508

DOC.

488

MARCH

1918

488. From

Gustav

Mie

Halle-on-S[aale],

47

I

Magdeburger St., 21

March

1918

Dear

Colleague,

Through

personal circumstances, namely, my

wife’s

falling

quite

seriously

ill

which,

thank

God,

we

have

weathered,

I

was

prevented

from

answering your

letter

of

22 February sooner.[1]

By

now,

each of

us

has

probably presented

his

point

of

view

sufficiently,

in the main.

I would just like

to

say

one more thing:

You

think

I

had

totally

misunder-

stood

your paper “Cosmological

Considerations.”[2] This

I

do not

believe,

though.

I

merely

make

a

sharp

distinction

between

what

you

wish

to

attain

with the

grav-

itational

equations posed

there

and

what,

as

far

as

I

can see, really

is attainable

with

them.[3]

I

am

convinced

that

if

a

reasonable

integral

solution of

your equa-

tions

really

is

gained

with

A,

then

p

in

this

integral

in

the

vast

spaces

between

the individual

fixed

stars must have

a

constant

value,

thus

must

occur as a mass

density continuously

permeating

the

space.

I

have considered

the

matter

very

thoroughly

and do not

believe

that

I

am

mistaken.[4]

The

equation

system

with

A

differing

from

zero

seems

to

me

to be

of

very

great

interest for

epistemology, though.

We

all know

that

the

parallel

axiom

is

a

physi-

cal

law;[5]

it

indicates,

to

use

my terminology

for

once,

a

specific

characteristic

of

ether

physics

and thus

is

on

the

same

level

as

the

principle

of

relativity,

Hamil-

ton’s

principle,

etc.

However,

until

now

it

has

always

been puzzling-to

me,

at

least-at

what

place

exactly

the

parallel

axiom enters

into the fundamental

phys-

ical

equations because,

given

the

way

in which the

fundamental

equations

had

always

been

formulated before

your publication “Cosmological Considerations,”

the

parallel

axiom

was

always

silently

assumed

from

the

outset.

Now

this

is

sud-

denly

different;

in

your

new

equations

one can

finally

see

clearly

in what

way

the

parallel

axiom

is

contained

in

the fundamental

equations

of

ether

physics,

which

are

accessible to

experimental

verification.

It

simply

involves

the

experimentally

determinable

coefficient

[A];

if

it

is

zero

the

parallel

axiom

is valid,

if

it

differs

from

zero

then the

space

has

a

constant curvature which

can

be

calculated

from

A.

I still do not

quite

understand

why you

are so

unsatisfied

with

my

interpreta-

tion of

your

theory of gravitation

of

1915,[6]

but

on

this

point

we

shall

probably

never

be able

to

agree.

To

make

another

attempt, nevertheless,

I

would like to

present my

point

of view

once

in

an

entirely

new

form

that has

occurred to

me

since.

I

would

like

to

imagine

the Earth

as an

“Einsteinian

coupé,”[7]

from

which,

as

a

consequence

of

a

perennial

thick

fog,

shall

we

say, no

other

celestial bodies

at

all

can

be observed.

We

are

then

still

going

to

be able to determine

the rotation