[Kryptid]

Einstein is very clever and he is fully correct.
I fully agree with him that it takes an infinite amount of energy to accelerate an object with mass up to the speed of light.
However, he didn't consider the scenario which I have offered.

As a matter of fact, he did. He deduced that you cannot add velocities linearly when the speed of the objects is relativistic. Here is a link explaining it: http://hyperphysics.phy-astr.gsu.edu/hbase/Relativ/einvel.html

Based on my theory, any baby galaxy is ejected from its mother galaxy at only 220Km/s.
This is very normal as most of the stars are ejected from the galaxy at that range of speed.
So, I assume that Einstein has no problem with that.
However, I discuss about ejection over ejection over... ejection.
Each ejection represents a speed of only 220 Km/s.
Let me use the following example-
Let's assume that we can create a rocket with 1370 stages.
So, the main rocket carries 1369 rockets. The second rocket carries 1368 rockets,.... the last one doesn't carry any more rockets.
It works as follow:
We launch the main rocket from a fixed point in space. As it gain a speed of 220Km/s, it launches the second rocket. As the second rocket gain a speed of 220Km/s with regards to the main rocket, it launches the third rocket.
So, let me ask you the following:
Do you agree that the speed of the second rocket (at the moment of launching the third rocket) is 440 Km/s with regards to the fixed starting point?

At such low speeds, linear velocity addition is an okay assumption.

If so, let's continue with the launching process with the 4th 5th and the other entire rockets till the last one.
So, do you see any violation of law in this process?

If you're assuming that the velocities always add together linearly, then yes, there is a problem because that doesn't happen when velocities begin to reach a significant fraction of the speed of light. If one stage of the rocket has reached a speed of 200,000 km/s and then launches another stage at a speed of 220 km/s relative to itself, then the observed velocity of that next stage for an outside observer is not 200,220 km/s, but rather 200,122 km/s. This is less than the sum of the two velocities. That problem gets worse and worse as you get closer and closer to the speed of light. The reason for this seeming discrepancy is length contraction, time dilation and relativistic mass gain. Here is a calculator that will let you do your own calculations for relativistic velocity addition: https://www.omnicalculator.com/physics/velocity-addition

What is the relative velocity between the fixed point in space to the last rocket?

I don't know because I don't feel like using that calculator 1,370 times in order to find the answer. It would definitely be less than the speed of light, though.

What Einstein might say about it?

He would say that you always get a total velocity less than that of light: https://en.wikipedia.org/wiki/Velocity-addition_formula

Why can't we add all the velocities?

Relativistic mass gain. The faster something is moving, the heavier it gets, and so takes even more energy to accelerate it. It's a positive feedback loop that approaches infinity as you near the speed of light. Each stage of the rocket gets heavier and heavier as you try to make it go faster, requiring more and more energy. You can never give that last stage enough energy to push it up to the speed of light.

I really don't see any violation in law.

Then you need to study relativity in greater detail.

[Dave Lev (OP)]

He would say that you always get a total velocity less than that of light: https://en.wikipedia.org/wiki/Velocity-addition_formula

Thanks
In the article it is stated:
"According to the theory of special relativity, the frame of the ship has a different clock rate and distance measure, and the notion of simultaneity in the direction of motion is altered, so the addition law for velocities is changed. "
So, they discuss about the "frame of the ship". It is clear that for local aria those formulas are perfectly OK.
However, we discuss now about the infinite open space and therefore It is totally different scale.
Einstein didn't know the total size of our Universe. So, if we just focus on a limited aria - those formulas are perfectly OK.
Let me ask you the following based on the following example:
We stay at galaxy B
If we look to our left side - we see galaxy A at a distance of 13 BLY that is moving away at almost the speed of light.
If we look to exactly to the opposite side (right) - we see galaxy C at a distance of 13 BLY that is moving away at almost the speed of light.
Therefore -
The relative velocity between A to B is almost the speed of light, the relative velocity between B to C is also almost the speed of light - and A B C is located on the same direct line.
Hence, the distance between A to C is 26 BLY.
What is the relative velocity between galaxy A to galaxy C?

