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Do We See Light In The Space Between Objects?

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#52 exchemist

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Posted 16 June 2016 - 06:45 AM

The post did not need a response, I am well aware of how ''things'' work which I already explained in a prior post.  There is no wilful misinterpretation on my part, I am asking questions, how is a question a misinterpretation? 

 

My question is do we observe/see light in space, by the replies I now interpret you don't actually see anything in space, you do not see distance or objects, you see pictures in your head, that is what the replies have said to me. 

 

Pv is out because I have asked a question is quite strange...

Nothing wrong with asking sensible questions, certainly.

 

But what does it mean to ask "do we see light in space?" Do you mean, do astronauts see light when they are in space? The answer to that is yes, if they are looking at a source of light. Or do you mean, can we, here on Earth, see light in space?  The answer to that is strictly speaking no, because we are not in space. We see light from sources of light in space.  

 

And if you know some optics you will know that our eyes form what is called an "image" on the retina, and the optic nerve and our brains can interpret that.  

 

The point behind your question remains far from obvious, I'm afraid. 



#53 xyz

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Posted 16 June 2016 - 06:52 AM

Nothing wrong with asking sensible questions, certainly.

 

But what does it mean to ask "do we see light in space?" Do you mean, do astronauts see light when they are in space? The answer to that is yes, if they are looking at a source of light. Or do you mean, can we, here on Earth, see light in space?  The answer to that is strictly speaking no, because we are not in space. We see light from sources of light in space.  

 

And if you know some optics you will know that our eyes form what is called an "image" on the retina, and the optic nerve and our brains can interpret that.  

 

The point behind your question remains far from obvious, I'm afraid. 

By space I mean ''room'', volume that is visible ''empty''. 

 

e.g  the space between your eye and computer screen.

 

Subjectively I ''see'' empty space between my eye and monitor.

 

I do not see this space to be dark, I see this space to be ''invisible'' light?



#54 exchemist

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Posted 16 June 2016 - 07:38 AM

By space I mean ''room'', volume that is visible ''empty''. 

 

e.g  the space between your eye and computer screen.

 

Subjectively I ''see'' empty space between my eye and monitor.

 

I do not see this space to be dark, I see this space to be ''invisible'' light?

Ah OK. I think you are using "see" in the wider linguistic sense of "perceive". 

 

If we simply look at the physics (optics), then it makes no sense to speak of "seeing" something that is transparent and colourless. "Sight" in the physical sense implies forming an image from visible light rays received by the eye. Plainly, one cannot form such an image of something that is transparent and colourless.

 

However we certainly do perceive that there is something in between a computer monitor and our eyes,  which we call "transparent" because it does not emit, absorb or scatter any of the light from a source beyond it. But that, I suggest, is because  (i) we know from our various senses and previous observations that the computer screen is some distance from our eyes and (ii)  we can nevertheless see it perfectly. So we become aware that there is this transparent something in between. 

 

So, if I have now understood your point, I would say it all depends what you mean by "see": whether you mean it in the narrower optical sense or in the wider sense of perception-by-our-minds-as-a result-of-visual-and-other-stimuli.


Edited by exchemist, 16 June 2016 - 07:44 AM.


#55 xyz

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Posted 16 June 2016 - 07:57 AM

Ah OK. I think you are using "see" in the wider linguistic sense of "perceive". 

 

If we simply look at the physics (optics), then it makes no sense to speak of "seeing" something that is transparent and colourless. "Sight" in the physical sense implies forming an image from visible light rays received by the eye. Plainly, one cannot form such an image of something that is transparent and colourless.

 

However we certainly do perceive that there is something in between a computer monitor and our eyes,  which we call "transparent" because it does not emit, absorb or scatter any of the light from a source beyond it. But that, I suggest, is because  (i) we know from our various senses and previous observations that the computer screen is some distance from our eyes and (ii)  we can nevertheless see it perfectly. So we become aware that there is this transparent something in between. 

 

So, if I have now understood your point, I would say it all depends what you mean by "see": whether you mean it in the narrower optical sense or in the wider sense of perception-by-our-minds-as-a result-of-visual-and-other-stimuli.

