Talk:A Brief History of Time

Untitled
Any astrophysicistsWhat is wrong with the equation? I don't know how to fix it. -Shih-Arng

Mistake in first edition
In my copy of the first edition, on page 110, (Chapter 7, 'Black Holes Ain't so Black') it states "... distance of about a thousand million kilometers, or about as far away as Pluto, ..." Pluto orbits between 4.4 and 7.3 thousand million kilometers. One thousand million kilometers is actually just outside the orbit of Jupiter. Has anyone seen the same in later editions? Does it warrant mention in the article? Ronbennett2001 (talk) 03:14, 10 July 2013 (UTC)

Equations count

 * "The author notes that for every equation in the book the readership will be halved, hence it includes only a single equation: E=mc²."

But isn't the author's note itself an equation, making the total 2?--StanZegel 17:46, 25 Jun 2005 (UTC)

Yes. In fact there are plenty of equations in the book, but he wrote them out in word form so there wouldn't be any "equations". For example, he describes the law of gravity as being the product of the first mass times the product of the second mass divided by... etc. He used a loophole to get past the 'no equation' rule. In my opinion this made the book less readable. Carbon cat 17:56, 26 February 2007 (UTC)

Film
I find it a bit odd that the book was apparently made into a film, evidenced by the infobox and the categories it's in, but there's no mention of the film in the main text. --Last Malthusian 13:00, 9 January 2006 (UTC)
 * Apparently, there is a separate wikipedia entry for the film here. Should the film infobox be moved to that entry? --Kooky (talk) 06:58, 16 March 2006 (UTC)
 * Yes, I think so. It could be moved out again when the film article has grown.--I hate to register 20:51, 2 March 2007 (UTC)

Trivia: Ian Brown is reading A Brief History of Time during his cameo in Harry Potter and the Prisoner of Azkaban — Preceding unsigned comment added by 86.6.80.129 (talk) 16:01, 26 March 2013 (UTC)

What's with the film picture?
Why is the picture and info, on the right hand side, of the movie and not the book?

Fair use rationale for Image:BriefHistoryTime.jpg
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WikiProject class rating
This article was automatically assessed because at least one WikiProject had rated the article as start, and the rating on other projects was brought up to start class. BetacommandBot 13:27, 9 November 2007 (UTC)

How many copies sold? How much money?
How many copies were sold? Did this book help Hawking with the $$$ situation? --Zybez (talk) 21:33, 9 September 2008 (UTC)

doubt not explained in a brief story of time
i have a question can anyone answer me as stated in a brief story of time that the universe is expanding and the galaxies that are moving away from us has its its spectrum shift towards red and spectrum shift towards blue indicates that they are moving towards us can anyone explain with example of a balloon if a balloon is inflated how can two points on it can actually make sense to make a spectrum shift towards blue if the points on the balloon are considered as galaxies. Please inform if anyone has this answer on biswasdeepankar@gmail.com thank you. —Preceding unsigned comment added by 203.197.117.165 (talk) 21:00, 27 October 2008 (UTC)

No, I don't believe that any points on an inflating sphere will be moving closer together, or even remaining equidistant, which if they were galaxies would mean that all galaxies would appear to be redshifted from every vantage point (ie, every galaxy would be moving away from every other galaxy). This matches observation: all other galaxies appear redshifted to us. However, that doesn't mean that nothing appears blueshifted in the cosmos. Stars within our galaxy moving towards us would, for instance, but I would expect the magnitude of the shift to be small. I suspect the book mention blueshifting to complete the explanation of Doppler shift as applied to light waves. 80.235.56.123 (talk) 01:07, 11 November 2008 (UTC)

Scientific mumbojumbo! There is only one Book that explains everything and it is written by the One who knows all. 169.252.4.21 (talk) 11:28, 6 December 2016 (UTC)Kerrigan

How he write books?
Anyone has any information on how he writes his books? (He can't move) That would be informative. —Preceding unsigned comment added by Knight177 (talk • contribs) 06:49, 3 November 2010 (UTC)


 * I would guess in a similar way to how he talks, using his cheek to type input into a computer program (he can move a little). I know the voice synthesiser has predictive text to speed things up a little although it's still very slow. There are probably other software helpers, and possibly some of the more mechanical parts of the writing process are delegated out. If anyone has any real details I think that would be really interesting! --142.25.98.192 (talk) 18:51, 18 November 2011 (UTC)

