Is the universe at least 136 billion years old, is the universe not expanding at all, did the universe begin its expansion when Hubble measured its redshift for the first time or was light twice as fast 13.5 billion years ago than it is today?

[Ghideon]

In case @tmdarkmatter is interested in common misconceptions and confusions and to get some insight in established models this paper may be helpful: "Expanding Confusion: common misconceptions of cosmological horizons and the superluminal expansion of the Universe"

Quote

We use standard general relativity to illustrate and clarify several common misconceptions about the expansion of the Universe. To show the abundance of these misconceptions we cite numerous misleading, or easily misinterpreted, statements in the literature. In the context of the new standard Lambda-CDM cosmology we point out confusions regarding the particle horizon, the event horizon, the ``observable universe'' and the Hubble sphere

https://arxiv.org/abs/astro-ph/0310808

 

(Thanks to @joigus comment I remembered the paper and the possible connection to this thread.)

[DanMP]

On 8/10/2023 at 11:13 AM, tmdarkmatter said:

I came to this conclusion:

"If asking questions reduces the reputation, then this is the wrong place to ask questions."

"And if this is not a place to ask questions, then it is not a "scientific" forum at all."

I understand what you mean (I am also "redshifted" 😛), but still, this forum is much better than physicsforums, where the moderators are very quick to close the topic, or restrict your right to write in it, when you insist asking uncomfortable questions. Just search/see my activity there. They are like a Physics Inquisition. This is not the case here.

Regarding this thread, I believe that your misconception was to consider the balloon analogy with the Earth in the center ... Consider the Earth as another point on the surface of the inflating balloon and you will understand the responses you get.

 

I also have some questions and observations regarding big bang theory:

When they assessed the time from big bang, what reference frame they used? There is no absolute time.

Just after big bang, the mass was confined in a small volume, yes? We know from GR that the clocks are slower when they are situated in/near a place with high density. Also light originating from such a place would be redshifted. Was this redshift considered (subtracted) when the speed of expansion was calculated? 

Last but not least:

 

 

[exchemist]

17 minutes ago, DanMP said:

I understand what you mean (I am also "redshifted" 😛), but still, this forum is much better than physicsforums, where the moderators are very quick to close the topic, or restrict your right to write in it, when you insist asking uncomfortable questions. Just search/see my activity there. They are like a Physics Inquisition. This is not the case here.

Regarding this thread, I believe that your misconception was to consider the balloon analogy with the Earth in the center ... Consider the Earth as another point on the surface of the inflating balloon and you will understand the responses you get.

 

I also have some questions and observations regarding big bang theory:

When they assessed the time from big bang, what reference frame they used? There is no absolute time.

Just after big bang, the mass was confined in a small volume, yes? We know from GR that the clocks are slower when they are situated in/near a place with high density. Also light originating from such a place would be redshifted. Was this redshift considered (subtracted) when the speed of expansion was calculated? 

Last but not least:

 

 

One thing to bear in mind is that light only started travelling through dark space from the surface of last scattering, 380,000 years after the Big Bang, by which time a great deal of expansion had already occurred.   

[Genady]

1 hour ago, DanMP said:

When they assessed the time from big bang, what reference frame they used? There is no absolute time.

This is the time of comoving reference frame.

 

1 hour ago, DanMP said:

the clocks are slower when they are situated in/near a place with high density

Slower than what? Slower than a clock which is situated away from this high density. But the entire universe was this high density. There was or is nothing away from it.

[DanMP]

2 hours ago, exchemist said:

One thing to bear in mind is that light only started travelling through dark space from the surface of last scattering, 380,000 years after the Big Bang, by which time a great deal of expansion had already occurred.

Yes, good point. Still, the universe was much denser than today.

1 hour ago, Genady said:

This is the time of comoving reference frame.

Comoving with what? Also, where, on Earth surface, between galaxies or on a neutron star "surface" 😀? Keep in mind that the Earth was not there in the beginning, nor any neutron star, nor the current intergalactic space, which is almost empty now. We shouldn't neglect gravitational time dilation, nor gravitational redshift. Probably they didn't, but I'm not sure. 

1 hour ago, Genady said:

Slower than what?

Slower than our clocks, situated on Earth today.

