218 BROWNIAN
MOTION
features
of
his
theory
accessible to
mathematically
less
sophisticated
readers.[77]
In late
1907
or early
1908,
the need for
an elementary
account
of
Brownian motion
was
suggested
to Einstein
by
Richard
Lorenz,
Professor of
Electrochemistry
and
Physical
Chemistry
at
the ETH,
who
pointed
out
that
such
an
account
would
be
appreciated by
chemists.[78]
Misunderstandings
of Einstein's
theory among
those
trying
to
provide
experimental
sup-
port
for it
reinforced the need
for such
a
theory.[79]
Einstein 1908c
(Doc. 50)
was
prepared
in
response
to this.
In
1909,
Einstein sent
a reprint
of
at
least
one
of
his
papers on
Brownian motion to
Ernst
Mach. In the
accompanying
letter,
as
in later
popular
accounts,
he
emphasized
the
direct
relationship
between
Brownian motion and
"thermal motion"
("Wärmebewegung").
[80]
In
1915,
Einstein wrote:
"Under
the
microscope
one,
to
some
extent,
immediately
sees a
part
of thermal
energy
in
the form
of
mechanical
energy
of
moving particles"
("Man sieht
gewissermaßen
unter
dem
Mikroskop
unmittelbar einen Teil
der
Wärmeenergie
in Form
von
mechanischer
Energie bewegter Teilchen").[81] Later,
he stated his view
of
the influ-
ence
his work
on
Brownian motion had
on
his
contemporaries:
"The
agreement
of
these
considerations
[on
Brownian
motion]
with
experience together
with
Planck's
determina-
tion of the true molecular size from the law
of
radiation
(for
high
temperatures)
convinced
the
skeptics,
who
were quite numerous
at that
time
(Ostwald, Mach),
of the
reality
of
atoms" ("Die
Ubereinstimmung
dieser
Betrachtung
mit der
Erfahrung zusammen
mit
der
Planck'schen
Bestimmung
der wahren
Molekülgrösse aus
dem
Strahlungsgesetz (für
hohe
Temperaturen) überzeugte
die damals zahlreichen
Skeptiker
(Ostwald,
Mach)
von
der
Realität
der
Atome").[82]
The
new
results
on
Brownian motion indeed
played a
decisive
role in
convincing
Ostwald
of
the existence
of
atoms.[83]
Mach, on
the
other
hand,
re-
mained
skeptical
on
this
point
until
at
least
1910.[84]
for
us"
("Die
Durchschnittsgesetze
der Erfah-
rung
täuschen
uns
also nach
Boltzmann die
Nichtumkehrbarkeit
der
thermischen Prozesse
vor").
[77]
See
especially
Einstein 1907c
(Doc. 40);
Einstein
1907f (Doc. 43);
Einstein 1908c
(Doc.
50);
and Einstein 1915a.
[78]
For evidence
of Lorenz's
suggestion, see
Einstein
1908c
(Doc. 50),
p.
235. Lorenz asked
Einstein
for
reprints
of
his statistical
papers,
to
which his attention
was
drawn
by
Einstein 1905k
(Doc. 16) (Richard
Lorenz to
Einstein, 15
No-
vember
1907).
[79]
For
a
discussion
of
these misunderstand-
ings, see
the
following
section.
[80]
Einstein
to
Ernst
Mach, 9
August
1909.
Einstein
forgot
to include his
papers,
and
actu-
ally
sent them with his letter
of
17
August
1909.
[81]
Einstein
1915a,
p.
261.
[82]
Einstein
1979,
p.
44; translation,
p.
45.
[83]
In
1906, Ostwald,
reacting
to
the ultrami-
croscopic
observations
of
colloidal
particles
re-
ported
in
Zsigmondy 1905,
admitted
for
the first
time in
the existence of limitations
to
clas-
sical
thermodynamics
(see
Ostwald 1907 and the
preface
to
Ostwald
1909,
p.
IV).
For
a
discus-
sion
of Ostwald's
reaction to the
new
work
on
Brownian
motion,
see
Brush
1968,
p.
35.
[84]
In
1909,
Mach
reprinted
his
essay
on
the
principle
of
conservation
of
energy
(Mach
1872),
which is critical
of
the kinetic
theory
of
heat,
and
sent
a copy
to Einstein
(see
Einstein to
Ernst
Mach
9
August
1909).
In Mach
1910,
he
reiterated
his criticism of kinetic
theory as
"hy-
pothetical-fictive
physics" ("hypothetisch-fik-
tive
Physik")
(Mach
1910,
p.
231).
For discus-
sions
of
the controversial
question
whether
Mach
ever accepted
the
reality
of
atoms,
see
Blackmore
1972, appendix, pp.
319-323, and
Wolters
1988,
§
2,
pp.
172-175.
For
a
discus-
sion
of
the Einstein-Mach
relationship
and the
problem
of
atomism,
see
Klein 1986.