Four Laws That Drive the Universe

142 Pages·2007·1.5 MB·English

by  Peter Atkins

     
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FOUR LAWS
   
Peter Atkins
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PREFACE
Among the hundreds of laws that describe the universe, there
lurks a mighty handful. These are the laws of thermodynamics,
whichsummarizethepropertiesofenergyanditstransformation
fromoneformtoanother.Ihesitatedtoincludetheword‘ther-
modynamics’inthetitleofthislittleintroductiontothisbound-
lesslyimportantandfascinatingaspectofnature,hopingthatyou
wouldreadatleastthisfar,fortheworddoesnotsuggestalight
read. And, indeed, I cannot pretend that it will be a light read.
When in due course, however, you emerge from the other end
ofthisslimvolume,withyourbrainmoresinewyandexercised,
youwillhaveaprofoundunderstandingoftheroleofenergyin
theworld.Inshort,youwillknowwhatdrivestheuniverse.
Do not think that thermodynamics is only about steam
engines: it is about almost everything. The concepts did indeed
emerge during the nineteenth century when steam was the hot
topicoftheday,butasthelawsofthermodynamicsbecamefor-
mulatedandtheirramificationsexploreditbecameclearthatthe
subject could touch an enormously wide range of phenomena,
from the efficiency of heat engines, heat pumps, and refrigera-
tors, taking in chemistry on the way, and reaching as far as the
processes of life. We shall travel across that range in the pages
thatfollow.
vi Preface
Themightyhandfulconsistsoffourlaws,withthenumbering
starting inconveniently at zero and ending at three. The first
two laws (the ‘zeroth’ and the ‘first’) introduce two familiar
but nevertheless enigmatic properties, the temperature and the
energy.Thethirdofthefour(the‘secondlaw’)introduceswhat
many take to be an even more elusive property, the entropy,
but which I hope to show is easier to comprehend than the
seemingly more familiar properties of temperature and energy.
The second law is one of the all-time great laws of science, for
it illuminates why anything—anything from the cooling of hot
matter to the formulation of a thought—happens at all. The
fourth of the laws (the ‘third law’) has a more technical role,
but rounds out the structure of the subject and both enables
and foils its applications. Although the third law establishes
a barrier that prevents us from reaching the absolute zero of
temperature, of becoming absolutely cold, we shall see that
there is a bizarre and attainable mirror world that lies below
zero.
Thermodynamicsgrewfromobservationsonbulkmatter—as
bulkyassteamengines,insomecases—andbecameestablished
beforemanyscientistswereconfidentthatatomsweremorethan
mereaccountingdevices.Thesubjectisimmeasurablyenriched,
however,iftheobservation-basedformulationofthermodynam-
icsisinterpretedintermsofatomsandmolecules.Inthisaccount
weconsiderfirsttheobservationalaspectsofeachlaw,thendive
below the surface of bulk matter and discover the illumination
that comes from the interpretation of the laws in terms of con-
ceptsthatinhabittheunderworldofatoms.
Preface vii
Inconclusion,andbeforeyourollupthesleevesofyourmind
and get on with the business of understanding the workings of
the universe, I must thank Sir John Rowlinson for commenting
in detail on two drafts of the manuscript: his scholarly advice
wasenormouslyhelpful.Iferrorsremain,theywillnodoubtbe
tracedtowhereIdisagreedwithhim.
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CONTENTS
Preface v
1. THE ZEROTH LAW:Theconceptoftemperature 1
2. THE FIRST LAW:Theconservationofenergy 21
3. THE SECOND LAW:Theincreaseinentropy 47
4. FREE ENERGY:Theavailabilityofwork 79
5. THE THIRD LAW:Theunattainabilityofzero 101
Conclusion 123
Furtherreading 125
Index 127
Symbolandunitindex 131