[Genady]

8 minutes ago, DanMP said:

Comoving with what?

Comoving with the on average homogeneous and isotropic space.

8 minutes ago, DanMP said:

Slower than our clocks, situated on Earth today.

How do you compare time then with time today? 

Edited August 13, 2023 by Genady

[DanMP]

1 minute ago, Genady said:

How you compare time then with time today?

I knew that you would say that. We probably can't.

So, the age of the universe was not "converted" to "today time" on Earth.

 

Still, there may be an unaccounted "gravitational" redshift, because the "ancient" light originates from a denser region than we have now, here.

[Genady]

2 minutes ago, DanMP said:

So, the age of the universe was not "converted" to "today time" on Earth.

Correct.

 

2 minutes ago, DanMP said:

Still, there may be an unaccounted "gravitational" redshift, because the "ancient" light originates from a denser region than we have now, here.

This is already taken in account in the Friedmann equations.

[DanMP]

7 minutes ago, Genady said:

Correct.

 

This is already taken in account in the Friedmann equations.

OK, thank you! 

[DanMP]

On 8/13/2023 at 8:30 PM, Genady said:

This is already taken in account in the Friedmann equations.

I didn't check but I agreed that Friedmann equations would account for increased redshift due to higher density back than. Still, there are other possible issues due to that higher density: more matter (mostly hydrogen) between stars/galaxies would absorb and/or scatter more light, decreasing the luminosity and making the source to appear farther ... It is very obvious, so I expect to be accounted for, but how?

Another thing, nobody commented about the video I posted: the new estimation of the age of the universe and the possibility that part of the redshift may be from "tired light". I wonder if the late would also account for the increased expansion caused(?) by "dark energy". 

[Genady]

17 minutes ago, DanMP said:

I didn't check but I agreed that Friedmann equations would account for increased redshift due to higher density back than. Still, there are other possible issues due to that higher density: more matter (mostly hydrogen) between stars/galaxies would absorb and/or scatter more light, decreasing the luminosity and making the source to appear farther ... It is very obvious, so I expect to be accounted for, but how?

Another thing, nobody commented about the video I posted: the new estimation of the age of the universe and the possibility that part of the redshift may be from "tired light". I wonder if the late would also account for the increased expansion caused(?) by "dark energy". 

All these factors go under the "tired light" hypotheses. They were investigated quite thoroughly, and the general conclusion is that they don't fit observations. There are many articles about them, their predictions and tests. Perhaps other members here will give you more specific answers.

[DanMP]

14 minutes ago, Genady said:

All these factors go under the "tired light" hypotheses

Not all. An extra scattering and absorption due to higher interstellar gas density would decrease luminosity of the source in any scenario. How was this addressed? 

[Genady]

1 hour ago, DanMP said:

Not all. An extra scattering and absorption due to higher interstellar gas density would decrease luminosity of the source in any scenario. How was this addressed? 

I don't know. But this factor is so obvious that I doubt it was not addressed. How do you know that it was not addressed?

[Janus]

1 hour ago, DanMP said:

Not all. An extra scattering and absorption due to higher interstellar gas density would decrease luminosity of the source in any scenario. How was this addressed? 

Scattering and absorption doesn't mean that the light energy energy goes away.  For example, our atmosphere scatters Sunlight, largely in the blue end of the spectrum.  We see that blue light as coming from all parts of the sky. Scattered light from a distant object would also aririve, just not directly from the object.

  Likewise, with absorption, the dust will reach thermal equilibrium and radiate energy at the rate it is receiving it. In the case of interstellar gas, in the infrared or radio frequencies.  

In addition, light coming from a distant object which has had light scattered or absorbed won't be dimmed equally in all frequencies, but would instead show absorption bands in its spectrum.  And since some electromagnetic frequencies are more subject to scattering/absorption than others, Observations are made over a wide range(visible, infrared, radio...) to get a picture of what is happening.

 

[tmdarkmatter]

Hello, I am wondering why this topic was not closed yet, as usually happens with my topics. So what is beeing discussed here is that light is "getting tired" over long distances. In that case why should we still think that the universe is expanding, if all the redshift can just be because of this "getting tired" effect?