Thank you for your post, I think you understand .   I must however correct you ,  we do not call something transparent because it does not emit or absorb  light,  transparent means something that allows light to pass through it , 

 

 

transparent
tranˈspar(ə)nt,trɑːn-,-ˈspɛː-/
adjective
 
  1. 1.
    (of a material or article) allowing light to pass through so that objects behind can be distinctly seen.[/quote]
     
     
    We know in the space between your eye and screen is air, air is transparent and allows light to pass through it.  
     
     
     
    Yes , by see I mean what you ''see'' in your head.
     
     
     
     
     
     
     

Edited by xyz, 16 June 2016 - 07:59 AM.


#56 exchemist

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Posted 16 June 2016 - 08:16 AM

 

Thank you for your post, I think you understand .   I must however correct you ,  we do not call something transparent because it does not emit or absorb  light,  transparent means something that allows light to pass through it , 

 

 

tranˈspar(ə)nt,trɑːn-,-ˈspɛː-/
adjective
 
  1. 1.
    (of a material or article) allowing light to pass through so that objects behind can be distinctly seen.
     
     
    We know in the space between your eye and screen is air, air is transparent and allows light to pass through it.  
     
     
     
    Yes , by see I mean what you ''see'' in your head.
     
     
     
     
     
     
     

 

This is school level physics question really. What do you think "allowing light to pass through  means, physically?

 

Or, to turn it round to lead towards an answer, if something does not allow light to pass through, what do you think it does to the light? 

 

There are three possibilities:

 

1) it absorbs all the light. We call such substances opaque 

 

2) It absorbs some frequencies and lets others pass through. We call such substances coloured

 

3) It scatters light, making it look to us cloudy, i.e. passes some light through, but makes the image of anything beyond indistinct. We call such substances translucent. 

 

(There is in principle another possible behaviour of substances where light is concerned which is to emit light, like a bulb filament, but I agree that is perhaps complicating matters unnecessarily.)

 

So when you say something transparent "lets light through", what it means in physical terms is that it does not do any of 1-3 above


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#57 xyz

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Posted 16 June 2016 - 08:38 AM

This is school level physics question really. What do you think "allowing light to pass through  means, physically?

 

Or, to turn it round to lead towards an answer, if something does not allow light to pass through, what do you think it does to the light? 

 

There are three possibilities:

 

1) it absorbs all the light. We call such substances opaque 

 

2) It absorbs some frequencies and lets others pass through. We call such substances coloured

 

3) It scatters light, making it look to us cloudy, i.e. passes some light through, but makes the image of anything beyond indistinct. We call such substances translucent. 

 

(There is in principle another possible behaviour of substances where light is concerned which is to emit light, like a bulb filament, but I agree that is perhaps complicating matters unnecessarily.)

 

So when you say something transparent "lets light through", what it means in physical terms is that it does not do any of 1-3 above

Thank you for a great discussion, you are learning me and  helping me. 

 

I am a painter and decorator, I understand opacity of paint and also understand your definitions of opaque, colour and translucent. Yes I agree that when something is transparent it does not do any of the three. 

 

This is school level physics question really. What do you think "allowing light to pass through  means, physically?

 

It means to  me,  the ''something'' that the light is passing through is passive and offers no resistant force to the ''light''. A low refractive index such as air does not ''compress'' light.

 

Or, to turn it round to lead towards an answer, if something does not allow light to pass through, what do you think it does to the light?

 

Objective - I think an obstruction causes a temporal distortion of the light and that ''red'' is slightly ''slower'' than ''gin-clear''.   A sort of congestion where the light ''meets'' ''sponges'' of different molecular structures.  

 

subjective- But my perceived observation and thought is that a red apple, is just a red apple and also red ''outside'' of my head and light plays no part , apart from illumination?



#58 exchemist

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Posted 16 June 2016 - 09:14 AM

Thank you for a great discussion, you are learning me and  helping me. 

 

I am a painter and decorator, I understand opacity of paint and also understand your definitions of opaque, colour and translucent. Yes I agree that when something is transparent it does not do any of the three. 