Let's make it more difficult:
If we jump to galaxy C, I assume that we should see a similar view.
If we look ahead at the same ABC line we see a galaxy D at a distance of 13 BLY which also moving away at almost the speed of light.
Let's continue to jump from D to E and so on till the 11th galaxy - K.
Hence, there are 10 segments of 13BLY between those 11 galaxies.
The distance between galaxy A to galaxy K is 130 BLY.
In each segment we see that the relative speed between the galaxies (on that segment) is almost the speed of light.
So, what is the relative velocity between A to K?
Is it still " less than that of light"?

[Kryptid]

Thanks
In the article it is stated:
"According to the theory of special relativity, the frame of the ship has a different clock rate and distance measure, and the notion of simultaneity in the direction of motion is altered, so the addition law for velocities is changed. "
So, they discuss about the "frame of the ship". It is clear that for local aria those formulas are perfectly OK.
However, we discuss now about the infinite open space and therefore It is totally different scale.

Reference frames are about direction, speed or acceleration (or equivalently, in gravitational fields). Distance isn't what it is about. A ship 2 feet away from that first ship that is travelling in a different direction or a different speed or deeper into a gravitational potential is in a different reference frame from the first ship, whereas a ship a billion light-years away travelling in the same direction at the same speed/acceleration is in the same reference frame as the first ship.

Einstein didn't know the total size of our Universe.

He didn't need to because distance doesn't matter.

Let me ask you the following based on the following example:
We stay at galaxy B
If we look to our left side - we see galaxy A at a distance of 13 BLY that is moving away at almost the speed of light.
If we look to exactly to the opposite side (right) - we see galaxy C at a distance of 13 BLY that is moving away at almost the speed of light.
Therefore -
The relative velocity between A to B is almost the speed of light, the relative velocity between B to C is also almost the speed of light - and A B C is located on the same direct line.
Hence, the distance between A to C is 26 BLY.
What is the relative velocity between galaxy A to galaxy C?

If galaxy A is moving away from galaxy B at 90% the speed of light to the left while galaxy C is moving away from galaxy B at 90% the speed of light to the right, then the speed that galaxy C looks like it's moving from the reference frame of galaxy A would be 99.45% the speed of light (based on the calculator I posted earlier).

Let's make it more difficult:
If we jump to galaxy C, I assume that we should see a similar view.
If we look ahead at the same ABC line we see a galaxy D at a distance of 13 BLY which also moving away at almost the speed of light.
Let's continue to jump from D to E and so on till the 11th galaxy - K.
Hence, there are 10 segments of 13BLY between those 11 galaxies.
The distance between galaxy A to galaxy K is 130 BLY.
In each segment we see that the relative speed between the galaxies (on that segment) is almost the speed of light.
So, what is the relative velocity between A to K?
Is it still " less than that of light"?

Yes, it's still less than the speed of light and for the same reason that the speed of C relative to A is below the speed of light. It gets closer and closer with each galaxy, but never quite gets there.

[Dave Lev (OP)]

Thanks

The distance between galaxy A to galaxy K is 130 BLY.
In each segment we see that the relative speed between the galaxies (on that segment) is almost the speed of light.
So, what is the relative velocity between A to K?
Is it still " less than that of light"?

Yes, it's still less than the speed of light and for the same reason that the speed of C relative to A is below the speed of light. It gets closer and closer with each galaxy, but never quite gets there.

If our universe is infinite, there must be infinite segments of galaxies in a row that are moving away from each other (at the same segment) at almost the speed of light.
Therefore, if we take those infinite segments with almost speed of light (in each segment)- you claim that the relatively speed between the first one to the infinity one is still less than the speed of light.
Wow.
How can we believe in this answer?

If I recall it correctly, in one of your answers you have stated that due to the expansion, there is a possibility that far end galaxies are moving away from each other faster than the speed of light.
If so, how could it be that the relative velocity between the galaxies is less than the speed of light, while we know that they are moving away from each other at a speed which is faster than the speed of light?

[Halc]

Yes, it's still less than the speed of light and for the same reason that the speed of C relative to A is below the speed of light. It gets closer and closer with each galaxy, but never quite gets there.

If our universe is infinite, there must be infinite segments of galaxies in a row that are moving away from each other (at the same segment) at almost the speed of light.

