It's About Time: Understanding Einstein's Relativity

N. David Mermin

Princeton University Press, 2005

I shall post errata at this website as I find them. If you discover any not listed below, please email

--- David Mermin

Figure 4.1

Between my final approval of the page proofs and the appearance of the book, all the arrows in Figure 4.1 lost their shafts . The figure should look like this.

The web address given on page 27 for Einstein's 1905 paper no longer works. There is, however, a link to it at
It is paper 8 on the list. You can also get to it directly by clicking here.

Some trivial errata:

p3: 29.9798452 ---> 29.9792458; second line from bottom
p14: phenominally ---> phenomenally; 2nd paragraph, 4th line
p15: objection ---> object; last paragraph, 1st line
p23: the the ---> the; last line
p48: simutaneous ---> simultaneous; last paragraph, 2nd line
p154: nonrelavistic ---> nonrelativistic; 2nd line
p174: verticl ---> vertical; last paragraph, 4th line
p184: collosal ---> colossal; 4th paragraph, 2nd line

As of July, 2006, all of the above except for the web address have been corrected in the second printing.

Lee Groth has called my attention to a source of confusion. The lengths a, b, A, and B that appear from the paragraph on the bottom of page 141 through Equation (10.20) (including Figure 10.27) are not the same as the lengths a, b, A, and B that appear in Figure 10.21 and from Equation (10.21) to the end of page 143. In a new printing (in April or May 2007) the former set of lengths will be relabeled e, f, E, and F.

On page 92, 13th line below the figure, the last sentence of the paragraph should begin "So gray rocket 0 took 10 ticks to go two rockets...."

On page 143, line below equation (10.23), b/A should be b/a.

On page 91, line 2, the c in u/c should be squared.

On page 42, on the line below equation (4.31), the reference to equation (4.29) should be to equation (4.27).

On page 51, on the second line below equation (5.2), it should say "subtract the first equation from the second".

On page 131, in the figure caption, "equitemps and equilocs" should be "equilocs and equitemps", both on the third line and on lines 4 and 5; and on line five t-sub-b should be d-sub-a.

On page 148, line above equation (11.3), u should be in bold face.

On page 189, line 9, "clocks run" should be "clocks to run"

On page 87 in the paragraph leading to Eq. (8.12), t-sub-2 and t-sub-3 should be interchanged, to be consistent with Figures 10.25 and 10.26 on pages 139 and 141.

On page 121, the 4th line in the 3rd paragraph ends in the word "actually" with a missing "l".

16 January 2018