[Dave Lev (OP)]

Because distance is also relative. Ever heard of length contraction?

So, relative velocity / distance means real velocity /distance.
Two examples -
1. We look at a picture of a small boy standing at the front while the biggest elephant in the planet is somewhere in the background. We can see that in this photo the Boy is relatively bigger than the elephant.
So, does it mean that the boy is really bigger than this elephant?
2. Let's assume that there are 1001 point in a row in space that are all moving in the same direction.
Each one is moving at 0.9c with reference to the one before.
Therefore, there are 1000 segments where in each segment the distance is increasing by 0.9c T.
Due to the relatively velocity law, the first one can still observe the last one as their relative velocity must be less than the speed of light.
I must say that it is very difficult for me to accept the idea that also in this case the real distance between the two ends of this raw (with 1000 segments in between) is increasing at the maximum by only c(almost) * T .

The distances between those different objects for any given moment of time is going to differ between reference frames

Why can't we use one single frame (the Universe frame) to all?

In any case, as your message is clear and there is nothing for me to change this message, there is no need to continue the discussion about this issue.

[Kryptid]

1. We look at a picture of a small boy standing at the front while the biggest elephant in the planet is somewhere in the background. We can see that in this photo the Boy is relatively bigger than the elephant.
So, does it mean that the boy is bigger than this elephant?

False analogy. Relativity is about actual changes in distance, not illusory changes caused by perspective.

Therefore, there are 1000 segments where in each segment the distance is increasing by 0.9c T.

That would be viable if you are saying, from the reference frame of each individual segment, that it sees the next segment in the line moving away from it at 0.9c. However, you can't say that the first segment in the line sees each subsequent segment moving at 0.9c away from every segment that preceded it. That would mean that each segment was moving at 0.9c, 1.8c, 2.7c, etc. in its reference frame, which would violate special relativity.

However, I must say that it is very difficult for me to accept that idea that also in this case the real distance between the two ends of this raw (with 1000 segments in between) is increasing at the maximum by only c(almost) * T .

The speed of light is the upper limit to movement through space, so that's all it can increase by. Length contraction and time dilation is how that problem is solved.

[Dave Lev (OP)]

The speed of light is the upper limit to movement through space, so that's all it can increase by.

When you say "space" do you mean the entire space - even if it is infinite?
Is there any possibility to claim that?
"The speed of light is the upper limit to movement through "any local space"?
Therefore, let's look again at the following image:
https://www.researchgate.net/figure/The-Hubble-diagram-or-the-velocity-distance-relation-plot-for-type-Ia-supernovae_fig1_331983227
We are located at the red dot in this graph.
As we move further away, the velocity of the galaxies is increasing almost linearity.
However, nothing around any point can move faster than the speed of light up to the maximal distance (let's call it P1) in this graph.
Now, do you agree that if we jump to that P1 (or n times P1), we should see a very similar linear graph?
So, why can't we understand that at any point (up to the infinity) all the galaxies there should move at low velocity with reference to each other (local space), however, due to the linearity at some far away space (or different space time) the velocity with reference to our location should be higher than c?

[Kryptid]

When you say "space" do you mean the entire space - even if it is infinite?

Yes.

Is there any possibility to claim that?

Yes.

"The speed of light is the upper limit to movement through "any local space"?

Not "local" space. Just space in general.

However, nothing around any point can move faster than the speed of light up to the maximal distance (let's call it P1) in this graph.

Distance doesn't matter, so I don't know why you are claiming this.

Now, do you agree that if we jump to that P1 (or n times P1), we should see a very similar linear graph?

Your "P1" doesn't exist on the graph because it doesn't make sense.

Now, do you agree that if we jump to that P1 (or n times P1), we should see a very similar linear graph?
So, why can't we understand that at any point (up to the infinity) all the galaxies there should move at low velocity with reference to each other (local space), however, due to the linearity at some far away space (or different space time) the velocity with reference to our location should be higher than c?

Because that violates special relativity. No two objects can move relative to each other through space faster than light.