 

 

 

 

It means to  me,  the ''something'' that the light is passing through is passive and offers no resistant force to the ''light''. A low refractive index such as air does not ''compress'' light.

 

 

 

 

Objective - I think an obstruction causes a temporal distortion of the light and that ''red'' is slightly ''slower'' than ''gin-clear''.   A sort of congestion where the light ''meets'' ''sponges'' of different molecular structures.  

 

subjective- But my perceived observation and thought is that a red apple, is just a red apple and also red ''outside'' of my head and light plays no part , apart from illumination?

I'm glad this has been useful and sorry for the bad start on my side. 

 

The thing about "temporal distortion" is quite subtle, though.

 

All light and other forms of electromagnetic radiation such as radio waves, microwaves and X ray travel at the same speed in a vacuum. In an "optically denser" medium, such as glass or water, i.e something with a refractive index >1, you get something called "dispersion" by which red light is in effect slowed down* more than blue light. This is why a prism splits white light into colours with red being refracted through a greater angle than blue.

 

You get this dispersion when the the frequencies of the light are getting close to a frequency at which the medium absorbs light. Because the light is close to, but not at, the "resonant frequency" at which light is absorbed, the electrons of the material start to oscillate in sympathy with the waves of light, either slowing it down or speeding it up. This "coupling" of the medium to the radiation depends on how close to the resonant frequency the frequency (colour) of the radiation is. In the case of glass and water the absorption band is outside the visible region of the spectrum so the material appears transparent, but this dispersion of colours is due to its presence, out there somewhere.   

 

* strictly speaking it is something called the "phase velocity" that is slowed down. With wave bundles like light there is also a "front velocity" and a "group velocity" and these may all go at different speeds in a medium. This is quite a big and complex subject. 

 

But that is all quantum physics (or chemistry). It is not a bad summary to think of red light as simply being slowed down by more than blue light when it enters a medium.

 

"Red" inside your head is a perception, caused by your retina receiving light in the wavelength range of : 620-750 nanometres.

 

(A nanometre is 1/1000,000,000 metres. A typical atom has a radius of about one tenth of this.)   


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#59 xyz

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Posted 16 June 2016 - 02:00 PM

I'm glad this has been useful and sorry for the bad start on my side. 

 

The thing about "temporal distortion" is quite subtle, though.

 

All light and other forms of electromagnetic radiation such as radio waves, microwaves and X ray travel at the same speed in a vacuum. In an "optically denser" medium, such as glass or water, i.e something with a refractive index >1, you get something called "dispersion" by which red light is in effect slowed down* more than blue light. This is why a prism splits white light into colours with red being refracted through a greater angle than blue.

 

You get this dispersion when the the frequencies of the light are getting close to a frequency at which the medium absorbs light. Because the light is close to, but not at, the "resonant frequency" at which light is absorbed, the electrons of the material start to oscillate in sympathy with the waves of light, either slowing it down or speeding it up. This "coupling" of the medium to the radiation depends on how close to the resonant frequency the frequency (colour) of the radiation is. In the case of glass and water the absorption band is outside the visible region of the spectrum so the material appears transparent, but this dispersion of colours is due to its presence, out there somewhere.   

 

* strictly speaking it is something called the "phase velocity" that is slowed down. With wave bundles like light there is also a "front velocity" and a "group velocity" and these may all go at different speeds in a medium. This is quite a big and complex subject. 

 

But that is all quantum physics (or chemistry). It is not a bad summary to think of red light as simply being slowed down by more than blue light when it enters a medium.

 

"Red" inside your head is a perception, caused by your retina receiving light in the wavelength range of : 620-750 nanometres.

 

(A nanometre is 1/1000,000,000 metres. A typical atom has a radius of about one tenth of this.)   

Thank you for your informative post. 

 

I have another question about the subjective visual experience, would you agree that you ''see''   the  ''empty'' space of the visual Universe  as a ''visual'' whole?  that contains ''things'' ?

 

Would you also agree that in the subjective visual experience we ''see'' the entirety of the length of space between eye and object?


