Interstellar Chapter

Author: Editorial Committee of "Exploring Nature Series"
Publisher:
Publish Date: 2004-04-01
Features: Exploring Nature Series. The universe refers to the vast space and the various celestial bodies and diffuse matter within it. There are concepts of the "observed universe" and the "physical universe." The "observed universe" is the entire cosmic space and the various celestial bodies and diffuse matter that can be observed by the naked eye or instruments. It has a boundary, which is the limit that current detection tools can reach. Currently, it is possible to observe stars up to 20 billion light-years away. This range contains over 1 billion galaxies.