[Arnie O'Dell]

I would if the event was in the past. Now that you mention it the light from stars is often very old and so is in the past so maybe that is the correct view, that the field of vision narrows for light signals received. The fact that we have no access to the past except through records may make that a moot point. The only light signals that can be experienced are in the now. It is possible that each observation needs to be accompanied by a Lorentz frame.

[guest39538]

I would if the event was in the past. Now that you mention it the light from stars is often very old and so is in the past so maybe that is the correct view, that the field of vision narrows for light signals received. The fact that we have no access to the past except through records may make that a moot point. The only light signals that can be experienced are in the now. It is possible that each observation needs to be accompanied by a Lorentz frame.

Well, I can't go into simultaneity or the thread will be removed to new theories, So I can only really discuss the actual question although simultaneity is relative the question in my opinion.

[alancalverd]

Can you or anybody please describe in your own words what (A) observes of (B) as (B) moves way? 

B subtends a smaller angle at A as he moves away. At some distance the angle will be less than the angular resolution of A's equipment so A will not be able to determine the size or shape of B (by direct observation, but there are indirect methods of estimating the mass of B at any distance)  but if he is emitting or reflecting light he will always appear at least as a point source of photons.

[guest39538]

Can you or anybody please describe in your own words what (A) observes of (B) as (B) moves way? 

B subtends a smaller angle at A as he moves away. At some distance the angle will be less than the angular resolution of A's equipment so A will not be able to determine the size or shape of B (by direct observation, but there are indirect methods of estimating the mass of B at any distance)  but if he is emitting or reflecting light he will always appear at least as a point source of photons.

You say he will always appear as a point source of photons, what do you mean by will always and point source ? 

 

[alancalverd]

My words have their usual meanings to those familiar with English, which has succeeded Latin as the principal means of communication between scientists and businessmen on Earth. What planet are you from? And do the words "at least" not figure in your mathematics?

[guest39538]

My words have their usual meanings to those familiar with English, which has succeeded Latin as the principal means of communication between scientists and businessmen on Earth. What planet are you from? And do the words "at least" not figure in your mathematics?

Will always means like indefinitely, infinite, forever, several thing.

Point source means bugger all.

[Colin2B]

Point source means bugger all.

It means precisely what it says.
Imagine you blackout a room by covering the windows with lightproof black paper, now take a pin and make the smallest hole you can in the paper. Point source. You can in theory make it as small as you like eg one atom.
What's so difficult about that.

[guest39538]

Point source means bugger all.

It means precisely what it says.
Imagine you blackout a room by covering the windows with lightproof black paper, now take a pin and make the smallest hole you can in the paper. Point source. You can in theory make it as small as you like eg one atom.
What's so difficult about that.

It is not difficult now you  have clarified what Alan meant by point source.   It is what I thought he meant, but I wanted to clarify for my understanding we mean the same thing.   What is wrong in wanting to be sure?


Now take your paper and point source and move it away from you, you will observe no pin hole after a short distance, what is hard to understand about that?

Move the paper even further away, and you will observe no paper, what is hard to understand about that?

[Colin2B]

Not that difficult to understand, but you are still missing Alan's point  []

[guest39538]

Not that difficult to understand, but you are still missing Alan's point  []

Alan made the point of always, I miss no points , it is only distance when we miss points.

Can I try some maths on you ?




d=0→σ 4/3 pi ∞0³


which says distance is equal to,  zero to  a zero infinite sphere

L=r=0→σ0

which says a length or radius is equal to 0 to a variation of 0.

[evan_au]

You say he will always appear as a point source of photons, what do you mean by will always and point source ?

Like your headlamp on a dark night, your fishing friend can still see the light source (perhaps 2-20mm across) even though he cannot see you.
1. This assumes that the light source is bright enough to be above the random nerve activity in your eyeballs. I have heard that this requires at least 2 photons to strike the same rod cell in your retina within a fairly short time interval.
2. It also requires that the light source be much brighter than the surroundings (ie very dark night, and a very bright light).

But given these conditions, your dim friend can still see your lamp, even though its apparent size might be far less than the resolving power of the human eye. It has become a "point source".

Stars are also "point sources", but we can still see them; the reason they appear to twinkle is that specks of dust in the upper atmosphere get between the star and your eyeball (plus heat haze in the atmosphere diffracts it a bit).