Authorial credit
The cover of my 1988 UK edition (ISBN 0-593-01518-5) is credited to Stephen W. Hawking rather than Stephen Hawking. Presumably SH decided to drop the middle initial at some stage. This is obviously a minor matter, but would be worth documenting in an article covering this important and influential book. Does anybody know the full story? --Ef80 (talk) 16:05, 25 August 2017 (UTC)

Harry Potter Prisoner of Azkaban film cameo
In Prisoner of Azkaban you can see this book at the Leaky Cauldron (someone is reading it). if someone could add this that would be great. 75.91.86.216 (talk) 12:18, 30 March 2018 (UTC)

Incorrect Kepler Picture
The image captioned "Kepler's sun-centric elliptical orbit model of the solar system" does not depict that. Rather, it shows an image from an earlier work of Kepler where he was trying to model the radius of the planets' orbits as those that fit perfectly within nested platonic solids. Rknop (talk) 12:29, 5 May 2018 (UTC)

Chapter 9: The Arrow of Time
I (somewhat) object to the WikiProject Physics expert attention needed template on this page. This is not physics, it is the philosophy of physics. This is something physicists are trained to avoid until retirement. I will, however, write out as what I see as the problems with the way this section is written, from one physicist's point of view:
 * It talks about the thermodynamic arrow of time as if it were actually fact, not just a discussion in the book. This is a matter of philosophy and, as such, it is not a fact. This must be reworded (or qualified).
 * The statement "Because of the "no boundary" proposal for the Universe, after a period of expansion, the Universe will probably start to contract. It will probably not go backwards in time to a smoother, orderly state." is horrible and must be either qualified as Hawking's personal, non-scientific prediction or otherwise be removed as fallacious.
 * The following sentence, "The thermodynamic arrow in the contracting phase will not be as strong." must also be qualified as either Hawking's prediction or make reference to a part of the book where he works out some math.
 * Need to replace "firstly, there is" with "Hawking's first arrow of time,". This was confusing when I first read it.
 * Finally, replace "thirdly" with "finally". Just because it sounds better.

The final paragraph is good. They should all be like that. every sentence that sounds factual should be qualified with something like "Hawking postulates" or "He thinks". I think the whole section was meant to be read that way, but it comes across as teaching us about these concepts, which are inherently a matter of philosophy.

It has been a very, very long while since I indulged in popular physics books, but if need be, I can get a copy and fix this section up. It would be greatly appreciated, though, if others, that have the book, could take the initiative. Thanks! Footlessmouse (talk) 09:53, 15 August 2020 (UTC)

I have read the chapter in question! It is not hard to rent e-books these days. So I will list out here everything I see a problem with, and implement those changes afterwards. If anyone has any objections, please let me know here. Rewrite: as
 * In this chapter Hawking talks about why "real time" as humans observe and experience it (in contrast to the "imaginary time" in the laws of science) seems to have a certain direction, notably from the past towards the future. The things that give time this property are the arrows of time.
 * "In this chapter Hawking talks about why "real time", as Hawking calls time as humans observe and experience it, (in contrast to what Hawking calls the "imaginary time" in the laws of physics) seems to have a certain direction, notably from the past towards the future. Hawking then discusses three "arrows of time" which, in his view, give time this property."

Rewrite as
 * Firstly, there is the thermodynamic arrow of time. According to this, starting from any higher order organized state, the overall disorderliness in the world always increases as time passes. This is why we never see the broken pieces of a cup gather themselves together to form a whole cup. Even though human civilizations have tried to make things more orderly, the energy dissipated in this process has created more overall disorder in the Universe.
 * Hawking's first arrow of time is the thermodynamic arrow of time. This is the given by the direction in which entropy (which Hawking calls disorder) increases. According to Hawking, this is why we never see the broken pieces of a cup gather themselves together to form a whole cup.

Rewrite as
 * The second arrow is the psychological arrow of time. Our subjective sense of time seems to flow in one direction, which is why we remember the past and not the future. Hawking claims that our brain measures time in a way where disorder increases in the direction of time. We never observe it working in the opposite direction. In other words, the psychological arrow of time is intertwined with the thermodynamic arrow of time.
 * Hawking's second arrow is the psychological arrow of time. In Hawking's model, this is the direction in which we "feel" time passing. Our subjective sense of time seems to flow in one direction, which is why we remember the past and not the future. Hawking claims that our brains measures time in a way where disorder (entropy) increases in the direction of time -- we never observe it working in the opposite direction. In other words, Hawking argues that the subjective psychological arrow of time is intertwined with the thermodynamic arrow of time.

