An Introduction to Modern Cosmology: errata

As of April 2003, there is a new second edition of the book! It contains considerable new material, as well as correcting all the relevant errors listed below (while no doubt adding in some whole new blunders). Accordingly, I am no longer going to update this errata page. Buy the new edition instead!

As of January 2001 there is a new reprint of the book which, to my knowledge, has only the errors given below.

Page x (in preamble): I inexplicably managed to get the neutron half-life wrong, both by using an old value and by confusing mean lifetime with half-life. The correct value for the neutron half-life is 614 seconds, corresponding to a mean lifetime of 886 seconds. This affects material in Chapter 11; see item below for pages 87-89 and 94.

Page 12: At the bottom this makes the highly dubious statement that electrons are included under the title baryon. Particle physicists won't be impressed to read that since electrons are certainly leptons. What it should say is "... traditionally also included under the title baryon by cosmologists.", the reason for that terminology being given in the remainder of that paragraph.

Page 45: After Eq5.2, the text should say "with `-' for positive k and `+' for negative k ...".

Pages 87-89: Following from the page x item above, at the bottom of page 87 the neutron half-life should be 614 seconds, not 940 seconds. The same correction needs to be made twice on page 89. This generates the result Nn/Np = 1/8 in Eq11.8, giving a helium fraction of 22% rather than 25% in Eq11.9 and in the rest of that page. As it happens the presently-favoured values lie roughly between these two estimates, so this change hasn't made the very oversimplistic approximation any worse. The number of hydrogen nuclei per helium nucleus should be increased to 14.

Page 91: The lower x-axis of the figure unfortunately uses c-g-s units rather than m-k-s, as used in the rest of the book, and so the numbers are incompatible with those used earlier (eg in Eq6.4). To convert, they should be multiplied by a factor of one thousand (so starting at 10-29 and running to 10-26), so that the critical density as illustrated does indeed match the earlier equations.

Page 94: In the first two questions, the half-life should be corrected from 940 seconds to 614 seconds (see  above).

If however you have the original printing from 1999, the main additional known errors are the following:

The most embarrassing blunder is that the Einstein equation is wrong! Oops! On page 26, equation (3.21), the speed of light should be to the fourth power, not squared. This happened because there ought to be a factor of c2accompanying the dt2 in equation (3.20). Mistakes like that make you understand why cosmologists always like to set the factors of c to unity.

On page 88, Eq11.3 should be written as a two-body interaction, not a decay, because the reverse process of three particles creating one is exceedingly unlikely.  Delete the electron anti-neutrino on the right-hand side of the reaction and add an electron neutrino to the left-hand side; in the sentence immediately following Eq11.3 remove the bar from the neutrino and delete `anti'.

On page 36, the first paragraph of Section 4.5 should acknowledge more explicitly that these results are not true if there is a cosmological constant, which cosmologists increasingly believe is the case (see the new developments page). Change `should also apply' to `may apply', and add `though these conclusions are modified if there is a cosmological constant as introduced in Section 6.4.' to the end of the sentence.

The second part of the answer to Question 6.4 is quoted wrongly. It should be  rho_Lambda = Lambda/8 pi G.

There are also a few typos:

Page 1, there is an implication that Ptolemy was Greek but he was in fact Alexandrian.

Page 68, `throws' should be `throes'.

Page 79, Question 9.4, `electron mass' should be `electron mass-energy'.

Page 94: Q11.2, `were 100 seconds' to `is 100 seconds'.

Page 112, figure caption: `cobe' should be `cube'. Don't ask me what a cobe is.

In addition, if you want to be super-accurate the best current estimate of the microwave background temperature is
T = 2.725 +- 0.001 Kelvin.

If you've spotted something else, why not tell me at

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