- #31
Yukterez
- 85
- 14
Did I mix that up? If so, I of course meant it the other way around (:Bandersnatch said:
Edit: I see, I was obviously too stupid to read my own chart (:
Are Galaxies Moving Faster Than Light Due to Space Expansion?
Click For Summary
Discussion Overview
The discussion revolves around the motion of galaxies in relation to the speed of light and the concept of space expansion. Participants explore whether galaxies can move faster than light due to the expansion of space, the nature of their motion, and the implications of absolute frames of reference.
Discussion Character
- Exploratory
- Debate/contested
- Conceptual clarification
- Technical explanation
Main Points Raised
- Some participants question whether galaxies are moving by themselves or due to the expansion of space, and how this relates to the speed of light.
- It is proposed that the speed of light is a local speed limit, allowing galaxies to recede from each other at velocities greater than light due to space expansion.
- Some argue that there is no observable difference between galaxies moving with space versus moving through space.
- There is a suggestion that if galaxies and space have their own motions, the maximum observable velocity could be greater than the speed of light, but this is contested.
- Participants discuss the implications of an absolute frame of reference and whether it could exist, with some asserting that observations rule out such a frame.
- Concerns are raised about the validity of measurements made in inertial frames without a known absolute frame, leading to questions about the nature of relative measurements.
- Some participants clarify that measurements in a single inertial frame yield consistent results, but this does not apply to external observations.
- Newtonian gravity is mentioned as applicable on smaller scales but not at cosmic scales, indicating limitations in its application to the universe.
Areas of Agreement / Disagreement
Participants express multiple competing views regarding the nature of galaxy motion, the concept of absolute frames, and the implications of measurements in different reference frames. The discussion remains unresolved with no consensus reached.
Contextual Notes
Limitations include the dependence on definitions of motion and reference frames, as well as unresolved questions about the nature of space and its expansion.
Edit: I see, I was obviously too stupid to read my own chart (:
- #32
Dale
Mentor
- 36,704
- 15,617
No. It isn't correct. The 5km/s value is simply relative to some arbitrary reference frame.user9003 said:
- #33
PeterDonis
Mentor
- 49,621
- 25,739
Bandersnatch said:
Ah, got it.
- #34
Yukterez
- 85
- 14
On the x-axis you have the redshift (as observed today), and on the y-axis the recessional velocity (orange is the velocity at emission and brown at absorption)
You see that objects with z < 1.8963 are faster today than they were when they emitted the light we receive now (the relative distance since then has changed more than the scale factor), while objects with z > 1.8963 are slower now than they were when they emitted their light (the expansion rate fell more than the distance increased while the light travelled).
You see that objects with z < 1.8963 are faster today than they were when they emitted the light we receive now (the relative distance since then has changed more than the scale factor), while objects with z > 1.8963 are slower now than they were when they emitted their light (the expansion rate fell more than the distance increased while the light travelled).
Similar threads
- · Replies 7 ·
- · Replies 5 ·
- · Replies 23 ·
- · Replies 22 ·
High School
Cosmological Redshift in Simulated Universe
- · Replies 39 ·
- · Replies 8 ·
- · Replies 5 ·
- · Replies 65 ·
- · Replies 9 ·
- · Replies 10 ·