# Thread: Rate of Expansion of the universe

1. I have one question:

If the universe is expanding at the Hubble constant, then how fast is the universe speeding up its expansion?

2.

3. I heard it has soemthing to do with dark matter and dark energy... I'm no pro at cosmology. Maybe you could find answers on Wikipedia.

4. Sorry if I was not clear, I meant the numbers.

5. Originally Posted by Devon Keogh
I have one question:

If the universe is expanding at the Hubble constant, then how fast is the universe speeding up its expansion?
We don't know yet.

But I should point out that the universe is always expanding at the Hubble constant, but the Hubble constant is always changing as it is just the average rate of expansion taken from the increase in scale factor. So the real question is how is the Hubble constant changing, over time - and the answer is that we don't know yet, although there are a few projects out there that aim to put some constraints on the figure over the next few years.

6. Ok, because I was just thinking that if we got the difference between three equally spaced years we could calculate the yearly difference.

Now I am the new Leonardo da Vinci!

7. Maybe I could ask a few different questions then.

Question 1: How many Hubble Constants have been recorded in history? (Unless regularly recorded)
Question 2: Could I have three samples from even time periods?

8. The Hubble constant was only formulated within the past century, so we have no historical record, as such (expansion rates do not change that quickly!). But based on the value of the Hubble constant today, when combined with the redshift - distance relationships we measure for galaxies at different distances, we can extrapolate backwards.

This does not, however, give any obvious information about the acceleration of the expansion, if that is what you hoped. The Hubble constant has always been decreasing over time, and the expansion of the universe will have to accelerate for an even longer time (perhaps for ever!) before the Hubble constant would even settle towards a constant rate, let alone increase!

The Hubble constant is a "proportionality constant", and is based on the change in the scale factor of the universe over time. Even though the expansion was decelerating for 8 -7 billion years, and has been accelerating for the past 5 - 6 billion years, the universe has been scaling up throughout that time, and the Hubble constant has been continually decreasing. This is quite a complicated concept to get your head around.

The only time that the Hubble constant would actually even remain constant (let alone increase) would be during what is known as "exponential expansion", and this is a state of affairs that is theorised to have occurred only in the inflationary epoch (within a fraction of the first second of the history of the universe), and is not theorised to happen again due to accelerating expansion until future infinity, unless the acceleration is due to "phantom" dark energy which would eventually lead to a Big-Rip scenario.

Some definitions for you.

Decelerating expansion. If you look at a certain galaxy and calculate how fast it is receding, and then look again at the same galaxy in a billion years, it will be more distant but will be receding at a slower rate. The galaxy is moving away at a decelerating rate. The Hubble constant is decreasing - the distance where a galaxy recedes at the speed of light gets larger over time. The "Hubble distance", where objects recede at c, is itself accelerating away from you.

Constant expansion. Whenever you look at a certian galaxy, however distant it becomes, it always recedes at the same speed. The galaxy is moving away at a constant rate. The Hubble constant is still decreasing - the distance where a galaxy recedes at the speed of light still gets larger over time. The Hubble distance recedes at a constant speed. (If the universe was always expanding constantly, the Hubble distance always equals the age of the universe)

Accelerating expansion. If you look at a certain galaxy and calculate how fast it is receding, and then look again at the same galaxy in a billion years, it will be more distant but will be receding at a faster rate. The galaxy is moving away at an accelerating rate. The Hubble constant is still decreasing - the distance where a galaxy recedes at the speed of light still gets larger over time! The Hubble distance recedes at a decelerating speed.

Exponential expansion. Galaxies are accelerating away such that they always reach the speed of light, in relation to you, at the same distance. The Hubble constant remains constant - the distance where a galaxy recedes at the speed light of remains constant. The Hubble distance remains at a constant distance.

More than exponential expansion. Galaxies are accelerating in the way they accelerate away, such that they reach the speed of light at a distance that decreases over time. The Hubble constant decreases. The Hubble distance comes back towards us. Eventually we reach a Big-Rip scenario.

Source: [astro-ph/0310808] Expanding Confusion: common misconceptions of cosmological horizons and the superluminal expansion of the Universe

Do you still want to know some figures for the Hubble constant in the past?

9. Originally Posted by SpeedFreek
The Hubble constant was only formulated within the past century, so we have no historical record, as such (expansion rates do not change that quickly!). But based on the value of the Hubble constant today, when combined with the redshift - distance relationships we measure for galaxies at different distances, we can extrapolate backwards.

This does not, however, give any obvious information about the acceleration of the expansion, if that is what you hoped. The Hubble constant has always been decreasing over time, and the expansion of the universe will have to accelerate for an even longer time (perhaps for ever!) before the Hubble constant would even settle towards a constant rate, let alone increase!

The Hubble constant is a "proportionality constant", and is based on the change in the scale factor of the universe over time. Even though the expansion was decelerating for 8 -7 billion years, and has been accelerating for the past 5 - 6 billion years, the universe has been scaling up throughout that time, and the Hubble constant has been continually decreasing. This is quite a complicated concept to get your head around.

The only time that the Hubble constant would actually even remain constant (let alone increase) would be during what is known as "exponential expansion", and this is a state of affairs that is theorised to have occurred only in the inflationary epoch (within a fraction of the first second of the history of the universe), and is not theorised to happen again due to accelerating expansion until future infinity, unless the acceleration is due to "phantom" dark energy which would eventually lead to a Big-Rip scenario.

Some definitions for you.

Decelerating expansion. If you look at a certain galaxy and calculate how fast it is receding, and then look again at the same galaxy in a billion years, it will be more distant but will be receding at a slower rate. The galaxy is moving away at a decelerating rate. The Hubble constant is decreasing - the distance where a galaxy recedes at the speed of light gets larger over time. The "Hubble distance", where objects recede at c, is itself accelerating away from you.

Constant expansion. Whenever you look at a certian galaxy, however distant it becomes, it always recedes at the same speed. The galaxy is moving away at a constant rate. The Hubble constant is still decreasing - the distance where a galaxy recedes at the speed of light still gets larger over time. The Hubble distance recedes at a constant speed. (If the universe was always expanding constantly, the Hubble distance always equals the age of the universe)

Accelerating expansion. If you look at a certain galaxy and calculate how fast it is receding, and then look again at the same galaxy in a billion years, it will be more distant but will be receding at a faster rate. The galaxy is moving away at an accelerating rate. The Hubble constant is still decreasing - the distance where a galaxy recedes at the speed of light still gets larger over time! The Hubble distance recedes at a decelerating speed.

Exponential expansion. Galaxies are accelerating away such that they always reach the speed of light, in relation to you, at the same distance. The Hubble constant remains constant - the distance where a galaxy recedes at the speed light of remains constant. The Hubble distance remains at a constant distance.

More than exponential expansion. Galaxies are accelerating in the way they accelerate away, such that they reach the speed of light at a distance that decreases over time. The Hubble constant decreases. The Hubble distance comes back towards us. Eventually we reach a Big-Rip scenario.

Source: [astro-ph/0310808] Expanding Confusion: common misconceptions of cosmological horizons and the superluminal expansion of the Universe

Do you still want to know some figures for the Hubble constant in the past?
Damn... to know that acceleration was decreasing then increased is a real pain.

Want to know my aim? To calculate the size of the universe at current via the backtracking of acceleration.

10. [QUOTE=Devon Keogh;381490]
Originally Posted by SpeedFreek
The Hubble constant was only formulated within the past century, so we have no historical record, as such (expansion rates do not change that quickly!). But based on the value of the Hubble constant today, when combined with the redshift - distance relationships we measure for galaxies at different distances, we can extrapolate backwards.

This does not, however, give any obvious information about the acceleration of the expansion, if that is what you hoped. The Hubble constant has always been decreasing over time, and the expansion of the universe will have to accelerate for an even longer time (perhaps for ever!) before the Hubble constant would even settle towards a constant rate, let alone increase!

The Hubble constant is a "proportionality constant", and is based on the change in the scale factor of the universe over time. Even though the expansion was decelerating for 8 -7 billion years, and has been accelerating for the past 5 - 6 billion years, the universe has been scaling up throughout that time, and the Hubble constant has been continually decreasing. This is quite a complicated concept to get your head around.

The only time that the Hubble constant would actually even remain constant (let alone increase) would be during what is known as "exponential expansion", and this is a state of affairs that is theorised to have occurred only in the inflationary epoch (within a fraction of the first second of the history of the universe), and is not theorised to happen again due to accelerating expansion until future infinity, unless the acceleration is due to "phantom" dark energy which would eventually lead to a Big-Rip scenario.

Some definitions for you.

Decelerating expansion. If you look at a certain galaxy and calculate how fast it is receding, and then look again at the same galaxy in a billion years, it will be more distant but will be receding at a slower rate. The galaxy is moving away at a decelerating rate. The Hubble constant is decreasing - the distance where a galaxy recedes at the speed of light gets larger over time. The "Hubble distance", where objects recede at c, is itself accelerating away from you.

Constant expansion. Whenever you look at a certian galaxy, however distant it becomes, it always recedes at the same speed. The galaxy is moving away at a constant rate. The Hubble constant is still decreasing - the distance where a galaxy recedes at the speed of light still gets larger over time. The Hubble distance recedes at a constant speed. (If the universe was always expanding constantly, the Hubble distance always equals the age of the universe)

Accelerating expansion. If you look at a certain galaxy and calculate how fast it is receding, and then look again at the same galaxy in a billion years, it will be more distant but will be receding at a faster rate. The galaxy is moving away at an accelerating rate. The Hubble constant is still decreasing - the distance where a galaxy recedes at the speed of light still gets larger over time! The Hubble distance recedes at a decelerating speed.

Exponential expansion. Galaxies are accelerating away such that they always reach the speed of light, in relation to you, at the same distance. The Hubble constant remains constant - the distance where a galaxy recedes at the speed light of remains constant. The Hubble distance remains at a constant distance.

More than exponential expansion. Galaxies are accelerating in the way they accelerate away, such that they reach the speed of light at a distance that decreases over time. The Hubble constant decreases. The Hubble distance comes back towards us. Eventually we reach a Big-Rip scenario.

Source: [astro-ph/0310808] Expanding Confusion: common misconceptions of cosmological horizons and the superluminal expansion of the Universe

Do you still want to know some figures for the Hubble constant in the past?
To know that acceleration was decreasing then increased is a real pain.