This is why I didn't like answering this question with the SR answer.  Yes, in the flat SR universe I described, there are infinite galaxies, the vast majority of which are moving just under light speed from any given point, and hence are way to young to actually be galaxies yet.  You can't talk about them being galaxies because they're not.  They're not even matter yet.  So mathematically, if you view such a universe as populated with mathematical points, there are infinitely many such points and they're almost all moving away at nearly c.  This model doesn't correspond to our universe since we have accelerating expansion, which pushes all but a finite amount of material past the event horizon that doesn't exist in the SR model.  Space is not flat, and these distant galaxies don't exist at all in our reference frame, nor do we exist in theirs.  Mutually nonexistent things don't have relationships, and coordinate velocity is such a relationship.

Therefore, if we take those infinite segments with almost speed of light (in each segment)- you claim that the relatively speed between the first one to the infinity one is still less than the speed of light.

In the SR universe, yes. There is no infinity one. The most distant point in space is 13.8 BLY from Earth in Earth's reference frame, so these not-galaxies are no further than that, and Hubbles-law says that anything in the Hubble Sphere is moving away at sub-light speed. Again, we don't live in a SR universe. I'm using it to illustrate the concepts.

If I recall it correctly, in one of your answers you have stated that due to the expansion, there is a possibility that far end galaxies are moving away from each other faster than the speed of light.

This is not the SR universe. So yes, anything outside the Hubble sphere is moving faster than light, as measured in comoving coordinates.

If so, how could it be that the relative velocity between the galaxies is less than the speed of light, while we know that they are moving away from each other at a speed which is faster than the speed of light?

Things cannot have a coordinate speed faster than c in an inertial reference frame (the coordinate system), but no inertial frame covers all of space, so things outside that frame don't have a defined coordinate speed.  So we use comoving coordinates since that does actually cover all of spacetime. The coordinate system is a little weird since the length of a meter stick changes with time, and there are no meaningful inertial frames.

[Kryptid]

If our universe is infinite, there must be infinite segments of galaxies in a row that are moving away from each other (at the same segment) at almost the speed of light.
Therefore, if we take those infinite segments with almost speed of light (in each segment)- you claim that the relatively speed between the first one to the infinity one is still less than the speed of light.
Wow.
How can we believe in this answer?

Because it's what the laws of physics say. You can't go faster than light.

If I recall it correctly, in one of your answers you have stated that due to the expansion, there is a possibility that far end galaxies are moving away from each other faster than the speed of light.
If so, how could it be that the relative velocity between the galaxies is less than the speed of light, while we know that they are moving away from each other at a speed which is faster than the speed of light?

The metric expansion of space is not the same thing as moving through space. The galaxies are not actually moving away from each other faster than light, it's that the space between them is expanding faster than light. Actually, we can't even see any galaxies that are receding from us faster than light (obviously). We assume that they are out there because we assume that the universe still continues beyond our ability to see it.

[Dave Lev (OP)]

Actually, we can't even see any galaxies that are receding from us faster than light (obviously). We assume that they are out there because we assume that the universe still continues beyond our ability to see it.

So, do you mean that you assume that there are galaxies that are moving away from us faster than the light?

If I recall it correctly, in one of your answers you have stated that due to the expansion, there is a possibility that far end galaxies are moving away from each other faster than the speed of light.

This is not the SR universe. So yes, anything outside the Hubble sphere is moving faster than light, as measured in comoving coordinates.

I have tried to understand the meaning of comoving coordinates:
It is stated:
https://en.wikipedia.org/wiki/Faster-than-light
"Rules that apply to relative velocities in special relativity, such as the rule that relative velocities cannot increase past the speed of light, do not apply to relative velocities in comoving coordinates, which are often described in terms of the "expansion of space" between galaxies. "
"However, because the expansion of the universe is accelerating, it is projected that most galaxies will eventually cross a type of cosmological event horizon where any light they emit past that point will never be able to reach us at any time in the infinite future.."
"There are many galaxies visible in telescopes with red shift numbers of 1.4 or higher. All of these are currently traveling away from us at speeds greater than the speed of light. Because the Hubble parameter is decreasing with time, there can actually be cases where a galaxy that is receding from us faster than light does manage to emit a signal which reaches us eventually"
So, there is a clear message that galaxies can move faster than light.
I didn't ask about Hubble. So, it can be in or out - but it is there!

Because it's what the laws of physics say. You can't go faster than light.

Why do we insist that the same law that works locally should also works at the infinity?
Why don't we adjust our physics law based on what we see (or actually - don't see)?

[Kryptid]

So, do you mean that you assume that there are galaxies that are moving away from us faster than the light?

