Historical Order
 Horlogerie, Plate IX-7. Encyclopédie, ou Dictionnaire Raisonné des Sciences, des Arts et des Métiers. Edited by Denis Diderot and Jean le Rond d'Alembert, Paris 1768. Photograph by D Dunlop.

Our knowledge of time's arrow comes from the ordinary run of human affairs. So for WikiMechanics, the direction of time is derived from the historical record of human events; our collective experience, as recorded in the newspapers. Arbitrary sequences of events can be compared with such mundane proceedings, and a binary description of their relationship made as follows. The historical record is introduced via the reference sensation of touching the Earth. And the very common human experience of keeping in touch with some selection of terrestrial events is assumed to provide an ordered set of sensations that we note by $\Psi ^{\sf{ Earth}}$. Compare these events with any other chain $\Psi ^{\sf{P}}$ using $\delta _{ t}$ the temporal orientation. Definition: If

$\delta _{ t}^{\, \sf{ P}} = \delta _{ t}^{\sf{\, Earth}} = \pm 1$

then we say that P's events are in historical order. That is, they are organized like a calendar, almanac or diary. Or perhaps rather like a laboratory notebook where measurements are recorded along with the date. When we call a chain-of-events a history, we imply that it is historically ordered. The widespread practice of using the Earth as a frame of reference is deeply embedded in our use of language. We recognize this with a nomenclature that applies to any pair of events noted as $\sf{P}_{\it{i}}$ and $\sf{P}_{ \it{f}}$ that are members of a chain $\Psi$. Definition: if $\Psi$ is in historical order and $\it{i} < \it{f} \;$ then we call $\sf{P}_{ \it{i}}$ the initial event and $\sf{P}_{ \it{f}}$ the final event of the pair.

 Next step: solar clocks.
 Summary
 Adjective Definition Historical Order $\delta _{ t}^{\, \sf{ P}} = \delta _{ t}^{\sf{\, Earth}} = \pm 1$ 6-6
 Adjective Definition History $\sf{\text{A chain of events that is in historical order.}}$ 6-7
 Noun Definition Initial Event The event with the lowest event-index in a historically ordered pair of events. 6-8
 Noun Definition Final Event The event with the highest event-index in a historically ordered pair of events. 6-9
page revision: 200, last edited: 18 Nov 2016 22:44