[Dave Lev (OP)]

Because that violates special relativity. No two objects can move relative to each other through space faster than light.

OK
We have actually two messages that contradicts each other:

1. Relative velocity -
This is clear. Nothing can move faster than c.

2. Observation:
We clearly observe that the following graph is linear:
https://www.researchgate.net/figure/The-Hubble-diagram-or-the-velocity-distance-relation-plot-for-type-Ia-supernovae_fig1_331983227
Due to the symmetric of the Universe don't you agree that it should continue to be linear up to the infinity?
If so - the Observation tells us that at some distance the velocity with reference to our location should be higher than c.

However, I assume that relativity wins.
This issue is clear

[Dave Lev (OP)]

Once we close the discussion about relativity, let's move on to the following image:
https://en.wikipedia.org/wiki/Hubble%27s_law#/media/File:Hubble_constant.JPG
We see that all the galaxies sit very nicely on the linear graph.
However, suddenly at the Virgo cluster (15MPC) we clearly observe severe dispersion in the velocities.
Do you have any idea for the source of this dispersion in the velocities?

[Kryptid]

You are, once again, confusing moving through space faster than light with receding faster than light due to spatial expansion. The first one violates special relativity, whereas the second one does not. They are not the same thing.

[Origin]

However, suddenly at the Virgo cluster (15MPC) we clearly observe severe dispersion in the velocities.
Do you have any idea for the source of this dispersion in the velocities?

Yes.  It takes about 2 minutes to look it up on google.

[Bored chemist]

You are, once again, confusing moving through space faster than light with receding faster than light due to spatial expansion. The first one violates special relativity, whereas the second one does not. They are not the same thing.

Dave has been doing that since he joined the forum.

[evan_au]

1.  Why can't we ask about the time before the bang? Why do we need to start from that point?

A bit of speculation...

We are, by now, fairly familiar with black holes (we now have seen the shadow cast by two of them).
- Matter entering the event horizon is on a 1-way trip into the singularity.
- Once matter has reached the singularity, it is not meaningful to extrapolate backwards to where it came from

The theory that predicts black holes also allows for "White Holes" - but we haven't seen any examples in our galaxy.
- But maybe the Big Bang has some characteristics of a white hole?
- Matter leaving the big bang is on a 1-way trip out of the singularity.
- Once matter has left the singularity, it is not meaningful to extrapolate backwards to where it came from

[Dave Lev (OP)]

- Matter entering the event horizon is on a 1-way trip into the singularity.
- Once matter has reached the singularity, it is not meaningful to extrapolate backwards to where it came from

- Matter leaving the big bang is on a 1-way trip out of the singularity.
- Once matter has left the singularity, it is not meaningful to extrapolate backwards to where it came from

Why do you claim that it is not meaningful to extrapolate backwards to where it came from???
In my understanding, that is THE most important issue in the entire universe.

The rest of this post was moved onto page 23(!) of another of Dave's threads: "Theory D - The Ultimate Theory for the Universe", since it merely repeats previous questions about the structure of galaxies - mod
https://www.thenakedscientists.com/forum/index.php?topic=79004

[Bored chemist]

Why do you claim that it is not meaningful to extrapolate backwards to where it came from???

OK, it's a fair question.
Imagine I have a doubling machine, if you put  a number into it, the machine spits out twice that number.
If I put 3 into it I get 6
I can extrapolative backwards- if the number 10 comes out of the machine, I can say that the number 5 must have gone into it.

If I also have a machine that multiplies by 3 I can do the same sort of thing.
If I see that 21 has come out, I can deduce that the number 7 went into it

But if I have a machine that multiplies by zero I can't do that.
It doesn't matter if I put 3,5,7, or any other number into it, the output is always zero.

So I can't extrapolate backwards from the output to calculate the input.
While the concept of infinity is a bit complicated mathematically, you can see how a "multiply by infinity" machine has the same property; it trashes the input data.

Passing through a singularity multiplies all the measurements by either zero or infinity.

