Top Document: [sci.astro] Cosmology (Astronomy Frequently Asked Questions) (9/9) Previous Document: I.06. What is inflation? Next Document: I.08. If the Universe is only 10 billion years old, how can we see objects that are now 30 billion light years away? Why See reader questions & answers on this topic! - Help others by sharing your knowledge (Also, can objects expand away from us faster than the speed of light?) In the Big Bang model the *distance* between galaxies increases, but the galaxies don't move. Since nothing's moving, there is no violation of the restriction that nothing can move faster than light. Hence, it is quite possible that the distance between two objects is so great that the distance between them expands faster than the speed of light. What does it mean for the distance between galaxies to increase without them moving? Consider two galaxies in a one-dimensional Big Bang model: *-|-|-|-* 0 1 2 3 4 There are four distance units between the two galaxies. Over time the distance between the two galaxies increases: * - | - | - | - * 0 1 2 3 4 However, they remain in the same position, namely one galaxy remains at "0" and the other remains at "4." They haven't moved. (Astronomers typically divide the distance between two galaxies into two parts, D = a(t)*R. The function a(t) describes how the size of the Universe increases, while the distance R is independent of any changes in the size of the Universe. The coordinates based on R are called "co-moving coordinates.") User Contributions:Top Document: [sci.astro] Cosmology (Astronomy Frequently Asked Questions) (9/9) Previous Document: I.06. What is inflation? Next Document: I.08. If the Universe is only 10 billion years old, how can we see objects that are now 30 billion light years away? Why Part0 - Part1 - Part2 - Part3 - Part4 - Part5 - Part6 - Part7 - Part8 - Single Page [ Usenet FAQs | Web FAQs | Documents | RFC Index ] Send corrections/additions to the FAQ Maintainer: jlazio@patriot.net
Last Update March 27 2014 @ 02:11 PM
|
Comment about this article, ask questions, or add new information about this topic: