[Ophiolite]

I am not trying to relate it to relativity, it is an axiom that it is related to relativity, things at a distance relative to the observer look smaller than they actually are.

Things that move away relatively to the observer decrease in visual size.
I am not relating it, it is already related, I miss your point.

The point is that when you say relativity on a science forum it is understood that you are referring to Einstein's theories of Special and General Relativity unless you explicitly state otherwise. Ignoring this basic point is at best foolish and at worst deliberately obtuse, hence rude.

[guest39538]

I am not trying to relate it to relativity, it is an axiom that it is related to relativity, things at a distance relative to the observer look smaller than they actually are.

Things that move away relatively to the observer decrease in visual size.
I am not relating it, it is already related, I miss your point.

The point is that when you say relativity on a science forum it is understood that you are referring to Einstein's theories of Special and General Relativity unless you explicitly state otherwise. Ignoring this basic point is at best foolish and at worst deliberately obtuse, hence rude.

Did I even say relativity?  I said relatively

''relatively
ˈrɛlətɪvli/Submit
adverb
in relation, comparison, or proportion to something else.
"they were very poor, but, relatively speaking, they had been lucky"
regarded in comparison with something else rather than absolutely; quite.''

added- yes I did say relativity but I mean the relativity of something.

[guest39538]

HUh ? I thought light diminishes at a distance in compliance with the inverse square law?

Exactly. And 1/r² > 0 for all values of r, so there will always be a photon if you wait long enough.

The devil is in that last detail - if you wait long enough. As I pointed out way back in this discussion, yopu won't be able to distinguish a single photon from noise in the real world, so you need a bigger flashlight to see objects further away in the presence of air, dust, starlight, and the thermal noise in your brain, but you could use an integrating image amplifier (your mobile phone camera set to "night" mode) or a photomultiplier attached to a telescope instead.   

You always elude the actually question and reply with seemingly irrelevant  answers to the actual question.

[Arnie O'Dell]

Are you talking about light cones?

[guest39538]

Are you talking about light cones?

I am asking about light ''spheres'' that diminish at a distance from an ''inside'' observers perspective.

Putting the question a different way.

Hello science , I go night fishing, which means I go fishing in the dark, I use a head lamp, however my vision is limited to the wattage of the bulb, I can only observe so far then all things fade out , I can not see  the other side of the lake, I can not see my friend who is on the next fishing spot along the bank side, he assures  me though he can see me and my head lamp, I can see my rods reflecting light, why can't I see my friend reflecting light, why does this happen?

[Colin2B]

A vanishing point has no meaning in physics?  I find that very strange when it is a fundamental aspect of relativity.

As Orphiolite pointed out relativity has a very specific meaning in physics, misuse it and you will be misunderstood.

You always elude the actually question and reply with seemingly irrelevant  answers to the actual question.

Alan is not eluding anything, his reply is very relevant to the question.

[guest39538]

A vanishing point has no meaning in physics?  I find that very strange when it is a fundamental aspect of relativity.

As Orphiolite pointed out relativity has a very specific meaning in physics, misuse it and you will be misunderstood.

You always elude the actually question and reply with seemingly irrelevant  answers to the actual question.

Alan is not eluding anything, his reply is very relevant to the question.

Then I do not understand Alan's post or answers relevance.

Can you please answer the fishing question Colin?

[Arnie O'Dell]

humans see by the light reflected from the objects around them. The fishing light casts a light and objects close by reflect light back and they can be seen. Objects further away are dimmer as the reflected light spreads and so fades until the far away objects are not discernable. the radius of the "light sphere would depend on the circumstance.

[evan_au]

I can not see my friend who is on the next fishing spot along the bank side, he assures  me though he can see me and my head lamp

This is because the light from your headlamp obeys the "inverse square law". The light is dimmer by the time it reaches your friend on the other side of the lake, but it is still bright enough for him to perceive it.

However, for you to see your friend by the light of your headlamp, the light undergoes an inverse square law to reach your friend. Then any light reflected from your friend undergoes another inverse square law before it reaches you. This is an "inverse fourth law", and it means that you can't see your friend by the light of your headlamp, even though he can see your headlamp.
- It is not helped by the fact that you are partly dazzled by the bright light reflecting off nearby objects, so your eyes can't see dim things (like your friend)

This applies in a number of areas:
- Weather radar, Police radar or laser speed checks follow this inverse fourth law
- This problem is overcome for commercial aircraft by having an electronic transponder on the aircraft. When it is interrogated by a radar pulse (inverse square law), the transponder responds with a message describing its location and heading (subject to an inverse square law). This gives the radar much greater range than a radar with the same transmit power, relying on passive reflection (inverse fourth law).

[guest39538]

I can not see my friend who is on the next fishing spot along the bank side, he assures  me though he can see me and my head lamp

This is because the light from your headlamp obeys the "inverse square law". The light is dimmer by the time it reaches your friend on the other side of the lake, but it is still bright enough for him to perceive it.

However, for you to see your friend by the light of your headlamp, the light undergoes an inverse square law to reach your friend. Then any light reflected from your friend undergoes another inverse square law before it reaches you. This is an "inverse fourth law", and it means that you can't see your friend by the light of your headlamp, even though he can see your headlamp.
- It is not helped by the fact that you are partly dazzled by the bright light reflecting off nearby objects, so your eyes can't see dim things (like your friend)

This applies in a number of areas:
- Weather radar, Police radar or laser speed checks follow this inverse fourth law
- This problem is overcome for commercial aircraft by having an electronic transponder on the aircraft. When it is interrogated by a radar pulse (inverse square law), the transponder responds with a message describing its location and heading (subject to an inverse square law). This gives the radar much greater range than a radar with the same transmit power, relying on passive reflection (inverse fourth law).

Thank you Evan for confirming my understanding, Do we know  a radius limit of observation compared to the wattage of the light?

[guest39538]

humans see by the light reflected from the objects around them. The fishing light casts a light and objects close by reflect light back and they can be seen. Objects further away are dimmer as the reflected light spreads and so fades until the far away objects are not discernable. the radius of the "light sphere would depend on the circumstance.

Thank  you Arnie, so are you saying that any objects beyond a certain distance, could be there but not observed dependent to the light?

[alancalverd]

No, he is just restating reply #3.

[guest39538]

No, he is just restating reply #3.

Alan please think about what I am asking with some genuine interest and thought and not just reply based on your knowledge. I know you are not stupid and have a good mind, I would really appreciate your own input without the knowledge you recall.

Let us discuss an analogy,

Let us take A and B divided by a length of space.

We can imagine a train track and both observers are standing on the same track a length apart.


r=X

A...................................................................B


It is daylight ,  (A) can see (B) and (B) can see (A)   


(B) moves away from (A) while (A) remains in a fixed position,


A..................................................................→→→→→→→→→→→→→→→→→→→→→→→→→→→→→B



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

 [ Invalid Attachment ]

This is NOT a new theory , it is a discussion between us, if we make a new theory by the end between us, that is another story.

[evan_au]

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

In daylight:
- Let us say that the distance to B has doubled.
- That means that the apparent "area" of B (as seen by A) has dropped by a factor of 4.
- The angular resolution of the human eye is about 1 arcminute, ie it is impossible to recognize B as human beyond about 1 km (although you might be able to recognize him by the way he walks).

If the only illumination is at A, then the illumination of B will drop by a factor of 4 (as seen by B).
- If A is trying to see B, he will see the brightness of B will drop by a factor of 16.

[guest39538]

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

In daylight:
- Let us say that the distance to B has doubled.
- That means that the apparent "area" of B (as seen by A) has dropped by a factor of 4.
- The angular resolution of the human eye is about 1 arcminute, ie it is impossible to recognize B as human beyond about 1 km (although you might be able to recognize him by the way he walks).

If the only illumination is at A, then the illumination of B will drop by a factor of 4 (as seen by B).
- If A is trying to see B, he will see the brightness of B will drop by a factor of 16.

Thank you Evan I would shake your hand if I was there your brilliant.

Yes indeed the area of (B) contacts relative to (A)'s perspective but also the area of (A) contracts relative to (B)'s perspective.  Relatively both (A) and (B) contract to the factor of 4.


So at what radius apart would the factor decrease cause  more than  it is impossible to recognize B as human, it would be impossible to even see  (B) was even there?

 [ Invalid Attachment ]

 [ Invalid Attachment ]

 [ Invalid Attachment ]


 [ Invalid Attachment ]

[Colin2B]

So at what radius apart would the factor decrease cause  more than  it is impossible to recognize B as human, it would be impossible to even see  (B) was even there?

You can work it out from info Evan gave "The angular resolution of the human eye is about 1 arcminute". Make it easy by assuming the human is 2m tall - not quite accurate because the theory assumes a disc/point source. Remember resolution assumes adequate contrast and illumination eg human dressed in white against a black background or black against white, reduced contract will reduce the resolving power.
As you can see from all of this, there is no set sphere or radius of observation, it depends on size, reflection (albedo) and illumination of the objects you are viewing and as Alan has pointed out it is different for a light source.

[puppypower]

The relationship between distance and apparent height of objects is an inverse-linear function:
h=a\d   where h is the apparent height, d is the distance of the object, and a is the actual size of the object. if we solve this for d we get d=a/h

Say we can detect one photon per cm of height (or width). The source light emits X photons/cm of height (or width). As the light moves away the brightness gets less and less; d=X.

A one light year distance, is 9.461 x10 <sup>17  cm.

The source will need this same light density of photons/cm height to be seen from earth.</sup>
 

[Arnie O'Dell]

I think the limiting factor would be the speed of light. I can see the light from the stars that outline the big dipper and they are many light years away. They are within the light cone from my vantage point. Any light signals outside my light cone would appear dark. The farther away the light source the wider the field of vision.

[guest39538]

The relationship between distance and apparent height of objects is an inverse-linear function:
h=a\d   where h is the apparent height, d is the distance of the object, and a is the actual size of the object. if we solve this for d we get d=a/h

Say we can detect one photon per cm of height (or width). The source light emits X photons/cm of height (or width). As the light moves away the brightness gets less and less; d=X.

A one light year distance, is 9.461 x10 <sup>17  cm.

The source will need this same light density of photons/cm height to be seen from earth.</sup>
 

Thank you Puppy, I think sometimes when we get to discussing the technical aspect and fine details I get lost as the knowledge I don't always know.


Your diagram only looks at one perspective view, the view is mirrored relatively, what I mean by this is that (A) and (B) both experience the contraction perspective of each other to a point where neither exist to each other because the light is ''narrowed'' to a ''vanishing'' point.

Do you account for this?

 [ Invalid Attachment ]

[guest39538]

I think the limiting factor would be the speed of light. I can see the light from the stars that outline the big dipper and they are many light years away. They are within the light cone from my vantage point. Any light signals outside my light cone would appear dark. The farther away the light source the wider the field of vision.

The farther away the source the narrower the field of vision?