Is the universe NOT accelerating ?

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    Accelerating Universe
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Discussion Overview

The discussion revolves around the concept of whether the universe is accelerating in its expansion. Participants explore interpretations of Hubble's observations and the implications of galaxy velocities over time, focusing on the distinction between expansion and acceleration.

Discussion Character

  • Debate/contested

Main Points Raised

  • One participant references a video and seeks feedback on its validity regarding the universe's acceleration.
  • Another participant expresses skepticism about the video's claims, suggesting that the idea of a non-accelerating universe is frequently debunked.
  • A participant clarifies their position, stating that while the universe is expanding, it is not accelerating, noting that older galaxies appear to move away faster.
  • Another participant points out that Hubble's graph represents velocity against distance, not acceleration, and argues that this indicates deceleration.
  • A different participant explains that the acceleration of the universe was identified in the 1990s through supernova observations, emphasizing that the rate of expansion can be steady despite varying velocities of receding galaxies.
  • This participant also clarifies that acceleration refers to changes in the rate of expansion rather than the velocities of individual objects.
  • The thread concludes with a moderator's intervention, indicating that the topic is misrepresented in the referenced video and suggesting the creation of a new thread for specific questions about expansion.

Areas of Agreement / Disagreement

Participants express differing views on the interpretation of Hubble's observations and the nature of cosmic expansion. There is no consensus on the validity of the video's claims or the implications of the data presented.

Contextual Notes

Participants highlight the distinction between velocity and acceleration in the context of cosmic expansion, indicating potential misunderstandings in the interpretation of observational data. The discussion reflects varying levels of familiarity with cosmological concepts.

fencewalker
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I tweeted neil Tyson, michio kaku and brian green the following:
[link deleted by moderator]

no responses yet, would like feedback - does the video make sense?
 
Last edited by a moderator:
Astronomy news on Phys.org
What video?

Even without seeing the video, I'd hazard a guess that no, it does not make sense. The concept of the universe not accelerating is debunked here fairly regularly.
 
Last edited:
on youtube, search hubblesmisinterpretation.
and I didn't say it's not expanding, it's not accelerating - since the older the galaxy is, the faster it is
 
fencewalker said:
on youtube, search hubblesmisinterpretation.
and I didn't say it's not expanding, it's not accelerating - since the older the galaxy is, the faster it is

Sorry, my post should have the word accelerating where I have expanding. My corrected statement stands. The age of the light from the distant stars is taken into account.
 
but hubble's graph is velocity plotted against distance, which is not acceleration - it's velocity plotted against time. from oldest to newest, the graph shows DEceleration
 
The acceleration of the universe was not discovered in Hubble's time, but in the 1990's by many observations of specific types of supernovas. You are correct in that Hubble's graph shows velocity, not acceleration, however your argument that the since older galaxies are moving away faster than closer ones means the universe is decelerating is not correct. Objects within expanding space naturally recede at different velocities depending on how far apart they are. The further apart two objects are, the faster they recede from each other. This holds even when the expansion is steady and is neither accelerating nor decelerating. Let's be clear here. In this context, acceleration/deceleration means an increase or decrease in the rate of expansion, not the velocity of objects.

There are many posts here on PF's cosmology forum explaining this, so I suggest you start there. I believe the link in Phind's signature block may also help.

Now, since this thread's topic is about a video that inaccurately explains expansion, I have deleted the link to your twitter and am locking the thread. If you have specific questions about expansion, you may start a new thread in the cosmology section.
 

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