Why galaxies are further from us

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In summary: Thanks Mordred.In summary, without a reasonable explanation of why galaxies are further from us this year than they were last year, why isn't the proposition that new space is coming into existence from out of extra dimensions given any credibility? There is a reasonable explanation for expansion. A major contributor is vacuum energy or the cosmological constant. You keep wanting to give space substance. Space itself is just geometric dimensions.
  • #1
keepit
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Sorry to harp on the same subject but here's a point of view - without a reasonable explanation of why galaxies are further from us this year than they were last year, why isn't the proposition that new space is coming into existence from out of extra dimensions given any credibility?
Do mathematical explanations of geometry really give a cause to increasing distances?
 
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  • #2
There is a reasonable explanation for expansion. A major contributor is vacuum energy or the cosmological constant. You keep wanting to give space substance. Space itself is just geometric dimensions.

Take a read through the two articles I posted in this thread.

Perhaps with a better understanding of geometry and expansion you will see there us no need to invoke alternate dimension sources.

https://www.physicsforums.com/showthread.php?t=709478
 
  • #3
I'm just a rank amateur so believe me, i feel silly being argumentative here, but anyway - as i understand it the cosmological constant is just a mathematical description, not a mechanism. Is vacuum energy the same?
 
  • #4
Ok think of it this way. Energy-mass density/volume is the same as pressure. So vacuum energy is the same as negative pressure. Gravity sources are positive pressure. Locally gravity pressure is stronger than the negative pressure.
However in the voids between galaxy clusters. vacuum pressure becomes dominant. As the amount of space increases the vacuum pressure does not change. Hence constant. Ie cosmological constant. As the volume of the dominant vacuum pressure increases expansion rates also increase overall. However not per cubic metre
 
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  • #5
As i understand it vacuum energy is a viable mechanism but as i understand it the numbers don't add up correctly. I hate to be simplistic but where does that leave us?
 
  • #6
The fact that vacuum pressure exists isn't in question in point of fact Einstein predicted either a contracting or expanding universe. The question as to why that pressure is constant as to the source of energy to maintains that constant pressure is the mystery. Is it one or many contributors. Dark energy is one strong candidate, others include quantum processes.
 
  • #7
keepit said:
I'm just a rank amateur so believe me, i feel silly being argumentative here, but anyway - as i understand it the cosmological constant is just a mathematical description, not a mechanism. Is vacuum energy the same?

My understanding:

You're right in that the constant isn't "physically acting" on space, it is simply a part of the math. But without the constant the math simply wouldn't work at a universal scale. Since GR is a theory of geometry, this constant is an important part. Dark energy is an attempt to put a physical mechanism in place to explain the expansion. But it really isn't necessary, as the geometry of the universe can simply cause an expansion regardless of a physical mechanism. Space doesn't need something to cause it to behave that way if it's "built in" to the geometry.

Does that make sense?
 
  • #8
Thanks Drakkith. What if it's a multidimensional geometry that is causing measurements to expand i.e. Calabai yau space moving in and out of our 3 dimensions?
 
  • #9
Its one of many possible conjectures, although string theory has a ways to go to prove the possibility. string theory is not one of my strong suits. Thus far I have never heard of a testable string theory prediction. Not to say that their aren't any, super strings have the same problem. Without being testable its difficult to validate beyond conjecture.
 
  • #10
keepit said:
Thanks Drakkith. What if it's a multidimensional geometry that is causing measurements to expand i.e. Calabai yau space moving in and out of our 3 dimensions?

If it happens to be multidimensional geometry, then that's what it is. But as of now we only know of our own 3 spatial dimensions. I'm not sure what kind of answers you're seeking.
 
  • #11
i asked my question in a vague way for lack of a more precise way. I guess I'm just fishing for ideas.
 
  • #12
if the LHC validates the possibility of extra dimensions, what will that say about space being more than nothing?
 
  • #13
keepit said:
if the LHC validates the possibility of extra dimensions, what will that say about space being more than nothing?

It will remain nothing. The math just gets more complicated.

I don't understand the concept of more space coming from some other dimension. That seems like asking if space from the Y dimension moves into the X dimension or Z dimension. (Where X, Y, and Z are our normal 3 dimensions)
 
  • #14
Mordred,
maybe i misunderstood but you said "It's one of many possible conjectures". Could you point me to some research on the possibility?
 
  • #15
Not sure I still have the paper. I will look. Been a coupke of years since I last read the article
 

1. Why do galaxies appear to be moving away from us?

The apparent movement of galaxies away from us is due to the expansion of the universe. This expansion causes the space between objects to increase, resulting in the perception that galaxies are moving away from each other.

2. How do we know that galaxies are further from us?

Scientists use a variety of methods, such as redshift measurements and the Hubble's law, to determine the distance of galaxies from Earth. These methods involve measuring the light emitted by galaxies and analyzing the changes in its wavelength to determine the distance the light has traveled.

3. Are all galaxies moving away from us?

No, not all galaxies are moving away from us. In fact, the Andromeda galaxy, our closest neighboring galaxy, is actually moving towards our Milky Way galaxy. The direction of movement depends on the location of the galaxy and the expansion of the universe in that specific area.

4. Will galaxies continue to move further away from us?

Yes, due to the ongoing expansion of the universe, galaxies will continue to move further away from us. However, the rate of this expansion may change in the future depending on various factors, such as the amount of dark matter and dark energy present in the universe.

5. How does the distance of galaxies affect our understanding of the universe?

The distance of galaxies is crucial in understanding the history and evolution of the universe. By studying the light from distant galaxies, scientists can gather information about the early stages of the universe, including the formation of galaxies and the expansion of the universe. Additionally, understanding the distance of galaxies helps us better understand the distribution of matter and the structure of the universe.

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