Do you want to know my aim? To calculate the size of the universe at current via the backtracking of acceleration.

11. To calculate the size of the universe at current via the backtracking of acceleration.
Been done. 48 billion lys. (for the observable universe, which is all we can know)

12. Originally Posted by Devon Keogh
To know that expansion was decreasing then increased is a real pain.

Do you want to know my aim? To calculate the size of the universe at current via the backtracking of acceleration.
(My change in bold)

I take it you mean the size of the observable universe, as we can't know how much larger the universe is when compared to our observable volume. That is a complicated calculation, and you can't do it simply using different Hubble constants over different epochs. The Hubble constant is an expression of recession speed per unit of distance and is currently around ~70 km/s per Megaparsec. But how are you going to know what to multiply that by, even if you know various Hubble parameters from the past?

The current size of the observable universe is ~46.5 billion light-years in radius, by the way. That is the proper distance from here to the release coordinates of the cosmic microwave background (known as the surface of last scattering or particle horizon), assuming those coordinates have receded due to the overall change in scale factor. Regardless of the changing rate of expansion, the end result is that the universe has scaled up by a factor of 1090 since the CMB was released.

13. The difference between two Hubble Constants gives me the rate of acceleration speeding up over a period of time so I do believe this is certainly possible to calculate and we can know how big the universe actually is, in my opinion and philosophy on the subject.

14. Unfortunately, there is no way to calculate the full size of the universe, as we have no idea how large the whole universe was to begin with.

Cosmology FAQ: How can the Universe be infinite if it was all concentrated into a point at the Big Bang?

The Universe was not concentrated into a point at the time of the Big Bang. But the observable Universe was concentrated into a point. The distinction between the whole Universe and the part of it that we can see is important.
The whole universe could be any size larger than our observable part of it, and this would have been the case all along, if the whole universe expands like our observable part does.

15. Originally Posted by Devon Keogh
No I mean the full size of the universe
The size of the whole universe is simply hypothetical. If you adhere to the Big Bang model then the size of the universe is a function of the Inflation hypothesis that first supposedly expanded super-luminally for an indetermined period of time. Next you would have to define your meaning of the word universe. Could it, for instance, include space without matter, energy, or field? Bottom line, all of this is just pure speculation. The consensus Big Bang model proposes a universe generally finite in matter/ energy, while some other models might propose an infinite universe in all aspects.

16. Originally Posted by forrest noble
Originally Posted by Devon Keogh
No I mean the full size of the universe
The size of the whole universe is simply hypothetical. If you adhere to the Big Bang model then the size of the universe is a function of the Inflation hypothesis that first supposedly expanded super-luminally for an indetermined period of time. Next you would have to define your meaning of the word universe. Could it, for instance, include space without matter, energy, or field. Bottom line, all of this is just pure speculation. The consensus Big Bang model proposes a universe generally finite in matter/ energy, while some other models might propose an infinite universe in all aspects.
I am adhedering to a big bang model with finite space.

17. The Big-Bang model, even if space is finite, cannot be used to find the totality of that space, as we can only relate it to our observable portion of a finite universe, and we do not know how much larger the finite universe is, when compared to our observable portion of it.

18. Originally Posted by forrest noble
Originally Posted by Devon Keogh
No I mean the full size of the universe
The size of the whole universe is simply hypothetical. If you adhere to the Big Bang model then the size of the universe is a function of the Inflation hypothesis that first supposedly expanded super-luminally for an indetermined period of time. Next you would have to define your meaning of the word universe. Could it, for instance, include space without matter, energy, or field. Bottom line, all of this is just pure speculation. The consensus Big Bang model proposes a universe generally finite in matter/ energy, while some other models might propose an infinite universe in all aspects.
I definitely agree with your statement. The big bang theory seems to be based on finite matter/energy; outside of that the speculations begin to get blurry based on the different angles of observation. The main problem as I see it is the definition of space/time, and universe.

19. Can I please have three samples of Hubble Constants from equal time differences, as this will help greatly.

20. Well, as I said, the Hubble constant has always been decreasing, so I'm at a loss as to what you are going to do with these figures, but if you insist..

1 billion years after the Big Bang, the Hubble constant was:
656 km/s/Mpc
___________________________

4 billion years after the Big Bang, the Hubble constant was:
171 km/s/Mpc

8 billion years after the Big Bang, the Hubble constant was:
95.9 km/s/Mpc (this is around the time that the deceleration turned into an acceleration)

12 billion years after the Big Bang, the Hubble constant was:
74.9 km/s/Mpc
___________________________

Today, 13.7 billion years after the Big Bang, the Hubble constant is:
70.5 km/s/Mpc

(Mpc = Megaparsec, or 3.26 million light-years.)

If you want to look into the figures further, a good source to compute them (based on the current cosmological model) is Wolfram Alpha

21. is this like how mass is related to the reference frame (observer?) is relativity to the measurement and knowability tied together in determining the property of size of the universe? --> I mean the particle version (or segment) of it

22. Wait, this makes little sense... if the Hubble Constant (and it is represented by xx km/s/megaparasec) is decreasing, then how is the universe accelerating its expansion?

23. Well, that is what I was trying to explain to you in post #7, but it is pretty complicated!

The Hubble constant, at any given time, is simply an average of the way the universe has scaled up since the beginning of the universe. But early on the expansion was really really fast, so the universe scaled up much much more in the first billion years than it has done since.

The universe has scaled up by a factor of 1100 since the CMBR was released, 13.7 billion years ago.

But the universe has only scaled up by a factor of 9 in the past 13 billion years.

The CMBR (that we currently detect) was originally released only 42 million light-years away, 13.7 billion years ago, but the radial distance to those coordinates has increased by a factor of 1100 since, putting the release coordinates of the CMBR something around 46 billion light-years away today.

For a distant galaxy whose light has been travelling only 13 billion years, that galaxy was originally 3.3 billion light-years away when the light was emitted. Today that galaxy (if it has receded with the expansion of the universe) would be around 29.7 billion light-years away. That distance has increased by a factor of only 9.

It is the increase in scale factor that determines the Hubble constant, and for the constant to increase the universe has to scale up more, later on, than it did earlier!

So whilst galaxies started out decelerating in their recession from us and more recently have started to accelerate away, the change in scale factor is still very small in comparison to the change in scale factor early on, and thus the Hubble constant continues to decrease until such a time that the universe is scaling up as fast as it was early on.

This is why I have been telling you that you cannot calculate the rate of acceleration using the Hubble constant.

24. Originally Posted by SpeedFreek
Well, as I said, the Hubble constant has always been decreasing, so I'm at a loss as to what you are going to do with these figures, but if you insist..

1 billion years after the Big Bang, the Hubble constant was:
656 km/s/Mpc
___________________________

4 billion years after the Big Bang, the Hubble constant was:
171 km/s/Mpc

8 billion years after the Big Bang, the Hubble constant was:
95.9 km/s/Mpc (this is around the time that the deceleration turned into an acceleration)

12 billion years after the Big Bang, the Hubble constant was:
74.9 km/s/Mpc
___________________________

Today, 13.7 billion years after the Big Bang, the Hubble constant is:
70.5 km/s/Mpc

(Mpc = Megaparsec, or 3.26 million light-years.)

If you want to look into the figures further, a good source to compute them (based on the current cosmological model) is Wolfram Alpha
I think these figures can be misleading concerning the dark energy hypothesis. In the beginning, the expansion of the universe accordingly started accelerating for a very short period of time known as the inflation era (hypothesis), supposedly expanding many times the speed of light. Then supposedly soon thereafter this period ended and the universe's expansion began decelerating. This accordingly continued until about 6 billion years ago when the universe's expansion was supposedly at its least amount, whereby at that time the universe began accelerating again until the present time where this expansion is thought to be accelerating again for the last 6 billion years.

It should be pointed out that dark energy is still hypothetical in that it has never been directly observed. There is no doubt that there is a correlation between distance and the observed redshift of galaxies, based upon secondary confirmations in general based upon the inverse square law of light. But whether the universe is actually expanding or not is based upon the Big Bang theory and of the expansion of space hypothesis, whereby GR can predict an expanding universe, a steady state universe, an accelerated expansion, decelerating expansion, thus allowing for the dark energy hypothesis, or a contracting universe based upon the Big Crunch model. The expansion of space hypothesis is solely based upon the observed galactic redshifts, which might be otherwise explained other than by the expansion of space.

25. Originally Posted by forrest noble
The expansion of space hypothesis is solely based upon the observed galactic redshifts, which might be otherwise explained other than by the expansion of space.
Well, nobody has found an alternative explanation so far.

26. Originally Posted by forrest noble
It should be pointed out that dark energy is still hypothetical in that it has never been directly observed. There is no doubt that there is a correlation between distance and the observed redshift of galaxies, based upon secondary confirmations in general based upon the inverse square law of light. But whether the universe is actually expanding or not is based upon the Big Bang model and the of the expansion of space hypothesis, whereby GR can predict an expanding universe, a steady state universe, accelerated expansion, decelerated expansion, allowing for the dark energy hypothesis, or a contracting universe based upon the Big Crunch model. The expansion of space hypothesis is solely based upon the observed galactic redshifts, which might be otherwise explained other than by the expansion of space.
Could you squeeze a few more "hypothetical" or "hypothesis" in there. It isn't quite clear that you are doubtful of the solid evidence supporting the mainstream models. And I it is almost possible to follow your sentences.

It should be pointed out that dark energy is still hypothetical in that it has never been directly observed.

No, but the accelerating expnasion has. The label "dark energy" is just used to name the unknown explanation for this.

There is no doubt that there is a correlation between distance and the observed redshift of galaxies, based upon secondary confirmations in general based upon the inverse square law of light.

Well, the first half makes sense (it is nice to see you say that there are at least some things without doubt). But I have no idea where the inverse square law comes into to it. Unless it is because it is involved in some parts of the cosmological distance ladder? Surely there are other parts of the distance ladder that you could throw doubt on?

But whether the universe is actually expanding or not is based upon the Big Bang model ...

I am going to have to take this sentence a bit at a time as it is quite a monster.

It might be more accurate to say that the big bang model is based on the apparent expansion.

But whether the universe is actually expanding or not is based ... the expansion of space hypothesis

That is rather a circular argument, isn't it?

whereby GR can predict an expanding universe, a steady state universe, accelerated expansion, decelerated expansion, allowing for the dark energy hypothesis, or a contracting universe based upon the Big Crunch model.