That's why  you can't calculate back past it.

That's not the same as extrapolating back to very near the singularity. We can do that quite well.

[Dave Lev (OP)]

Quote from: Dave Lev on Today at 07:05:53
Why do you claim that it is not meaningful to extrapolate backwards to where it came from???

OK, it's a fair question.

Thanks

But if I have a machine that multiplies by zero I can't do that.
It doesn't matter if I put 3,5,7, or any other number into it, the output is always zero.

This isn't the case with regards to the SMBH.
The input (stars that falls in) is absolutely ZERO. Out of the billions SMBH, we can't detect even one falling star.
However, the output ( the accretion disc) is full with matter and we clearly observe that this matter is ejected outwards.

Therefore, it is not that we can't see the output.
The reality is that we don't see any input while we clearly see the output!

Our scientists estimate that the far away quasar eats about 25 stars per year (or about one star per two weeks):

https://www.space.com/most-distant-quasar-discovery-giant-black-hole
"In fact, scientists estimate that, on average, this particular quasar's black hole ingests an amount of mass equivalent to 25 suns every year."
Hence, on average, this particular quasar's black hole ingests an amount of mass equivalent to one sun every two weeks.
We have supper advanced technology.
We can detect stars at the most-distant-galaxy (at a similar distance as this quasar) and even verify their structure.
So, how could it be that after observing that quasar for quite long time, we didn't observe even one tinny star as it falls inwards with amazing fireworks?

So far they didn't detect even one falling star. Not in this quasar and not in any SMBH in the entire Universe.
Therefore, when we discuss about how the SMBH works and what is not meaningful - it is our obligation to first verify that your understanding (or misunderstanding) is correct or incorrect.

[Kryptid]

This thread is starting to look more and more like your Theory D thread. That's a problem because it would count as an evasion of the closing of the original thread. Let's not do that.

[Halc]

- But maybe the Big Bang has some characteristics of a white hole?
- Matter leaving the big bang is on a 1-way trip out of the singularity.

This doesn’t work.  A white hole, like a black one, is a massive differene in gravitational potential near a location in space, while BBT describes a flat universe with uniform potential everywhere with minor local variations forming over time.

The formula is as follow:u = (v+u') / (1+ vu'/c^2)

The formula for relative velocity is 100% correct.

It is not. It is a simplified case, applicable only to inertial frames, and applicable only to addition of parallel velocities. The full equation allows addition of velocity vectors in general.

However, don't forget that Einstein had called it the "relative" velocity and not the "real" velocity.

In all the subsequent posts you do not define what you mean by 'real' velocity or distance or whatever as is distinct from velocity. So all the twaddle that follows is meaningless.
As Kryptid says, all velocity is by definition relative, and all of it real. So there is no distinction.

1. What is the distance formula?
Is it:
S = V T

There no one 'the distance formula'. The one you give works for the change in location for an unaccelerated object. V and T are coordinate system dependent, and thus so is distance. Far galaxies do not recede at constant velocity, so the formula is entirely inappropriate for galaxies except for short durations of time.

What is the real distance that B moved away from A at a given time T?

Zero of course. A given time T is but a moment, and no change in location can occur at an instant.
If you're asking the distance B moved away from A over a period of time T, it depends on the velocity curve over that time, and the velocity at a given time is coordinate system dependent.

4. What is the real distance that C moved away from A at a given time T
Is it:
Sca = Sba + Scb = v T + u' T = (v + u') T

No. You're adding distances computed in different frames, which is invalid for inertial frames. You know this, but you continue to troll this nonsense.

Where is the error in this calculation?

Your errors have been pointed out in several posts prior to this one, and yet you ignore it all.

You [Halc] clearly claim that Cosmological coordinates are not inertial, and the formula is different.
So, why we can't assume that based on the Cosmological coordinates we get the real velocity?

I don't know what you think 'real velocity' is, so the question, and others like it, are meaningless.

