THEORY OF
RELATIVITY
271
careful
analysis,
and concluded that
Kaufmann's
work could not be
regarded as a
defini-
tive refutation
of
the Lorentz-Einstein
predictions.[117]
Röntgen, one
of
the
leading
German
experimentalists,
is
reported
also
to
have felt that
Kaufmann's
results
were
not
decisive,
because his observations
were
not that
accurate.[118]
In
his
1907 review,
Einstein
discussed
Kaufmann's
results
at
some
length, especially
their
apparent irreconcilability
with the
Lorentz-Einstein
predictions.[119]
Commenting on a figure showing
Kaufmann's
results
and the relativistic
predictions,
Einstein wrote:
"Considering
the
difficulty
of
the
experi-
ment,
one might
be inclined to
regard
the
agreement as
satisfactory"
("In Anbetracht der
Schwierigkeit
der
Untersuchung
möchte
man geneigt
sein,
die
Ubereinstimmung
als eine
genügende
anzusehen").
However,
he noted that
the
deviations
are systematic
and well
outside
Kaufmann's
error
limits.
Whether
the
systematic
deviations
are
based
upon
a
source
of
error
not
yet con-
sidered,
or on
lack
of
correspondence
between the foundations
of
the
theory
of
relativity
and the
facts,
can only
be decided with
certainty
when
more
manifold
observational data
are
at hand.
Ob die
systematischen Abweichungen
in einer noch nicht
gewürdigten
Fehler-
quelle
oder darin ihren Grund
haben,
daß die
Grundlagen
der
Relativitätstheorie
nicht den Tatsachen
entsprechen,
kann wohl erst dann mit Sicherheit entschie-
den
werden,
wenn
ein
mannigfaltigeres Beobachtungsmaterial vorliegen
wird.
Although
Einstein
evidently accepted experiment as
the ultimate arbiter
of
the fate
of
any
theory,
he
was
cautious about
accepting
Kaufmann's
results
as
definitive,
perhaps
because
of
his
familiarity
with
Planck's
critical
analyses
of
the
experiments.[120]
What he found
even more
difficult to
accept were
alternative
equations
of
motion for the
electron that
are
based
on
what he
regarded as arbitrary
dynamical assumptions
about the
shape
of
a moving
electron. While
conceding
that
Kaufmann's
data seemed to favor the theories
of
Abraham
and
Bucherer,[121]
Einstein concluded:
In
my opinion,
however,
a
rather small
probability
should be ascribed
to
these
theories,
since
their
fundamental
assumptions
about the
mass
of
a moving
elec-
tron
are
not
supported by
theoretical
systems
that embrace wider
complexes
of
phenomena.
Jenen
Theorien kommt aber nach meiner
Meinung
eine
ziemlich
geringe
[117]
See
Planck
1906b,
and the discussion fol-
lowing
his
paper,
reported
in
Discussion/Planck
1906;
see
also
Planck 1907b.
[118] Röntgen's
views
were
expressed
in
a
talk
to the Bavarian
Academy
of
Sciences,
reported
in
a
letter
of
Arnold Sommerfeld to
Wien, 23
November 1906
(GyMDM,
Wien
Nachlaß,
Mappe Sommerfeld).
[119]
See Einstein
1907j (Doc. 47),
pp.
437-
439.
[120]
On
1
November
1907,
Einstein thanked
Stark for
calling
his attention to
Planck's
work
on
Kaufmann's
experiments
(Planck
1906b).
Einstein
evidently
wrote
to
Planck
requesting a
copy,
for
Planck
replied by postcard on
9 No-
vember,
stating
that he had
sent
copies
of his
two
papers
on
the
subject
(Planck
1906b,
1907b)
to Einstein, and
adding
further
com-
ments
on
the
experiments.
[121]
See note 115.