If we want to evaluate how "tired" light gets, we would need to have two spaceships beaming each other at increasing distances. Unfortunately, the gravity of our solar system would always manipulate this experiment, because we just cannot move away far enough into interstellar space.

On the other hand, it should even be this gravitational pull what might be creating the redshift. I know that according to current theory, a gravitational well should increase the frequency when "going down" and decresing it when "going up" in the gravitational well and that the total effect should be zero. But what about light beeing bent while travelling through the universe? Can we affirm that light is beeing bent more the further away the source was?

For example, if there are 5 stars in between us and the source, maybe the light is slightly beeing bent into one direction by one star, then in the other by the second star, then maybe the same direction by the third star and again back into the original direction by the fourth and fifth star. Maybe the total "shift" might not be very obvious to us, but we should admit that there was more graviational pull exerted than if there were only 3 or 4 stars in between or if the stars had less space/time to bend light.

This would mean that on average light is more manipulated the further the source is away from us and this should be the cause of the "getting tired" effect. If that´s the case, there might be no expansion at all and we just have no clue about how old the universe actually is. And what is worse, we might even have to stop using redshift as a "best method" to define the distance between us and the stars.

[zapatos]

8 minutes ago, tmdarkmatter said:

In that case why should we still think that the universe is expanding, if all the redshift can just be because of this "getting tired" effect?

Um, because there is no evidence of a "getting tired" effect?

[tmdarkmatter]

11 minutes ago, zapatos said:

Um, because there is no evidence of a "getting tired" effect?

Well, the evidence would be red shifting and the cause would be gravitational pull.

Why would light that changed its direction millions of times have the same energy than light that never changed its direction?

Your question would now be: "why should it not? lol

We could define a ray entering a gravitational well as losing a small amount of its energy when it leaves the gravitational well because you would need a certain amount of energy to bend the light back to its original direction. And these little losses of energy would just sum up, even if the gravitational pull of different stars might override each other.

[zapatos]

23 minutes ago, tmdarkmatter said:

Why would light that changed its direction millions of times have the same energy than light that never changed its direction?

 

Good question. Can you show evidence that when light changes direction its energy changes?

[tmdarkmatter]

5 minutes ago, zapatos said:

Can you show evidence that when light changes direction its energy changes?

Once again, the only evidence is red shift.

This is like the current explanation of gravity: "The only proof of space-time curvature is gravity and the only explanation for gravity is space-time curvature."

By the way we can say: "The only cause of red shift is expansion of the universe" or "The only cause of red shift is gravitational pull." but we cannot say "Sometimes the cause of red shift is expansion of the universe and sometimes the cause of red shift is gravitational pull (according to need)." So far, we could only confirm the existance of red shift due to gravitational pull so why should we seriously believe in some kind of expansion of the universe? 

If we say that all the red shift in the universe is only caused by the expansion of the universe, this would mean that the only place where graviational pull causes red shift is in the Harvard tower or that the galaxies out there simply have no mass at all.

[zapatos]

1 hour ago, tmdarkmatter said:

...we cannot say "Sometimes the cause of red shift is expansion of the universe and sometimes the cause of red shift is gravitational pull (according to need)."

Why not? We have evidence of both.

[tmdarkmatter]

What proof do we have that expansion of the universe creates red shift?

[zapatos]

7 minutes ago, tmdarkmatter said:

What proof do we have that expansion of the universe creates red shift?

There is no 'proof'. There is evidence that receding light sources redshift.

Edited November 13, 2023 by zapatos

[tmdarkmatter]

2 minutes ago, zapatos said:

There is evidence that receding light sources redshift.

What experiment can I do to get that evidence?

So far, the closest possible object where we have detected "blueshift" is Andromeda and I guess it is not possible for us to speed up a light source to 15 km/s to measure a very slight redshift, especially not in a lab.

We cannot even detect the red/blue shifting of the planets of our solar system.

[zapatos]

48 minutes ago, tmdarkmatter said:

What experiment can I do to get that evidence?

I suppose you could get a radar gun or a doppler radar system and use that as the basis of your test.

[tmdarkmatter]

It is interesting that they measured the blue shifting of the light coming from the sun due to the graviational well (about 633m/s), but not the red shifting because of its movement into our direction in the morning or away from us in the evening (difference of about 600 m/s as a maximum).