Constancy of SOL from all objects

[michel123456]

 

I suppose so. It seems an unnecessarily complicated way of saying "c is invariant".

 

 

As you are talking about the impossible, there isn't really a scientific answer to that.

 

 

Not really. The fact that we can observe objects with an apparent recessional rate greater than c is a consequence of expansion, not the reason.

 

I'm not sure what any of that means.

 

 

And, again, c is invariant. With or without expansion.

 

And before you ask again: without expansion, c is invariant. You know, it is the same for all observers.

Oh, and with expansion, c is invariant. You know, it is the same for all observers.

 

In other words, c is invariant.

 

OK?

 

(Of course, one consequence of c being invariant is the theory of relativity. And hence expansion.)

 

Now, what was the question we don't understand? Oh yes, whether c is invariant without expansion. I think the answer to that is yes.

So it should not be complicated to accept that for the right part of the diagram (over-c velocities), c is still invariant. And it observed to be so.

.

Even if we are obliged to introduce expansion in order to explain something that we have declared being physically impossible. (you said "impossible")

[swansont]

So it should not be complicated to accept that for the right part of the diagram (over-c velocities), c is still invariant. And it observed to be so.

.

Even if we are obliged to introduce expansion in order to explain something that we have declared being physically impossible. (you said "impossible")

 

 

"Nothing happens faster than c" is not a correct statement. That we observe phenomena that happen faster than c is not a violation of anything. You are, in effect, attacking a straw man.

 

c is an invariant in inertial reference frames. Information and anything with mass are limited by this. But go away from an inertial frame and the value you measure for light will not necessarily be c, if you assume that you are still in an inertial frame.

[Delta1212]

You seem to be under the impression that the only reason that we think the universe is expanding is that there are distant objects traveling away from us at faster than c.

 

You are picking out one of the things that expansion explains and acting as if it is just a fudge intended to explain that one thing, rather than a model that is built on a great deal of other evidence that also happens to explain that one thing, among other things.

 

You can't just say "Well, couldn't there be a different explanation for this phenomenon than expansion" and ignore all of the other reasons why expansion makes the most sense.

[Strange]

So it should not be complicated to accept that for the right part of the diagram (over-c velocities), c is still invariant. And it observed to be so.

 

There is no such part of the diagram. Nothing can move faster than c. Nothing with mass can move at c.

 

 

Even if we are obliged to introduce expansion in order to explain something that we have declared being physically impossible. (you said "impossible")

 

I have no idea what you are talking about.

 

Expansion is (a) predicted by theory and (b) consistent with evidence (e.g. the CMB).

 

And as both expansion and the speed limit of c are a consequence of the same theory, then there is no contradiction between them.

c is an invariant in inertial reference frames. Information and anything with mass are limited by this. But go away from an inertial frame and the value you measure for light will not necessarily be c, if you assume that you are still in an inertial frame.

 

Hence the earlier distinction between constant and invariant!

You seem to be under the impression that the only reason that we think the universe is expanding is that there are distant objects traveling away from us at faster than c.

 

Indeed. We wouldn't even know that we can see objects receding faster than c if it weren't for the theory of relativity and the consequent expansion.

Edited July 25, 2016 by Strange

[swansont]

 

Hence the earlier distinction between constant and invariant!

 

 

The limitation of being true only in an inertial frame was missing from most of these distinctions, and it's an important caveat.

[michel123456]

You seem to be under the impression that the only reason that we think the universe is expanding is that there are distant objects traveling away from us at faster than c.

 

You are picking out one of the things that expansion explains and acting as if it is just a fudge intended to explain that one thing, rather than a model that is built on a great deal of other evidence that also happens to explain that one thing, among other things.

 

You can't just say "Well, couldn't there be a different explanation for this phenomenon than expansion" and ignore all of the other reasons why expansion makes the most sense.

I didn't bring expansion in the discussion.

My question was about a world without expansion.

From what I understand the answer to my question is

There is no such part of the diagram. Nothing can move faster than c. Nothing with mass can move at c.

 

However, we are actually observing such things (which brings automatically expansion, ok ok cool down).

 

------------------

Indeed. We wouldn't even know that we can see objects receding faster than c if it weren't for the theory of relativity and the consequent expansion.

 

 

We know because of the spectral lines (of hydrogen if I am not mistaken). Light that comes from those objects arrives at c. As I am proposing. At the right side of the diagram (that does not exist following your posts)

----------------------

What I was trying to say is that with a very very slight differentiation to the interpretation of Relativity, the expansion of space-time is not necessary.

The pieces of the puzzle are:

c is the upper bound velocity of information (1)

c is the upper bound velocity of causality (2)

c is the upper bound velocity of input.(3)

c is invariant (4)

 

(1) means that you cannot directly receive or send any information faster than c

(2) means what it says. Faster than c would violate causality

(3) means that you cannot input to anything a velocity higher than c

(4) means what it says

 

And that's it.

Edited July 25, 2016 by michel123456

[Strange]

What I was trying to say is that with a very very slight differentiation to the interpretation of Relativity, the expansion of space-time is not necessary.