His formula tells us that even if the far away object (C) is moving away at real velocity - u (real) -  which is higher than the speed of light, the Observer A would still be able to see it as the relative velocity is:
u (relative) = (v+u') / (1+ vu'/c^2)
Therefore, we clearly observe galaxies that are moving away at velocities that are greater than c.

You are mixing values from different coordinate systems, which makes all this entirely wrong.

Sorry, it isn't a sum of velocities but sum of distances.
Where is it stated that it isn't allowed to sum distances?

You are summing inertial distances computed in different inertial frames, which is neglecting the necessary frame transforms. You did not express the distances in cosmic coordinates, but if you did, then you can simply add them like that so long as they are both distances at the same time. Also, remember that these are vector quantities and must use vector addition.

I assume that "Inertial" frames means - relative.

That's not what that means. "Inertial" means that the observer is not accelerating.

If one is not properly accelerating in one kind of frame (intertial), one is also not accelerating in any other kind of frame (Rindler, Cosmological, rotating, etc) so no objective fact distinguishes the different abstract coordinate system types.

An inertial frame (1st CS) is a fixed (not changing over time) set of rectilinear coordinates in Minkowskian spacetime that has arbitrary orientation of the axes. It is the property of Minkowskian spacetime that necessitates the Lorentz transforms whenever rotating the axes between frames. I'm sure there's a better definition than that somewhere, but I'm trying to hit the points relevant to this topic.
Cosmic coordinates are not rectilinear, but are absolute. One cannot rotate the coordinates. With proper distance CS (2nd CS), different transforms are used to change the spatial origin from one location to another. With comoving coordinates (3rd CS), even that is not needed.

We can see that in this photo the Boy is relatively bigger than the elephant.

We can see that the boy subtends a larger angle in the  camera’s field of view. That by no means implies the boy is larger.

[/quote]Let's assume that there are 1001 point in a row in space that are all moving in the same direction.
Each one is moving at 0.9c with reference to the one before.[/quote]An inertial description.
Therefore, there are 1000 segments where in each segment the distance is increasing by 0.9c T.[/quote]No frame specified, so wrong.

Due to the relatively velocity law, the first one can still observe the last one as their relative velocity must be less than the speed of light.

In Minkowskian spacetime, yes. This would be true regardless of the coordinate system used to express distances and speed and such. But you can do this with galaxies and can only see the first one or two, partly because the more distant ones have not always been emitting light, and more importantly, the universe at large scale isn’t Minkowskian.

I must say that it is very difficult for me to accept the idea that also in this case the real distance between the two ends of this raw (with 1000 segments in between) is increasing at the maximum by only c(almost) * T.

In Minkowskian spacetime it is. Your incredulity doesn’t change the mathematics. But it also means that no matter how many dots you add, the furthest one has a maximum distance it can be from you, depending on how long it’s been since the dots have all been together.

As we move further away, the velocity of the galaxies is increasing almost linearity.

Yes, it does that both inertial and proper-distance cosmic coordinates. Not so in comoving coordinates, where the (peculiar) velocity of almost any galaxy anywhere is much lower than c, giving them pretty much fixed distance over time. But that distance is comoving distance, not proper distance, so it isn’t measured with say a tape measure.

However, nothing around any point can move faster than the speed of light up to the maximal distance (let's call it P1) in this graph.

Only under inertial coordinates. Under cosmic coordinates, there is no limit to the distance and therefore recession rate of a really distant object. The graph can be extended indefinitely. Under inertial coordinates, the graph necessarily must stop at recession rate c, and all those most distant objects are clustered near that end of the line.

So, why can't we understand that at any point (up to the infinity)

Under inertial coordinates, you can’t go to infinity with the graph. Just around 4300 mpc.

We see that all the galaxies sit very nicely on the linear graph.
However, suddenly at the Virgo cluster (15MPC) we clearly observe severe dispersion in the velocities.
Do you have any idea for the source of this dispersion in the velocities?

