- On the dimensionality of spacetime (space.mit.edu)
Some superstring theories have more than one effective low-energy limit corresponding to classical spacetimes with different dimensionalities. We argue that all but the (3 + 1)-dimensional one might correspond to ‘dead worlds’, devoid of observers, in which case all such ensemble theories would actually predict that we should find ourselves inhabiting a (3 + 1)-dimensional spacetime. With more or less than one time dimension, the partial differential equations of nature would lack the hyperbolicity property that enables observers to make predictions. In a space with more than three dimensions, there can be no traditional atoms and perhaps no stable structures. A space with less than three dimensions allows no gravitational force and may be too simple and barren to contain observers.
- History of the alphabet (Wikipedia)
The history of the alphabet goes back to the consonantal writing system used for Semitic languages in the Levant in the 2nd millennium BCE. Most or nearly all alphabetic scripts used throughout the world today ultimately go back to this Semitic proto-alphabet. Its first origins can be traced back to a Proto-Sinaitic script developed in Ancient Egypt to represent the language of Semitic-speaking workers and slaves in Egypt. Unskilled in the complex hieroglyphic system used to write the Egyptian language, which required a large number of pictograms, they selected a small number of those commonly seen in their Egyptian surroundings to describe the sounds, as opposed to the semantic values, of their own Canaanite language. This script was partly influenced by the older Egyptian hieratic, a cursive script related to Egyptian hieroglyphs. The Semitic alphabet became the ancestor of multiple writing systems across the Middle East, Europe, northern Africa, and Pakistan, mainly through Ancient South Arabian, Phoenician, Paleo-Hebrew (closely related and initially virtually identical to the Phoenician alphabet or even derived from it) and later Aramaic (derived from the Phoenician alphabet), four closely related members of the Semitic family of scripts that were in use during the early first millennium BCE.