The pieces of the puzzle are:

c is the upper bound velocity of information (1)

c is the upper bound velocity of causality (2)

c is the upper bound velocity of input.(3)

c is invariant (4)

 

(1) means that you cannot directly receive or send any information faster than c

(2) means what it says. Faster than c would violate causality

(3) means that you cannot input to anything a velocity higher than c

(4) means what it says

 

And that's it.

 

 

1. Please show in appropriate mathematical detail that this is consistent with observations.

 

2. Please explain the source of the CMB if the universe is not expanding.

[swansont]

I didn't bring expansion in the discussion.

My question was about a world without expansion.

From what I understand the answer to my question is

 

 

 

However, we are actually observing such things (which brings automatically expansion, ok ok cool down).

 

 

 

A problem here is that you keep flipping between discussing a scenario with no expansion, and then discussing expansion. If there was no expansion, our observations would be different, so any mention of our actual observations necessarily includes expansion.

[michel123456]

 

 

A problem here is that you keep flipping between discussing a scenario with no expansion, and then discussing expansion. If there was no expansion, our observations would be different, so any mention of our actual observations necessarily includes expansion.

OK

Let me rephrase:

 

My question was about a world without expansion.

From what I understand the answer to my question is

Quote

There is no such part of the diagram. Nothing can move faster than c. Nothing with mass can move at c.

 

However, we are actually observing such things.

[Strange]

However, we are actually observing such things.

 

 

Actually, we aren't. See this explanation: http://www.scienceforums.net/topic/96762-actual-vs-apparent-universal-expansion-rate/?p=934158

 

However, let us concede that we see apparent recessional velocities greater than c. Then that must mean that one of your initial premises was wrong.

 

Premise 1: nothing can move faster than c

Premise 2: there is no expansion

 

Observation: [apparent] speeds greater than c

 

Conclusion: premise 2 is wrong and there is expansion.

 

Good.

[michel123456]

 

 

Actually, we aren't. See this explanation: http://www.scienceforums.net/topic/96762-actual-vs-apparent-universal-expansion-rate/?p=934158

 

However, let us concede that we see apparent recessional velocities greater than c. Then that must mean that one of your initial premises was wrong.

 

Premise 1: nothing can move faster than c

Premise 2: there is no expansion

 

Observation: [apparent] speeds greater than c

 

Conclusion: premise 2 is wrong and there is expansion.

 

Good.

Expansion "of space-time" is the question (expansion of space)

Simplistic (Newtonian) expansion there can be. Since as you noted (for the sake of my argument) that [apparent] speeds greater than c are observed.

Edited July 27, 2016 by michel123456

[Strange]

Expansion "of space-time" is the question (expansion of space)

Simplistic (Newtonian) expansion there can be. Since as you noted (for the sake of my argument) that [apparent] speeds greater than c are observed.

 

 

What is "Newtonian expansion"?

 

And how well does a model based on that fit the observations?

[michel123456]

 

 

What is "Newtonian expansion"?

 

And how well does a model based on that fit the observations?

expansion of the Universe without inserting gaps in space. Regular stuff.

[Strange]

expansion of the Universe without inserting gaps in space. Regular stuff.

 

 

So you are saying that the Earth is literally in the centre of the universe, there was a large explosion here and everything is heading away from us?

 

How well does a model based on that fit the observations?

For example, if everything was flying away form us for "Newtonian" reasons, then why would recessional speed increase with distance?

Perhaps you should read up on the history of the science in this area. You are not suggesting anything that hasn't been considered and, eventually, rejected.

 

I may have said this before (once or twice) but the killer blow for models like this was the confirmation of the CMB.

[swansont]

OK

Let me rephrase:

 

My question was about a world without expansion.

From what I understand the answer to my question is

Quote

However, we are actually observing such things.

You frikkin' did it again! WE are in a universe with expansion, so anything WE observe can't be applied to a scenario without expansion!

 

[michel123456]

So you are saying that the Earth is literally in the centre of the universe, there was a large explosion here and everything is heading away from us?

 

How well does a model based on that fit the observations?

Did I say anything like that?

For example, if everything was flying away form us for "Newtonian" reasons, then why would recessional speed increase with distance?

Because of some acceleration**. Either applied to the objects that we are observing, either applied to us, either on both (most probably)

Perhaps you should read up on the history of the science in this area. You are not suggesting anything that hasn't been considered and, eventually, rejected.

How can I refute such an argument? It is like throwing out any proposition.

I may have said this before (once or twice) but the killer blow for models like this was the confirmation of the CMB.

You are correct, it is difficult not to say impossible to introduce concepts that match all observations just like that.

My personal view on this is that one must take things one by one and clear the subject bit by bit.

Einstein introduced the concept of Space-time growing and shrinking. Some other understood this as if it was really happening* and introduced the concept of space expansion although it has been proved (by Einstein) that Space & time have no "fabric". I prefer to stick to this "no fabric" concept than to accept "space expansion".

 

*I know many people believe firmly this.

 

You frikkin' did it again! WE are in a universe with expansion, so anything WE observe can't be applied to a scenario without expansion!

 

Argument from Authority. OK I stop here.