Edited by xyz, 16 June 2016 - 02:04 PM.


#60 exchemist

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Posted 16 June 2016 - 03:05 PM

Thank you for your informative post. 

 

I have another question about the subjective visual experience, would you agree that you ''see''   the  ''empty'' space of the visual Universe  as a ''visual'' whole?  that contains ''things'' ?

 

Would you also agree that in the subjective visual experience we ''see'' the entirety of the length of space between eye and object?

No. As someone with scientific training, I would much prefer the term perceive, for the sorts of reasons I have previously indicated.

 

We have a mental image of empty space, with things in it, as a result of the incoming sources of light that we see, combined with the knowledge of the nature of space and celestial objects that have learned about, through our education and culture. The ancients thought they saw crystal spheres with planets attached to them describing epicycles, but they were seeing just the same light sources (sun, moon, planets and stars) as we see today. Our interpretation of what see is different today of course, as a result of the knowledge - or models of the world - imparted to us by modern society, including our astronomy. 

 

And similarly we are aware of (perceive) the presence of the empty space between eye and object. I suppose we do say in colloquial speech things like "You can see there's nothing there". But of course that means you do not see anything. :)



#61 xyz

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Posted 17 June 2016 - 01:56 AM

No. As someone with scientific training, I would much prefer the term perceive, for the sorts of reasons I have previously indicated.

 

We have a mental image of empty space, with things in it, as a result of the incoming sources of light that we see, combined with the knowledge of the nature of space and celestial objects that have learned about, through our education and culture. The ancients thought they saw crystal spheres with planets attached to them describing epicycles, but they were seeing just the same light sources (sun, moon, planets and stars) as we see today. Our interpretation of what see is different today of course, as a result of the knowledge - or models of the world - imparted to us by modern society, including our astronomy. 

 

And similarly we are aware of (perceive) the presence of the empty space between eye and object. I suppose we do say in colloquial speech things like "You can see there's nothing there". But of course that means you do not see anything. :)

Ok , thanks for your thoughts. 

 

Before Einstein came up with the idea of a single particle called the Photon, I presume the nature of light and sight was thought of differently?

 

Before science came along I presume the thoughts of light were and could only be based on the perceived image?

 

The thought of a photon coming much later in time and being a thought of the mind.

 

The word subjective means of the mind, I see a photon as subjective and education is  also subjective and ''forced'' discipline.

 

 

How do we know that the perceived experience  is not the reality we observe and the objective? and the photon is actually subjective and nothing more than an idea?

 

I have searched for a picture/photo of a single photon and I find no evidence of this?


Edited by xyz, 17 June 2016 - 02:00 AM.


#62 exchemist

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Posted 17 June 2016 - 02:48 AM

Ok , thanks for your thoughts. 

 

Before Einstein came up with the idea of a single particle called the Photon, I presume the nature of light and sight was thought of differently?

 

Before science came along I presume the thoughts of light were and could only be based on the perceived image?

 

The thought of a photon coming much later in time and being a thought of the mind.

 

The word subjective means of the mind, I see a photon as subjective and education is  also subjective and ''forced'' discipline.

 

 

How do we know that the perceived experience  is not the reality we observe and the objective? and the photon is actually subjective and nothing more than an idea?

 

I have searched for a picture/photo of a single photon and I find no evidence of this?

Optics, i.e. the understanding of light rays, how they are affected by what they pass through and how images are formed by lenses, including the eye, was known  from before the time of Galileo. There was in the c.17th and 18th a "corpuscular" theory of light and a rival wave theory. Newton favoured corpuscules and Huygens favoured waves. In the c.19th Maxwell connected the wave theory to electromagnetism and put it on a sound basis in mathematical physics. And then in the early c.20th, Planck and Einstein came forward with the modern quantum theory concept of the photon, which embodies both particle and wave behaviour. 

 

There is plenty of objective evidence for the photon, perhaps most famously Einstein's work on the photo-electric effect, which is what led to his Nobel prize. Of course you can't "photograph" a photon: a moment's consideration reveals the absurdity of such a thing.

