do that – he created the universe? However, what the Bible tells us is that God is a god of order, and if he is a god of order then does it not make sense that the universe that he created is an ordered universe?

tSo, maybe you are looking for a whiz bang conclusion to my exposition on this book, but all I can say is that what I have written above pretty much sums up what I have learnt from this book. In a nutshell (hey, this is me in a nutshell), all I can say is that what I have learnt from this book is that the world is an amazingly ordered place in which we live, and having now completed this book I am just as committed to my Christian faith as I ever was. However, if theoretical physics fascinates you, then this is certainly a book that you should give a read (though you have probably done that already).

This review also appears on my blog. I have also commented on this book in my review on Interstellar.

Oh, this is definitely one of my favorite books of science and my favorite one of Stephen Hawking. I love the way Hawking explains concepts so abstract and difficult to understand as time or black holes. It's a science book for the general public; you don't need to know math or physics to understand the amazing concepts about the Universe he tries to explain us. I totally recommend A Brief History Of Time to everyone, not only the lovers of science.

Spanish version:
Éste es sin duda uno de mis libros favoritos de ciencia y mi favorito de Stephen Hawking. Me encanta la manera como Hawking explica conceptos tan abstractos y de difícil comprensión como el tiempo o los agujeros negros. Es un libro de divulgación científica para todos los públicos, en los que no hace falta saber de matemáticas o física para comprender los increíbles conceptos que nos cuenta del universo. Lo recomiendo a todo el mundo, no solo a los amantes de la ciencia.

الكتاب جيد فيما يتعلق بخصوص مناقشة ومحاولة بلورة الصيغة النهائية للقوانين الحاكمة للكون في إطار نظريات ومقاربات مفاهيم وصيغ الزمان والمكان والمفهوم الكمومي و مبدأ اللايقين في إطار رؤية جديدة وأوسع وأكثر شمولية للكون الذي نعيش فيه.. الأسئلة التي طرحت من قبل هوكينج ليست بتلك السذاجة التي يعتقد بها البعض حول الزمان والسفر عبر الزمن حسب مفهوم الفيزياء الفلكية المتعلقة بالزمكان، وأيضاً إيجاد نظريات أكثر وضوحاً حول ماهية الثقوب السوداء وما علاقتها بنشأة الكون وإنهياره المحتمل على نفسه، هوكينج عندما طرح تلك الإستنتاجات والمقاربات كان يعتر رائداً وأول من طرح تلك الأسئلة على العلماء، لم يكن القارئ العادي إنذاك مطلعاً إطلاقاً على مثل هذه التساؤلات والرؤية الجديدة للكون، بمعنى آخر أن تساؤلات هوكينج هنا وأفكاره كانت ثورية ومثيرة للدهشة والإعجاب.. بالتأكيد لم يصل إلى الصغية النهائية المتعلقة بالكون التي كان يرجوها، الأفكار فيها متشابكة ومتشعبة ويصعب كثيراً الخروج بنظرية موحدة حتى الآن ولذلك لوجود خلافات بين العلماء حول أبسط النظريات العلمية التي كانت تعتبر فيما سبق والتي تتعلق بجوهر المادة نفسها وتفسيرها على إطر متعددة، لذلك دائماً تطرح تساؤلات جديدة وتلغى نظريات وتأتي أخرى، ناهيك عن مسألة الزمان والمكان ونظرية الكم واللايقين وحتى وجود الكواركات وماهية المادة نفسها..


فلسفياً الكتاب غير جيد من وجهة نظري، فهو كما معلوم عن العلماء الغربيين عموماً ،عندما يتوصلون الى كيفية عمل منظومة في الكون مباشرة يستبعدون دور الخالق فيها وكأن معرفة طريقة عمل تلك القوانين تكفي أن تعمل لوحدها وعلى ذلك الشكل الذي تدركه عقولنا على الأقل، يذكر وبصورة غير مباشرة هوكينج أنه إذا توصلنا إلى نظرية نهائية تشرح عمل الكون ونشأته لن نحتاج حينها إلى فكرة الخالق .. وهذا المفهوم الخاطئ الذي يتورط فيه للأسف معظم الملاحدة وخاصة في العالم الغربي الذي تأثر عبر قرون وبلورها بالصيغة الفلسفية العقيمة التي نراها اليوم..