 

**I have other threads on that. How acceleration & expansion appear from delay, for example. How expansion appears from acceleration and delay. And how the world around you appears geometrically distorded (perspective) and the relation of this geometric distortion with acceleration.

Edited July 27, 2016 by michel123456

[swansont]

 

Argument from Authority. OK I stop here.

 

**I have other threads on that. How acceleration & expansion appear from delay, for example.

 

 

It's not argument from authority; I'm not asserting something is true just because I say so and have some credentials. It's mainstream science with plenty of evidence to back it up. You can look it up.

 

When you cite your speculative assertions as accepted fact, you're doing it wrong. You can either talk about a hypothetical universe without expansion, or you can use accepted science which includes observation. You can't do both at the same time.

[Strange]

Did I say anything like that?

 

I have no idea. Because you made up some terminology, I had to guess what it means.

 

 

How can I refute such an argument? It is like throwing out any proposition.

 

It wasn't an argument to be refuted. It was a suggestion that you get a basic education in the subject you are discussing.

 

 

Einstein introduced the concept of Space-time growing and shrinking. Some other understood this as if it was really happening* and introduced the concept of space expansion although it has been proved (by Einstein) that Space & time have no "fabric". I prefer to stick to this "no fabric" concept than to accept "space expansion".

 

You seem to be confusing pop-sci metaphors with physics. Again: get an education.

 

 

Argument from Authority. OK I stop here.

 

That wasn't an argument from authority. He was just pointing out that your argument is incoherent.

 

 

**I have other threads on that. How acceleration & expansion appear from delay, for example. How expansion appears from acceleration and delay. And how the world around you appears geometrically distorded (perspective) and the relation of this geometric distortion with acceleration.

 

But you have always failed to justify these arguments. They are simply assertions (that appear to be incorrect).

[Delta1212]

expansion of the Universe without inserting gaps in space. Regular stuff.

But the expansion of space is the only way you can get faster than c recessional speeds without breaking the speed of light.

 

Stuff just moving apart from each other wouldn't give you the observations that we presently make.

[michel123456]

But the expansion of space is the only way you can get faster than c recessional speeds without breaking the speed of light.

 

Stuff just moving apart from each other wouldn't give you the observations that we presently make.

Ah at last, this is my question.

 

If velocity of the stuff doesn't matter then I think they would.

 

At this moment we are receiving light from objects receding faster than c. This light arrives at c. It is a confirmation of the statement that says the velocity of the source doesn't matter.

The velocity of the photons is totally independent of the velocity of the source. IOW there is no velocity input from the source to the photons (it is not like like throwing little marbles).

But then, why do we believe that over c (even if produced by spatial expansion if you prefer) there would be an effect on photons, that the photons will stop mid air over even go reverse ?

*see the link & the photo attached in page 1 of this thread.

[Strange]

But then, why do we believe that over c (even if produced by spatial expansion if you prefer) there would be an effect on photons, that the photons will stop mid air over even go reverse ?

 

As you seem to be the only person on the planet who believes that, maybe you should answer it.

[Endy0816]

They don't.

 

But then, why do we believe that over c (even if produced by spatial expansion if you prefer) there would be an effect on photons, that the photons will stop mid air over even go reverse ?

*see the link & the photo attached in page 1 of this thread.

 

 

Light never stops or goes backwards, it only has further to go.

 

 

Imagine you are driving down the road and a construction crew adds another 100 km to the road between you and your destination.

 

You don't stop, you don't reverse, but the distance to your destination has increased.

[michel123456]

As you seem to be the only person on the planet who believes that, maybe you should answer it.

from this link mentioned in the beginning of this thread

 

 

Page 3

Consider a galaxy located beyond the Hubble radius at a distance r > dH that emits a photon towards Earth. Of course, locally this photon is traveling at v pec=c in accordance with special relativity. But, on account of the expansion, the photon is initially moving away from Earth with a speed vtot=vrec -c>04 (where positive velocities point away from Earth, in the direction of expansion.) Because this galaxy and the light it emits are being swept away from us by the expansion of space, it would indeed seem like this galaxy is forever unobservable. But that would be wrong.

And page 4.

 

As measured from Earth, the photon goes reversed, or stops mid air. That's not me.

They don't.

 

 

 

Light never stops or goes backwards, it only has further to go.

 

 

Imagine you are driving down the road and a construction crew adds another 100 km to the road between you and your destination.

 

You don't stop, you don't reverse, but the distance to your destination has increased.

Kilometers are added also between me and the source. As explained in the link, it is supposed, according to the distance I am, sometimes I go backward, sometimes I stop, sometimes I go forward, as measured by the destination point .

Edited July 27, 2016 by michel123456

[Strange]

There you are then. Perfectly well explained. So why do you keep asking the same question?

[swansont]

 

But then, why do we believe that over c (even if produced by spatial expansion if you prefer) there would be an effect on photons, that the photons will stop mid air over even go reverse ?

*see the link & the photo attached in page 1 of this thread.

 

 

As measured from Earth, the photon goes reversed, or stops mid air. That's not me.

 

You might notice that nothing you quoted says that the photon stops. That's you.