Yes, because there's no particular reason that the universe should stop conveniently at the exact the point where those photons from the most red-shifted galaxies came from.

Why do we insist that the same law that works locally should also works at the infinity?

Because we have yet to find a reason to think otherwise. There are no cases that I know of where scientists have detected with high confidence that the laws of physics are different far away from us than they are close to us.

So, there is a clear message that galaxies can move faster than light.

I already explained to you that moving through space faster than light is not the same thing as receding faster than light due to the metric expansion of space. The first is forbidden by relativity, the second is not. Nothing need be actually moving in the second case.

Why don't we adjust our physics law based on what we see (or actually - don't see)?

We do. There is not yet any need to alter relativity because we have yet to find any cases where the speed of light limit is broken.

[Dave Lev (OP)]

Speed is not a property.
A rock cannot go 1 km/sec, but it can go 1 km/sec relative to another rock.

Yes, I fully agree.
Therefore I have asked:

So, what is the relative velocity between A to K?

and...

If so, how could it be that the relative velocity between the galaxies is less than the speed of light, while we know that they are moving away from each other at a speed which is faster than the speed of light?

Quite so.  You can see things that are receding faster than light.  Such objects are the dotted black lines.  If they touch the red line, we can see them today.  Notice the dotted lines are vertical in the comoving coordinates, meaning comoving objects are stationary, and almost all galaxies are within a percent of being comoving.  See the 2nd vertical dotted line at about 21 BLY?  That one is outside the Hubble Sphere and always has been, but the red line touches it at age ~3BY so we can see that galaxy if it had formed before the universe was 3BY old.  It is moving at about 1.2c and is currently outside the event horizon which means we can never see it after it's state when the universe was 9 billion years old (about when life began here) where it touches the orange line.  Light from after that event will never get here.

Thanks for the excellent explanation.
Now I start to understand the answers for some of my questions.
However, it is based on the BBT theory (as the time frame is a direct outcome of the BBT -13.8 BY).
This is quite problematic.
How can we confirm or disconfirm one theory based on another theory which fully contradicts the first one?
In this thread we discuss on new Theory.
As it is new theory - it is forbidden to take your argument from another theory.
You can use any confirmed law. That is perfectly OK. But sorry - you can't reject theory D based on BBT assumption.
There are big gap between the two theories as follow:
1. Universe age: BBT - 13.8BLY, D - Infinite
2. Universe size: BBT - finite. D - Infinite
3. CMB: BBT - Direct product of the bang, D - Direct product of the infinite Universe.
4. Mass creation: BBT - no mass creation, only transformation or evolvement. D - Constantly new mass creation in low quantity at the execration disc of spiral galaxy
5. Receding faster than light: BBT -

receding faster than light due to the metric expansion of space

D - Due to "galaxy generation" or rocket over rocket phenomenon. (no need for metric expansion of space)
and many more.
So, based on theory D there is no limit in time frame as there is in the BBT.
If we discuss just about the time frame (age)
This is my estimation for the age -
The Solar system age -
Based on theory D all the Planets and Moons had been formed at the same day with our Sun. All the rocky planets/moons had been formed as a hot gas objects - with the same matter as the Sun and in the same gas cloud around the SMBH.
With regards to the Earth - its current size is less than 2% from its size in the first day (that represents the solid matter ratio in the gas cloud).  So, in order to understand the minimum age of the Earth, we must verify the requested time for Earth to eject all the gas from the planet (Hydrogen, Hellion...).
Our scientists assume that the earth had got its rock shape about 4 BY. Therefore, I estimate than the minimum age of the earth (or the moon) is 400BY. This is also set the requested time for the solar system to drift outwards from the gas cloud near the SMBH to our current location.
I also estimate that the age of the Milky Way is at least 40,000BY. (From the moment of a compact BH with a small excretion disc till this day). The age of Andromeda must be much more than that.
Therefore, It is clear to me that there is a sever mistake about the "time frame" of the Universe based on the BBT.
Therefore, the following answer is not applicable for theory D

No galaxy existed back then.  The ones we see are much closer, as evan_au points out.

You base your answers on a the assumption that our universe is quite young (13.8BY). That leads to sever misunderstanding about the feasibility of the receding faster than light.
Actually, if you take that diagram to the infinity age & infinity Size - you would find that most of the galaxies are receding faster than light.
I think that there is high similarity between the rocket over rocket theory (based on theory D) to the space expansion (based on BBT). I can show it if you wish.

