[Dave Lev (OP)]

Dear Kryptid & Halc
In my opinion, there are several problems with the BBT. However, the main problems are:
Energy and space expansion.
Energy is a key issue in any object or theory.
We can't move a finger without having real energy.
That energy should come from somewhere.
Unfortunately, the BBT doesn't offer any idea how the energy for our universe had been created/delivered...
Instead you claim:

It wasn't delivered to the Universe. It was already there.

So, we have to accept the idea that the whole BBT energy was already there.
However, I have few questions:
1.  Why can't we ask about the time before the bang? Why do we need to start from that point?
2. For how long it was already there? Is it just one second or infinite time?
3. Why can't we understand how the energy had created/accumulated?
4. If it was already there before the bang, then why it didn't bang long before?

BBT is not a creation theory any more than evolution theory is an explanation of abiogenesis. It does not posit something from nothing. It only describes the evolution of the universe from the initial singularity.

Don't you agree that based on the BBT we are living in a space that had been created by the BBT due to the expansion?
So as the BBT creates new space in the Universe why do you call it evolvement and not creation?
I still don't understand why do you insist that the observation proves that there is expansion in space while we can't monitor the space itself (only the galaxies as they cross the space)?

With regards to "evolve"
The BBT evolves from a very specific starting point while the energy is already there.
Based on this logic, why can't we technically start from any starting point that we wish?
Why can't we start a theory while the matter and the space is already there or even when the Erath itself is there?
How can we decide what is the correct starting point for a theory?

What other theory are you referencing?

I personally think that a theory without clear explanation about the source of energy can't be considered as real theory.
Somehow, energy must be created somewhere - even if you believe that it was already there.
So please - If it was already there - please try to explain how it got there.
If you can't do so, then why don't we open our mind to another theory that can explain how energy could be created?
Don't you agree that it is our obligation to offer a solution for the source of energy?
Therefore, I refer to a theory that can explain how energy could be created out of something in our Universe.
We must remember that energy can't be created out of nothing.
Therefore, as the BBT starts out of nothing - there is no possibility to get any energy under those conditions.

[Kryptid]

Energy is a key issue in any object or theory.
We can't move a finger without having real energy.
That energy should come from somewhere.

No other theory in science explains the ultimate source of the energy involved in the processes that it describes. The theory of evolution obviously involves energy, but it isn't a theory about what that energy's ultimate origins are. Since the Big Bang theory is an explanation for how the Universe evolved once it came into existence, and not how the Universe actually came into existence in the first place, then it shouldn't have to explain it either.

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

If the Big Bang represents the beginning of time, then it doesn't make sense to ask about what came before. You can't go back before the beginning of time because there is no such thing.

2. For how long it was already there? Is it just one second or infinite time?

Possibly zero time (hence the idea of it being the beginning of time).

3. Why can't we understand how the energy had created/accumulated?

Who knows? The Big Bang doesn't answer that question (it never had to).

4. If it was already there before the bang, then why it didn't bang long before?

If it was the beginning of time, then the energy was there at the same time as the Big Bang, not before.

Don't you agree that based on the BBT we are living in a space that had been created by the BBT due to the expansion?
So as the BBT creates new space in the Universe why do you call it evolvement and not creation?

If there was an infinite amount of space at the beginning of time and an infinite amount of space now, then the Big Bang didn't create all of space. It did create new space, but space was already there as well.

I still don't understand why do you insist that the observation proves that there is expansion in space while we can't monitor the space itself (only the galaxies as they cross the space)?

Because the alternative (galaxies travelling through space faster than light) violates special relativity.

Based on this logic, why can't we technically start from any starting point that we wish?

You could, but scientists are interested in just how far back we can start. The Big Bang, so far, is as far back as we can currently make models that are testable.

I personally think that a theory without clear explanation about the source of energy can't be considered as real theory.

Then there is no such thing as a real theory, as no theory explains the ultimate source of the energy that it uses.

I personally think that a theory without clear explanation about the source of energy can't be considered as real theory.
Somehow, energy must be created somewhere - even if you believe that it was already there.
So please - If it was already there - please try to explain how it got there.

I can speculate on that all day, but if I can't test those speculations, then it isn't science.

