DOCUMENT 118 SEPTEMBER 1908 135
ALS.
[6 188].
[1]See
Bucherer 1907b. Bucherer's
apparatus
consisted of
a
charged capacitor placed
in
a
uniform
magnetic
field
parallel
to its
plates.
In
the middle of
the
capacitor
a
radioactive
source
emitting Becquerel rays
(ß-rays)
was
placed.
The total force
in
the direction
perpendicular to
the
plates
on
electrons
leaving
the
source
is
determined
by
the
magnitude
of the electric field
between the
plates
of the
capacitor,
the
magnetic field,
the direction with
respect to
the
mag-
netic field
in
which the electrons
move,
and
the
speed
of the electrons. For the electrons
to
es-
cape
from between the
plates,
which
are
very
close
together,
the
net
force
in
the direction
per-
pendicular
to
the
plates
has
to
be
zero.
Thus for
a
given
combination of electric and
magnetic
field
strengths
and direction of motion
only
electrons with
a
speed
determined
by
these
param-
eters
can
escape.
After
leaving
the
capacitor
the electrons
are
deflected
by
the
magnetic
field
only
and
registered
on a
cylindrical photographic plate surrounding
the
capacitor.
From the
speed
of
the
electrons and their deflection Bucherer calculated their
charge
to
mass
ratio, using
two
different theoretical frameworks
(see below).
See
Goldberg 1968, chap.
2.A,
and Miller
1981,
secs.
1.9, 1.11,
7.4.1-7.4.3,
and
12.4,
for historical discussions of Bucherer's work and
other determinations of the
charge-mass
ratio of electrons.
See
also Laub
1910,
sec.
IIc,
and
Lorentz
1922,
chap. 7,
for critical discussions of
experiments
on
the
charge-mass
ratio.
[2]Here
Bucherer
uses
the
terms "Relativprincip"
and
"Relativitätsprincip"
to
denote what
he
calls the "Lorentz-Einstein
theory." (Note
a
different
usage
later
on
in
this
letter, however.)
Like
many contemporaries,
Bucherer made
no
fundamental distinction between Lorentz's
electron
theory
and
special relativity. Initially,
Bucherer did
not
believe
in
Einstein's
theory
(see
Doc. 47 for
more
details;
see
also the last
paragraph
of Doc.
119).
See Bucherer 1908b,
the
paper
in
which Bucherer
published
the results of his
experiments,
and which has the
term
"Lorentz-Einsteinsche Theorie"
in
its
title,
for
more on
Bucherer's views
on
Lorentz's and
Einstein's theories
(p.
756).
[3]The
current
in the solenoid that
generated
the
magnetic
field.
[4]Bucherer's
results,
as
summarized
in
the table
above,
occur
in
the
same
form
in
Bucherer
1908b.
A later,
more
detailed
publication (Bucherer 1909) presents slightly
different values
(which
are
still in
support
of the "Lorentz-Einstein
theory").
[5]See
Bucherer
1906,
1907a,
for Bucherer's
principle
of
relativity.
It
postulates
that for
any
two interacting electromagnetic systems
in
relative
motion,
each
system experiences
the
same
force
as
it would
according to
Maxwell's
theory
if it
were
at
rest
in
the ether while the other
system
is
moving relatively to
it.
[6]Ebenezer
Cunningham
(1881-1977);
see
Cunningham
1908,
which
was a
reaction
to
Bucherer 1908a. See also Doc.
119
and Bucherer's
reply
to
Cunningham (Bucherer 1908c)
for
Bucherer's
maintaining
of
his
own
point
of
view.
The
Bucherer-Cunningham
discussion
is
an-
alyzed
in
Goldberg
1968,
chap.
2.A.3.
118.
From Max Planck
[Hotel Bellevue,]
Axalp
8. IX. 08.
Verehrtester
Hr. Dr!
Seit
14 Tagen
weile ich hier mit meiner
Familie;[1]
doch ist
es
sehr schwie-
rig
Ihnen einen bestimmten Ort
u.
Zeitpunkt
für ein Zusammentreffen
vorzu-
schlagen,
da das Wetter einen
gar
zu
maßgebenden
Faktor
in
allen
unseren
Plänen bildet. Das
einzige
Sichere,
was
ich
sagen
kann, ist,
daß ich Sonn-
abend
d.
12.
Abends
in Brienz,
Hotel
du Lac,
sein
werde,
da wir
am
13.
früh
die Heimreise über den
Brünig
antreten.
Wäre
es
aber nicht
praktischer,
wir
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