GR predicts expansion or contraction. A steady state would require a very carefully balanced and finely tuned set of conditions that, as far as I understand it, is pretty much infeasible. And, of course, is plainly contradicted by evidence.

The expansion of space hypothesis is solely based upon the observed galactic redshifts, which might be otherwise explained other than by the expansion of space

And yet no other models have managed to explain both the observed red-shifts and all the other evidence.

You do like to throw around "could be explained by other models" while failing to point out that no such models work...

27. [QUOTE=Strange;382990]
Originally Posted by forrest noble
It should be pointed out that dark energy is still hypothetical in that it has never been directly observed. There is no doubt that there is a correlation between distance and the observed redshift of galaxies, based upon secondary confirmations in general based upon the inverse square law of light. But whether the universe is actually expanding or not is based upon the Big Bang model and the of the expansion of space hypothesis, whereby GR can predict an expanding universe, a steady state universe, accelerated expansion, decelerated expansion, allowing for the dark energy hypothesis, or a contracting universe based upon the Big Crunch model. The expansion of space hypothesis is solely based upon the observed galactic redshifts, which might be otherwise explained other than by the expansion of space.
Could you squeeze a few more "hypothetical" or "hypothesis" in there. It isn't quite clear that you are doubtful of the solid evidence supporting the mainstream models. And I it is almost possible to follow your sentences.
Of course you have long been aware of my doubts concerning mainstream theory in general, and for you I would not have to ever use the word "hypothesis" so many times, but others might consider these ideas as almost certainly fact, in which case I am conveying the idea that there may be less than certain evidence to support some of these ideas, "theories."

It should be pointed out that dark energy is still hypothetical in that it has never been directly observed.
No, but the accelerating expansion has. The label "dark energy" is just used to name the unknown explanation for this.
Even this, I think, could have been misinterpreted based upon an incomplete Hubble formulation, but we are in agreement that dark energy is a placeholder for the unknown explanation.

There is no doubt that there is a correlation between distance and the observed redshift of galaxies, based upon secondary confirmations in general based upon the inverse square law of light.
Well, the first half makes sense (it is nice to see you say that there are at least some things without doubt). But I have no idea where the inverse square law comes into to it. Unless it is because it is involved in some parts of the cosmological distance ladder?
This statement has its basis: Calculate the distance to a galaxy outside the local supercluster. Upon redshift distance calculation, recalculate the galaxies distance based upon its estimated size and apparent luminosity. There almost always be similar estimates concerning the galaxies distance. A third method might be angular size. In a telescope at an estimated distance, a galaxy of a certain size will represent a certain arc angle from side to side in the telescope. All three methods can give an estimate as to the galaxies distance, and in most cases all three methods of distance estimation will yield similar estimations, where redshift is most often the most accurate.

Surely there are other parts of the distance ladder that you could throw doubt on?
In my opinion the distance ladder is goofed up as much as 11% based upon the inaccuracies in the Hubble formula, which for the same reason, in my opinion, led to the wrong conclusion that resulted in the dark energy hypothesis.

But whether the universe is actually expanding or not is based upon the Big Bang model ...

I am going to have to take this sentence a bit at a time as it is quite a monster.
It might be more accurate to say that the big bang model is based on the apparent expansion.
I agree, this is probably a more accurate description.

But whether the universe is actually expanding or not is based ... the expansion of space hypothesis

That is rather a circular argument, isn't it?
If space is not expanding, then the universe is probably not expanding, and the BB model would seem to be the wrong explanation of the universe.

Hopefully this time I made no circular reasoning

whereby GR can predict an expanding universe, a steady state universe, accelerated expansion, decelerated expansion, allowing for the dark energy hypothesis, or a contracting universe based upon the Big Crunch model.

GR predicts expansion or contraction. A steady state would require a very carefully balanced and finely tuned set of conditions that, as far as I understand it, is pretty much infeasible. And, of course, is plainly contradicted by evidence.
I think I agree. Although Hoyle steady state model was based upon an expanding universe the density of it was accordingly stead state. He used GR also as his basis.

I believe GR is the wrong model of gravity, and if so then Einstein's cosmological equations would also then be the wrong model of the universe. I think that dark matter might exist in the form of a type of aether, but not as the large gravitational entity they are now proposing for dark matter.

The expansion of space hypothesis is solely based upon the observed galactic redshifts, which might be otherwise explained other than by the expansion of space

And yet no other models have managed to explain both the observed red-shifts and all the other evidence.
I am not aware of any other evidence other than redshifts, to support the expansion of space idea. Other hypothesis can equally explain redshifts, whereby there is no mechanism observed that can explain the expansion of space outside of hypothetical, that I can think of .

You do like to throw around "could be explained by other models" while failing to point out that no such models work...
I don't know what you might mean by "no such models work." There are no other models that are presently thought by the mainstream to be competition for the BB model, true. Some may exist without a strong "marketing" program . Some maybe only one-man gigs, so to speak

28. Originally Posted by forrest noble
I am not aware of any other evidence other than redshifts, to support the expansion of space idea.
And that is the problem. You are either largely ignorant of, fail to understand or simply ignore the many differing lines of evidence that support or are consistent with the big bang theory.

Other hypothesis can equally explain redshifts
That may be true, although all the ones I am aware of have been discredited by observation and theory. But none of them can explain everything else in a consistent way.

The reason that big bang cosmology is so successful is because it explains so many (seemingly unconnected) facts and observations with a single theory.

29. Originally Posted by forrest noble
I am not aware of any other evidence other than redshifts, to support the expansion of space idea.
If the universe expands from a hot dense state, the standard model predicts nuceosynthesis, which would mean an abundance of light elements in the early universe. We have evidence for this in the observed abundance of light elements in distant galaxies.

If the universe expands from a hot dense state, nucleosynthesis results in the formation of atoms and the first freeing of photons. We have evidence for this in the background radiation, which has the most perfect black-body spectrum as would be expected in a universe that would have been a "perfect absorber" of light before this time.

If the universe expands, it cools. We have evidence for this in measurements of the heating of distant gas clouds by the background radiation, in comparison to more local gas clouds.

If the universe expands, we should be able to see galaxies that were closer to us in the early universe with an apparent size that reflects their original distance, as their light is only just reaching us. We have evidence of this through the Tolman test for expansion.

If the universe expands, then the redshifting of distant objects is expected, along with cosmological time-dilation caused by that redshift. No other proposed source of redshift I know of can also account for that time-dilation. We have overwhelming evidence for both.

30. Originally Posted by Devon Keogh
Wait, this makes little sense... if the Hubble Constant (and it is represented by xx km/s/megaparasec) is decreasing, then how is the universe accelerating its expansion?
Another way to answer this is to explain how we come to the current figure of ~70 km/s/Mpc

An object that is 13.7 billion light-years away today, would have had to have constantly receded at the speed of light for the entire history of the universe. So if the rate of expansion were constant, which means all galaxies recede at a constant speed, then a galaxy receding at the speed of light would be 13.7 billion light-years away.

The rate of expansion is proportional to distance, so a galaxy half that distance away would have had to have constantly receded at half the speed of light to get there.

If we divide that distance up into megaparsecs, then a galaxy 1 Mpc away would have been receding at 70 km/s for the whole history of the universe, in order to reach 3.2 million light-years away in 13.7 billion years. A galaxy 2 Mpc away would have had to recede at 140 km/s, and so on.

So you see, the ~70 km/s/Mpc figure is just an average that represents how fast, on average, a galaxy would have had to recede since the Big-Bang, to get where it is today.

It does not take the deceleration or acceleration into account, it just gives us the average speed throughout time.

Seeing as the universe has not been accelerating throughout time, and scaled up much more during deceleration than it has done during the subsequent acceleration, that average across the whole of time is still falling.

31. (deleted dumb comment)

32. Originally Posted by Strange
Originally Posted by forrest noble
I am not aware of any other evidence other than redshifts, to support the expansion of space idea.
And that is the problem. You are either largely ignorant of, fail to understand or simply ignore the many differing lines of evidence that support or are consistent with the big bang theory.
The expansion of space hypothesis is not the sole evidence for the BB model, of course. But I said I know of no evidence other than the observed galactic redshifts to support the expansion of space hypothesis. Can you think of any other evidence that supports this hypothesis?

Other hypothesis can equally explain redshifts
That may be true, although all the ones I am aware of have been discredited by observation and theory.

There are other redshift proposals such as gravitational redshifts/ stretch theory, new versions of tired light that accordingly explain time dilation, diminution of matter theory, aether absorption theory, the Compton effect, dark energy stretching, dark matter stretching, EM radiation cross-stretching, matter absorption/ re-radiation loss of energy, etc. etc.
....But none of them can explain everything else in a consistent way
Yes, this is the mainstream belief but otherwise theorized to the contrary by those mainstream and non-mainstream proponents.

The reason that big bang cosmology is so successful is because it explains so many (seemingly unconnected) facts and observations with a single theory.
Yes, this is the present belief. I think it will all depend upon the James Webb telescope. If it confirms BB predictions then I think almost all other cosmological models will be summarily eliminated. If instead at the farthest distances we see the same galaxies as we observe in our neighborhood, then I think the BB model will be eliminated as a possibility and will be eventually be replaced, after first proposing a new BB hypothesis to greatly increase the age of the universe according to that model.

33. Originally Posted by forrest noble
[I am not aware of any other evidence other than redshifts, to support the expansion of space idea. Other hypothesis can equally explain redshifts, whereby there is no mechanism observed that can explain the expansion of space outside of hypothetical, that I can think of
The big bang model fits well together and there does not exist any other explanation to explain all the data simultaneously. I recall attempts at other explanations of redshift but everything I've seen so far fails in some other respect.

I'm curious. What are these "other hypotheses" that you mentioned? Please list a few.

34. Originally Posted by SpeedFreek
Originally Posted by forrest noble
I am not aware of any other evidence other than redshifts, to support the expansion of space idea.
If the universe expands from a hot dense state, the standard model predicts nucleosynthesis, which would mean an abundance of light elements in the early universe. We have evidence for this in the observed abundance of light elements in distant galaxies.
This, I agree is considered evidence for the BB model. There are some problems with this proposal such as the observed abundance of Lithium, but if such problems could be validly explained, it would still not be evidence to support expanding space.

