In order to explain the Lorentz transformation, it is advantageous to use its eigencoordinates rather than Cartesian coordinates. In this manner, the matrix can be diagonalized. Moreover, the diagonal entries have a direct physical meaning—permitting their determination without the need of algebraic equations. This yields a proof that is easier to remember and reproduce.

1.
Einstein's original derivation is in the famous 1905 paper:
A.
Einstein
, “
Zur Elektrodynamik bewegter Körper
,”
Ann. Phys.
322
(
10
),
891
921
(
1905
).
English translation by
George Barker
Jeffery
and
Wilfrid
Perrett
, “
On the electrodynamics of moving bodies
,” in
The Principle of Relativity
(
Dover Publications
,
New York
,
1952
). Chap. III.
2.
One attempt at a simple derivation—by Einstein himself—may be found in:
Albert
Einstein
,
Relativity, The Special and the General Theory, A Popular Exposition
(
Crown Publishers
,
New York
,
1961
), Appendix I.
3.
Minkowski's landmark 1908 address, introducing spacetime, may be found here:
Hermann
Minkowski
, “
Space and time
,” translated by
George Barker
Jeffery
and
Wilfrid
Perrett
, in
The Principle of Relativity
(
Dover Publications
,
New York
,
1952
), Chap. V.
4.
Pais′ incomparable biography of Einstein contains a representative history of special relativity:
Abraham
Pais
,
Subtle is the Lord: The Science and the Life of Albert Einstein
(
Oxford U. P.
,
Oxford
,
1982
).
5.
H. R. Brown's monograph is an invaluable historical resource, itself containing a vast bibliography of many sources not directly needed in the context of this paper:
Harvey R.
Brown
,
Physical Relativity: Space-Time Structure from a Dynamical Perspective
(
Clarendon Press
,
Oxford
,
2005
).
6.
Any student of relativity ought to explore the works of Wolfgang Rindler. A wonderfully precise author, his books on the subject are full of insight and contain beautiful exercises for the reader to enhance his/her understanding of the subject. These books include:
Special Relativity
(
Interscience Publishers
,
New York
,
1960
);
Introduction to Special Relativity
, 2nd ed. (
Clarendon Press
,
Oxford
,
1991
);
Relativity: Special, General, and Cosmological
, 2nd ed. (
Oxford U. P
.,
Oxford
,
2006
).
In addition, the following paper is of historical interest
W.
Rindler
, “
Einstein's priority in recognizing time dilation physically
,”
Am. J. Phys.
38
,
1111
1115
(
1970
).
7.
This book is one of a kind, a remarkable and creative introduction to relativity:
Edwin F.
Taylor
and
John Archibald
Wheeler
,
Spacetime Physics: Introduction to Special Relativity
, 2nd ed. (
W. H. Freeman
,
New York
,
1992
). It contains a wealth of exercises, with solutions provided for odd-numbered problems.
8.
Lest anyone take the reciprocity principle for granted, see
P.
Moylan
, “
Velocity reciprocity and the relativity principle
,”
Am. J. Phys.
90
(
2
),
126
134
(
2022
).
9.
Compare
L. J.
Eisenberg
, “
Necessity of the linearity of relativistic transformations between inertial systems
,”
Am. J. Phys.
35
(
7
),
649
649
(
1967
);
also see Lévy–Leblond below. The differentiability assumption is made only for brevity. For a proof without this assumption, see
V.
Berzi
and
V.
Gorini
, “
Reciprocity principle and the Lorentz transformations
,”
J. Math. Phys.
10
,
1518
1524
(
1969
).
10.
Seminal works by
W.
von Ignatowsky
include: “
Der starre Körper und das Relativitätsprinzip
,”
Ann. Phys.
338
(
13
),
607
630
(
1910
);
Einige allgemeine Bemerkungen über das Relativitätsprinzip
,”
Phys. Z.
11
,
972
976
(
1910
);
Das Relativitätsprinzip
,”
Arch. Math. Phys.
17
,
1
24
(
1911
);
Das Relativitätsprinzip
,”
Arch. Math. Phys.
18
,
17
40
(
1911
);
Eine Bemerkung zu meiner Arbeit: ‘Einige allgemeine Bemerkungen zum Relativitätsprinzip
,’”
Phys. Z.
12
,
779
779
(
1911
).
Compare
P.
Frank
and
H.
Rothe
, “
Uber die Transformation der Raumzeitkoordinaten von ruhenden auf bewegte Systeme
,”
Ann. Phys.
339
(
5
),
825
855
(
1911
).
Also see
Vladimir
Fock
,
Theory of Space Time and Gravitation
, 2nd ed. (
Pergamon Press
,
New York
,
1964
), Appendix A.
More modern papers include:
A. R.
Lee
and
T. M.
Kalotas
, “
Lorentz transformations from the first postulate
,”
Am. J. Phys.
43
,
434
437
(
1975
);
J. M.
Lévy-Leblond
, “
One more derivation of the Lorentz transformation
,”
Am. J. Phys.
44
,
271
277
(
1976
);
R. J.
Cook
, “
Comment on “Self-inverse form of the Lorentz transformation
,”
Am. J. Phys.
47
,
117
118
(
1979
);
W. N.
Mathews
, Jr.
, “
Seven formulations of the kinematics of special relativity
,”
Am. J. Phys.
88
,
269
278
(
2020
).
11.

[ξη]=P1[xt]=12c[1c1c][xt]=12c[x+ctx+ct].Thus, ξη is proportional to c2t2x2.

12.
L.
Parker
and
G. M.
Schmieg
, “
Special relativity and diagonal transformations
,”
Am. J. Phys.
38
(
2
),
218
222
(
1970
);
S.
Chao
, “
Lorentz transformations from intrinsic symmetries
,”
Symmetry
8
,
94
(
2016
).
13.
Malcolm S.
Longair
,
Theoretical Concepts in Physics
(
Cambridge U. P
.,
Cambridge
,
1984
), pp.
262
264
.
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