Yea. Virgo is a large mass that accelerates the galaxies around it. Their peculiar velocities diverge from zero as expected. The graph only shows very nearby galaxies. If you extend it much further (to galaxies not part of the Shapley supercluster), you’ll find the data points much closer to the linear line

[Bored chemist]

The input (stars that falls in) is absolutely ZERO.

You have no basis for saying that. We have only been watching then for a few decades. Cosmology happens ofver a timescale of thousands or millions of years.
And, of course, you are wrong.
We do have pictures of things falling into black holes.
https://en.wikipedia.org/wiki/Accretion_disk#/media/File:Black_hole_-_Messier_87_crop_max_res.jpg

This has been pointed out to you before.

[Dave Lev (OP)]

This thread is starting to look more and more like your Theory D thread. That's a problem because it would count as an evasion of the closing of the original thread. Let's not do that.

Dear Kryptid
You gave me the permission to take out the BBT filter:

Quote from: Dave Lev on 20/05/2022 06:07:46
Is there any possibility for us to look again on all the current observations/measurements without the BBT glass/filter?

You can, but so far the Big Bang theory is still the best candidate for explaining the observations.

The Idea that the SMBH eats stars is a key element in the BBT.
If you don't give me the permission to discuss about the SMBH, how can I offer better candidate for explaining the observations.
Please try to forget the Theory D.
We discuss on real solution for the Universe.
Is it relevant if I'm using now some ideas from BG, some from you, some from Halc some from Theory D and other from Z?
Evan Au started the discussion about the BH.

We are, by now, fairly familiar with black holes (we now have seen the shadow cast by two of them).

We know that the BBT is constantly evolve due to new discovery.
So, do you give me the permission to evolve my ideas and discuss about BH or not?

[Kryptid]

Dear Kryptid
You gave me the permission to take out the BBT filter:

I didn't give you permission to promote the same falsehoods that you talked about so much in your Theory D thread.

The Idea that the SMBH eats stars is a key element in the BBT.
If you don't give me the permission to discuss about the SMBH, how can I offer better candidate for explaining the observations.
Please try to forget the Theory D.
We discuss on real solution for the Universe.
Is it relevant if I'm using now some ideas from BG, some from you, some from Halc some from Theory D and other from Z?
Evan Au started the discussion about the BH.

See? You've been talking about the same things in this thread (galaxies moving faster than light, super massive black holes emitting matter instead of ingesting it) as you were in your other thread. You are well on your way to turning this into a duplicate of a closed thread, which is against the rules. I'm considering closing it for that reason. Just because you aren't calling it Theory D doesn't mean you aren't saying mostly the same things.

So, do you give me the permission to evolve my ideas and discuss about BH or not?

If you can do so without saying the same things you did in your other threads, yes. If you are just going to repeat statements that have been debunked numerous times in your closed thread, then I'd say not. I'm now wondering if we can even responsibly allow you to reply to threads about the Big Bang theory because it always seems to come back to this.

[Origin]

The Idea that the SMBH eats stars is a key element in the BBT.

No it isn't.  Where do you come up with this junk?

[evan_au]

A white hole, like a black one, is a massive difference in gravitational potential near a location in space, while BBT describes a flat universe with uniform potential everywhere with minor local variations forming over time.

Continuing this slight sideline of a speculation within a New Theory thread...

I agree that:
- A black hole in a galaxy produces a massive difference in gravitational potential near a location in space
- A white hole in a galaxy would produce a massive difference in gravitational potential near a location in space (only we haven't seen any, yet)

I agree that the BBT describes a flat universe with uniform potential everywhere with minor local variations forming over time
- If the Big Bang singularity were not a point in space, but represented all of spacetime, then this objection would not apply: Within that spacetime, it could be "a flat universe with uniform potential everywhere with minor local variations forming over time"
- The same is true if a white hole singularity represented all of spacetime

Note that the Big Bang itself represents a rapidly changing gravitational potential over time, which is why some cosmologists are hoping to detect relic gravitational waves, with frequencies that I found surprisingly high (10¹⁰ Hz)

See: https://en.wikipedia.org/wiki/Gravitational_wave#Gravitational_wave_astronomy