6 1 6 A P P E N D I X C
andere Bedeutung koennen wir raeumlichen Aussagen deshalb nicht geben. Nun haben wir
gesehen, die Gesetze der Lichtlagerung haengen ab vom Gravitationsfeld, das Gravitations-
feld selbst haengt wieder ab von der Verteilung der Koerper, und so kommen wir dazu zu
sagen, dass die Gesetze der Lagerung der Koerper von der Lage der Masse abhaengen und
es kommt den Gesetzen der raeumlichen Lagerung deshalb genau wie den Koerpern unab-
haengige Existenz zu und es erscheint also, was Urteil ueber raeumliches und zeitliches be-
trifft und so eng verbunden mit den uebrigen physikalischen Gesetzen, dass es keiner Weise
von ihnen losgetrennt werden kann, sodass wir also nicht mehr so vorgehen koennen, dass
wir zunaechst bei der Konstruktion des Gebietes der Physik den Raum und die Zeit setzen
und nachher erst die Gegenstaende, welche sich im Gefaess gewissermassen bewegen, son-
dern es ist so, dass die raeumlichen und zeitlichen untruegbar mit den uebrigen verbunden
sind, und damit habe ich meine allgemeinen Ueber-legungen beschlossen und ich will an-
fangen, die Sache vom mehr mathematischen Gesichtspunkt zu behandeln.
Summary
Second Lecture
The lecture yesterday had to do with the special theory of relativity, and the conclusion
which was arrived at the end was that all inertial systems, that is, all systems which move
relatively to each other with uniform rectilinear motion, are equivalent for describing phys-
ical phenomena. The special theory of relativity depends upon one hypothesis, that the ve-
locity with which light waves travel is the same in every case when referred to an inertial
system, that is, systems which move relatively to each other with velocities which are uni-
form and rectilinear.
Now, the striking thing about this is that it appears to hold only for a particular type of
systems; that is, systems which move with a particular type of motion relatively to each oth-
er. The question that we have to ask ourselves is whether the natural laws are such that there
should be such type of motion, whether it should not be so with all kinds of motion—sys-
tems moving with perfectly arbitrary velocities with respect to each other should not be
wholly equivalent as far as describing physical phenomena.
Now, there is one thing which has been known for a long time which helped a great deal
in getting at what we call the general principle of relativity. This is the principle of inertia.
We know that in respect to any one of our inertial systems a single mass point, if it is far
enough away from another body, moves with uniform velocity in a straight line. But this
principle of inertia certainly does not hold when we refer the motion of a body to a system
moving in arbitrary motion, say, in particular, a system which is moving with a motion of
rotation. In that case, instead of the motion of the particle that we considered first being in
a straight line it may in certain cases be in a very complicated curve.
Now, if all systems, no matter what their type of motion, are to be equivalent for describ-
ing physical phenomena, then we have got to change the whole foundation of our mechan-
ics. The principal thing which helps in this change is the known law that the inertia of a