The discussion revolves around the nature of the universe's expansion, particularly focusing on the limits of the observable universe and the velocities of distant stars. Participants explore concepts related to redshift, general relativity, and the implications of cosmic acceleration, while addressing the complexities of measuring distances and speeds in an expanding universe.
Participants express differing views on the nature of velocities at the universe's edge and the implications of cosmic expansion. There is no consensus on the specifics of these phenomena, and the discussion remains unresolved regarding the underlying causes of the universe's acceleration.
Limitations include the complexity of measuring speeds over vast distances, the dependence on definitions of observable versus actual universe, and the unresolved nature of the factors influencing cosmic acceleration.
This discussion may be of interest to those exploring cosmology, general relativity, and the dynamics of the universe's expansion, particularly beginners seeking to understand these concepts in a community setting.
Do you mean the observable universe? Then it is by definition that we can only observe stars from which the light can reach us. The actual universe is bigger than the observable universe.jbander said:What are peoples thoughts on the fact that at the exact limit of our universe. the stars are moving at just less then the speed of light away from us. If there wasn't a limit to the speed of light , isn't that what we would be seeing but the real fact then would be that it isn't the boundaries of our universe.
Your "fact" is erroneous. The objects out close to the edge of our observable universe are receding from us at about 3c, not "just less than c"jbander said:What are peoples thoughts on the fact that at the exact limit of our universe. the stars are moving at just less then the speed of light away from us.
Matterwave said:What's the "exact limit of our universe"? For objects very distant to us, a measurement of speed relative to us, is no longer simple. This is because on large scales, one must consider general relativistic effects and not just simple special relativity. Objects very far away have red shifts greater than 1 which makes their "recessional velocities" greater than the speed of light. But that's simply because we are not performing a local measurement of speed (how can we, they are billions of light years from us). In the general relativistic sense, these far away galaxies are approximately "stationary" with respect to us, since both our galaxy and these far away galaxies are in the rest-frame of the CMBR, it is only the space in between these galaxies and us that is expanding. See: http://en.wikipedia.org/wiki/Metric_expansion_of_space
jbander said:I'm really interested in this but really have very little knowledge of this subject but I hope you can respond to these very simple questions by a willingness to advise a raw beginner
So is the influence of time just a matter of the difference between the period of deceleration and the acceleration now. And does that mean then that at some time these observed stars will blink out when the deceleration/ acceleration time balance is reached as far as our relationship to this observable star at our perceived maximum visibility.
If you also would respond to one more question. Is there a Idea on what is making the expanding universe increase in acceleration. The idea that at one time it was decelerating and now accelerating is a idea that is wonderful just because of the question why.
If anyone could advise me of literature that may be helpful for a interested beginner. I would appreciate it.