If you can't do so, then why don't we open our mind to another theory that can explain how energy could be created?

If a theory shows up that can explain it, then I'm sure scientists would indeed be open to it.

Don't you agree that it is our obligation to offer a solution for the source of energy?

If such a thing can be discovered. It might be impossible.

Therefore, I refer to a theory that can explain how energy could be created out of something in our Universe.

Such a (viable) theory does not yet exist.

We must remember that energy can't be created out of nothing.
Therefore, as the BBT starts out of nothing - there is no possibility to get any energy under those conditions.

The Big Bang theory does not start out with nothing. As has been said before, it starts with energy and space already there.

[Origin]

So as the BBT creates new space in the Universe why do you call it evolvement and not creation?
I still don't understand why do you insist that the observation proves that there is expansion in space while we can't monitor the space itself (only the galaxies as they cross the space)?

The reasons are many but the 2 most obvious are:
1.  All distant galaxies are moving away from us.
2.  The farther away a galaxy is from us the faster the galaxy is receding.
The only logical answer to these 2 observations is that space between the galaxies is expanding.

[Dave Lev (OP)]

So as the BBT creates new space in the Universe why do you call it evolvement and not creation?
I still don't understand why do you insist that the observation proves that there is expansion in space while we can't monitor the space itself (only the galaxies as they cross the space)?

The reasons are many but the 2 most obvious are:
1.  All distant galaxies are moving away from us.
2.  The farther away a galaxy is from us the faster the galaxy is receding.

So you clearly confirm that we measure ONLY the galaxies!

The only logical answer to these 2 observations is that space between the galaxies is expanding.

Let me reuse this brilliant logic:
Let's assume that we are living on a different planet.
We have no knowledge about the Earth.
However, based on our technology we can only observe houses in LA.
Just houses. Nothing else. Not even the land.
Based on our observation we see an expansion of houses in LA.
We all try to find a solution for the expansion of houses in LA.
More than that, we have discovered that in the last years there is acceleration in that expansion.
One of our scientist even found the acceleration rate of the houses in LA.
So, we all wonder how it could be that those houses expand so dramatically.
After long discussion we have decided that the only logical answer for that is: expansion in LA land.

Would you accept this brilliant logic???

Sorry, there is no expansion in land or in space.
This is just imagination!
Not even one Pico Millimeter per 10^1000...000 Billion of a trillion Light year.
The universe has a fixed infinite space, it was fixed for the last infinite time and it would stay fix for the coming infinite time.
It is your obligation to explain the galaxies expansion without using the imagination that is called space expansion.

Unless - you can really measure the space coordinates of the Universe and prove this wrong logic.

The Big Bang theory does not start out with nothing. As has been said before, it starts with energy and space already there.

If it starts with energy and space, then how can you claim that?

If the Big Bang represents the beginning of time, then it doesn't make sense to ask about what came before

Don't you see the contradiction?
Sorry, if there was energy and/or space in the pre bang era - then you can't claim that there was no time.The
You can't ignore that era.
It is your obligation to fully understand the conditions/ process that creates the bang including its energy.

The theory of evolution obviously involves energy, but it isn't a theory about what that energy's ultimate origins are.

This is a big mistake.

Since the Big Bang theory is an explanation for how the Universe evolved once it came into existence,

Sorry - the expansion of the space creates new space. It is not evolvement - it is creation!
So please, if based on the BBT it creates new space (due to the expansion in the Universe - even if it is infinite) then this theory should be considered as creation and not evolvement.

then it shouldn't have to explain it either.

Sorry - you have to explain it all.
You can't just explain the section that you wish.

If the Big Bang represents the beginning of time, then it doesn't make sense to ask about what came before. You can't go back before the beginning of time because there is no such thing.

As you claim that there was energy and space before the bang - then it is your obligation to explain it before the bang.

Quote from: Dave Lev on Yesterday at 19:52:57
3. Why can't we understand how the energy had created/accumulated?
Who knows? The Big Bang doesn't answer that question (it never had to).

We should know.
If we don't know - then there is a fatal error in the BBT.

If it was the beginning of time, then the energy was there at the same time as the Big Bang, not before.

