Do Galaxies Move? Rotation Around Something?

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Discussion Overview

The discussion centers on the movement of galaxies, specifically whether they rotate around a common center and how they interact gravitationally with one another. Participants explore concepts related to galaxy motion, including the dynamics within clusters and the effects of gravitational forces.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Some participants propose that galaxies rotate around a common center of gravity within groups or clusters.
  • Others mention that galaxy clusters exhibit movement relative to each other and are affected by the expansion of space.
  • One participant highlights the use of the Doppler Effect to measure the speed and direction of galaxies, although this is noted as not directly addressing the original question about their relative motion.
  • A correction is made regarding the motion of the solar system, clarifying that it moves in a circular path within the Milky Way, not relative to all galaxies in the universe.

Areas of Agreement / Disagreement

Participants express multiple competing views regarding the nature of galaxy movement, particularly in relation to gravitational interactions and the broader universe. The discussion remains unresolved with differing interpretations of galaxy motion.

Contextual Notes

There are limitations in the discussion regarding the definitions of motion and the assumptions about gravitational interactions. The complexity of galaxy dynamics and the effects of cosmic expansion are acknowledged but not fully explored.

mdmaaz
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Moons revolve around planets. Planets revolve around stars. The entire solar system moves in a circular path within the galaxies. I was wondering whether galaxies also move in a circular path around something. Do galaxies rotate?
 
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Galaxies collect gravitationally into groups and clusters. The individual galaxies in each orbit around the common center of gravity of the group or cluster.
 
Galaxies speed and direction can be measured by the Doppler Effect. If the spectrum is shifted to the Red they are moving away and to the Blue they are moving towards us.
 
Last edited:
Philosophaie said:
Galaxies speed and direction can be measured by the Doppler Effect. If the spectrum is shifted to thhe Red they are moving away and to the Blue they are moving towards us.

True but irrelevant to the OPs question, which as nothing to do with how galaxies are moving relative to US but rather how they are moving relative to themselves and to any objects by which they are gravitationally affected, and with the rest of the galaxy.

mdmazz, your statement "The entire solar system moves in a circular path within the galaxies" is incorrect. The solar system moves in a circular (more or less) path IN THE MILKY WAY. Its motion relative to the REST of the galaxies in the universe, which is to say, its motion relative to the whole universe (the "observable universe" that is), is not circular.

Check out: http://hypertextbook.com/facts/1999/PatriciaKong.shtml
 
As noted above, galaxies move with respect to each other due to gravitational interactions (orbiting each other within galaxy clusters).

Galaxy clusters also "move" apart from each other due to the expansion of space.
 

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