Is the universe NOT accelerating ?

In summary, Neil Tyson, Michio Kaku, and Brian Green's video does not accurately explain the concept of the universe expanding.
  • #1
fencewalker
17
1
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:
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  • #2
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:
  • #3
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
 
  • #4
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.
 
  • #5
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
 
  • #6
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.
 

1. Is it true that the universe is not accelerating?

Currently, there is no consensus among scientists about whether the universe is accelerating or not. Some evidence suggests that the expansion of the universe is accelerating, while other evidence suggests that it is not. This is an ongoing and active area of research in cosmology.

2. What is the evidence for the universe not accelerating?

One of the main pieces of evidence for the universe not accelerating is the measurement of the Hubble constant, which describes the rate of expansion of the universe. If the universe were accelerating, we would expect to see an increase in the value of the Hubble constant, but current measurements suggest that it is not increasing at a significant rate.

3. How can we know for sure if the universe is not accelerating?

To determine whether the universe is accelerating, scientists use various observational techniques such as measuring the distances and velocities of distant galaxies, studying the cosmic microwave background radiation, and analyzing the distribution of matter in the universe. These methods help to provide a more complete picture of the expansion of the universe and can help us understand whether it is accelerating or not.

4. What would it mean if the universe is not accelerating?

If the universe is not accelerating, it would suggest that the expansion of the universe is slowing down. This could have implications for our understanding of the future of the universe and whether it will continue to expand forever or eventually collapse in a "Big Crunch". It could also potentially challenge our current theories of dark energy, which is thought to be the driving force behind the acceleration of the universe.

5. Are there any alternative explanations for the observations that suggest the universe is not accelerating?

Some scientists have proposed alternative theories to explain the observations that suggest the universe is not accelerating, such as modified theories of gravity. However, these theories are still being studied and have not yet been widely accepted by the scientific community. Further research and evidence are needed to fully understand the acceleration of the universe and to determine if there are any alternative explanations.

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