So, you specifically claim that the energy had popped out at the moment of the bang.
Therefore, it is not about "already there" but it is absolutely new energy that popped in.

If there was an infinite amount of space at the beginning of time and an infinite amount of space now, then the Big Bang didn't create all of space.

If it didn't create any space, then the whole idea of space expansion is irrelevant.

Because the alternative (galaxies travelling through space faster than light) violates special relativity.

You claim that nothing can move faster than the speed of light.
So far so good.
So why do we need a space expansion to prove that galaxies are moving faster than the speed of light.

Please take a decision - do they move faster than light or not?
If they are not moving faster than light - there is no need for space expansion.
If they are moving faster than light then the understanding that they do not move faster due to relativity is wrong.

Would you kindly explain the contradiction?

[Bored chemist]

Would you kindly explain the contradiction?

What would be the point?
It has already been explained.
You don't listen.

They don't say how they measure distance in that graph. There are many ways to do so, and they're approximately the same only for nearby objects. That graph goes only to about 2 billion light years away, so yea, it doesn't matter much. But we see galaxies much further away than that, and distances become meaningless without specification of coordinate system used.  My example object is GN-z11, a very distant galaxy. Some typical choices:

1) Inertial coordinates: Only in inertial coordinates is light speed a constant c, and the coordinate system only applies to space that is more or less Minkowskian (flat), which is not true at large scales. In such coordinates, light can get from anywhere to anywhere else given enough time. There are no event horizons. The Milne solution uses such coordinates. Using such coordinates, the current size of the entire universe (relative to the inertial frame of Earth) is a sphere of radius about 13.8 BLY. Distances are measured along lines of simultaneity in the chosen frame. GN-z11 is about 13.5 BLY away, and the light we see now was emitted 6.7 BY ago.

2) Proper distance, comoving coordinates: This is the only coordinate system where H0 is meaningful. There is no maximum speed for anything, so there is no problem with objects at arbitrarily large separations after finite time. Distances are proper distance (measured by adjacent comoving rulers at a given time) traced on lines of constant cosmological time.
GN-z11 is a proper distance of about 31 BLY away and the light we see now was emitted 13.2 BY ago from only about 2 BLY away. Light from sufficiently distant events will not reach us due to acceleration of expansion forming event horizons.

Et seq.

[Dave Lev (OP)]

OK

If I understand Halc correctly, the following CS is used by the BBT in order to find a solution for the H0.

2) Proper distance, commoving coordinates: This is the only coordinate system where H0 is meaningful. There is no maximum speed for anything, so there is no problem with objects at arbitrarily large separations after finite time. Distances are proper distance (measured by adjacent commoving rulers at a given time) traced on lines of constant cosmological time.
GN-z11 is a proper distance of about 31 BLY away and the light we see now was emitted 13.2 BY ago from only about 2 BLY away. Light from sufficiently distant events will not reach us due to acceleration of expansion forming event horizons.

So, the idea is that our scientists think that H0 sets the age of the universe regardless of its size.
As it is very clear to our scientists that there is no way to fit all galaxies in the universe (even if it is just the observable one) in just 13.8 BY, they have invented a brilliant idea - the space itself is expanding and they call it - commoving coordinates.

Hence, the job of those commoving coordinates is to carry those galaxies that refuse to move at velocity that is higher than the speed of light, to very far locations in a finite time that is - 13.8 BY.
Hence, the universe must obey to the H0 formula.
As the H0 formula tells us that the age of the Universe is 13.8By it is our obligation to fit the entire universe to this finite time.
However, how do we know the real size of the Universe and which universe we are using? Is it the observable universe or the real universe which could be infinite?
I do recall that Halc has stated that in order to get a size of one millions times the size of the observable universe - about 30 B years are needed.
So, why we can't give longer age to our Universe, Why do we insist on 13.8 BY (based on H0)?
Do you consider a possibility for error in this H0 calculation/formula?
How can you try to fit a mighty universe that technically could be infinite in its size to this formulas that might be incorrect?

With regards to space-energy:
The BBT is based on the Idea that the Energy is fixed while the space is increasing.
Why you refuse to think on the other way: The space is fixed while the energy is increasing.
If you don't know how the energy could be increased - it doesn't mean that the energy doesn't increase.

