Shireen's Reviews > A Briefer History of Time

A Briefer History of Time by Stephen Hawking
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's review
Aug 01, 11

really liked it
bookshelves: 2011, non-fiction, writing
Read from July 14 to 31, 2011 , read count: 1

**I'm not really sure you can have spoilers in a non-fiction book and one that was extensively discussed in the press, but if so, there is a tiny bit of a spoiler four paragraphs down and on.**

In preparation for my next-next novel, I decided to read the briefer (and, I assume, easier) of Stephen Hawking's books on time and space for the lay person. It's something I would've been loathe to do even six months ago because of the state of my reading ability. But Goodreads has done for me what I'd hoped it would: gotten me to practice, practice, practice reading. And as you know, practice makes better and gives a person the confidence to try harder material. Also my rehab team had told me when choosing books that material I was already familiar with would be easier to read than new material. Fortunately, I am familiar with all of the physics discussed in this book up until about the 1980s and Feynman's work. I just didn't recall it all that well.

Hawking and his co-author Leonard Mlodinow (of Star Trek: The Next Generation) do a nice job of building the physics story from centuries ago up to the present day. You get a good sense of how laws and theories progressed and of the obstacles the various physicists faced, whether from within their own theories, from their rivals, or from the politics of the day. By the time you get to the meat of the book -- Einstein -- you've received a good background.

But that's when I ran into problems. The language was as simple as could be. They used effective illustrations, for the most part, to help you visualize what they're talking about. I liked how they inserted Hawking into some of the images. They also came up with examples people could relate to to help explain these mind-bending concepts. Unfortunately, when they got to the good stuff on time, their language broke down. Maybe the editor had a brain cramp or something because a key example was rather imprecise.

"Suppose that one twin goes to live on the top of a mountain while the other stays at sea level. The first twin would age faster than the second. Thus, if they met again, one would be older than the other." (pg 43)

OK, so twin #1 is at the top and is older than twin #2 at the earth's surface, right? I assume that based on logic sequence -- the first twin mentioned is the one on the mountain, and so must be "first twin." However, I did have to assume, and that's the trouble, for then came this passage:

"...if one of the twins went for a long trip in a spaceship in which he accelerated to nearly the speed of light. When he returned, he would be much younger than the one who stayed on earth."

Um, isn't the one in the spaceship like the one on the mountain? This confusion could've been avoided with some judicious editing. It happens again elsewhere, but only this one made me really go spare. Luckily, I have an engineer friend I could confer with, and I decided to forget the mountain man example and focus on rocket man.

In a way, this is a small quibble except for the fact that this book is aimed at a lay audience, whose physics knowledge is low and thus will need the authors to connect the dots for them with clear, precise language.

The chapter on going back in time was interesting. I learnt something new physics-wise although Hawking's philosophizing against backward time travel was not new as his stance has been discussed many times in the popular press or on television. Physics is, in a sense, about philosophy because to get to a new theory you have to think about the possibilities and the whys and wherefores of both sides of the equation. Still, Hawking focuses on the reasons against backward time travel to such an extent that his ending statement that "the possibility of time travel remains open" comes as a bit of a surprise.

I like their little bios at the end, especially of Newton. I had no idea he was a man such as that! All in all, a good read, and it has given me a few ideas too for my novel.
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Reading Progress

07/14/2011 "This is such a large file, with fewer pages than most ebooks I've read, that it crashed Overdrive on my iPad and Adobe Digital Editions said it downloaded it but wouldn't move it to my Reader. Sony Reader software actually worked! And the Bluefire Reader app on the iPad handles it just fine. I've read the Foreword. And already I'm lost! lol!"
15.0% "Written well. So far, about stuff I already know, which is a good thing. I like the compactness of the chapters and the structure. Makes logical sense."
20.0% "It's probably not a good idea trying to read this while the high heat in Toronto works against working, thinking, doing much of anything."
29.0% "I'd, ahem, forgotten I'd taken this book out of the library and was supposed to be reading it. Back at it this morn. I'm up to relativity and am reminded once again that things happened earlier than I'd thought. Einstein theorized relativity in 1905." 2 comments
45.0% "Still reading stuff I learnt in high school or university, yet some concepts are easier to remember and regrasp than others. I really should be writing notes."
49.0% "I have 6 days left to finish this. Eek! I'm up to Heisenberg's uncertainty principle, and it is not certain I will get to the end of the whole."

Comments (showing 1-5 of 5) (5 new)

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message 1: by Ann (new)

Ann Douglas I loved your review, particularly the comment about the need to make the first twin/second twin example clearer. The reader shouldn't be slowed down by something that could be cleared up by a simple edit -- not in a book that is covering such important material.

message 2: by Ben (new)

Ben Babcock I'm afraid I don't really understand why it's unclear. The first twin mentioned is the one who lives on the mountain, and the second twin mentioned is the one who lives at sea level. So it makes sense to refer to them as "first twin" and "second twin", respectively. One could also have used "former" and "latter". Where is the confusion here?