 

Perhaps what you are getting at is the undoubted fact that we rely on indirect evidence all the time, both in science and in other aspects of life. Have you seen a molecule? Have you seen a magnetic field? Can you see gravitational pull? Nope. But we perceive these things to be there, by means of experiments that provide objective (not subjective) evidence for them.


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#63 xyz

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Posted 17 June 2016 - 03:01 AM



Optics, i.e. the understanding of light rays, how they are affected by what they pass through and how images are formed by lenses, including the eye, was known  from before the time of Galileo. There was in the c.17th and 18th a "corpuscular" theory of light and a rival wave theory. Newton favoured corpuscules and Huygens favoured waves. In the c.19th Maxwell connected the wave theory to electromagnetism and put it on a sound basis in mathematical physics. And then in the early c.20th, Planck and Einstein came forward with the modern quantum theory concept of the photon, which embodies both particle and wave behaviour. 

 

There is plenty of objective evidence for the photon, perhaps most famously Einstein's work on the photo-electric effect, which is what led to his Nobel prize. Of course you can't "photograph" a photon: a moment's consideration reveals the absurdity of such a thing.

 

Perhaps what you are getting at is the undoubted fact that we rely on indirect evidence all the time, both in science and in other aspects of life. Have you seen a molecule? Have you seen a magnetic field? Can you see gravitational pull? Nope. But we perceive these things to be there, by means of experiments that provide objective (not subjective) evidence for them.

Your posts are really good and you certainly understand me, thanks  :spin:

 

 

The fact of indirect evidence, I suppose the answer is yes, that is what I am getting at.   If I said I had discovered a dragon, you would ask for observation evidence to prove the Dragon existed, without the observation evidence it is in my ''eyes''  no more than a ''Godly'' nature or a pink fluffy Unicorn nature. 

I prefer axioms that I know are 100% fact and agreeable by observation. 

 

Gravitation , magnetic fields and likes are ''invisible'' to our perception, only the imagination can imagine these things to be such as a curvature of space etc. 

 

However I am open minded and willing to listen to ''evidence'',  whether direct or indirect. 

 

So what do you consider is evidence that a ''Photon'' exists?

 

 

Added - I also consider in reply to your Photo-electric effect  that Kmax=hf/S  where  S is entropy.

 

and also 

 

E=hf

 

>hf/S=W    where W is work?


Edited by xyz, 17 June 2016 - 04:15 AM.


#64 CraigD

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Posted 17 June 2016 - 06:46 AM

So what do you consider is evidence that a ''Photon'' exists?

The most obvious evidence that I know of that electromagnetic radiation is carried in discrete packets, or quanta – what we call photons – comes from experiments like the ones described in G I Taylor’s 1909 “Interference fringes with feeble light”.

Though concerned mostly with the fact that interference patterns are not dependent on the power, or rate, of light, only its wavelength, total energy, and the arrangement of the interference-producing and photographing apparatus, you can extract the following experiment from these famous, and much reproduced (reproducing it was part of my undergraduate modern physics lab class) experiments:
  • Start with a light source (Taylor used a gas flame) and a light detector (Taylor used chemical photographic plates – my class used a charge-coupling device);
  • With nothing between them, the detector detects light from the source;
  • Now insert an optical filter (Taylor used smoke-stained glass plates - so did my class);
  • The detector now detects half the amount of light;
  • Continue inserting plates;
  • After some number of plates, the detector no matter how sensitive, no longer detect half as much light, but detects none.
This is because energy of the light is below that of a single photon of the light source, which is given by the Planck equation, E=hf.

In 1909, Taylor and his colleagues didn’t use the term “photons” or “quanta”, but rather called them things like “regions of maximum energy widely separated by undisturbed areas” and “indivisible units”.

There’s some weird quantum stuff going on in this experiment, because it turns out that even if you increase the exposure time – the amount of time light source and detector are on – so that many time the energy of a single photon should have been detected, you still don’t detect any light – but if you’re just looking for evidence that light is carried in quanta conventionally called photons, you should delay going down this rabbit hole. :)
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#65 exchemist

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Posted 17 June 2016 - 11:12 AM

Your posts are really good and you certainly understand me, thanks  :spin:

 

 

The fact of indirect evidence, I suppose the answer is yes, that is what I am getting at.   If I said I had discovered a dragon, you would ask for observation evidence to prove the Dragon existed, without the observation evidence it is in my ''eyes''  no more than a ''Godly'' nature or a pink fluffy Unicorn nature. 