So please - try to fit the theory to the Universe and not the universe to your incorrect formula!
In order to do so we must first understand the size and age of the Universe - and just then try to find some sort of Theory, formulas to this universe.
Those scientists that are puzzled almost on every new discovery/observation - prove that they don't really understand how our infinite universe really works.
They need some technical support.
So please - try to look again on all the observations without the BBT filtering, remember that the space is always fixed and try to find a way how to increase the energy.
If you do so, you would solve the enigma of the Universe.
Any new observation should fit our theory by 100% - no less than that!
In the first no fit (or puzzled scientists) it is our obligation to ignore the current theory (any theory that we might have) and look for better on.

[Origin]

Let me reuse this brilliant logic:
Let's assume that we are living on a different planet.
We have no knowledge about the Earth.
However, based on our technology we can only observe houses in LA.
Just houses. Nothing else. Not even the land.
Based on our observation we see an expansion of houses in LA.
We all try to find a solution for the expansion of houses in LA.
More than that, we have discovered that in the last years there is acceleration in that expansion.
One of our scientist even found the acceleration rate of the houses in LA.
So, we all wonder how it could be that those houses expand so dramatically.
After long discussion we have decided that the only logical answer for that is: expansion in LA land.

Would you accept this brilliant logic???

I don't detect any logic at all.  All I see is some nonsensical rambling reply that has nothing to do with with the point I made. 

[Origin]

You claim that nothing can move faster than the speed of light.
So far so good.
So why do we need a space expansion to prove that galaxies are moving faster than the speed of light.

Please take a decision - do they move faster than light or not?

It is truly unfortunate that you cannot even understand this rather simple point.  If you cannot even understand this it is no wonder that the finer points of the BBT have completely baffled you.  I fear this is a waste of time since it seems this whole discussion is just a bit over your head.

[Kryptid]

Let me reuse this brilliant logic:
Let's assume that we are living on a different planet.
We have no knowledge about the Earth.
However, based on our technology we can only observe houses in LA.
Just houses. Nothing else. Not even the land.
Based on our observation we see an expansion of houses in LA.
We all try to find a solution for the expansion of houses in LA.
More than that, we have discovered that in the last years there is acceleration in that expansion.
One of our scientist even found the acceleration rate of the houses in LA.
So, we all wonder how it could be that those houses expand so dramatically.
After long discussion we have decided that the only logical answer for that is: expansion in LA land.

Would you accept this brilliant logic???

The distances between the houses in LA doesn't increase over time, so this is a false analogy.

Don't you see the contradiction?

No, I don't.

Sorry, if there was energy and/or space in the pre bang era

I don't claim that. Remember, if the Big Bang happened at the beginning of time, then there is no such thing as "the pre-Big Bang era".

You can't ignore that era.

Unless such an era didn't exist (which it wouldn't if the Big Bang happened at the beginning of time).

It is your obligation to fully understand the conditions/ process that creates the bang including its energy.

I have no such obligation.

This is a big mistake.

So the theory of evolution has to explain where the energy involved in life processes ultimately comes from? That does not follow.

Sorry - the expansion of the space creates new space. It is not evolvement - it is creation!

The creation of new space, yes. The creation of the Universe, no.

Sorry - you have to explain it all.
You can't just explain the section that you wish.

That's not how that works. Theories don't have to explain things outside of their area of interest.

As you claim that there was energy and space before the bang

I did not claim that. I claimed that there was energy and space in simultaneous existence with the bang.

We should know.
If we don't know - then there is a fatal error in the BBT.

No, it isn't. As has been pointed out before, what you are doing is akin to claiming that evolution has to explain abiogenesis when it doesn't.

So, you specifically claim that the energy had popped out at the moment of the bang.

I did not claim that. I do not claim that the Universe went from a state of no energy to a state of energy. I claim that the Universe had energy for as far back as the beginning of time. There was no zero-energy Universe before the beginning of time because such a statement makes no sense. You can't have something before the beginning of time.

If it didn't create any space

I didn't say that. I said that it didn't create all of space.

