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mrcotton
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I heard sometime ago that the cosmic microwave background may be a candidate for an absolute frame of reference. Did this idea ever get any credence?
That isn't a unique frame. That is a different frame for every location in the universe, all moving wrt each other.tom.stoer said:Then the CMB defines a unique frame by demanding that all observed multipoles (except for the monopole) vanish.
From the CMB data it is seen that our local group of galaxies (the galactic cluster that includes the Solar System's Milky Way Galaxy) appears to be moving at 627±22 km/s relative to the reference frame of the CMB (also called the CMB rest frame, or the frame of reference in which there is no motion through the CMB) in the direction of galactic longitude l = 276±3°, b = 30±3°.[66] This motion results in an anisotropy of the data (CMB appearing slightly warmer in the direction of movement than in the opposite direction).[67] The standard interpretation of this temperature variation is a simple velocity red shift and blue shift due to motion relative to the CMB
Suppose CMB has no fluctuations. Then the CMB defines a unique frame by demanding that all observed multipoles (except for the monopole) vanish.
DiracPool said:We touched on this subject some time ago in this thread:So, it seems as if they are implying an absolute reference frame, or one global static frame that sits relative to our local group at least, by the detection of a doppler shift in these galaxies. But what constitues that rest frame?
DaleSpam said:That isn't a unique frame. That is a different frame for every location in the universe, all moving wrt each other.
That is my point, the CMB doesn't even define a unique frame, let alone an absolute frame. It is simply an idea that is "dead on arrival".
First of all let me say that there is no rest frame w.r.t. CMB b/c CMB is light-like.DiracPool said:tom.stoer, can you eaborate on this? I'm not sure I understand what multipoles are.
Cosmic microwave background (CMB) is a form of electromagnetic radiation that permeates the entire universe. It is the remnant of the Big Bang and is often referred to as the "echo" of the universe's creation. CMB is the oldest light in the universe, dating back to about 380,000 years after the Big Bang.
The existence of CMB was first predicted by physicist George Gamow in the 1940s. It was then accidentally discovered in 1964 by radio astronomers Arno Penzias and Robert Wilson, who were studying radio waves in the universe. They found a mysterious noise that seemed to come from all directions, which turned out to be the CMB.
CMB provides crucial insights into the early universe, including its age, composition, and expansion rate. By studying the fluctuations in the CMB, scientists can also learn about the distribution of matter and energy in the universe, and how structures like galaxies and clusters of galaxies formed.
CMB is measured using specialized instruments called microwave telescopes. These telescopes are designed to detect and measure the faint microwaves that make up the CMB. The most famous of these instruments is the Cosmic Background Explorer (COBE), which was launched by NASA in 1989.
The discovery of CMB was a major piece of evidence supporting the Big Bang theory, which states that the universe began as a hot, dense, and rapidly expanding point about 13.8 billion years ago. The existence and properties of CMB align with the predictions of the theory, further solidifying its validity as the most widely accepted explanation for the origin of the universe.