If the confusion only enters during the second quotation, because you aren't sure which twin is supposed to be on the spaceship, then the answer is: it doesn't matter. Your first quotation is an example of gravitational time dilation, a phenomenon explained by general relativity. The second quotation is an example of velocity time dilation, a phenomenon explained by special relativity.

The twin on the mountain is technically farther away from the Earth's centre than the twin at sea level, and so the Earth exerts a weaker gravitational force for the twin on the mountain. According to Einstein's theory of general relativity, gravitation affects the passage of time relative to an observer: a clock closer to a gravity well (the Earth) will measure time slower than one farther away. So the twin on the mountain is going to age "more quickly". The effect will be negligible at that altitude (I think the difference between someone like you or me and an astronaut who has spent months in space is a matter of seconds).

It doesn't matter which twin goes on the spaceship, because the time dilation in this example will be much greater than that experienced by the twins when they lived at different altitudes. So even if you put the older twin, the one who lived on the mountain, on the spaceship, he or she would still age slower than the one who remains on Earth.

It's unfortunate if the book's phrasing is not clear enough when it comes to explaining these things. I agree that the second example, being more dramatic, is a more clear demonstration of time dilation. Nevertheless, the two examples are really complementary, because they each demonstrate a different type of time dilation.

(I'm sure your friend explained all this to you, but not everyone who reads you review will have been so lucky. Hopefully others will find that helpful.)

Still, Hawking focuses on the reasons against backward time travel to such an extent that his ending statement that "the possibility of time travel remains open" comes as a bit of a surprise.

Hahaha, yeah. He's like that. And I love him for it, because science is all about being able to admit you're wrong. He's famous for making bets with other physicists—perhaps most famous is his bet with Kip Thorne against the existence of "naked singularities", which he has conceded. He is not afraid to express confident opinions on things like time travel or naked singularities but always acknowledges that we ultimately won't know until we have better theories than what relativity and quantum mechanics provide right now.

Shireen Ah Ben, it's not confusing to you because you know the physics well. But as Ann said, "The reader shouldn't be slowed down by something that could be cleared up by a simple edit." A very good point Ann! As a former copyeditor of medical books, I had to do a lot of that clearing up.

I would also note that the way it was written in the book the spaceship and mountain examples were given as equivalents, so that it read as if the man on the mountain would be the same as the man in the spaceship, which makes no sense when he says that the man in the spaceship doesn't age as quickly as the man on earth yet the man on the mountain ages faster than the man at sea level.

Thank you for that explanation -- not only for readers of this review, but also I find it useful to hear the same concept explained differently by different people. And the penny has finally dropped. The acceleration of gravity is higher at sea level than on top of the mountain. Basically the closer you are to the Earth's centre, the faster you're going due to stronger and stronger gravity, just as the man in the spaceship accelerates faster and faster as he flies away from the earth. I had understood that the faster the acceleration, the slower the time.

I had no idea that Hawking was like that, but anyone who is in a Star Trek episode has to have a playful side. And so true about admitting you're wrong or even that you don't know. My father is in demand by patients because he has no hesitation in telling them he doesn't know when he doesn't, instead of fudging like so many docs, and then goes off to find out what he can.

I gather Hawking is on a quest for the complete unified theory of everything, sort of like the Holy Grail for physicists. I wonder if such a thing exists...

message 4: by Ben (new)

Ben Babcock Shireen wrote: "I gather Hawking is on a quest for the complete unified theory of everything, sort of like the Holy Grail for physicists. I wonder if such a thing exists..."

Speaking philosophically I have my doubts (and this is coming from someone who is otherwise very usually a reductionist). I took a philosophy of science course two years ago, and my prof said something very striking about how having a life-size version of a map is useless. (I now realize he was paraphrasing Borges, himself influenced by Lewis Carroll.)

The point stands for science as well: I doubt we'll ever find a single theory that neatly explains everything. If we did, it would be next to useless anyway. I suspect instead we'll end up with several complementary models.

Hawking expresses a similar opinion in some of his more recent books. He gives a nice overview of various theories (like string theory) that have competed to be the "unifying theory" in the past. In a 2002 lecture he explains that he used to believe a theory of everything was achievable but doubts that now:

Up to now, most people have implicitly assumed that there is an ultimate theory that we will eventually discover. Indeed, I myself have suggested we might find it quite soon. However, M-theory has made me wonder if this is true. Maybe it is not possible to formulate the theory of the universe in a finite number of statements. This is very reminiscent of Godel's theorem. This says that any finite system of axioms is not sufficient to prove every result in mathematics.

Shireen It's like the more we know, the less we know. It seemed to me as I was reading it from the perspective of one who couldn't care less about having one theory neatly wrapping everything up in a bow, that though Hawking aspired to finding such a theory, he was doubting whether he could or even its very existence.

I took a philosophy of medicine course at university because I had to, and it turned out to be one of my favourite courses, probably because it opened up new vistas by teaching us various ways of thinking.

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