If the universe expands from a hot dense state, nucleosynthesis results in the formation of atoms and the first freeing of photons. We have evidence for this in the background radiation, which has the most perfect black-body spectrum as would be expected in a universe that would have been a "perfect absorber" of light before this time.
This, again, is asserted evidence to support the BB model. That the background radiation is not just stellar radiation from galaxies, is a contention of the BB model. It, of course, is not evidence to support the expanding space hypothesis.

If the universe expands, it cools. We have evidence for this in measurements of the heating of distant gas clouds by the background radiation, in comparison to more local gas clouds.
This again, if valid, is asserted to support the BB model but not the expansion of space hypothesis.

If the universe expands, we should be able to see galaxies that were closer to us in the early universe with an apparent size that reflects their original distance, as their light is only just reaching us. We have evidence of this through the Tolman test for expansion.
I just looked up the Tolman test, which I hadn't heard of before. Although I think this can be explained by other cosmological models and redshift models.

From this link: Tolman surface brightness test - Wikipedia, the free encyclopedia

This quote seems less definitive: "The exponent found is not 4 as expected in the simplest expanding model, but 2.6 or 3.4, depending on the frequency band"....... But accordingly is consistent with the expanding universe model, but, I think, not necessarily evidence for the expansion of space.

If the universe expands, then the redshifting of distant objects is expected, along with cosmological time-dilation caused by that redshift. No other proposed source of redshift I know of can also account for that time-dilation. We have overwhelming evidence for both.
The redshift of galaxies might otherwise be explained. Time dilation can be explained by all redshift proposals which "stretch" out the light, providing for a longer lasting event.

35. Originally Posted by pmb
Originally Posted by forrest noble
[I am not aware of any other evidence other than redshifts, to support the expansion of space idea. Other hypothesis can equally explain redshifts, whereby there is no mechanism observed that can explain the expansion of space outside of hypothetical, that I can think of
The big bang model fits well together and there does not exist any other explanation to explain all the data simultaneously. I recall attempts at other explanations of redshift but everything I've seen so far fails in some other respect.

I'm curious. What are these "other hypotheses" that you mentioned? Please list a few.
These are a few of such proposals that I can recall:

There are many redshift proposals such as gravitational redshifts/ stretch theory, new versions of tired light that accordingly explain time dilation, diminution of matter theory, aether absorption theory, the Compton effect, dark energy stretching, dark matter stretching, EM radiation cross-stretching, matter absorption/ re-radiation loss of energy, etc. etc.

If you have never heard of some of them you can look them up, or I can explain them to you.

36. Originally Posted by SpeedFreek
The Big-Bang model, even if space is finite, cannot be used to find the totality of that space, as we can only relate it to our observable portion of a finite universe, and we do not know how much larger the finite universe is, when compared to our observable portion of it.
If we know what the rate of expansion has been at all previous epochs, and how long those epochs lasted, then wouldn't we be able to extrapolate the size of the universe (both observable and unobservable) from that?

We know the size it started at, don't we? (That being approximately 0)

Originally Posted by SpeedFreek
Originally Posted by forrest noble
The expansion of space hypothesis is solely based upon the observed galactic redshifts, which might be otherwise explained other than by the expansion of space.
Well, nobody has found an alternative explanation so far.
Not one anyone is willing to take seriously anyway.

37. Originally Posted by forrest noble
This, I agree is considered evidence for the BB model. ... it would still not be evidence to support expanding space.
...
This, again, is asserted evidence to support the BB model. ... It, of course, is not evidence to support the expanding space hypothesis.
...
This again, if valid, is asserted to support the BB model but not the expansion of space hypothesis.
Two points.

1. These comments are self-contradictory; if these observations support the big bang model then they also support expanding space. It is all part of the same thing.

2. You could come up with different ad-hoc explanations for each of these observations. You might even be able to make up explanations that are not incompatible and contradictory (although that is doubtful).

OR: you could use a single explanation for all of them.

Are you able to see why most people would prefer one explanation for all observations rather than separate (and probably contradictory) explanations for each?

38. Originally Posted by Strange
Originally Posted by forrest noble
This, I agree is considered evidence for the BB model. ... it would still not be evidence to support expanding space.
...
This, again, is asserted evidence to support the BB model. ... It, of course, is not evidence to support the expanding space hypothesis.
...
This again, if valid, is asserted to support the BB model but not the expansion of space hypothesis.
Two points.

1. These comments are self-contradictory; if these observations support the big bang model then they also support expanding space. It is all part of the same thing.
As you know, galaxies actually moving away from each other also supports observations. Some have proposed that the observable universe is expanding by moving away from each other, while other portions of the universe may be contracting, and still other volumes maintaining about the same density.

Evidence supporting a particular proposal like the expansion of the universe is not necessarily conclusive or certain. There is no evidence in particular, that I can think of, that specifically supports the expansion of space hypothesis, that could have no other explanation -- like the many given and other possible redshift explanations.

2. You could come up with different ad-hoc explanations for each of these observations. You might even be able to make up explanations that are not incompatible and contradictory (although that is doubtful).

OR: you could use a single explanation for all of them. Are you able to see why most people would prefer one explanation for all observations rather than separate (and probably contradictory) explanations for each?
The Big Bang model is presently the only consensus mainstream explanation for the above, but the James Webb is going up in a half-dozen years and we will see what happens after that.

39. Oh, this makes sense, so the Hubble constant depends on the size of the universe and the speed per megaparasec, so the universe is expanding at a faster rate all the time but the speed per mpc has decreased being that its expansion is spreading out?

40. Originally Posted by forrest noble
But accordingly is consistent with the expanding universe model, but, I think, not necessarily evidence for the expansion of space.
You seem to think the "expansion of space" and the expanding universe are different things. They are not.

[0707.0380] Expanding Space: the Root of all Evil?

While it remains the staple of virtually all cosmological teaching, the concept of expanding space in explaining the increasing separation of galaxies has recently come under fire as a dangerous idea whose application leads to the development of confusion and the establishment of misconceptions. In this paper, we develop a notion of expanding space that is completely valid as a framework for the description of the evolution of the universe and whose application allows an intuitive understanding of the influence of universal expansion. We also demonstrate how arguments against the concept in general have failed thus far, as they imbue expanding space with physical properties not consistent with the expectations of general relativity.
You seem to be suffering from the misconceptions the paper is talking about, and thinking that space itself is supposed to have its own property of expansion, which flies in the face of GR.

Stop thinking of the "expansion of space" as something different from the expansion of the universe.

41. Originally Posted by SpeedFreek
Originally Posted by forrest noble
But accordingly is consistent with the expanding universe model, but, I think, not necessarily evidence for the expansion of space.
You seem to think the "expansion of space" and the expanding universe are different things. They are not.

[0707.0380] Expanding Space: the Root of all Evil?
No, but it might seem that way. I think there is no evidence for either other than the observed galactic redshifts, that might otherwise be explained.

While it remains the staple of virtually all cosmological teaching, the concept of expanding space in explaining the increasing separation of galaxies has recently come under fire as a dangerous idea whose application leads to the development of confusion and the establishment of misconceptions. In this paper, we develop a notion of expanding space that is completely valid as a framework for the description of the evolution of the universe and whose application allows an intuitive understanding of the influence of universal expansion. We also demonstrate how arguments against the concept in general have failed thus far, as they imbue expanding space with physical properties not consistent with the expectations of general relativity.
You seem to be suffering from the misconceptions the paper is talking about, and thinking that space itself is supposed to have its own property of expansion, which flies in the face of GR.

Stop thinking of the "expansion of space" as something different from the expansion of the universe.
Yeah, I read this abstract when it was first published. I believe the BB model is entirely based upon the expansion of the universe model, which itself is entirely based upon the galactic redshift hypothesis being "proof" of this expansion. If it were somehow discovered that there was certainly another reason that was the source of galactic redshifts, I think the BB model would very quickly be "dumped." Many SS models would then be in competition to become the mainstream model.

42. Originally Posted by forrest noble
I think there is no evidence for either other than the observed galactic redshifts, that might otherwise be explained.
Whereas, there are several complementary lines of evidence. As has been explained already.

Yeah, I read this abstract when it was first published.
Maybe you should read more than the abstract.

I believe the BB model is entirely based upon the expansion of the universe model, which itself is entirely based upon the galactic redshift hypothesis being "proof" of this expansion.

If it were somehow discovered that there was certainly another reason that was the source of galactic redshifts, I think the BB model would very quickly be "dumped."
IF such a thing were discovered, then maybe. On the other hand, if that failed to explain all the other evidence it might not be considered very useful.

Many SS models would then be in competition to become the mainstream model.
Not necessarily. And of course, this is all hypothetical, as you like to say.

43. Originally Posted by forrest noble
I believe the BB model is entirely based upon the expansion of the universe model, which itself is entirely based upon the galactic redshift hypothesis being "proof" of this expansion.
Why do you repeat this when you were given a list in post 28?

44. Originally Posted by Harold14370
Originally Posted by forrest noble
I believe the BB model is entirely based upon the expansion of the universe model, which itself is entirely based upon the galactic redshift hypothesis being "proof" of this expansion.
Why do you repeat this when you were given a list in post 28?
I gave a point for point rebuttal to posting #28, in my posting #33. The point was that there is no evidence, that I have ever heard of, that the universe is expanding other than the hypothesis that galactic redshifts supposedly are evidence for the expansion of the space/universe. If expansion of the universe is the correct model, the universe should have been much more dense with galaxies in the past, which is contrary to observations. No matter how far back we look in time, the universe seems to have been about the same density or less, according to my research.

This thread asks about the expansion rate and the accelerated expansion rate of the universe, of which both ideas seem to be based upon meager evidence, in my opinion. Still, quantitative numbers can be given if the models and related formulations are correct.

45. Originally Posted by forrest noble
If expansion of the universe is the correct model, the universe should have been much more dense with galaxies in the past, which is contrary to observations. No matter how far back we look in time, the universe seems to have about the same density or less.
The model for the expanding universe actually does does predict a higher matter denser in the past. I doubt that there's no evidence for that. But you have to compensate for the fact that the further back in time you look the less chance there was for galaxies to form. The density is greater, you just can't see it from galaxy density. I'll have to look this up though but it sounds right. Its dangerous to make assuptions like the number of galaxies was a constant throughout time as you have assumed here though.