Rewrite as
 * Thirdly, there is the cosmological arrow of time, the direction of time in which our Universe is expanding and not contracting. Hawking believes that in order for us to observe and experience the first two arrows of time, the Universe would have to begin in a very smooth and orderly state. And then as it expanded, it became more disorderly. So the thermodynamic arrow agrees with the cosmological arrow.
 * Finally, Hawking's final arrow of time is the cosmological arrow of time. This is the direction of time in which the Universe is expanding rather than contracting. Note that during a contraction phase of the universe, the thermodynamic and cosmological arrows of time would therefore not agree.

Replace with
 * Because of the "no boundary proposal" for the Universe, after a period of expansion, the Universe will probably start to contract. It will probably not go backwards in time to a smoother, orderly state. The thermodynamic arrow in the contracting phase will not be as strong.
 * Hawking claims the "no boundary proposal" for the universe seems to imply that the universe will expand for some time before contracting back again. He goes on to argue that the no boundary proposal is what drives entropy and that, only in an expanding universe, it predicts the existence of a well-defined thermodynamic arrow of time, as it implies the universe must have started in a smooth and ordered state that must grow toward disorder as time advances.

Rewrite as Footlessmouse (talk) 21:06, 15 August 2020 (UTC)
 * As for why humans experience these three arrows of time going in the same direction, Hawking postulates that humans have been living in the expanding phase of the Universe. He thinks that intelligent life couldn't exist in the contracting phase of the Universe. Only the expanding phase of the Universe is suitable for intelligent beings like humans to exist, because it contains a strong thermodynamic arrow. Hawking calls this the "weak anthropic principle".
 * Hawking argues that, because of the no boundary proposal, a contracting universe would not have a well-defined thermodynamic arrow and therefore only a Universe which is in an expansion phase can support intelligent life. Using the weak anthropic principle, Hawking goes on to argue that the thermodynamic arrow must agree with the cosmological arrow in order for either to be observed by intelligent life. This, in hawking's view, is why humans experience these three arrows of time going in the same direction.
 * Note: I missed this on my first review. Hawking did not invent the weak anthropic principle, that should be linked to the article on the topic.
 * I believe that the "imaginary time" to which that chapter refers is not just time as expressed in the laws of physics, but actually imaginary time, i.e., what you get when you Wick rotate a path integral to make it look like a partition function. XOR&#39;easter (talk) 21:35, 15 August 2020 (UTC)
 * Thank you. You are correct, they are one and the same. I left that part mostly unchanged as I was not sure how to reword it. Hawking argues that general relativity and quantum mechanics cannot be reconciled without using said imaginary time and, therefore, claims that all of physics is dependent upon imaginary time. I am not sure how to reword that part. Footlessmouse (talk) 22:12, 15 August 2020 (UTC)
 * . Thank you for the comment. I have fixed the article to link to the imaginary time article and changed it to say "in contrast to "imaginary time", which Hawking claims is inherent to the laws of science". I believe this fixes the issue. I have also reworded a few parts and added in some extra links to time perception and entropy (arrow of time) articles. Please let me know if you find any other issues. Footlessmouse (talk) 22:58, 15 August 2020 (UTC)

Summary length
The 'contents' section seems absurdly long for a wikipedia article on a book, even if it's non-fiction. It's almost 10% the word count of the book itself. Do we need that many words do summarize this book? It's not like it's a highly technical work. I'm tempted to put a long summary template up unless someone has a good explanation of why it's like this. 161.221.87.4 (talk) 19:00, 23 January 2022 (UTC)

A Brief History of Time has around 53,000 words. The content summary section has about 4,700 words, which is around 9% of the book. A typical summary contains about 10%-15% of the original text. By that standard, the content summary in this article is not that lengthy. Besides, it can be whittled down even further by reformulating and cutting out redundancies and other superfluous elements. I am working on it. Zaheen (talk) 19:32, 26 May 2022 (UTC)

Hawking, in later years, rejected the eternal inflation theory.
Maybe that should be included in the article where eternal inflation is mentioned. 2600:8801:BE31:D300:BD48:F698:AD4C:752E (talk) 21:54, 29 May 2022 (UTC) James

Most unread book of all time according to Hawking Index.
On the article for Hawking Index, this book is cited as "the most unread book of all time". We could sync this by putting it somewhere along side the citation.

Danidamiobi (talk) 13:21, 5 December 2023 (UTC)


 * First, it's not cited as the most unread book - it comes in fourth among the examples; and second this is not a serious index and it has not been computed for a large number of books; I don't think referencing it here adds valuable knowledge about A brief history of time. --Qcomp (talk) 20:35, 5 December 2023 (UTC)