With regards to the CMB:

The matter that emitted that CMB light we see is now about 45 GLY (proper distance) away.  We don't see stuff like it is now, we see things in the past. That matter has been moving at more than 3x light speed relative to us, so it was much much closer when that light was emitted.  Just divide 45 by 13.8 billion years and multiply it by 379000, and you get something like 1¼ light years.

You also base your understanding about the CMB on the 13.8 BY time frame.
So, I can fully agree and understand your following answer:

In an inertial frame, the relative velocity is a relation between two objects at some point in time.  Those distant galaxies don't exist at any point in time in our reference frame, so there is no defined velocity relation in that framework. 

But again - In theory D the Universe time frame (age is infinite)
That is another error. Remember - In theory D the Universe is infinite in its age and in its size. Therefore, we must extract the projected amplitude/features of the CMB based on the assumptions that the Universe is Infinite in its size and in its age. We also must add to that the idea that galaxies that are located far enough - must move away from us higher than the speed of light. So, we need to understand what is the maximal distance that we still get radiation from galaxies.
I had the impression that if the galaxy is moving faster than the speed of light - we shouldn't get its radiation.
 Would you kindly explain how could it be that there is a possibility to get in a future a radiation from a galaxy which is moving today at the speed faster than light.
 Again - Please do not mix up with the BBT theory and claim that in the past they we were close enough. That idea isn't relevant in this infinite Universe.

It isn't about infinity.

It seems to me that it is all about infinity.
If you knew that our universe is infinite in its size & age - the whole story about the BBT was totally different.

A very good idea.  So why is it you are positing all this nonsense that nobody sees?

Why do you all insist on the BBT
What is needed to convince you that the time frame of our real universe is much bigger than 13.8BLY and our universe is infinite in its size.
What kind of data would convince you that there is a sever mistake with the BBT?

[Kryptid]

Constantly new mass creation in low quantity at the execration disc of spiral galaxy

As we've said before, we can throw this idea out then because it violates conservation of mass. No known process in the universe creates new mass. It is only transformed from one form to another.

D - Due to "galaxy generation" or rocket over rocket phenomenon. (no need for metric expansion of space)
and many more.

We already explained to you that you can't exceed the speed of light that way. Relativity forbids it. You can't cheat your way past the speed of light like that. So that's two laws of physics that your idea violates. No one has ever seen mass being created or objects with mass moving faster than light.

If I was aboard the first stage of your hypothetical rocket and tried to measure the kinetic energy of the final stage of the rocket (the one that you claim should be going faster than light), what do you think I would measure the kinetic energy as? It would be more than infinite, which makes no sense. Where did that final rocket stage get its more than infinite kinetic energy from? It would have to have come from the rocket fuel carried by the previous stages plus whatever fuel it carried. So explain to me how you can carry more than an infinite amount of rocket fuel on any real rocket.

Why do you all insist on the BBT

It's what the evidence supports.

What is needed to convince you that the time frame of our real universe is much bigger than 13.8BLY and our universe is infinite in its size.
What kind of data would convince you that there is a sever mistake with the BBT?

Any kind of verifiable scientific evidence.

[Halc]

Therefore I have asked:
So, what is the relative velocity between A to K?

Depends on the way you measure velocity.  So in a universe with finite age of 13.8 BY, A and K are moving at about 9c in comoving coordinates.  The two don't exist in any one inertial frame, so they can't have that kind of velocity relative to each other.

If so, how could it be that the relative velocity between the galaxies is less than the speed of light, while we know that they are moving away from each other at a speed which is faster than the speed of light?

The relative speed between those two galaxies is not sub-light speed, at least not in the finite age universe.  In a universe described by SR, speeds add up to something less than but nearly c, as per the velocity adder.  A and K would be able to see each other in such a universe.

Quite so.  You can see things that are receding faster than light.  Such objects are the dotted black lines.  If they touch the red line, we can see them today.  Notice the dotted lines are vertical in the comoving coordinates, meaning comoving objects are stationary, and almost all galaxies are within a percent of being comoving.  See the 2nd vertical dotted line at about 21 BLY?  That one is outside the Hubble Sphere and always has been, but the red line touches it at age ~3BY so we can see that galaxy if it had formed before the universe was 3BY old.  It is moving at about 1.2c and is currently outside the event horizon which means we can never see it after it's state when the universe was 9 billion years old (about when life began here) where it touches the orange line.  Light from after that event will never get here.