46. Originally Posted by Strange
Originally Posted by forrest noble
I think there is no evidence for either other than the observed galactic redshifts, that might otherwise be explained.
Whereas, there are several complementary lines of evidence. As has been explained already.

Yeah, I read this abstract when it was first published.
Maybe you should read more than the abstract.

I believe the BB model is entirely based upon the expansion of the universe model, which itself is entirely based upon the galactic redshift hypothesis being "proof" of this expansion.

If it were somehow discovered that there was certainly another reason that was the source of galactic redshifts, I think the BB model would very quickly be "dumped."
IF such a thing were discovered, then maybe. On the other hand, if that failed to explain all the other evidence it might not be considered very useful.

Many SS models would then be in competition to become the mainstream model.
Not necessarily. And of course, this is all hypothetical, as you like to say.
Yes, the BB model itself is clearly theory, but the expansion of space and of the universe, seems to be solely based upon the hypothesis that galactic redshifts equate with the universe's expansion, when a number of other hypothesis concerning the cause of redshifts, cannot be discredited. If so then the BB theory was built upon at least one hypothesis. Since GR can predict or support any condition of the universe, expansion, steady state, or contraction, if it turns out that the dark matter hypothesis is wrong, then GR would seemingly also be wrong and there would be no mathematical support or basis for the BB model either. That makes at least two hypothesis which seem to be part of the foundation of the BB model.

47. Originally Posted by pmb
Originally Posted by forrest noble
If expansion of the universe is the correct model, the universe should have been much more dense with galaxies in the past, which is contrary to observations. No matter how far back we look in time, the universe seems to have about the same density or less.
The model for the expanding universe actually does predict a higher matter denser in the past. I doubt that there's no evidence for that.
Do the online research now, or later. I think you will find no observations, at least none that I have ever heard of, that claim that the universe was denser in the past based upon their observations.

48. Originally Posted by forrest noble
I gave a point for point rebuttal to posting #28, in my posting #33.
Your rebuttals appeared to consist of agreeing that these were all evidence for the big bang theory.

The point was that there is no evidence, that I have ever heard of, that the universe is expanding other than the hypothesis that galactic redshifts supposedly are evidence for the expansion of the space/universe.
There are many separate lines of evidence supporting the expansion of the universe. See post #28, for a few of them.

49. Originally Posted by forrest noble
Yes, the BB model itself is clearly theory, but the expansion of space and of the universe, seems to be solely based upon the hypothesis that galactic redshifts equate with the universe's expansion
As has been explained hundreds of times now, that is not true.

, when a number of other hypothesis concerning the cause of redshifts, cannot be discredited.
I am not aware of any that have not been discredited. Also, the big bang model is the only one that explains all the data, not just red-shifts. (Why do I get a weird feeling of deja vu?)

50. Originally Posted by forrest noble
These are a few of such proposals that I can recall:

There are many redshift proposals such as gravitational redshifts/ stretch theory, new versions of tired light that accordingly explain time dilation, diminution of matter theory, aether absorption theory, the Compton effect, dark energy stretching, dark matter stretching, EM radiation cross-stretching, matter absorption/ re-radiation loss of energy, etc. etc.

If you have never heard of some of them you can look them up, or I can explain them to you.
If you'd like.

I will warn you that after so many years studying physics I've come to believe that, as a group, physicists are one clever bunch of SOBs and as such when given alternatives to existing theories they do consider them carefully. Not considering alternatives is a mistake I’ve never seen a physicist make, ever! That one thing I know as a profound truth in life.

Plus, Ihave a lot of my plate right now, such as overcomming this damn para-flu that's kicking my ass. I'm aslo proof reading a new edition of Exploring Black Holes. I found this thread of interest because lately I've been studying cosmology in full. And that's the next chapter of the text I'll be proof reading. So if you list all that stuff and explain it all please don't be too dissapointed if I don't follow it up, okay?

Have you considered the reasons given as to why those alternatives aren’t considered? I'm certain can be found online. After all, that's the first thing I'll do if I so choose.,

Also I'm getting old and tired and have little wish to debate things anymore. After doing this for well over a decade I find it to be a useless exercise. I see no reason for me to try to convince people of things which they don't believe. So I won't be trying to convince you of anything. Convincing has only one place in my life, and that's in any article I choose to sumbit to a journal or an explantion I give to someone who wants to learn the physics. Otherwise I'm getting too old or too lazy, or a combination of the two.

Thanks for the response.

51. Hey pmb,

"I can explain them to you." (my quote)

If you like.
You're a cool guy

There are many redshift proposals/ explanations such as gravitational redshifts/ stretch theory, new versions of tired light that accordingly explain time dilation, diminution of matter theory, aether absorption theory, the Compton effect, dark energy stretching, dark matter stretching, EM radiation cross-stretching, matter absorption/ re-radiation loss of energy, etc. etc.
These are the only redshift explanations that I know of but there are probably other cool possibilities for redshift mechanisms that I could not find or never heard of

The idea of gravitational redshifts is one of the oldest, it is also called Einstein redshifts. The idea is that gravity effects EM radiation and after millions and billions of years of traveling, the influence of gravity would stretch out EM radiation. Accordingly as EM radiation passes gravitational influences it becomes stretched out and redshifted.

Tired light is one of the oldest redshift explanation. The idea was that light as it travels through the eons loses energy becoming redshifted. This original model was discredited because of supernovas that were time dilated, and the losing of energy did not explain the observed longer lasting events of supernova, called time dilation. More modern versions propose that each wave loses energy as it travels, resulting in the same number of total but longer waves, lasting for a longer period of time.

The next concept is the diminution of matter over time. This is one of the models of "scaling theory." The idea is that matter was larger in size in the past and is steadily becoming smaller consistently. Larger atoms in the past would have produced longer wave lengths of EM radiation, while the scale of time would have been considered slower in the past. The most well-known diminution of matter model was proposed by Hoyle and Narlikar in the early 1960's. The first Scaling theory was the opposite. It was proposed by Paul Dirac in the late 1920's early 30's, whereby he proposed that both matter and space were expanding explaining the observed galactic redshifts.

Next is aether absorption theory to explain redshifts. The model requires an aether field something like dark matter particles. The idea is that EM radiation would interact with such aether like particulates that would absorb some the energy, causing the EM waves to become longer and redshifted, which generally would be based upon the distance traveled.
The Compton effect concerning redshifts proposed that electrons absorb EM radiation and re-radiate it at lower energy levels and longer wavelengths.

Dark energy stretching is a more modern explanation based upon dark energy stretching out and redshifting EM radiation over great distances. Dark matter stretching is based upon the idea the EM radiation does not interact with EM radiation. One idea is that dark matter takes up some space within EM waves, and over time stretches it out. Another idea involves dark matter currents that would stretch out EM radiation that was moving relative to it.

EM radiation cross-stretching is based upon the idea that over 100's of millions and billions of years EM radiation crosses through other EM radiation slowly stretching it out. Accordingly such a process would be based upon the distance traveled.

Matter absorption/ re-radiation: The idea is that matter when coming in contact with EM radiation will/can absorb it and re-radiate it at a longer wavelength and lesser frequency.

These are some of the redshift possibilities including some known effects, and others possibilities simply hypothesized. These known redshift processes/ effects are presently thought to have only a minor effect concerning galactic redshifts in general. The hypothetical processes have no certain evidence for their existence concerning galactic redshifts.

I'm sure there are other models that I did not find, or could not recall, that cannot easily be discredited

52. Originally Posted by forrest noble
Originally Posted by forrest noble
You're a cool guy

Thanks. I appreciate the sentiment.

These are the only redshift explanations that I know of but there are probably other cool possibilities for redshift mechanisms that I could not find or never heard of

In physics I tend only to believe what I see. If you’ve never heard of them then I’ll assume they don’t exist. Just because something explains something in an of itself doesn’t mean that it’s a proper description. It could conflict in other not so obvious ways.

Originally Posted by forrest noble
The idea of gravitational redshifts is one of the oldest, it is also called Einstein redshifts. The idea is that gravity effects EM radiation and after millions and billions of years of traveling, the influence of gravity would stretch out EM radiation. Accordingly as EM radiation passes gravitational influences it becomes stretched out and redshifted.
Originally Posted by forrest noble

That’s not an explanation because that’s not what gravitational redshift does. Light does not stretch out merely because its traveling for a long time. There must be a reason for it. Gravitational redshift is due to radiation climbing out of a gravitational well. The gravitational field does work on the light thus reducing its wavelength. This cannot be used to explain the redshift associated with galaxies

Originally Posted by forrest noble
Tired light is one of the oldest redshift explanation.
Originally Posted by forrest noble

I’m only interested in explanations which haven’t been discredited. I see no basis for saying “there are other explanations” and include those explanations which proved to be wrong.

Originally Posted by forrest noble
More modern versions propose that each wave loses energy as it travels, resulting in the same number of total but longer waves, lasting for a longer period of time.

Sorry but I don’t buy it. Falsyfying observations have been made which discredit tired light theories. See Tired light - Wikipedia, the free encyclopedia

Originally Posted by forrest noble
The next concept is the diminution of matter over time. This is one of the models of "scaling theory." The idea is that matter was larger in size in the past and is steadily becoming smaller consistently. Larger atoms in the past would have produced longer wave lengths of EM radiation, while the scale of time would have been considered slower in the past. The most well-known diminution of matter model was proposed by Hoyle and Narlikar in the early 1960's. The first Scaling theory was the opposite. It was proposed by Paul Dirac in the late 1920's early 30's, whereby he proposed that both matter and space were expanding explaining the observed galactic redshifts.
Originally Posted by forrest noble

That doesn’t sound viable even on a cursory look of it. E.g. an atom cannot be larger if the mass and charg of the electrons, protons and neutrons don’t change. And there’s no reason to assume they’d change with time. I seriously doubt that Dirac kept that idea throughout his life….

Etc.

Sorry but none of those sound viable at all. There are very good reasons none of those things are ever considered by modern cosmologists.

I'm sure there are other models that I did not find, or could not recall, that cannot easily be discredited
That kind of thing isn't worthy of being mentioned or discussed. Nobody can counter a opposition to "I'm sure one exists" so there's no reason to even think about it.

Thanks for taking your time and posting all of that. I can see that it took time and effort and that's what's appreciated. Thanks.

