DOC. 29 ERNST
MACH
143
modification
by
the
theory
of
relativity. Nobody
can
deny
that
epistemologists paved
the road for
progress;
and for
myself,
I
know
at least that
Hume and Mach have
helped
me a lot,
both
directly
and
indirectly.
I ask the reader to look at
Mach's
opus,
[3]
"Die Mechanik in ihrer
Entwicklung," especially
the deliberations under
6.
and
7.
of
chapter
2
("Newton's opinions on
time,
space
and movement" and
"Comprehensive
critique
of
Newton's
list").
There
one
finds
superbly explained thoughts
which,
up
to
now,
have
by
no
means
become
commonplace among physicists.
These
portions
are
especially
attractive because
they
are
tied to Newton with verbatim
quotations.
Here
are
just
some
of
these
nuggets:
Newton: "The
absolute,
true
and
mathematical time
flows,
by
itself and
by
its
%
nature, uniformly
and without relation to
any
extraneous
object.
It is also denoted
as
duration."
"Relative,
apparent,
and
ordinary
time
can
be felt
as an extraneous,
either
accurate
or changing, measure
of
duration,
and is
commonly
used
as
hour,
day, [p.
103]
month,
year,
instead
of
true time."
Mach:
".
. .
when
a thing
A
changes
in the
course
of
time,
it
means only
that the
circumstances
of
a thing A depend upon
the circumstances
of
another
thing
B.
The
oscillations
of
a
pendulum occur
in time if the excursion
depends upon
its
positions
relative to Earth.
Since
we
do
not need to
consider,
during
the observation of
a
pendulum,
its
dependence
upon
the
position
relative
to
Earth-we
could
compare
it
to
any
other
thing-(...)
it is
easy
to
get
the
opinion
that all these
things
are
irrelevant.
. . .
We
are
not
able to
measure
the
change
of
things
against
time. Time
is rather
an
abstraction which
we
reach
through
the
change
of
things,
because
we are
not
dependent upon a
distinct
measure,
since all
things hang mutually together."
Newton: "Absolute
space
remains,
by
its
nature
and without relation to
extraneous
objects,
always
the
same
and immovable."
"Relative
space
is
a measure or
a
movable
part
of
the former
and,
through
our
senses,
is denoted
by
its
position
relative
to
other
bodies,
and is
usually
taken
as
immovable
space."
This is followed
by
the
corresponding
definitions
of
"absolute motion" and
"relative motion."
Then follows:
"The active
causes by
which absolute and relative motion differ
are
the
centrifugal forces, pointing away
from the axis
of
motion. These forces do
not
exist
if
the circular motion is
only
relative;
but
they are
smaller
or larger depending upon
the ratio
of
(absolute)
motion."
Next follows
a
description
of
the well-known
experiment
with the
pail,
intended
to illustrate the
foregoing reasoning.
It is
interesting
to look at Mach's
critique
of this
position,
and I
quote
from
it
a
few
particularly
characteristic
portions.
"When
we see a
body
K
change
its
direction
and
velocity only
because
of
the influence
of
another
body
K',
then
we
cannot
even
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