You claim that nothing can move faster than the speed of light.

That isn't what I said. I said that galaxies can't move through space faster than light. Space itself can expand faster than light just fine.

If they are moving faster than light then the understanding that they do not move faster due to relativity is wrong.

Relativity is extremely well tested, so this option is off the table.

Would you kindly explain the contradiction?

There is no contradiction. You simply misunderstood what I said.

[Bored chemist]

If I understand Halc correctly,

The odds are against that.

[Halc]

So you clearly confirm that we measure ONLY the galaxies!

That and the CMB. There's not much more to measure at great distances.

It is your obligation to explain the galaxies expansion without using the imagination that is called space expansion.

It's actually your job since you're the one asserting it. You're the one insisting that the workings of the universe are obligated to be understandable in terms a child with 3rd grade mathematics skills can understand.

Unless - you can really measure the space coordinates of the Universe and prove this wrong logic.

Coordinate systems are not measured. They're abstract tools used to express locations, sizes, times and such.

You can't ignore that era.

If space and time are part of a bounded universe, then it makes no sense to speak of either outside those bounds. I've given several examples of similar things.

This is a big mistake.

This is apparently something you say when you cannot find fault with whatever has been said. You saying you want it to be wrong, but cannot demonstrate why.

If the Big Bang represents the beginning of time, then it doesn't make sense to ask about what came before. You can't go back before the beginning of time because there is no such thing.

As you claim that there was energy and space before the bang

Nobody claimed this. This is not a meaningful statement.

If we don't know - then there is a fatal error in the BBT.

I don't know what gift I'll get for my upcoming birthday, but it does not follow that my lack of that knowledge constitutes a fatal error in the BBT.

You claim that nothing can move faster than the speed of light.

Nothing can move faster than c relative to an inertial frame. Cosmic coordinates are not inertial. Newton's laws of motion don't apply. The energy conservation laws derived from those laws do not apply.
So relative to our inertial frame, indeed, nothing can move faster than c, and the size of the universe cannot be larger than ~14 BY would allow. But that's only relative to inertial coordinates, and since real spacetime isn't Minkowskian, inertial coordinates do not work at the largest scales. Using such coordinates makes predictions that contradict empirical observations, but it's subtle. It wasn't until quite recently (25 years) that this became obvious.

So why do we need a space expansion to prove that galaxies are moving faster than the speed of light.
Please take a decision - do they move faster than light or not?

Because only in an expanding coordinate system do those recession rates exceed c (but they don't recede faster than light, since light recedes even faster than the galaxies). Speed of light is constant only in inertial frames, so using any other coordinate system, one cannot reference 'the speed of light' since there isn't one.

If I understand Halc correctly, the following CS is used by the BBT in order to find a solution for the H0.

No, the measured H0 is used for an initial approximation of of the universe age. It has nothing to do with any CS. It actually works in inertial coordinates as well.
If expansion was linear, H0 would yield the age of the universe exactly, but it isn't linear.

So, the idea is that our scientists think that H0 sets the age of the universe regardless of its size.

Approximately, but yes, and it works with any of the first three coordinate systems. The 4th, as I've said, isn't a CS at all.

the job of those commoving coordinates is to carry those galaxies

Coordnates are abstractions, and abstractions describe things, they don't carry them.

Hence, the universe must obey to the H0 formula.

No, the H0 formula must obey the universe. The universe is under no obligation to obey anything humans say such as all the nonsense you seem to insist for it.

Is it the observable universe or the real universe which could be infinite?

What is the universe as is distinct from the real universe?

I do recall that Halc has stated that in order to get a size of one millions times the size of the observable universe - about 30 B years are needed.

I said no such thing.

The BBT is based on the Idea that the Energy is fixed

No it isn't based on that. Energy conservation is frame dependent.

[Dave Lev (OP)]

Let's focus on relative velocity:

Quote
You claim that nothing can move faster than the speed of light.

Nothing can move faster than c relative to an inertial frame.

http://hyperphysics.phy-astr.gsu.edu/hbase/Relativ/einvel.html

It is stated:

"The relative velocity of any two objects never exceeds the velocity of light. Applying the Lorentz transformation to the velocities, expressions are obtained for the relative velocities as seen by the different observers. They are called the Einstein velocity addition relationships."