Thanks for the excellent explanation.
Now I start to understand the answers for some of my questions.
However, it is based on the BBT theory (as the time frame is a direct outcome of the BBT -13.8 BY).

Yes, that picture makes no sense outside the BBT.  You can't use it to describe other theories.

This is quite problematic.

No it isn't.  Draw a different picture to match a different theory.

How can we confirm or disconfirm one theory based on another theory which fully contradicts the first one?

Find an empirical difference.  The CMB is such a difference since only BBT predicts it.  The discover of it was a fatal blow to Hoyle's theory which was already falsified in other less fatal ways.

In this thread we discuss on new Theory.
As it is new theory - it is forbidden to take your argument from another theory.

That's right.  Can't use my picture.  Can't just assert that stuff is the way we see it.  You have to justify your assertions: show that your belief is consistent with the numbers you claim.

you can't reject theory D based on BBT assumption.

I said your beliefs are wrong because they contradict themselves, not because they contradict BBT.

There are big gap between the two theories as follow:
4. Mass creation: BBT - no mass creation, only transformation or evolvement.

Lack of mass creation is not a BBT thing.  It is a law of thermodynamics, which is not based at all on BBT.  Take away BBT and this law still stands, as do all the laws of motion that are so heavily violated by your VHP thing.

5. Receding faster than light: BBT -
D - Due to "galaxy generation" or rocket over rocket phenomenon.

Rocket over rocket will not produce faster than light speeds.

So, based on theory D there is no limit in time frame as there is in the BBT.

You mean there is not a finite age to the universe relative to now?  Yes, I agree that such a thing would go away if you take away BBT.  There are cyclic models that say time is infinite with repeated bangs and the one we know is just the most recent bang.  That's still BBT, but with serial bangs, and it has a hard time explaining how expansion is accelerating when it predicts a slowing of it.

You also base your understanding about the CMB on the 13.8 BY time frame.

Yes, the only theory that predicts one. Your belief merely asserts one because you know about it.  Predicting something after it is known is not prediction, just observations.  You cannot explain it, so you resort to assertions.
I showed how your belief predicts the entire sky as bright as the sun, the same temperature that your oven would get to after infinite time baking like that with nowhere for the heat to go.  Yes, you assertions result in a CBR, but not a microwave one at 2.7°.

So, I can fully agree and understand your following answer:

In an inertial frame, the relative velocity is a relation between two objects at some point in time.  Those distant galaxies don't exist at any point in time in our reference frame, so there is no defined velocity relation in that framework.

But again - In theory D the Universe time frame (age is infinite)

Fine.  Then all those galaxies exist in a nearly inertial frame and exist in such a coordinate system.  Why can't we see them?  Another empirical falsification of this D belief.

Remember - In theory D the Universe is infinite in its age and in its size. ... We also must add to that the idea that galaxies that are located far enough - must move away from us higher than the speed of light.

No they don't, unless you deny relativity theory, or you take the expansion of space assertion from BBT (which makes it hard to posit infinite age).  If you posit space expansion, then the CBR is wiped out since there is nothing from which it might have been emitted.

I had the impression that if the galaxy is moving faster than the speed of light - we shouldn't get its radiation.
 Would you kindly explain how could it be that there is a possibility to get in a future a radiation from a galaxy which is moving today at the speed faster than light.

I didn't say that.  In a non-expanding universe, it isn't possible to move at greater than light speed. You need to deny relativity to do that, and I cannot tell you how such a universe would behave since I know of no consistent theory that denies relativity.
I did say that if an object can move faster than light, you would not be able to see it coming, but you would be able to see it receding if you're not outrunning light yourself.  The physics just gets stupid and predicts that most places can see almost nothing since almost nothing is stationary enough to allow light to keep up.

It isn't about infinity.

It seems to me that it is all about infinity.

I showed an example of an object moving at greater than c only 350000 km from here.  I'm saying you don't need to invoke infinity for an example of it.

A very good idea.  So why is it you are positing all this nonsense that nobody sees?

Why do you all insist on the BBT

I don't think I mentioned BBT there.  I just noticed that you consistently fail to adjust your physics law based on what is seen.  You commit the very fallacy that you accuse of us.  That's being hypocritical.