الكتاب عموماً جيد ولكن صعب بعض الشئ، يحتاج لمراجعة الكثير من المصطلحات والمفاهيم التي ذكرها الكتاب، ولحسن الحظ لا يحتوي الكتاب تقريباً على أية قوانين أو مسائل رياضية :)

Stephen Hawking's book is easy to read, but harder to comprehend. In every chapter came a point where my brain couldn't hold another permutation of a theory, and as the book progressed, I ended up taking the same approach as I do when reading a Norse saga for the first time. With sagas, I just read, even if my brain doesn't seem to retain all the information about who is related to who and what they named their horse. Inevitably, at the end, I have a reasonable basic grasp of the saga, and then I have to read it over again to fit more information into that basic understanding.

I don't know if the same will hold true here, but it's a nice hope.

Cam tot ce știu din / despre cosmologie provine din scrierile lui Hawking. Îndeosebi din acest volum care a fost un bestseller absolut. O glumă afirmă că toată lumea bună l-a cumpărat, dar foarte puțini l-au citit. Scurtă istorie a timpului ar fi, așadar, cel mai puțin citit bestseller dintre toate. Nu cred că pe autor l-a afectat prea tare acest amănunt nesemnificativ.

Mă aflu în situația bizară că știu multe fără să înțeleg totul. Știu, de pildă, că fizicienii încearcă să ofere „o descriere completă a universului”. Mai știu că o astfel de descriere nu este, deocamdată, cu putință. Mai știu că Hawking a fost obsedat de realizarea unei teorii fizice unificate (mecanica cuantică + teoria relativității generalizate), fără de care sus-numita descriere nu este posibilă. Prima teorie (cea cuantică) susține că „universul e guvernat de întîmplare”, fapt pe care Einstein nu l-a acceptat niciodată. A doua oferă o viziune deterministă.

Deși ne-am obișnuit să gîndim în termeni finaliști (omul ar fi scopul creației), știu, de asemenea, că evoluția universului nu este finalistă. Evoluția nu are un scop, o „intenție finală”: apariția unei conștiințe care să constate frumusețea și armonia acestei lumi. Pentru Pico della Mirandola, în schimb, acest lucru era evident: „Te-am așezat, Adame, în mijlocul universului, ca să-mi poți contempla măreția” (De dignitate hominis).

Știu că fizicienii au propus, la sfîrșitul anilor 60, un așa-zis Principiu antropic (îl comentează într-un articol și I. P. Culianu), care li s-a părut unora argumentul suprem al unei evoluții „dirijate după un plan” (un argument creaționist), dar mai știu că acest Principiu (comentat cu entuziasm odinioară de Penrose și Hawking) nu dovedește nimic. Formularea lui pare o imensă tautologie: „Vedem universul aşa cum este fiindcă, dacă ar fi diferit, noi nu am exista să-l observăm”. Altfel spus: „Vedem universul aşa cum este întrucît existăm". Afirmația lui Hawking seamănă cu alta, la fel de misterioasă, tot a lui: „Dezordinea creşte cu timpul, întrucît noi măsurăm timpul în direcţia în care dezordinea creşte”. Nimic mai limpede...

În fine, mai știu ce a afirmat Roger Penrose despre singularități și găuri negre (universul nostru provine dintr-o singularitate): „O stea care suferă un colaps datorită propriei gravitaţii este prinsă într-o regiune a cărei suprafaţă se reduce la dimensiunea zero. Şi deoarece suprafaţa regiunii se reduce la zero, aşa trebuie să se întîmple şi cu volumul său. Toată materia din stea va fi comprimată într-o regiune cu volum zero, astfel că densitatea materiei şi curbura spaţiu-timpului devin infinite. Cu alte cuvinte, există o singularitate conţinută într-o regiune a spaţiu-timpului numită gaură neagră”.

Cam atît...

Men can only hope to understand the universe, and if we did, then we would understand the mind of God. Likewise, there are lots of theories in this book I can only hope to understand.

One question I also wanna ask as did Hawking:

n  n    “If time travel is possible, where are the tourists from the future?”n  n

This book is not for everyone given it is based on the lecture by Stephen Hawking targeting a specific audience, yet anyone can pick it up and get a glimpse and the scope of the universe and this book succeeds at that.

n  

“Any physical theory is always provisional, in the sense that it is only a hypothesis: you can never prove it. No matter how many times the results of experiments agree with some theory, you can never be sure that the next time the result will not contradict the theory.”

n3 Stars // 78%
The thing about attempting to cram the maximum nutritional value into a tiny pill is that the resulting taste won't be pleasant. This principle applies to A Brief History of Time as well. In a 200-page book, Stephen Hawking attempts to sum up all of humanity's knowledge in quantum physics and cosmology. And while it's certainly a noble feat, the information inside is half-baked at best, and I can still hear the information overload rattling in my brain. (Shut up!)

I mentioned in my pre-review that the writing is bland in a very textbook-like style. There's little room for any sort of humor besides the occasional sarcastic quip, which is really a pity because it leaves very little entertainment value if you are not genuinely interested in the subjects covered. Though Hawking dumbs down the writing as much as possible, it's still quite technical—whether that's to its benefit or detriment depends on what sort of expectations you have.

But my main problem is, even if you ignore the writing style, the knowledge you leave with is so hole-ridden you might as well have never learned anything at all. You close the back cover knowing the applications of spin and the implications of the weak anthropic principle, but you still have no idea what the hell spin is (my new definition is "it's like a spinning ball, but there is no ball and it doesn't spin") or why the principle has credibility in the first place. You know things but at the same time you don't know anything; it's like the Schrödinger's cat of knowledge. For this reason, I was left deeply unsatisfied by many of the scientific explanations in this book.

I suppose the good thing about being unsatisfied is that it propels you to dig deeper for yourself. I believe that any nonfiction book worth its salt should make you think, and A Brief History of Time certainly did that—last night, while trying to sleep, I spent far too long wondering about positrons and string theory, and just ten minutes ago I found myself once again staring at the Wikipedia page called Religious interpretations of the Big Bang theory. So while not the most well-written science publication ever, A Brief History of Time was compelling enough (and original enough) to kindle a great deal of curiosity in me.

Three stars, because Stephen Hawking is one of my great idols and even if this did read like a textbook, it was a damn good one.

Disclaimer: I love math and physics and books that make me feel stupid, as in they are that intelligent. It was interesting learning about the development of science as it refers to the way we think about the universe and how scientific discoveries have been influenced and influence the way people think about God. My favorite section was the discussion of black holes and antimatter.

At times Hawking lost me. He wants to explain theory to the masses, but as he draws near to his own theory, he got excited and zoomed along, forgetting that us simpletons haven't memorized the ten theories he's building upon that he's given us a brief overview about. When I had to listen to a theory a few times or try to remember exactly what the uncertainty principle or thermodynamic arrow of time is, it was harder to take a mental pause in audio form, but had I been reading a physical book, I would have fallen asleep every few minutes. It's a book to make your brain hurt, maybe less so if you've recently taken an advanced physics class.

Nevertheless, it was fascinating and gives you much to mull over, especially about how little man knows about the laws governing the universe when he can only observe effects and describe them. The further theories develop, the more I am left to question the givens they take from other theories.

n  Rest In Peace Mr. Hawking, and Thank Youn

During my time with this text, I made a comment alongside the percentage update I have for books I'm reading on goodreads. I said it was a strange experience to be reading an important and well loved book, only to have the author pass away during the time of said reading. To add to this, I was actually given this book years ago by someone close, and I never made a full start on it until now. So it was as equally saddening as it was surreal when I woke up on the 14th March 2018 to hear Steven Hawking had died. I immediately looked at my copy of A Brief History of Time and settled on finishing it as soon as possible (it had been slow going until then).

Although I intend to be honest about my experience with this title, I actually want to make a separate statement regarding whether the average persons decision making process should lean more toward the positive end of the spectrum when considering this book. Having just finshed A Brief History of Time, I personally believe it's everyone's duty to pick this text up, engage with it, and carry through with it until the last page.

Coming from the position of a lay person with no background in Science (unless you include working on a fundraising team at the Institute of Cancer Research for two months. . . I personally think that's scraping the barrel) or Psychics, I found this hard to comprehended in places. In fact, the chapter on elementary particles murdered me. So much so, that my reading really slowed down toward the end of the book, even after learning of Mr. Hawkings death. Not only this, but just conceptualising some of the topics being explained was a nightmare for me at times. Believe me, you don't realise how much you rely on the above ability to carry you through a book, until you come across one that requires you to abandon said ability altogether and just 'role' with the topic at hand, knowing full well you're completley out of your imagination processing league.

Yet, despite the above said, I simply cannot lessen my high level of recommendation toward this book. I wish I'd read it when I was younger, as it provides some of the most important foundations to understanding our universe, and, as Mr. Hawkings mentions in the final chapter, science moves so fast that it's next to impossible for the many uninitiated individuals such as myself to understand what's new. So having books like this that really try to make the basic foundations of these huge topics understandable is a gift.