53. Originally Posted by pmb
Originally Posted by forrest noble
Originally Posted by forrest noble
You're a cool guy
Thanks. I appreciate the sentiment.

These are the only redshift explanations that I know of but there are probably other cool possibilities for redshift mechanisms that I could not find or never heard of

In physics I tend only to believe what I see. If you’ve never heard of them then I’ll assume they don’t exist. Just because something explains something in an of itself doesn’t mean that it’s a proper description. It could conflict in other not so obvious ways.

Originally Posted by forrest noble
The idea of gravitational redshifts is one of the oldest, it is also called Einstein redshifts. The idea is that gravity effects EM radiation and after millions and billions of years of traveling, the influence of gravity would stretch out EM radiation. Accordingly as EM radiation passes gravitational influences it becomes stretched out and redshifted.
Originally Posted by forrest noble
That’s not an explanation because that’s not what gravitational redshift does. Light does not stretch out merely because its traveling for a long time. There must be a reason for it. Gravitational redshift is due to radiation climbing out of a gravitational well. The gravitational field does work on the light thus reducing its wavelength. This cannot be used to explain the redshift associated with galaxies

Originally Posted by forrest noble
Tired light is one of the oldest redshift explanation.
Originally Posted by forrest noble
I’m only interested in explanations which haven’t been discredited. I see no basis for saying “there are other explanations” and include those explanations which proved to be wrong.

Originally Posted by forrest noble
More modern versions propose that each wave loses energy as it travels, resulting in the same number of total but longer waves, lasting for a longer period of time.
Sorry but I don’t buy it. Falsyfying observations have been made which discredit tired light theories. See Tired light - Wikipedia, the free encyclopedia

Originally Posted by forrest noble
The next concept is the diminution of matter over time. This is one of the models of "scaling theory." The idea is that matter was larger in size in the past and is steadily becoming smaller consistently. Larger atoms in the past would have produced longer wave lengths of EM radiation, while the scale of time would have been considered slower in the past. The most well-known diminution of matter model was proposed by Hoyle and Narlikar in the early 1960's. The first Scaling theory was the opposite. It was proposed by Paul Dirac in the late 1920's early 30's, whereby he proposed that both matter and space were expanding explaining the observed galactic redshifts.
Originally Posted by forrest noble
That doesn’t sound viable even on a cursory look of it. E.g. an atom cannot be larger if the mass and charg of the electrons, protons and neutrons don’t change. And there’s no reason to assume they’d change with time. I seriously doubt that Dirac kept that idea throughout his life…Etc..

Sorry but none of those sound viable at all. There are very good reasons none of those things are ever considered by modern cosmologists.

I'm sure there are other models that I did not find, or could not recall, that cannot easily be discredited

That kind of thing isn't worthy of being mentioned or discussed. Nobody can counter a opposition to "I'm sure one exists" so there's no reason to even think about it.

Thanks for taking your time and posting all of that. I can see that it took time and effort and that's what's appreciated. Thanks.
I have done personal research and strongly believe based upon more than one source that some of these are not only possible, but personally I believe one of these is the correct answer and that the universe is not expanding. The one that is the most well known is gravitational redshift. I think we can be certain that this happens to some extent.

The center of the sun is more redshifted that the corona, and in a distant galaxy cluster that we know is a group, the largest has a greater redshift but we strongly suspect that it is not farther away.

Tired light models require a medium like dark matter or an aether. It seems like a plausible mechanism to me. You can find several models online.

Scaling theories like the diminution of matter would absolutely explain redshifts as being caused by the change in scale of matter. If valid it would entirely change all of cosmology and much of physics. Based upon my studies some of such models cannot be disproved.

The dark energy and dark matter redshift models do not appeal to me, but I can't see how they can be disproved since we don't really know what either one is, or if either really exists.

Other redshift explanations seem more speculative to me. I would bet a six pack that the universe is not expanding at all because one of these alternative redshift explanations was the true reason for galactic redshifts, or another not mentioned. As I said before there is no other evidence that I have ever heard of that would indicate the universe is expanding, only the supposed "evidence" based upon galactic redshifts.

Cheers

54. Originally Posted by forrest noble
Based upon my studies some of such models cannot be disproved.
Not much of an endorsement there. You can't disprove my Santa-Claus-as-quantum-pink-unicorn theory, either. Doesn't make it valid.

On the other hand, there's a vast amount of interlocking data from a multitude of disciplines that have converged to give us the mainstream view that the universe is expanding. You can stick to your crackpot guns; I'll go with evidence.

55. Originally Posted by forrest noble
I have done personal research …
In what sense of the term? Did you do some calculations or observations of the universe or was it a study of the subject?

Originally Posted by forrest noble
and strongly believe based upon more than one source that some of these are not only possible, but personally I believe one of these is the correct answer and that the universe is not expanding. The one that is the most well known is gravitational redshift. I think we can be certain that this happens to some extent.
Okay. So you believe that gravitational redshift is responsible to some extent for the redshift of galaxies. Why do you believe it? In what way do you believe it? If you’re saying this then I’m assuming you believe that the universe is spatially flat? That galaxies aren’t moving other than a slight radom motion? If so then why? There’s nothing about the phenomena of gravitational redshift that would allow for it. You’re also saying that it fits all the data too. That’s a pretty complex set of data. To compare the redshift of all galaxies with your belief about gravitational redshift?

Originally Posted by forrest noble
The center of the sun is more redshifted that the corona, and in a distant galaxy cluster that we know is a group, the largest has a greater redshift but we strongly suspect that it is not farther away.
That’s a very poor analogy. Galaxies have their own spectrum and there’s no reason for our galaxy to have a different spectrum than other galaxies. It sounds to me like this is all qualitative. Have you actually tried to take the data and fit it towards your theory? Please be more specific. The source of the light coming from a galaxy is star light. In that light is certain spectra. It’s that spectra that is observed and measured. I have to admit here that I don’t know the details of the light coming from galaxies. The light is basically a superpopsition of all the light from all the stars. It seems odd that there should be one spectra that describes the entire galaxy and is the same for all galaxies.

Originally Posted by forrest noble
I would bet a six pack that the universe is not expanding at all because one of these alternative redshift explanations was the true reason for galactic redshifts, or another not mentioned.
Since that will never be proven nobody could win such a bet.

Originally Posted by forrest noble
As I said before there is no other evidence that I have ever heard of that would indicate the universe is expanding, only the supposed "evidence" based upon galactic redshifts.
And as I said, I have no wish to convert you.

Cheers.

Edit - This whole "expanding of space has always bugged me. I can vizualize it easily with a closed universe but not an open universe. I have trouble with what is meant by an exanding universe. If we have a flat surface and there are objects at rest on it initially. If all of a sudden that all start moving away from each other then I can picture that too. In this case the space isn't expanding but that the distance between the objects increase just as the distanc between me and my fridge will decrease when I go get a drink now. .......Hold please.......okay I'm back. But that didn't mean that the space between me and the chair was created when I walked away. It was there to begin with.

I looked in Schutz for this and found a warning.
Originally Posted by Shutz's text
It might be tempting to conclude from this that the cosmological expansion stretches space itself, just as our rubber-band universe was built out of stretching material. But this could be quite misleading from a physical point of view.
So I guess Schutzagrees with you to the extent that it's misleading from a physical point of view. More when I finish reading the chapter
SoSo That didn;t mea

56. Originally Posted by kojax
Originally Posted by SpeedFreek
The Big-Bang model, even if space is finite, cannot be used to find the totality of that space, as we can only relate it to our observable portion of a finite universe, and we do not know how much larger the finite universe is, when compared to our observable portion of it.
If we know what the rate of expansion has been at all previous epochs, and how long those epochs lasted, then wouldn't we be able to extrapolate the size of the universe (both observable and unobservable) from that?

We know the size it started at, don't we? (That being approximately 0)
It is not quite as simple as that.

Cosmology FAQ: How can the Universe be infinite if it was all concentrated into a point at the Big Bang?

The Universe was not concentrated into a point at the time of the Big Bang. But the observable Universe was concentrated into a point. The distinction between the whole Universe and the part of it that we can see is important.
What Ned Wright is saying here needs some explaining.

The "singularity" of the Big-Bang is found when we take our observations of the universe and rewind time back as far as we can. We come to a time when there is zero separation between everything in the observable universe - the observable universe was "concentrated into a point". But we don't know how much larger than our observable universe the whole universe is - it could even be infinite. The point he is making is that when we talk about the Big-Bang singularity we are only referring to our observable volume. We might infer from this that the there was zero separation across the whole universe, but not knowing the size of the whole universe relative to our observable volume means we cannot really include the whole universe in "our" singularity.

Or to put it another way:

If a universe can come from something that was once concentrated into a point, then what might limit how much stuff came from that point? We can use our observation limit as a guide, but we cannot impose an upper limit on the whole universe in the same way.

If you want to take the "something from nothing" angle (which I am not particularly fond of), then how much something can come from nothing? Can 100 times the amount of stuff in our observable universe come from nothing? Can an infinite something come from nothing?

57. pmb,

(my quote)
I have done personal research ....
In what sense of the term? Did you do some calculations or observations of the universe or was it a study of the subject?
I have been a alternative theorist in cosmology and theoretical physics for more than 50 years now. It's mostly a one-man dog and pony show but I do collaborate from time to time with other theorists and astronomers. I have written two papers of note. One explains why dark energy is unreal, while reformulating the Hubble formula. The other one concerns a collection of astronomical observations, whereby many of the most distant galaxies at a few hundred million years old, appear to be just as large and as old as the Milky Way galaxy.

You can see my papers here. http://pantheory.org/PDFs/technical-papers.pdf

Since that will never be proven nobody could win such a bet.
Like you said, some physicists, astronomers, and theorists are very clever. A few years after the James Webb is up, I suspect the BB model will try to at least double the age of the universe accordingly to their model. Soon their after new theories will replace the BB as being leading contenders. I think the James Webb will totally contradict the BB model, and it will be replaced soon thereafter.

Yeah, the whole expanding space thing is only about 20 years old, to my recollection. Before that it was theorized as simply galaxies moving away from each other.

