Changes

Until the development of [[statistical mechanics]], no one knew why this was so, or what temperature actually meant.  What was known was simply that a body with a higher temperature would send heat to a body with a lower temperature, no matter what the bodies were made of.

Until the development of [[statistical mechanics]], no one knew why this was so, or what temperature actually meant.  What was known was simply that a body with a higher temperature would send heat to a body with a lower temperature, no matter what the bodies were made of.

The fact that this kind of heat flow is irreversible makes the whole field of thermodyamics lie outside of the realm of classical Newtonian mechanics or Relativistic mechanics.  In Newtonian or Relativistic mechanics, every phenomenon can go in reverse order.  The catchy phrase "arrow of time" (or "time's arrow") was coined by [[Arthur Eddington]] to denote this one-way behavior not shared by other theories of physics.<ref>''The Nature of the Physical World'', Arthur Eddington, MacMillan, 1929, ISBN 0-8414-3885-4</ref>

The fact that this kind of heat flow is irreversible makes the whole field of thermodyamics lie outside of the realm of classical Newtonian mechanics or Relativistic mechanics.  In Newtonian or Relativistic mechanics, every phenomenon can go in reverse order.  The catchy phrase [[Arrow of time]] (or "time's arrow") was coined by [[Arthur Eddington]] to denote this one-way behavior not shared by other theories of physics.<ref>''The Nature of the Physical World'', Arthur Eddington, MacMillan, 1929, ISBN 0-8414-3885-4</ref>

The field of statistical mechanics attributes the increase in entropy to the statistical tendencies of huge aggregates of particles at the molecular or atomic level.  While Newtonian and Relativistic mechanics can, in principle, precisely describe assemblages of any number of particles, in practice they are not directly applied to the behavior of bulk material.  That is, they are not applied to a number of particles on the order of Avogadro's number.

The field of statistical mechanics attributes the increase in entropy to the statistical tendencies of huge aggregates of particles at the molecular or atomic level.  While Newtonian and Relativistic mechanics can, in principle, precisely describe assemblages of any number of particles, in practice they are not directly applied to the behavior of bulk material.  That is, they are not applied to a number of particles on the order of Avogadro's number.