A - Rest observer
B - Moving observer
C - Projectile fired by B
v - Velocity of B as seen by A
u' - velocity of projectile (C) as seen by B
u - Velocity of projectile as seen by A

The formula is as follow:
u = (v+u') / (1+ vu'/c^2)
This is the simple explanation based on relative velocity.

Now, let's try to understand the distance that C moved with reference to A at a given time - T.
The formula is:
S = V T
Hence,
Sba (The distance that B moved away from A) = v T
Scb (The distance that C moved away from B) = u' T

Therefore
The total distance that C moved away from A is:
Sca = Sba + Scb = v T + u' T = (v + u') T
Hence, with regards to distance that C moved away from A at a given time T, its velocity is:
u = Sca / T = (v + u') T / T = v + u'

If v=0.8c and u' = 0.7c
u = 1.5c
So how can you explain that discovery based on simple calculation that:
S = V T ?

Do you see any error in this calculation?

[Origin]

Hence, with regards to distance that C moved away from A at a given time T, its velocity is:
u = Sca / T = (v + u') T / T = v + u'

Nope.
Did you forget you wrote this

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

Dave, you should probably just give up, you're just making this worse.

Just to help you out, here is specifically where you went wrong:

Sca = Sba + Scb = v T + u' T = (v + u') T

From the frame of A the velocity of C would be u = (v+u') / (1+ vu'/c^2), because as you noted that is how you add velocities, NOT this [v +u'].  From the frame of B it would true that C has a velocity u'.

Hope that helps.

[Kryptid]

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

If v=0.8c and u' = 0.7c
u = 1.5c

Let's plug those numbers into the equation and see if you are right:

u = (v+u') / (1+ vu'/c²)
u = (0.8 + 0.7) / (1 + ((0.8)(0.7))/(1²))
u = (1.5) / (1 + ((0.56)/1))
u = (1.5) / (1.56)
u = ~0.9615c

Do you see any error in this calculation?

Yes. The answer is not 1.5c, it's ~0.9615c

[Dave Lev (OP)]

Quote
The formula is as follow:
u = (v+u') / (1+ vu'/c^2)
Interesting that you quote this formula but then don't use it.

The formula for relative velocity is 100% correct.
However, don't forget that Einstein had called it the "relative" velocity and not the "real" velocity.
So it should be:
u (relative) = (v+u') / (1+ vu'/c^2)

You very much know it's wrong, at least for inertial frames.

I assume that "Inertial" frames means - relative.
So again with regards to relative velocity, the above formula is fully correct.


Now, would you kindly answer the following questions with regards to Real distance?
1. What is the distance formula?
Is it:
S = V T

2. What is the real distance that B moved away from A at a given time T?
Is it:
Sba (The distance that B moved away from A) = v T

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

From the frame of B it would true that C has a velocity u'.

Is it:
Scb (The distance that C moved away from B) = u' T

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

Do you agree so far with the calculations of the real distance that C moved away from A in a given time T?
Yes or no - Please.

If so:

5. What is the simple velocity formula?
Is it
V = S / T

6. So, why we can't claim that:
The real velocity of C with reference to A based on the real distance that it moved away at a given time T is:

Vca = Sca / T = u (real) = v + u'

Where is the error in this calculation?

Don't you agree that it is perfectly OK that the "relative" velocity would be different from the real velocity that is based on real distance?

Do you claim that relative velocity means real velocity?

Cosmological coordinates are not inertial, and the formula is different. It is an absolute frame, not a relative one, so Lorentz transformations do not directly apply.

You 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?
Why can't we assume that the Cosmological coordinates are fixed and the object moves at REAL velocity that is higher than c?.
Hence:

u (relative) = (v+u') / (1+ vu'/c^2)
u (real) = v + u'

If you think that "relative" velocity means real velocity, then why Einstein didn't call it: The "real" velocity?
Don't you agree that the relative formula by Einstein show us that he was very cleaver?
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.

If you still think that there is an error in the above calculation for real distance/velocity - then please specify the exact error in those calculations.