My objection is not that "the redshift is caused by the expansion of the universe" seems as logical as some other explanations of galactic redshifts, it's that there is no other evidence that I known of that supports the expansion of the universe idea, and some evidence contradicts it. As I said before, an expanding universe would have been more dense in galaxies in the past, there is no such evidence. Instead by observation alone, the universe appears to have been equally as dense, or less dense in the past. If the universe is expanding, and because of the finite speed of light, distant galaxies would be very young and probably would have different characteristics than close-by galaxies, being small blue galaxies with much plasma forming new stars. Many distant galaxy observations look like the Milky Way and those in our local group.

We won't have to wait long to find out. The James Webb will have the capability to either prove of generally disprove the BB model, and do it quickly.

58. Originally Posted by forrest noble
The idea of gravitational redshifts is one of the oldest, it is also called Einstein redshifts. The idea is that gravity effects EM radiation and after millions and billions of years of traveling, the influence of gravity would stretch out EM radiation. Accordingly as EM radiation passes gravitational influences it becomes stretched out and redshifted.
Incorrect.

According to Einstein in General Relativity, gravitational redshift only occurs due to the difference in gravity between the source, and the detector. Any other gravitational influence the light passes on its journey has no net effect on the light, as the light is blueshifted on the way into the gravity well by the same amount as it is redshifted on the way out.

One might conclude that cosmological redshift was due to gravitational redshift if the universe itself used to be more gravitationally dense, however. But this would only be the case in an expanding universe! Unfortunately, that conclusion itself would be wrong too, as the difference in gravitational density across the universe would only account for a few percent of the overall cosmological redshift we measure.

Cosmolgical redshift cannot be gravitational redshift.

Originally Posted by forrest noble
Tired light is one of the oldest redshift explanation. The idea was that light as it travels through the eons loses energy becoming redshifted. This original model was discredited because of supernovas that were time dilated, and the losing of energy did not explain the observed longer lasting events of supernova, called time dilation. More modern versions propose that each wave loses energy as it travels, resulting in the same number of total but longer waves, lasting for a longer period of time.
Tired light has been completely ruled out.

"Tired-Light" Hypothesis Gets Re-Tired - ScienceNOW
[astro-ph/0106566] The Tolman Surface Brightness Test for the Reality of the Expansion. IV. A Measurement of the Tolman Signal and the Luminosity Evolution of Early-Type Galaxies

The HST data rule out the "tired light'' model at a significance level of better than 10 sigma.
Originally Posted by forrest noble
The next concept is the diminution of matter over time. This is one of the models of "scaling theory." The idea is that matter was larger in size in the past and is steadily becoming smaller consistently. Larger atoms in the past would have produced longer wave lengths of EM radiation, while the scale of time would have been considered slower in the past. The most well-known diminution of matter model was proposed by Hoyle and Narlikar in the early 1960's. The first Scaling theory was the opposite. It was proposed by Paul Dirac in the late 1920's early 30's, whereby he proposed that both matter and space were expanding explaining the observed galactic redshifts.
This is either entirely equivalent to universal expansion, but just using a different coordinate system where our rulers shrink over time and as such would make no predictions of any observations that the current cosmology wouldn't itself make (sophistry, in other words), or if we take Narlikars steady-state version we have no mechanism to explain the cosmic microwave backround.

Originally Posted by forrest noble
Next is aether absorption theory to explain redshifts. The model requires an aether field something like dark matter particles. The idea is that EM radiation would interact with such aether like particulates that would absorb some the energy, causing the EM waves to become longer and redshifted, which generally would be based upon the distance traveled.
The Compton effect concerning redshifts proposed that electrons absorb EM radiation and re-radiate it at lower energy levels and longer wavelengths.
This model completely fails to explain cosmological time-dilation whilst keeping images of distant events in a coherent form.

Imagine, as an exaggerated example for the purposes of illustration, a stream of light emitted as a 1 second burst, with a 1 second gap before the next 1 second burst. How would the medium manage to keep the gaps between the bursts the same length as the bursts themselves, but scale the whole thing up? Surely the next burst would have already arrived before the medium had finished delaying the first? Or does the medium also increase the gaps where there is no interaction?!

If we think in terms of photons instead of waves, how does the medium "know" to progressively delay each subsequent photon a little more than the one before, and also preserve the ordering of events?

Our observations of the time-dilations in distant supernovae would seem to preclude this model.

Originally Posted by forrest noble
Dark energy stretching is a more modern explanation based upon dark energy stretching out and redshifting EM radiation over great distances.
Dark energy? What?! The stuff that causes an acceleration of the expansion of the universe? Are you sure you aren't just making these up?

Originally Posted by forrest noble
Dark matter stretching is based upon the idea the EM radiation does not interact with EM radiation. One idea is that dark matter takes up some space within EM waves, and over time stretches it out. Another idea involves dark matter currents that would stretch out EM radiation that was moving relative to it.
Same problem as aether absorption. No mechanism for cosmological time-dilation without loss of coherence.

Originally Posted by forrest noble
EM radiation cross-stretching is based upon the idea that over 100's of millions and billions of years EM radiation crosses through other EM radiation slowly stretching it out. Accordingly such a process would be based upon the distance traveled.
Same problem again.

Originally Posted by forrest noble
Matter absorption/ re-radiation: The idea is that matter when coming in contact with EM radiation will/can absorb it and re-radiate it at a longer wavelength and lesser frequency.
Tired light by another name. Same problem again (no time-dilation), but with associated scattering issues.

As far as I know, ALL your alternatives have been ruled out or discounted. Do you have any actual sources that say otherwise?

59. Originally Posted by forrest noble
Yeah, the whole expanding space thing is only about 20 years old, to my recollection. Before that it was theorized as simply galaxies moving away from each other.
Incorrect.

It has always been "expanding space", since Lemaitre first proposed it in the early 1930's. That's what metric expansion means.

If you don't believe me, read this:

Blast of Giant Atom Created Our Universe | Modern Mechanix
(Popular Science Magazine, Published in December 1932, scans at that link, showing the text below)

Why, astronomers have asked, are the more distant objects moving faster? Why does the motion always seem to be away from us? If the motion is one of simple expansion, why should we find ourselves so nearly at the center, looking outward? Exponents of the theory of relativity have been inclined to accept the view that the universe is actually expanding. But the apparent central position of our earth, they believe, is an illusion, that may be illustrated by an analogy. Suppose that, during the night, the earth were to double in size, while everything upon its surface were to remain unchanged. In the morning you would awake to find that your neighbor, who previously lived only fifty feet away, was now one hundred feet away. The Smiths, who lived a mile away, would be two miles away. In every direction, there would be an apparent withdrawal, which would be greater for more distant objects. Everybody would be similarly affected and each would believe himself to be the center away from which the other objects had moved.

The case of the universe is analogous, except that the expansion, being of a three-dimensional volume, cannot be visualized. The phenomena are, however, comparable. The nebulae are not running away from us. Their recession is due to expansion of space. This may, perhaps, seem to be quibbling over terms, since it amounts to the same thing in the end. Nevertheless, the distinction is worth keeping. According to the relativity theory, there is a difference between the running away of the nebulae and expansion of the medium in which they are imbedded.
See? That's from 1932.

You really should be careful, as you are spreading misconceptions left, right and centre in this thread.

That old article is actually a really interesting read.

60. Originally Posted by SpeedFreek
Originally Posted by forrest noble
The idea of gravitational redshifts is one of the oldest, it is also called Einstein redshifts. The idea is that gravity effects EM radiation and after millions and billions of years of traveling, the influence of gravity would stretch out EM radiation. Accordingly as EM radiation passes gravitational influences it becomes stretched out and redshifted.
Incorrect.
According to Einstein in General Relativity, gravitational redshift only occurs due to the difference in gravity between the source, and the detector. Any other gravitational influence the light passes on its journey has no net effect on the light, as the light is blueshifted on the way into the gravity well by the same amount as it is redshifted on the way out.

One might conclude that cosmological redshift was due to gravitational redshift if the universe itself used to be more gravitationally dense, however. But this would only be the case in an expanding universe! Unfortunately, that conclusion itself would be wrong too, as the difference in gravitational density across the universe would only account for a few percent of the overall cosmological redshift we measure.

Cosmolgical redshift cannot be gravitational redshift.

Originally Posted by forrest noble
Tired light is one of the oldest redshift explanation. The idea was that light as it travels through the eons loses energy becoming redshifted. This original model was discredited because of supernovas that were time dilated, and the losing of energy did not explain the observed longer lasting events of supernova, called time dilation. More modern versions propose that each wave loses energy as it travels, resulting in the same number of total but longer waves, lasting for a longer period of time.
Tired light has been completely ruled out.

"Tired-Light" Hypothesis Gets Re-Tired - ScienceNOW
[astro-ph/0106566] The Tolman Surface Brightness Test for the Reality of the Expansion. IV. A Measurement of the Tolman Signal and the Luminosity Evolution of Early-Type Galaxies

The HST data rule out the "tired light'' model at a significance level of better than 10 sigma.
Originally Posted by forrest noble
The next concept is the diminution of matter over time. This is one of the models of "scaling theory." The idea is that matter was larger in size in the past and is steadily becoming smaller consistently. Larger atoms in the past would have produced longer wave lengths of EM radiation, while the scale of time would have been considered slower in the past. The most well-known diminution of matter model was proposed by Hoyle and Narlikar in the early 1960's. The first Scaling theory was the opposite. It was proposed by Paul Dirac in the late 1920's early 30's, whereby he proposed that both matter and space were expanding explaining the observed galactic redshifts.
This is either entirely equivalent to universal expansion, but just using a different coordinate system where our rulers shrink over time and as such would make no predictions of any observations that the current cosmology wouldn't itself make (sophistry, in other words), or if we take Narlikars steady-state version we have no mechanism to explain the cosmic microwave backround.

Originally Posted by forrest noble
Next is aether absorption theory to explain redshifts. The model requires an aether field something like dark matter particles. The idea is that EM radiation would interact with such aether like particulates that would absorb some the energy, causing the EM waves to become longer and redshifted, which generally would be based upon the distance traveled.
The Compton effect concerning redshifts proposed that electrons absorb EM radiation and re-radiate it at lower energy levels and longer wavelengths.
This model completely fails to explain cosmological time-dilation whilst keeping images of distant events in a coherent form.

Imagine, as an exaggerated example for the purposes of illustration, a stream of light emitted as a 1 second burst, with a 1 second gap before the next 1 second burst. How would the medium manage to keep the gaps between the bursts the same length as the bursts themselves, but scale the whole thing up? Surely the next burst would have already arrived before the medium had finished delaying the first? Or does the medium also increase the gaps where there is no interaction?!