For that I am immensely grateful toward the author, and I look forward to presenting this to my child when they're old enough to being to grasp these concepts (I mean, It's not really like any of us really can, but I won't tell him/her that).

On a side note, there are moments where the ideas broached upon in this book might mess with your head.

Case and point: at times, I found myself staring deeply into my hand- followed by my book- on multiple occasions, trying to comprehend that whilst I was staring at two completely different objects, they were ultimatley made up of the same stuff (at the micro level of course). It caused some odd stares on the tube more than once. Especially whenever my eyes widened at the thought I might also be staring at a different dimension I'm simply unable to comprehend or see.

Something I'm sure you'll inevitably do as well if you really drink the quantum kool aid.

Finally managed to finish this; I think having a reading space quiet enough helped. Here, Hawking talks about such things as the beginning of time, black holes, string theories, dimensions, wormholes and time-travel - things of the universe, and where things are going. There is no Carl Sagan introduction in my version, but there are some newer things included that weren't in the original but have been 'found' since then, like a flavor of quark (top), and new findings in string theory, which are easy to notice because of the time mentioned.

(what's with God popping up here and there? 8) )
Throughout there are some helpful figure-pictures, though some would benefit for being made a bit sharper (more readable). And at the end there is glossary plus three short biographies (Einstein, Newton, Galilei - learned something new things about each in there).

This has been a huge seller of a book, and I can see why. It is said in pretty understandable language for many average person's to understand, though no doubt some of it might go over one's head, at least for someone of average intelligence-level, like me (haha). But I feel that I got more out of it than when I first started it (leaving it unfinished until this moment).

Some of it reminded me on the "Interstellar" movie (I liked it, so...), and I feel like watching it again. I did learn many interesting things from my reading, let some whoosh over my head, and consider this a good reading adventure.

4.25 Stars (Rnd down⬇️) — Hawking’s Classic & most well-received book is one of those 0.1% of all books that goes beyond ‘best-seller’ & reaches what you could call a ‘stratosphere-piercing’ level of renown. Much akin to Peterson’s 12 Rules, RK’s Rich Dad poor dad & so forth and so on. This doesn’t guarantee that it’s any good of course, far from it.

Luckily for us, Hawking’s effort is genuinely a good-read. Sure, it’s not a novel that I personally could read cover to cover in a single session or a couple of long sittings even. To me, it’s a book to be savoured in small bite-size portions, enabling one to fully grasp its heavy scientific weight and the beautifully presented concepts, & their mind-bending revelations about the very earth we inhabit. Nonetheless, it is a book that is very much enjoyable and written for the layman.

A certified knowledge-spreading tool for generations, Hawking is effective in pulling-in us laymen-folk without scaring us away first with what can often be written in contemptuous, pompous & pretentious fashion. Hawking is anything but boring and most certainly aborts all pretence in the name of setting the record straight on the big-bang, blackholes, time & many other incredibly large topics.

A must read for any intelligent adult. Simple.

This still very readable book (almost 40 years old) did not teach me much new things about how we can look at time from a physical point of view (I already read some books on this topic). Of course, the theory of relativity is discussed, which shows that space (in 3 dimensions) and time (1 dimension) have been linked to each other since the creation of our universe. There was no time before the singularity of the Big Bang, or at least it is not relevant to pose the question about what came before it.

In one chapter Hawking elaborates extensively on the arrow of time, with the inevitable 2nd law of thermodynamics, but he also involves the psychological experience of time (we can only remember the past), and the cosmological time experience (only within an infinitely increasing expansion of the universe disorder increases). So these three different experiences all indicate the arrow of time cannot but point in one direction, within universe as we know it.

The most curious thing in this issue is the use Hawking makes of the "anthropic" argument: only under the conditions of a strong thermodynamic arrow (that pushes time in one direction) does it appear that intelligent life can be created in an expansive universe. The argument goes as follows: theoretically a lot of possible universes are imaginable, but only a tiny fraction of them make intelligent life possible; and since we are intelligent (we can ask questions about time and contemplate on the origin and evolution of the universe) this ascertainment is very relevant and distinct to the way the real universe can be imagined. So according to the anthropic principle the universe must be as we perceive it, otherwise nobody would be here to perceive it. So if we perceive the arrow of time in one direction, then that must be the way our universe functions. I must say I was really surprised to look at the question in this way, and to see a physicist use anthropic arguments to 'proof' certain theories. I'm wondering if other scientists follow him on this point.

Finally, Hawking also examines the possibility of time travel, an issue that he leaves undecided, although it's my impression he is very skeptic about it.