DOCS.
181,
182
JANUARY
1916 177
He is
an
old
man
and
no
longer
has
the
flexibility
needed to
delve
into
new
issues.
That
is
why
he
assumes a
negative
stance
on
technical
matters,
and this
negative
attitude
also extends
to
Freundlich,
whom he envisions somewhat
as an
incarnation
of these
things.
I
readily
believe
that
Freundlich
on
his side has
little
tact
and
lacks social
skills,
and in
general
has
little
psychological understanding
for his
fellows,
which
only
makes
the
circumstances
more
disagreeable.
I
do
not
take
Freundlich
for
a
very
great talent,
but
for
a
person
with
a
burning
interest
and
a
remarkable
tenacity.
He
was
the
first astronomer to
understand the
significance
of
the
general theory
of relativity
and
to address
enthusiastically
the
astronomical issues
attached
to
it.[5]
That is
why
I
would
regret
it
deeply
if he
were
deprived
the
possibility of working
in this
field.
I
know from
my
own
experience
that
the
necessary
technical
skills
can
be
acquired,
if the
requisite
understanding
and
a
great
interest
are
combined. Should such deficiencies
nevertheless
hamper
the
enterprise, help
from
a well-meaning
expert
could lead to valuable results.
Best
regards, yours truly,
A.
Einstein.
182. To
Paul Ehrenfest
[Berlin,]
17 January 1916
Dear
Ehrenfest,
I
am
enormously pleased
about
your
and Lorentz’s
concurrence,
which has
such
a
cheerful and
bright ring
to
it![1]
You
form
a
brilliant
nook
on
this barren
planet. Cleverness
there
is aplenty,
but
goodness
and
generosity are pitifully
scarce.[2]
Your
truly
Ehrenfestian
description
of
the
telescope
affair must be
accepted
without
protest.[3]
Now
to
some
of
your questions.
(1)
The
equation[4]
E¿(2Í
+ tí)
=
0
is
a
covariant
equation, whereby
tyo
is
not
a
tensor and
the
operation
performed
on a
tensor
Ed/dxA
does not lead to
any
covariant. The
equation
is
covariant
on
subst. of
det[erminant]
1,
because
both
of
the
main
equations
from which
it
is
derived
are
as
well.
(2)
Nevertheless,
there
is
something superfluous
in
both
equation systems. Namely,