If we think in terms of photons instead of waves, how does the medium "know" to progressively delay each subsequent photon a little more than the one before, and also preserve the ordering of events?

Our observations of the time-dilations in distant supernovae would seem to preclude this model.

Originally Posted by forrest noble
The next concept is the diminution of matter over time. This is one of the models of "scaling theory." The idea is that matter was larger in size in the past and is steadily becoming smaller consistently. Larger atoms in the past would have produced longer wave lengths of EM radiation, while the scale of time would have been considered slower in the past. The most well-known diminution of matter model was proposed by Hoyle and Narlikar in the early 1960's. The first Scaling theory was the opposite. It was proposed by Paul Dirac in the late 1920's early 30's, whereby he proposed that both matter and space were expanding explaining the observed galactic redshifts.
This is either entirely equivalent to universal expansion, but just using a different coordinate system where our rulers shrink over time and as such would make no predictions of any observations that the current cosmology wouldn't itself make (sophistry, in other words), or if we take Narlikars steady-state version we have no mechanism to explain the cosmic microwave background.

Yes, relatively speaking the diminusion of matter hypothesis is the same as the expanding space hypothesis, but in an absolute sense it would be very different. Such models would have a least two variations. Some propose the creation of new matter from the field discards of old matter which would be becoming smaller, like Hoyle Narlikar's SS models. The universe would then look very different in the past. The density would be relatively constant, but distant matter and galaxies would have been larger and older like the Milky Way. Without this new matter creation mechanism the distant universe would appear like the BB model proposes, but the universe would not be expanding and therefore would likely be much older or infinite in age, and some distant galaxies would as old as the Milky Way.

Originally Posted by forrest noble
Dark energy stretching is a more modern explanation based upon dark energy stretching out and redshifting EM radiation over great distances.
Dark energy? What?! The stuff that causes an acceleration of the expansion of the universe? Are you sure you aren't just making these up?

Originally Posted by forrest noble
Dark matter stretching is based upon the idea the EM radiation does not interact with EM radiation. One idea is that dark matter takes up some space within EM waves, and over time stretches it out. Another idea involves dark matter currents that would stretch out EM radiation that was moving relative to it.
Same problem as aether absorption. No mechanism for cosmological time-dilation without loss of coherence.
Originally Posted by forrest noble
EM radiation cross-stretching is based upon the idea that over 100's of millions and billions of years EM radiation crosses through other EM radiation slowly stretching it out. Accordingly such a process would be based upon the distance traveled.
Same problem again.

Mechanisms that propose stretching of EM waves provide for time dilation. Tired light models that propose energy loss alone, cannot account for time dilation.

Originally Posted by forrest noble
Matter absorption/ re-radiation: The idea is that matter when coming in contact with EM radiation will/can absorb it and re-radiate it at a longer wavelength and lesser frequency.
Tired light by another name. Same problem again (no time-dilation), but with associated scattering issues.
Yes, there are additional scattering issues, but a galactic or inter-galactic cloud will tend to re-radiate along the same line of its EM absorption, if primarily singular.

As far as I know, ALL your alternatives have been ruled out or discounted. Do you have any actual sources that say otherwise?
There is no direct evidence to support any of these hypothesis, nor is there conclusive evidence to support that redshifts relate to the expansion of the universe either, to my knowledge. And no certain consensus hypothesis or opinion to explain why the universe is supposedly still expanding, to my knowledge. There is however contradictory evidence in that the distant universe does not appear to have been more dense in galaxies in the past, and some of the most distant galaxies appear to be very old.

Cheers

61. Originally Posted by forrest noble
There is no direct evidence to support any of these hypothesis
Correct. And there are good reasons to say they are wrong (as noted above). So why bring up a load of unsupported and obviously wrong "explanations"? Why do you keep dragging the same old nonsense into serious discussions? Please stop it.

nor is there conclusive evidence to support that redshifts relate to the expansion of the universe either, to my knowledge.
There are mountains of diverse types of evidence fr this. As has been explained to you many, many times. And then you complain when you are accused of ignorance.

Please stop dragging every thread about cosmology down to the sewers of your ignorance. (And you might want to fix the quote tags in your post; currently it looks like you wrote something intelligent).

62. There are mountains of diverse types of evidence fr this. As has been explained to you many, many times. And then you complain when you are accused of ignorance.
I do not believe any spicific evidence that supports the expansion of the universe, other than galactic redshifts exists, which cannot be better explained in another way.

There is just one point to all of this; there is much speculation involved with mainstream cosmology, whereby definitive non-specualtive scientific answers to the OP question cannot be given, in my opinion, without the appropriate qualifications and disclaimers

The End. I think I have now said all that I wished to say on this subject

63. Originally Posted by forrest noble
The End. I think I have now said all that I wished to say on this subject
I wish that I could believe you, but history unfortunately suggests that you will continue to post your unsupported nonsense again and again.

64. Originally Posted by forrest noble
I do not believe ...
Why should anyone care what you believe when you have repeatedly admitted being ignorant of the evidence (depsite having it waved in front of your face).

galactic redshifts exists, which cannot be better explained in another way.
Even if that were all there was, that by definition would be enough to make it the best theory we have.

There is just one point to all of this; there is much speculation involved with mainstream cosmology, whereby definitive non-specualtive scientific answers to the OP question cannot be given, in my opinion, without the appropriate qualifications and disclaimers
Utter bollocks.

The End. I think I have now said all that I wished to say on this subject
If only.

65. Originally Posted by forrest noble
The End. I think I have now said all that I wished to say on this subject
Will you not even acknowledge you were completely wrong when you said
Yeah, the whole expanding space thing is only about 20 years old, to my recollection. Before that it was theorized as simply galaxies moving away from each other.
considering the popular science article from 1932, that I linked to and quoted from in post #58?

66. Originally Posted by SpeedFreek
Originally Posted by forrest noble
The End. I think I have now said all that I wished to say on this subject
Will you not even acknowledge you were completely wrong when you said
Yeah, the whole expanding space thing is only about 20 years old, to my recollection. Before that it was theorized as simply galaxies moving away from each other.
considering the popular science article from 1932, that I linked to and quoted from in post #58?
To my recollection, is just that. If you have evidence that they began proposing the expansion of space as the mainstream consensus hypothesis, longer ago than about 20 years ago, then my recollection might have been off imagine that

1932 was about the time that this expanding space hypotheses was proposal by Paul Dirac. At the same time he also proposed that matter was also expanding at the same rate

67. Originally Posted by forrest noble
To my recollection, is just that. If you have evidence that they began proposing the expansion of space as the mainstream consensus hypothesis, longer ago than about 20 years ago, then my recollection might have been off imagine that

Typical dishonest dodge, Forrest. Not surprising, but disappointing nonetheless. You have shifted goalposts, now adding the qualifier "mainstream consensus" that was not present earlier. Why can't you just be HONEST and 'fess up? Yeah, so you were talking about your recollection. So what? Your recollection was just plain wrong. SpeedFreek generously offered a correction.

You just look more and more crackpotty with each denial, especially when a full record of the exchange is in public view. Speedfreek presented the evidence in the form of a Popular Science article. You can't claim that the idea was thus buried in some obscure journal accessible only to a select few.

Jeebus.

68. This is either entirely equivalent to universal expansion, but just using a different coordinate system
No, that is not true. The difference is that the expanding universe leaves matter and the dynamics of the fundamental forces untouched, whereas the condensing matter models require a scaling of the force laws. And here's the problem - while you can make it work with just gravity and EM, neither the weak nor the strong force scale very well !

69. Originally Posted by forrest noble
To my recollection, is just that. If you have evidence that they began proposing the expansion of space as the mainstream consensus hypothesis, longer ago than about 20 years ago, then my recollection might have been off
Need a hand with those goalposts?

70. Originally Posted by Devon Keogh
I have one question:

If the universe is expanding at the Hubble constant, then how fast is the universe speeding up its expansion?
Perhaps expansion is a relative spatial geometry. It may just be an illusion caused by stretching the fabric of spacetime.

This may shed some light.

NOVA | The Fabric of the Cosmos

This presents a curious situation which seems contradictory to me.

My questions:
a) If rate of expansion (Hubble) is due to speed (SOL) or actually expanding spacetime geometry itself?
b) Then also, if the rate of expansion is increasing, how can we end up with a cold, dark, static (almost) emptiness?
c) And finally, is there any cosmic law that forbids universal expansion/contraction into itself?

Visualize a 2 Dimensional membrane along the outside of a doughnut shaped cosmos, where the coordinates actually expand in all directions toward the largest possible size along the equator of the doughnut.
Once past the equator, the spacetime coordinates will begin to shorten and the universe would shrink toward the doughnut hole at the "other side". Eventually all of universal potential and space will be compressed back into a singularity and boom......BB

This would avoid all those other contradictions of speed, acceleration, expansion, and size. I think it is elegant.

p.s. I wonder if "darkness" (absence of energy) has more or less mass than "lightness" (absence of matter). That would explain a lot. Is there a quantative difference in rest mass and relative mass?

71. Originally Posted by Write4U
a) If rate of expansion (Hubble) is due to speed (SOL) or actually expanding spacetime geometry itself?
Note that it is space that is expanding; spacetime is a static thing (after all, it inlucdes time as one of its dimensions so it can't change over time).

c) And finally, is there any cosmic law that forbids universal expansion/contraction into itself?
If anything, the reverse. Expansion (or contraction) is pretty much required by GR. A static universe would require incredibly finely balanced parameters, rather like trying to stand a pencil on its point.

72. Originally Posted by Markus Hanke
This is either entirely equivalent to universal expansion, but just using a different coordinate system
No, that is not true. The difference is that the expanding universe leaves matter and the dynamics of the fundamental forces untouched, whereas the condensing matter models require a scaling of the force laws. And here's the problem - while you can make it work with just gravity and EM, neither the weak nor the strong force scale very well !
Good point! That would seem to be the nail in the coffin of that particular alternative then.

73. Originally Posted by SpeedFreek
Good point! That would seem to be the nail in the coffin of that particular alternative then.
Yes, more than likely, even though the calculations required to confirm what happens during such a scaling of the weak & strong forces are beyond my abilities, so I can't present them here. It has been done though, just can't find the source right now.