What is needed to convince you that the time frame of our real universe is much bigger than 13.8BLY and our universe is infinite in its size.

A viable alternative model (which would not convince, but at least allow a 2nd interpretation).  To convince, the BBT would also need to be falsified.

What kind of data would convince you that there is a sever mistake with the BBT?

Different evidence than it predicts.

[Dave Lev (OP)]

Thanks Halc & Kryptid

Do appreciate your great support.
I should be in Nederland till the end of the month.
We will hopefully continue our discussion upon my return.
Best Regards

[Kryptid]

Have fun!

[Dave Lev (OP)]

Dank je wel

We are visiting my parents in law. (My wife is also dutch).
I would love to live there, but my wife prefers to stay at our current location.

Veel succes en geluk

[Dave Lev (OP)]

Hello Allemmal

After a very relaxing vacation I'm back.
I had the time to reconsider few ideas in our discussion.
I would like to start with - hypersphere

There is nothing about our universe that is incompatible with it being a hypersphere.
The universe being a hypersphere is not incompatible with our ability to see only three dimensions. A two-dimensional creature living embedded in the surface of a balloon is only aware of the two dimensional surface that they live in even though the balloon itself is three-dimensional. If the balloon was large enough, the creature wouldn't even be aware of the balloon's curvature and they could just as easily believe that their universe was a completely flat, 2-dimensional space. In the same manner, the universe being a sufficiently-large hypersphere would go unnoticed by us because the curvature would be too gradual to detect.

Based on the hypersphere idea, if one of us could jump all the way to the left, and the other one will jump all the way to the right - at some point they might meet with each other. (As a surface of a balloon).
That meeting point represents a distance from our location. Let's assume that the distance is symmetrical distance from both sides (left & right) and its value is X light year away (from our location).
Let's also assume that a galaxy which is located at that distance must move away from us at a relative velocity of n * c
Hence, a galaxy which is located at a distance of  x to the left is moving away from us at  n * c, while a galaxy which is located at the same distance to the right is also moving at n * c.
Therefore, at the meeting point of that hypersphere, we might have one galaxy from the left which is moving at a velocity of n * c, while from the other side (right) another galaxy is coming at a velocity of n * c.
So, theoretically at that meeting point, we might have two galaxies which are moving head to head at a relative velocity of 2n *c.
Do you agree with that?
If that is correct, do you agree that it contradicts the whole idea of the hypersphere?
In other words -
There is no way that we are living on a "surface of balloon".
Hence, the space of our universe has no limit. It must be infinite.

[Kryptid]

Do you agree with that?
If that is correct, do you agree that it contradicts the whole idea of the hypersphere?

No, because you're ignoring the fact that the "movement" of the galaxies in this model is actually just the balloon expanding.

[Dave Lev (OP)]

Welcome back!  BTW, my wife has only traces of dutch in her, but I'm almost 100%, despite never having lived there.  My mother emigrated as a refugee after the flood of 53, taking her fiancee with her.  All my blood relatives on her side live below sea level.

Thanks
Wow, what a life story...

No.  They're the same galaxy, and it is receding (increasing its comoving proper distance) from us at n*c in any direction.  Two dots on opposite side of a balloon are separated by X in any direction, and are moving apart as the balloon inflates.

Ok
That is clear.
However, do you agree that if the space is represented as a "surface of a balloon" - somehow, we must monitor a curvature in space?
So, why we can't see that curvature in space?
Why it is only a theoretical  idea?
Where is the real evidence for that curvature?
Let me use the surface of the Earth as an example -
"What is the minimum distance over water that, using a laser, the curvature of the earth can be clearly demonstrated?"
https://www.quora.com/What-is-the-minimum-distance-over-water-that-using-a-laser-the-curvature-of-the-earth-can-be-clearly-demonstrated-using-ordinary-household-measuring-devices
"The Earth’s curvature works out to 7.98 inches over one mile*"
7.98 inches = 7.98 *2.54 cm = 20 Cm
1 Mile = 1.6 km
So, in 1Km the curvature is 20/1.6 cm = 12.5 cm.
In 100 Meter the curvature is 1.25 cm.
I assume that based on a laser we should monitor that curvature (1.25 cm) even at 100M = 0.1 km.
Let's assume that below that distance, we couldn't verify the curvature.
The Earth's circumference is 40,075 km.
The ratio between 100 M to the Earth's circumference is:
0.1 km to 40,000 km = 1 to 400,000
In the same token - when we look at a distance of 13 Billion LY we don't see any curvature.
So, the minimal Space circumference should be:
13 BLY * 400,000 = 5,200,000 Billion Ly
Therefore, if you wish to believe in space curvature - the minimal Space circumference must be 5,200,000 Billion Ly.
So how can we create that size of Universe in only 13.8 Billion years?

