306 DOC.

31

ON THE RELATIVITY PROBLEM

Doc.

31

On the

Relativity

Problem

[Scientia 15 (1914):

337-348]

After

two

eminent

specialists

have

put

forth their

objections against

the

theory

of

relativity

in this

journal,

the readers

might

also wish to have

an

adherent of this

new

[1]

theoretical direction

present

his views. This shall be

done,

as

concisely

as

possible,

in

what follows.

At

present we

have to

distinguish

between

two

theoretical

systems,

both

falling

under the

designation "theory

of

relativity."

The first of

these,

which

we

shall call

"the

theory

of

relativity

in

the

narrower

sense," rests

on a

considerable

body

of

experience

and

is

now

accepted by

the

majority

of theoretical

physicists

as

the

simplest

theoretical

expression

of those

experiences.

The second

one

(which

we

call

"the

theory

of

relativity

in

the broader

sense") has,

up

to

now,

remained almost

[2] totally

unsubstantiated

by

physical experience.

The

majority

of

my

colleagues are

[3]

skeptical

toward

this

second

system

or are

inclined

to

reject

it.

Let it be noted

right

here that

one can

well be

a

supporter

of the

theory

of

relativity

in the

narrower sense

without

acknowledging

that

the

theory

of

relativity

in

the broader

sense

is

justified.

For that

reason we

will discuss the

two

theories

separately.

1.

The

Theory

of

Relativity

in the

Narrower

Sense

It

is

well known that the

equations

of the mechanics established

by

Galileo and

Newton

are

not

valid with

respect

to

an

arbitrarily

moving

coordinate

system

if

one

sticks with the

requirement

that

only

central forces

satisfying

the law of

equality

of

action and reaction be admitted

in

the

description

of motions. But if the motion

is

referred

to

a

system

K such that Newton's

equations

are

valid

in

the indicated

sense,

then this coordinate

system

is not

the

only one

with

respect

to

which those

mechanical laws

are

valid.

Instead,

regardless

of its

spatial

orientation,

every

coordinate

system

K' that

is

in uniform translational motion with

respect

to K

has the

property

that the

same

laws

are

valid relative

to it.

The

assumption

of

the

equivalence

of

all

of these

systems K,

K', etc.

for the formulation of the laws of

motion,

in

fact,

the

general

laws

of

physics,

is

called "the

relativity principle" (in

the

narrower

sense).

As

long as one

believed that the theoretical

description

of

all

the

processes

was

to

be based

on

classical

mechanics,

one

could

not

doubt the

validity

of that

relativity

principle.

But

even

apart

from

that,

it

is

difficult

to

doubt

the

validity

of this

principle

from

an empirical standpoint.

For if this

principle

were

not

valid,

then

processes

in