I prefer axioms that I know are 100% fact and agreeable by observation. 

 

Gravitation , magnetic fields and likes are ''invisible'' to our perception, only the imagination can imagine these things to be such as a curvature of space etc. 

 

However I am open minded and willing to listen to ''evidence'',  whether direct or indirect. 

 

So what do you consider is evidence that a ''Photon'' exists?

 

 

Added - I also consider in reply to your Photo-electric effect  that Kmax=hf/S  where  S is entropy.

 

and also 

 

E=hf

 

>hf/S=W    where W is work?

In the photo-electric effect it is found that shining light on a metal can cause electrons to be ejected from the surface which can then be accelerated towards a +ve charged electrode , causing a current to flow. It take energy to eject an electron, as the attraction between the electron and the +ve charged ions in the metal has to be overcome to do this. The amount of energy required is called the "work function", as it is the amount of work that has to be done on an electron to pull it out against the force of electrostatic attraction.

 

According to the classical (Maxwell-type) theory of light as waves, the energy from a light source depends on both the intensity of the beam and the frequency of the light. So what people expected to find was that if you had a beam of light of any frequency, by turning up the intensity, the rate of electron flow would increase, because more electrons would be ejected as a result of the the greater energy input from the light.  In fact what was found was that no electrons at all were ejected if the frequency of the light was below a certain threshhold value, which is characteristic of each metal.  Furthermore light above the threshhold frequency could still eject electrons, though not so many, even if its intensity was reduced to very low levels. Classical theory could not account for these observations. However Einstein realised they could be accounted for, if the light did not come in a continuous wavelike stream but in "quanta" of energy, the size of which depended on the frequency (E=hν). Then, at low frequencies the quanta would be too small to give an electron enough impulse to be ejected, but once the frequency was high enough for E to exceed the work function value, they would start to appear. 

 

This idea of E=hν, known by various names, one of which is the Planck-Einstein relation, could be fitted very nicely with the observations at the time about spectroscopy, by which it was apparent that atoms absorbed light at characteristic frequencies only. Using this idea one could explain spectra in terms of electrons occupying orbits at various distances from the atomic nucleus  and being promoted from lower energy ones closer in to more energetic ones further out as a result of absorbing only those "quanta" of light exactly matching the energy gap between orbits.

 

So a lot of things started to click into place. 

 

This is an example of indirect evidence in science. Note that there was never any "proof" of the existence of quanta of light - later called "photons". It was just that this hypothesis started to make sense of more and more previously separate phenomena, so the the quantum physicists and chemists of the time thought they must be on the right track. 

 

In conclusion it is time for one of my hobby horse statements about physical science. Scientific theories never claim to "prove" a theory "true". That is for logic, maths and law. In science, all "truth" is provisional, because something can always come along tomorrow and show us our ideas about the world are wrong or at least incomplete. The photon is part of the Quantum Theory model we have to explain certain phenomena. This model successfully accounts for many things and successfully predicts many more and that is why we think it is a good model.  But in the end, like all scientific theories, it is just a model of reality, which is probably imperfect, just as all its predecessors have been.


Edited by exchemist, 17 June 2016 - 11:15 AM.

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#66 xyz

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Posted 18 June 2016 - 02:49 AM

I would like to thank you all who have involved themselves in this thread, this thread has helped me to put ''things'' in its place, I feel I know understand ''everything''.

I feel my question as been answered, do we see light in space? Yes and no



In an objective sense I will exit the thread and leave this note ....


It may take 8 minutes for a ''photon'' to travel and arrive at your eyes, but relative to the first photon that arrives, the second photon that arrives is almost instantaneous with no spacing between photons.

Light is a medium for sight

Edited by xyz, 18 June 2016 - 02:53 AM.




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