What happens to EM waves outside the universe?

In summary: I don't believe there was any mention or discussion of quantum field theories in this conversation. The main point of discussion was the shape and potential edge of the universe. In summary, there is no consensus on the shape of the universe and whether it has an edge or not. Some theories suggest a finite but unbounded shape, while others suggest an infinite shape. The observable universe, however, is believed to be finite and spherical. The complexity of astrophysics and the various theories and concepts involved make it difficult for casual readers to fully understand the topic.
  • #1
yoyopizza
39
1
If the universe is expanding at less than the speed of light, what happens to EM radiation
that is emitted from stars at the edge of the universe?
 
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  • #2
  • #3
But if the universe were finite, wouldn't it then have an edge?
 
  • #4
yoyopizza said:
But if the universe were finite, wouldn't it then have an edge?
Not necessarily. The simplest k = +1 geometry, the 3-sphere, is compact ("finite") but has empty manifold boundary ("unbounded"). Such objects are called closed manifolds lending to why you may see the term closed universe.
 
  • #5
Is there a more in depth and simple explanation? I am very confused
 
  • #6
several I've already posted the FAQ sub forum and Ned wrights FAQ.

here is a useful balloon analogy

http://www.phinds.com/balloonanalogy/

this site describes loosely a few finite shapes with no edge.

http://abyss.uoregon.edu/~js/cosmo/lectures/lec15.html

this on going thread also has tons of descriptions and information on edge and shape

https://www.physicsforums.com/showthread.php?t=684006

also keep in mind the shape of what is called the Observable universe is finite and spherical. The observable universe is simply defined as the furthest we can measure. Due to speed of light and expansion.

http://en.wikipedia.org/wiki/Observable_universe
 
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  • #7
yoyopizza said:
But if the universe were finite, wouldn't it then have an edge?

Not it doesn't. If the Universe was finite and unbounded it just means that if you travel in one direction for long enough you will eventually end back at your starting point. In other words the Universe "loops" back on itself. Why is this so hard for people to understand?
 
  • #8
Its hard to grasp at first, but I think I get it. So there is no outside the universe, it instead might be curved in on itself right? Does gravity cause this?
 
  • #9
Flatland said:
In other words the Universe "loops" back on itself. Why is this so hard for people to understand?

Do you have a vested interest Flatland?
 
  • #10
astrophysics is complicated for the casual reader (like me) because there are usually several different theories illustrating a single concept, example the shape of the local universe or the shape of the entire universe. to make communication easier many of the theories are reduced to initials or a tag name. this complicates thing a lot for the casual reader.

Keep reading. It took me a week and a half to get thru this article the first time I read it. I had 40 pages of notes that I looked up to get through this one page

http://en.wikipedia.org/wiki/Shape_of_the_Universe
 
  • #11
rustytxrx said:
astrophysics is complicated for the casual reader (like me) because there are usually several different theories illustrating a single concept, example the shape of the local universe or the shape of the entire universe. to make communication easier many of the theories are reduced to initials or a tag name. this complicates thing a lot for the casual reader.

Keep reading. It took me a week and a half to get thru this article the first time I read it. I had 40 pages of notes that I looked up to get through this one page

http://en.wikipedia.org/wiki/Shape_of_the_Universe

I agree, I can normally read books in a day or so, but just getting through one book on relativity took me a month. Have you read "Relativity Demystified"? its a great book if you havn't read it or don;t know much on relativity
 
  • #12
rustytxrx said:
astrophysics is complicated for the casual reader (like me) because there are usually several different theories illustrating a single concept, example the shape of the local universe or the shape of the entire universe. [/url]

I've never seen ANY confusion about the shape of the "local" universe, assuming you mean what is more commonly called the "observable" universe. It is a sphere with a radius based on the speed of light and the age of the universe and it is centered on you. Right now it's about 47 billion light years in radius. There is no confusion or contention about that and I'm not aware of any other theories about it.
 
  • #13
yes of course. I should have given more thought in selecting my example.

Edit - maybe my point was to read astrophysics you have to have a vast underpinning of knowledge. how I got here is I was reading quantum physics. read how the quantum vacuum was related to the cosmological constant. Thus came into search around the forum. Interesting place
 
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  • #14
You are missing the point. And making a point that has no basis in fact. Show the math.
 
  • #15
A major outstanding problem is that most quantum field theories predict a huge value for the quantum vacuum. A common assumption is that the quantum vacuum is equivalent to the cosmological constant. Although no theory exists that supports this assumption, arguments can be made in its favor.

Such arguments are usually based on dimensional analysis and effective field theory. If the universe is described by an effective local quantum field theory down to the Planck scale, then we would expect a cosmological constant of the order of M_{\rm pl}^4. As noted above, the measured cosmological constant is smaller than this by a factor of 10−120. This discrepancy has been called "the worst theoretical prediction in the history of physics!".

Some supersymmetric theories require a cosmological constant that is exactly zero, which further complicates things. This is the cosmological constant problem, the worst problem of fine-tuning in physics: there is no known natural way to derive the tiny cosmological constant used in cosmology from particle physics. Structural Quantum Gravity is an approach of Quantum Gravity that predicts Einsteins field equations with cosmological constant as the classical limit of the action of Structural Quantum Gravity.



Sorry to step on your thread , yoyopizza
 

1. What is the nature of EM waves outside the universe?

The nature of EM waves outside the universe is largely unknown. It is theorized that they may behave differently or may not even exist in the same form as we know them within the universe.

2. Can EM waves travel outside the universe?

It is currently not known if EM waves can travel outside the universe. The laws of physics that govern EM waves may not apply in the same way outside the universe.

3. Is there any evidence of EM waves beyond the universe?

No, there is currently no evidence of EM waves beyond the universe. As our technology and understanding of the universe is limited, it is difficult to gather any concrete evidence of what exists outside the universe.

4. How do we know that EM waves don't extend infinitely beyond the universe?

We do not definitively know that EM waves do not extend infinitely beyond the universe. However, based on our current understanding of the universe and its boundaries, it is unlikely that EM waves would exist in the same form outside of it.

5. What implications does the existence of EM waves outside the universe have for our understanding of the universe?

The existence of EM waves outside the universe, if proven, could have significant implications for our understanding of the universe and the laws of physics. It could potentially lead to a complete shift in our current understanding of the universe and the fundamental forces that govern it.

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