Changes

It encompasses all observed and measured celestial bodies and the vacuum between them, and is apparently boundless.

It encompasses all observed and measured celestial bodies and the vacuum between them, and is apparently boundless.

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 transmit [[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 transmit [[sound wave]]s.

The ancient Greeks debated whether space was finite or infinite. If it was finite, what would happen if you tried to put your hand through the end of space? <ref>"The ancient Greeks recognized that it was difficult to imagine what an infinite universe might look like. But they also wondered that if the universe were finite, and you stuck out your hand at the edge, where would your hand go? The Greeks' two problems with the universe represented a paradox - the universe had to be either finite or infinite, and both alternatives presented problems." [http://skyserver.sdss.org/dr1/en/astro/universe/universe.asp The Expanding Universe], Sloan Sky Survey </ref>

The ancient Greeks debated whether space was finite or infinite. If it was finite, what would happen if you tried to put your hand through the end of space? <ref>"The ancient Greeks recognized that it was difficult to imagine what an infinite universe might look like. But they also wondered that if the universe were finite, and you stuck out your hand at the edge, where would your hand go? The Greeks' two problems with the universe represented a paradox - the universe had to be either finite or infinite, and both alternatives presented problems." [http://skyserver.sdss.org/dr1/en/astro/universe/universe.asp The Expanding Universe], Sloan Sky Survey </ref>