[evan_au]

I assume that based on a laser we should monitor (the Earth's) curvature (1.25 cm) even at 100M = 0.1 km.

There is an experiment proposed for the 2030s that would search for gravitational waves using lasers bounced of satellites, perhaps 2.5 million km apart.

The goal was to look for tiny variations in the phase of a laser beam over this distance - looking for variations of around 20 picometers with periods ranging from 1 second to 10 hours.

It is outside the mission goals, but the same equipment could be used in the same way as a surveyor's laser to measure the distance between the satellites with an accuracy of perhaps 1nm over a period of a year. That may reveal some deviation from flat space due to the nearby Sun (superimposed on orbital disturbances from Earth, the Moon, Jupiter, Venus and Mars - and the Milky Way itself).

As a bonus, it is expected that this device could get a measure of the expansion of the universe (the Hubble constant) which is independent of the two current (conflicting) answers based on various methods.

However, measuring deviation of intergalactic space from perfectly flat space of the universe would be beyond such a device.
See: https://en.wikipedia.org/wiki/Laser_Interferometer_Space_Antenna

[Dave Lev (OP)]

However, do you agree that if the space is represented as a "surface of a balloon" - somehow, we must monitor a curvature in space?

Not if the curvature is below the sensitivity of the instruments to measure it.

Thanks
So, you agree that based on our instruments we do not see any curvature in our Universe (as far as we can see and monitor - At least 13 Bly for any direction)

If the surface of Earth was 2D space, how could the 2D creatures on it measure the curvature?  Not by using altitude.  If space went in that direction, it wouldn't be 2D space.  Likewise, there is no direction in the hypersphere that is 'above' the surface that represents a specific moment in comoving time.  You can't see along the surface anyway.  You can only see light that comes from the past.

How can we claim in one hand that based on our mathematical theory the Universe should have a curvature, but on the Other hand we claim that there is no way for you to validate/prove this theory by real verification?
Our scientists must find a way how to verify the curvature in our Universe!
This is a mandatory request, otherwise, the whole idea of the curvature is problematic.
It was s a nice concept to place at the same diagram the space & time.
Based on this 4D concept, we have got an outcome that the space could be considered as "surface of a balloon"
However, if we could find that based on our formula, the Universe acts as a "surface of a balloon", we also must extract the Minimum size of that "Balloon"
In other words - as we see no curvature up to a minimal radius of 13 Billion light year, we must find what is the minimal circumference of  "surface of a balloon" that is needed to support that none curvature at that radius.

I fully accept/agree with the following answer from evan_au:

There is an experiment proposed for the 2030s that would search for gravitational waves using lasers bounced of satellites, perhaps 2.5 million km apart....

If I understand it correctly, our scientists try to find a breakthrough technology/ideas in order to give an answer to some of key questions including the idea of curvature.
Therefore, If for example, we might find in the future that there is some curvature in our "surface of a balloon" space, than based on that curvature verification, we could technically calculate what is the minimal circumference of  "surface of a balloon" that supports that kind of curvature.
Let's use the circumference of the Earth as an example-
At the early time, our scientists didn't really measure the circumference of the Earth.
They just measured the value of the surface Earth curvature, and extract mathematically the circumference of the Earth.
In the same token, we must calculate the value of the minimal circumference of the surface of a balloon/space that can still support a radius of 13 Billion LY universe without any verification for curvature.
That minimal space/universe size is vital information for our theory.

[Kryptid]

Our scientists must find a way how to verify the curvature in our Universe!
This is a mandatory request, otherwise, the whole idea of the curvature is problematic.

No, it isn't problematic. All it means is that it might be curved or it might not be curved. If it's possible that the Universe is closed, curved and finite in size, then you can't say that you've proven it to be infinite. You would somehow have to rule out even the possibility of a hyperspherical universe of finite size first. No experiment has done that.