Are Galaxies Moving or is Space-Time Expanding?

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SUMMARY

The discussion centers on the concept of metric expansion of space, which explains the observed movement of galaxies. Participants clarify that galaxies are not moving through space in a traditional sense; rather, they are stationary while space-time itself expands, causing them to appear to move away from each other. This phenomenon is coordinate-dependent, meaning that in local normal coordinates, galaxies exhibit proper motion. The analogy of a rubber belt with balls illustrates this expansion effectively.

PREREQUISITES
  • Understanding of metric expansion in cosmology
  • Familiarity with coordinate systems in physics
  • Basic knowledge of general relativity
  • Concept of proper motion in astronomy
NEXT STEPS
  • Research the implications of metric expansion on cosmic structures
  • Study the role of general relativity in understanding space-time
  • Explore the concept of proper motion and its measurement techniques
  • Investigate analogies used to explain cosmic expansion, such as the rubber band model
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Astronomers, physicists, and students of cosmology interested in the dynamics of galaxies and the nature of space-time expansion.

Arman777
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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 ?
 
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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..
 

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