Changes

'''Outer space''' is the physical realm beyond the [[Earth]]'s atmosphere. It encompasses all observed and measured [[celestial bodies]] and the vacuum between them, and is apparently boundless ([[infinite]] breadth).

'''Outer space''' is the physical realm beyond the [[Earth]]'s atmosphere. It encompasses all observed and measured [[celestial bodies]] and the vacuum between them, and is apparently boundless ([[infinite]] breadth).

In space, sound cannot travel because there is not enough air. Space is a nearly perfect [[vacuum]]. The few stray [[molecule]]s floating about in space are much too far apart to propogate [[sound wave]]s.

In space, sound cannot travel because there is not enough air. Space is a nearly perfect [[vacuum]]. The few stray [[molecule]]s floating about in space are much too far apart to propogate [[sound wave]]s. Space is also very cold - its average temperature is only fractionally above [[absolute zero]].

==Greek philosophy==

==Greek philosophy==