DOCS.

368,

369 AUGUST

1917 365

that

generates

few

gravitational

masses (Newton’s case). According

to

Newton,

the

number

of

lines

of

force sent forth

by

this

space

into

infinity depends only

on

the total

mass

of

the

bodies, according

to

the

results

of

the

special

theory

of

relativity,

therefore

from the total

energy. Now,

it

seems

to

me

beyond

doubt

that

(in

the static

case)

the

field

at

infinity

must be

fully

determined

by

the

energy

of

the

mass

and

of

the

gravitational

field

together.

This fits with

my

interpretation

of

the

tov’s,

as

you can easily prove

from

my

field

equations

in mixed

form.[9]

If

you

like,

I shall be

glad

to

present any

of

these

points

in

more

detail

than

has

been

done here. I have

no

supporting

literature with

me.

With

cordial

regards,

I

am

yours,

A.

Einstein

cur[rently]

16A

Bramberg St.,

Lucerne.

369.

To Hans

Thirring

Lucerne,

16A Bramberg

St., 2

August 1917

Dear

Colleague,

Thank

you

for

your

kind and

interesting letter,[1]

which

was

forwarded to

me

here. To

your

example

of

the

hollow

sphere

it must

just

be added that, aside

from

the

centrifugal

field,

whose axial

components you

interpreted

so nicely, a

Coriolis

field

also

results

which

corresponds

to

the

components

g41, g42, g43

of

the

potential

and

is

proportional

to the first

power

of

w.[2]

This

field

has

a

vertically

repulsive

influence

on moving masses,

and in

the

Foucault

experiment,

for

ex.,

causes

a

rotation of the

pendulum plane.

I have calculated

this

trailing

rotation

for

the

Earth;

it remains far below

any

observable

quantity.

This Coriolis

field is

also

produced by

the

rotation

of

the

Sun and

Jupiter

and

causes

secular

changes

in

the

orbital

paths

of

the

planets

(or moons)

which, however,

remain far below

the

margin

of

error.[3] All

in

all,

the

perihelion

motion

of

Mercury

seems

to

be

the

only

case

within the

field

of celestial mechanics where deviations from

classical

theory

are perceptible

nowadays.

Nevertheless,

the

Coriolis

fields

still

seem more

accessible

to

observation

than

your

supplementary

terms to

g44,

because

the latter

influences have

the

same

symmetry

properties

as

field

distortion

from

oblateness.[4]

With best

wishes for

the

holidays

and for

success

in

your work,

I

am

with

best

regards, yours

truly,

A.

Einstein.