[guest39538]

 [ Invalid Attachment ]

Let me explain this diagram

Observer A and Observer B are at a central point together, Observer B travels away from observer A who is relatively stationary.  Both observers can tell neither who is moving while at a constant speed , both observers always remain a linearity no matter what the velocity. Both observers equally contract following the lorentz  transformations and relative to each observation to a length of relative a zero point.

Showing that not only does light fail to give an observation at distance, but also Lorentz contraction causes the object to fail to give an observation at distance.

[guest39538]

You say he will always appear as a point source of photons, what do you mean by will always and point source ?

Like your headlamp on a dark night, your fishing friend can still see the light source (perhaps 2-20mm across) even though he cannot see you.
1. This assumes that the light source is bright enough to be above the random nerve activity in your eyeballs. I have heard that this requires at least 2 photons to strike the same rod cell in your retina within a fairly short time interval.
2. It also requires that the light source be much brighter than the surroundings (ie very dark night, and a very bright light).

But given these conditions, your dim friend can still see your lamp, even though its apparent size might be far less than the resolving power of the human eye. It has become a "point source".

Stars are also "point sources", but we can still see them; the reason they appear to twinkle is that specks of dust in the upper atmosphere get between the star and your eyeball (plus heat haze in the atmosphere diffracts it a bit).

Yes stars are point sources, what happens to the star point source when they continue down the railway track?  0 diameter I believe?

Which brings me to light limit and red shift, how do we know redshift is not the light limit and stretching of the limit, i.e the furthest away thing we can observe is at a position of its maximum stretch, so hence the light is weaker so we observe redshift, a bit like observing a rainbow effect in space?

 
For all those who may not understand what we are discussing is this -

We are considering either objects perceived observation of each other and the perceived contraction of each other as in Lorentz transformations relative to the inverse square law of light  and spherical radius of the affect on observation.

[alancalverd]

Will always means like indefinitely, infinite, forever, several thing.

correct.

Point source means bugger all.

or, more politely, of negligible or infinitesimal dimension - again, correct.

You see, we do speak the same language, but you just refuse to admit it!

[guest39538]

Will always means like indefinitely, infinite, forever, several thing.

correct.

Point source means bugger all.

or, more politely, of negligible or infinitesimal dimension - again, correct.

You see, we do speak the same language, but you just refuse to admit it!

Well sometimes my thoughts are before I know anything about the knowledge or what the knowledge is called, I have only just discovered Lorentz contraction and a full read me of relativity and special relativity, I had not read it before.   My ideas are from my own thinking and thinking about things but yes I agree we are starting to speak the same language the more I learn from discussion.

I think we should define it for discussion purpose,   as a ''zero point source'' to represent that not even a point of visual existence, exists, identifying relative ''empty''distance, then define point sources as objects to define spacial lengths between point sources.  Also I feel to express that all objects are in motion relative to each other but are also moving relative to the stationary observed space?

Also to consider in the discussion the ''expansion'', is it the length between point sources that is changing rather than the distance of zero point sources?

It is a part of the question, discussing radius and the affect observed .

[evan_au]

how do we know redshift is not the light limit and stretching of the limit, i.e the furthest away thing we can observe is at a position of its maximum stretch?

I think that you might be describing the concept of the observable universe?

There is a certain distance where, even if there is matter beyond it, we would not be able to observe it, due to the expansion of the
universe. Any light would have been red-shifted away to oblivion.

It is estimated that the diameter of the observable universe is about 28.5 gigaparsecs (93 billion light-years, 8.8×10²⁶ metres or 5.5×10²³ miles)

[guest39538]

how do we know redshift is not the light limit and stretching of the limit, i.e the furthest away thing we can observe is at a position of its maximum stretch?

I think that you might be describing the concept of the observable universe?

There is a certain distance where, even if there is matter beyond it, we would not be able to observe it, due to the expansion of the
universe. Any light would have been red-shifted away to oblivion.

It is estimated that the diameter of the observable universe is about 28.5 gigaparsecs (93 billion light-years, 8.8×10²⁶ metres or 5.5×10²³ miles)

Thank you, yes I refer to the  observable Universe , the observable Universe not being the size of space itself, but ''93 billion light-years'' being a length of space between two observers that takes ''time'' to travel at c.   
 
If you travelled 93 billion ly, you can be assured there after is another 93 bly