[Kryptid]

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

Because that would be redundant. He's talking about real velocities and not imaginary velocities. What relevance to physics would imaginary velocities be?

I assume that "Inertial" frames means - relative.

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

Don't you agree that it is perfectly OK that the "relative" velocity would be different from the real velocity that is based on real distance?

The relative velocity in a given frame is the real velocity in that frame. That's the whole point of special relativity: that there is no single, absolute velocity for an object. It can be sitting still in one frame, but moving in other frames. Both are equally valid and real.

Do you claim that relative velocity means real velocity?

Yes. Again, that's the point of special relativity.

If you think that "relative" velocity means real velocity, then why Einstein didn't call it: The "real" velocity?

It's redundant. Should we always call the charge on an electron "real" charge? Or the mass of the Earth "real" mass? When you say charge and mass, it's a given you are talking about real quantities. Same thing with relative velocity.

Therefore, we clearly observe galaxies that are moving away at velocities that are greater than c.

They are not moving through space faster than light relative to us. That would violate special relativity.

Why can't we assume that the Cosmological coordinates are fixed and the object moves at REAL velocity that is higher than c?.

Because that violates special relativity. Objects don't have one single, absolute, universal velocity.

u (relative) = (v+u') / (1+ vu'/c^2)
u (real) = v + u'

The second equation is wrong. The relative velocities are real, so you have to use the first equation.

[Dave Lev (OP)]

The second equation is wrong. The relative velocities are real, so you have to use the first equation.

So please, Where is the error in the following calculation:

Now, would you kindly answer the following questions with regards to Real distance?
1. What is the distance formula?
Is it:
S = V T

2. What is the real distance that B moved away from A at a given time T?
Is it:
Sba (The distance that B moved away from A) = v T

3. What is the real distance that C moved away from B at a given time T?
Quote from: Origin on Yesterday at 20:15:16
From the frame of B it would true that C has a velocity u'.
Is it:
Scb (The distance that C moved away from B) = u' T

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

Do you agree so far with the calculations of the real distance that C moved away from A in a given time T?
Yes or no - Please.

If so:

5. What is the simple velocity formula?
Is it
V = S / T

6. So, why we can't claim that:
The real velocity of C with reference to A based on the real distance that it moved away at a given time T is:

Vca = Sca / T = u (real) = v + u'

Where is the error in this calculation?

[Kryptid]

Sca = Sba + Scb

There's your error. You can't just add those quantities together linearly when you have objects moving so close to the speed of light.

[Dave Lev (OP)]

Sca = Sba + Scb

There's your error. You can't just add those quantities together linearly when you have objects moving so close to the speed of light.

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

So, in order to understand the situation let's assume the following:
At t0 the distance between A to B is S1 and the distance between C to B is S2.
Hence, do you agree that at t0 the distance between C to A is S1 + S2?
However after given time T:
Do you agree that B has to increase its distance to A by - Sba, while C has to increase its distance to B by - Scb?
Yes or no please.

If So, why can't we understand that after T the Total distance between C to A is:

S (Total - ca) = S1 + S2 + Sba + Sca

Can you please direct me to (Einstein, Lorentz or any) explanation that prevents the possibility to sum distances?

[Kryptid]

Sorry, it isn't a sum of velocities but sum of distances.

It's a related problem.

Where is it stated that it isn't allowed to sum distances?

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

So, in order to understand the situation let's assume the following:
At t0 the distance between A to B is S1 and the distance between C to B is S2.
Hence, do you agree that at t0 the distance between C to A is S1 + S2?
However after given time T:
Do you agree that B has to increase its distance to A by - Sba, while C has to increase its distance to B by - Scb?
Yes or no please.

If So, why can't we understand that after T the Total distance between C to A is:

S (Total - ca) = S1 + S2 + Sba + Sca

Can you please direct me to (Einstein, Lorentz or any) explanation that prevents the possibility to sum distances?

The distances between those different objects for any given moment of time is going to differ between reference frames (hence needing to take length contraction into consideration). So no, you can't just add those distances together because you are taking distances from different reference frames. A road that looks like it's a kilometer long to me standing on the ground will appear to be much shorter than that for an object moving close to the speed of light relative to the road.