I Are Galaxies Moving or is Space-Time Expanding?

  • I
  • Thread starter Thread starter Arman777
  • Start date Start date
  • Tags Tags
    Galaxies
AI Thread Summary
Galaxies appear to be moving away from each other due to the metric expansion of space-time rather than their own motion. This expansion is coordinate-dependent, meaning that in local coordinates, galaxies can be seen as moving away. The analogy of balls on a rubber belt illustrates how galaxies are carried along as space expands. The discussion raises the question of whether galaxies are truly moving or if they are stationary while space-time expands around them. Ultimately, the nature of this movement is tied to the concept of metric expansion.
Arman777
Insights Author
Gold Member
Messages
2,163
Reaction score
191
Are galaxies are really moving away.Or galaxies are stationary but space-time expends so galaxies move with it ? Or maybe they could be same thing ?
 
Space news on Phys.org
Google "metric expansion". There is no (well, very little and for a different reason) proper motion of far distant galaxies with respect to the Earth, it's metric expansion.
 
phinds said:
Google "metric expansion". There is no (well, very little and for a different reason) proper motion of far distant galaxies with respect to the Earth, it's metric expansion.
This is a coordinate dependent statement. In "local" normal coordinates, galaxies are certainly moving away.
 
Orodruin said:
This is a coordinate dependent statement. In "local" normal coordinates, galaxies are certainly moving away.
t16_Hubble_expansion.gif

Like here its metric expention I guess.Here galaxies are standing still but universe expends so galaxies are moving with a velocity.Galaxies are moving away with a velocity v but not for they have a speed itself,Space time carries galaxies ?
 
Arman777 said:
Are galaxies are really moving away.Or galaxies are stationary but space-time expends so galaxies move with it ? Or maybe they could be same thing ?
Take a rubber belt and put 5-6 balls on it as if it's a kind of bead. Then pull the belt in opposite directions. You'll see the process itself.
 
acidmatic said:
Take a rubber belt and put 5-6 balls on it as if it's a kind of bead. Then pull the belt in opposite directions. You'll see the process itself.

I understand..
 

Thread 'Matter density right after the decoupling'

https://en.wikipedia.org/wiki/Recombination_(cosmology) Was a matter density right after the decoupling low enough to consider the vacuum as the actual vacuum, and not the medium through which the light propagates with the speed lower than ##({\epsilon_0\mu_0})^{-1/2}##? I'm asking this in context of the calculation of the observable universe radius, where the time integral of the inverse of the scale factor is multiplied by the constant speed of light ##c##.
View full post »

Thread 'Rutgers finds a transparent Einstein Cross - apparently a dark matter "halo".'

The formal paper is here. The Rutgers University news has published a story about an image being closely examined at their New Brunswick campus. Here is an excerpt: Computer modeling of the gravitational lens by Keeton and Eid showed that the four visible foreground galaxies causing the gravitational bending couldn’t explain the details of the five-image pattern. Only with the addition of a large, invisible mass, in this case, a dark matter halo, could the model match the observations...
View full post »

Thread 'Big Bang and Infinite Universe'

Hi, I’m pretty new to cosmology and I’m trying to get my head around the Big Bang and the potential infinite extent of the universe as a whole. There’s lots of misleading info out there but this forum and a few others have helped me and I just wanted to check I have the right idea. The Big Bang was the creation of space and time. At this instant t=0 space was infinite in size but the scale factor was zero. I’m picturing it (hopefully correctly) like an excel spreadsheet with infinite...
View full post »

Similar threads

B Redshifts of nearby galaxies
Replies
14
Views
3K
I The Universe is expanding with acceleration
Replies
5
Views
3K
B Can the "creation" of space in the Universe affect the speed of light?
Replies
7
Views
3K
B Approximately how long does it take for a galaxy to form?
Replies
12
Views
3K
I Inflationary vs deflationary phase of Big Bang
Replies
10
Views
3K
B Bound Systems in an Expanding Universe: How Can Galaxies Merge?
Replies
9
Views
2K
I How Does Space Expansion Affect the Velocity of Galaxies?
2
Replies
65
Views
6K
I Questions about the Location of the Big Bang and the Age of the Universe
Replies
8
Views
3K
I How do you get to the conclusion that there is accelerating expansion?
Replies
23
Views
2K
A Largest Galaxy In An Infinite Universe
Replies
12
Views
2K

Hot Threads

Recent Insights

Back
Top