DOCS.
47,
48
JULY
1907 31
by
your
remark
(Ann.
23,
p.
372,
1907)
that the
electromagnetic
state in
a
[finite][3]
portion
of
space
is
determined
by
a
finite
number of
quantities,[4] you seem
to
answer
this
question
in
the
affirmative,
while
I
would
answer
it, at
least in line with
my
present
view,
in
the
negative.
For
I do not
seek
the
meaning
of
the
quantum
of
action
(light
quantum)
in
the
vacuum
but
at
the
sites
of
absorption
and
emission,
and
assume
that
the
processes
in
the
vacuum are
described
exactly
by
Maxwell's
equations.
At
least,
I
do
not
yet
see
any
compelling reason
to
abandon
this
assumption,
which
seems
to
me
the
simplest
for
the
time
being,
and
which also
expresses
the
contrast
between ether and
matter
in
a
characteristic manner.-[5]
But
more
urgent
than
this
surely
rather
old
question
is at
the
moment
the
question
of
the
admissibility
of
your relativity principle.
Mr.
Bucherer
has
already
announced
to
me
by
letter
his
strong opposition
to
my
last
investigation,
in
that
(without
giving a
reason,
to be
sure)
he
declares the
principle
of
relativity
incompatible
with
the
principle
of least
action.[6]
It
is
therefore
all
the
more
gratifying
to
me
to
see
from
your
card
that,
for the
present,
you
do not
share
the views
of
Mr.
B.
As
long
as
the
proponents
of
the
principle
of
relativity
constitute
such
a
modest
little
band
as
is
now
the
case,
it
is
doubly
important
that
they
agree
among
themselves.-
Returning to
a
remark
in
one
of
your
last letters,
I
would like
to
add
that
I
will
probably
come
to
the
Bern Oberland
next
year.
This
is
still
a long
time
off, to
be
sure,
but
I
nevertheless
delight
in
the
thought
that
I
might
then
have
the
pleasure
of
making
your personal acquaintance.
Commending
myself
to
you,
I
remain
yours very truly,
M.
Planck
48.
To
Conrad and Paul
Habicht
[Bern,
15
July 1907]
My
dear
Habichts,
I would
really
like to
see
you again
one
of
these
days!
Are
you willing
and
able to
come
soon?
Now,
in
July,
I
could
put
up
both of
you
because
my
sister
is
away.
It
would be
even
nicer
if
you
would
come
at
the
beginning
of
August
to
Lenk
in
Simmenthal,[1]
where
I
am
going on
August
1
with wife and
child[2]
for
a ca.
10-day
vacation;
there
I would be
free
all
day long. My
thanks
to Mr.
Paul for
his
interesting
letter.
I have
found
yet
another
new
method of
measuring
very
small
amounts
of
energy.
Greetings
from
all of
us
to all of
you, your
A. E.
Write
soon!