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bapowell
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They are closer to 46 billion light years away.nikkkom said:By now, the walls are (apparently) 13.7 billion light-years away from us.
They are closer to 46 billion light years away.nikkkom said:By now, the walls are (apparently) 13.7 billion light-years away from us.
bapowell said:They are closer to 46 billion light years away.
That's fine. Just pointing out that what you wrote is incorrect, lest it lead to confusion. Because of the expansion, the distance traveled by CMB photons is longer than just time multiplied by the speed of light.nikkkom said:I meant that CMB light we detect today traveled 13.7 billion years. I don't want to get into the discussion of many more different ways to express the distance to the surface of last scattering.
As bapowell said, you cannot multiply light travel time by c and hope to get any cosmological distance that makes sense. Some popular writings try to call it "light travel distance", but even that's wrong. The 13.7 billion years is just light travel time and that's that.Ophiolite said:In what way does the CMB not appear to be 13.7 billion years away?
Ophiolite, have a look at the section entitled "The edge of the observable universe" here: https://www.physicsforums.com/insights/inflationary-misconceptions-basics-cosmological-horizons/. In particular, Figure 5 illustrates why the expansion of the universe increases the travel distance of light as compared to a static universe.Ophiolite said:I appreciate your effort to help me understand. However, what you have said seems to align with my previous understanding. But - because he has included the words "apparently" - it also, to me, accords with what nikkom said. You and bapowell appear to be correcting something that nikkom has not actually said - but would have said if he had not included the word apparently.
That said, I do not wish to derail the thread any further with a discussion that revolves around my reading comprehension.
I really am reluctant to be taking this off-topic, however... I think I understand the article you have linked to. I believe it reflects the understanding I have had of the subject for three decades or so.bapowell said:Ophiolite, have a look at the section entitled "The edge of the observable universe" here: https://www.physicsforums.com/insights/inflationary-misconceptions-basics-cosmological-horizons/. In particular, Figure 5 illustrates why the expansion of the universe increases the travel distance of light as compared to a static universe.
What do you mean by "appear". A light beam hits a detector. It appears as a microwave. In what way does that lead you to conclude that it originated 13billion years ago? More to the point, in what way does that lead you to conclude that it started out 13 billion light years away?Ophiolite said:I really am reluctant to be taking this off-topic, however... I think I understand the article you have linked to. I believe it reflects the understanding I have had of the subject for three decades or so.
But, you are now causing me to thoroughly doubt any part of that understanding. Perhaps the answer to this question will bring the matter to a close. In what way do the most distant galaxies not appear to be 13 billion light years away? I understand they are much further than that; I think I understand why they are much further than that; I do not understand why you assert they do not appear to be some 13 billion light years away.
Thank you for your efforts.
The Big Bang theory is a scientific explanation for the origin and evolution of the universe. It suggests that the universe began as a singularity, a point of infinite density and temperature, and has been expanding and cooling ever since.
According to the Big Bang theory, the universe underwent a rapid period of expansion known as inflation. During this time, the universe was filled with a hot, dense soup of particles and energy. As the universe expanded, this energy cooled and formed into radiation, which is now known as the cosmic microwave background (CMB). The CMB is present in all directions because it is a remnant of the early stages of the universe's expansion.
The fact that radiation from the Big Bang is present in all directions is a key piece of evidence for the Big Bang theory. It supports the idea that the universe began as a singularity and has been expanding uniformly since then. The CMB also provides important information about the composition and structure of the early universe.
The CMB is detected using specialized instruments, such as the Cosmic Microwave Background Explorer (COBE) and the Wilkinson Microwave Anisotropy Probe (WMAP). These instruments are able to detect and measure the faint microwave radiation that permeates the entire universe. The data collected from these instruments has provided strong evidence for the Big Bang theory.
No, we cannot see the Big Bang itself. The universe was incredibly hot and dense in its early stages, making it impossible for light to travel freely. However, we can observe the afterglow of the Big Bang in the form of the CMB, which is essentially the oldest light in the universe. By studying the CMB, scientists can gain insight into the early stages of the universe and test the predictions of the Big Bang theory.