Page 26 - 2020SEP30 Brief Booklet C

302 LEO SZILAHI)

tiori according to the results of the ineasure- as well as the motor nervous systems a
nients. Presently, of course, we do not know degradation of energy is always involved,
whether we commit an error by not includ- quite apart from the fact that the very
ing the intervening man into the system and existence of a nervous system is dependent
by disregarding his biological phenomena. on continual dissipation of energy.
Apart froin this unresolved matter, it is Whether-considering these circuin-
known today that in a system left to itself no stances---real living beings could continually
“perpetuuni mobile’’ (perpetual niotion ma- or at least regularly produce energy at the
chine) of the second kind (more exactly, no expense of heat of the lowest temperature ap-
“automatic machine of continual finite pears very doubtful, even though our ignor-
work-yield which uses heat at the lowest ance of the biological phenomena does not
temperature”) can operate in spite of the allow a definite answer. However, the latter
fluctuation phenomena. A perpetuuni mobile questions lead beyond the scope of physics
would have to be a machine which in the in the strict sense.
long run could lift a weight at the expense of It appears that the ignorance of the bio-
thc heat content of a reservoir. In other logical phenomena need not prevent us frorn
words, if we want to use the fluctuation phe- understanding that which seems to us to be
noinena in order to gain energy at the ex- the essential thing. We may be sure that
pense of heat, we are in the same position as intelligent living beings-insofar as we are
playing a ganic of chance, in which we may dealing with their intervention in a ther-
win certain amounts now and then, although niodynaniic systen-can be replaced by non-
the expectation value of the winnings is zero living devices whose “biological phenomena”
or negat>ive. The same applies to a system one could follow and determine whether in
where the intervention from outside is per- fact a compensation of the entropy decrease
formed strictly periodically, say by periodi- takes place as a result of the intervention by
cally moving machines. We consider this as such a device in a system.
established (Szilard, 1925) and intend here In the first place, we wish to learn what
only to consider the difficulties that occur circumstance conditions the decrease of
when intelligent beings intervene in a sys- entropy which takcs place when intelligent
tem. We shall try to discover the quantita- living beings intervene in a therniodynamic
tive relations having to do with this inter- system. We shall see that this depends on a
vention. certain type of coupling between different
Snioluchowski (1914, p. 89) writes: “As parameters of the system. We shall consider
far as we know today, there is no automatic, an unusually simple type of these ominous
permanently effective perpetual motion ma- coup1ings.l For brevity we shall talk about a
chine, in spite of the molecular fluctuations, “measurement,” if we succeed in coupling
but such a device might, perhaps, function the value of a parameter y (for instance the
regularly if it were appropriately operated by position co-ordinate of a pointer of a meas-
intelligent beings.. . .” uring instrument) at one nioment with the
A perpetual motion machine therefore is simultaneous value of a fluctuating parame-
possible if-according to the general method ter x of the system, in such a way that, from
of physics-we view the experimenting man the value y, we can draw conclusions about
as a sort of deus ex machina, one who is con- the value that x had at the moment of the
tinuously and exactly informed of the exist- “measurement.” Then let x and y be un-
ing state of nature and who is able to start or coupled after the measurement, so that 5 can
interrupt the macroscopic course of nature change, while y retains its value for some
at any rnornent without expenditure of work. time. Such measurements are not harmless
Therefore he would definitely not have to interventions. A system in which such
possess the ability to catch single molecules measurements occur shows a sort of memory
like Maxwell’s demon, although he would
’The author evidently uses the word “omi-
definitely be different from real living beings nous” in the sense that the possibility of realizing
in possessing the above abilities. In eliciting the proposed arrangement threatens the validity
any physical effect by action of the sensory of the Second Law.-Translator