Light: visible or invisible?

[John Cuthber]

8 hours ago, Eise said:

Then you cannot see cars, because cars are not light.

That's exactly why you can't see cars in the dark

You see cars because they reflect light and you see that light

8 hours ago, Eise said:

And it is still wrong. You see an apple: but for you it looks blue.

FFS!
Will you read what I said; twice?

 

On 02/02/2018 at 6:55 PM, John Cuthber said:

On 02/02/2018 at 6:56 AM, John Cuthber said:

What I "see" is an image of the imperfections in my eye's lens; regardless of the source.

Strictly what I see is essentially the point spread function of the eye.
https://en.wikipedia.org/wiki/Point_spread_function

I don't see a goddamned apple.
And there is no blue apple for me to see.

However I see blue light.

8 hours ago, Eise said:

Literally it is not faulty.

Yes, because an image system that "sees" a blue apple which never exists in the universe is obviously working perfectly- in your world; those of us in this world may have a different view.

If your television did that and you were trying to watch snooker, would you get it repaired?

8 hours ago, Eise said:

Seeing things and seeing light are just different things.

Except that "light" is a subset of "things".

[koti]

This is escalating into something needlesly weird. I made a 78 break back in the day when I could SEE the cue ball well enough to hit it where I want.

Edited February 5, 2018 by koti

[dimreepr]

17 hours ago, Tub said:

On reflection, dim, i see your point............or do i?  

3

If you close your eyelids and stop light entering your eyes you can't see, ergo... 

[Eise]

On 02/02/2018 at 7:55 PM, John Cuthber said:

The idea of you telling me what I see is absurd- especially when I already told you.

To come one time back to this: with the blue apple/light you are not describing something you really have experienced. You are describing a thought experiment. And with thought experiments everyone can look if he agrees with the ideas about the occurrences that are described. I am criticising your thought experiment, more or less based on the fact that you are begging the question. You get out what you put in. The relativity aspect does not add anything to the discussion. You just argue that the only correct meaning of 'seeing' is 'seeing2', seeing light. But that is already a presumption you put in yourself. And it does not fit our daily use of language where we also see cars, tables and houses.

On 05/02/2018 at 2:53 PM, koti said:

I think this is faulty logic Eise. Technically, in the context that we are speaking here, cars that we see are light because they reflect light therefore we see them. If they wouldn't reflect light we wouldn't see them. It's crude and simple and I'm sure I don't need to explain this but that's really all there is to it.

'Cars are light?'. Now that sounds like faulty logic to me. 

Again: it is obvious that we all agree on the physical basis of seeing macro objects on the one side, and light at the other side. If we see light, it means the light enters the eye. If we see macro objects, the objects do not enter our eye. On the other side: we see cars because they reflect light, but we cannot see light that does not enter the eye, light does not reflect or emit light. Do we agree so far?

Now my position is that this difference in meaning of 'seeing' does not create any problem: not in daily life, not in science, and not in philosophy. So it really is a futile discussion. But: when somebody explicitly asks if light is visible, and even shows his assumption behind the question, it is time to realise that there is a physical difference between seeing macro objects and light. And a possible answer would be 'Well,  in the sense of ... of seeing, one could say light is invisible'. But immediately add that this is a bit artificial distinction, because we all know what somebody means when he says he is seeing light. 

On 05/02/2018 at 2:58 PM, StringJunky said:

We see a configuration of the light that represents the object the photons interacted with.

Yep. That is also an interesting way of describing the difference. We can make this representation, because light enters our eyes from different directions of the macro object, and our brain constructs this representation from it, unconsiously (we do not have to think "oh, all this light, let's calculate if the light was reflected by some object. Aha, all that light is reflected by a single object! It's a car!").

On 05/02/2018 at 11:14 PM, John Cuthber said:

You see cars because they reflect light and you see that light

You realise that use the word 'see' twice in this sentence. Do they mean exactly the same with the words 'see'?

On 05/02/2018 at 11:14 PM, John Cuthber said:

I don't see a goddamned apple.
And there is no blue apple for me to see.

See my remark about thought experiments above. You see a blue apple, even if the apple in its rest frame is red. 

On 05/02/2018 at 11:14 PM, John Cuthber said:

Except that "light" is a subset of "things".

Light is not a macro object. I very clearly made this distinction. But for the sake of argument: what does 'being a subset' mean?

It means that every attribute that applies to the superset, also applies to the subset. Now an attribute of macro objects is: can be seen by shining light on it. But this does not work for light. So light is not a subset of macro objects (even in this context).

Edited February 8, 2018 by Eise

[John Cuthber]

12 hours ago, Eise said:

See my remark about thought experiments above. You see a blue apple, even if the apple in its rest frame is red. 

Do you understands this assertion?
 

On 2/2/2018 at 6:56 AM, John Cuthber said:

Incidentally, I forgot my glasses.
What I "see" is an image of the imperfections in my eye's lens; regardless of the source.

I presume you don't, because you are steadfastly ignoring the fact that- in this thought experiment, without my glasses I don't see any goddamned apple.
What I see is the point spread function of the lens of my eye.

And I see that if I'm looking at a a streetlamp, an apple, a tomato a Christmas tree light, or down a (weak) laser beam.

I don't see an image of the object.

You are repeatedly ignoring what you are told.

Why are you doing that?
Are you too conceited to recognise that you might be wrong?

So, what I see- a blue blob- confirms the wavelength of the light (it's blue not green) and fails to provide any information about the source (which looks the same as any other bright small object of that colour).

Yet you insist that I can't see the light, but I can see the source.

How come the only information I receive is about the light if I can't see it?

 

Edited February 8, 2018 by John Cuthber

[koti]

14 hours ago, Eise said:

 

'Cars are light?'. Now that sounds like faulty logic to me. 

Again: it is obvious that we all agree on the physical basis of seeing macro objects on the one side, and light at the other side. If we see light, it means the light enters the eye. If we see macro objects, the objects do not enter our eye. On the other side: we see cars because they reflect light, but we cannot see light that does not enter the eye, light does not reflect or emit light. Do we agree so far?

You brought up the faulty car analogy, my mistake is I went with it to try to explain my view.

i will not make that mistake again:

No, I disagree with the above, it is wrong. It doesn’t matter if the object is macro or any other size, you always see light either at the source or reflected - that is all you see and that is all you will ever see unless you put on night vision goggles or thermal vision goggles which operate outside of the human visible spectrum of 390-700nm. You could also get an implant feeding your brain with something else than light to bypass your eyes. I am absolutely sure that you get this, Im not sure as to why you are keeping this argument alive - its ridiculous and you know it. All we can see is light - nothing less, nothing more - only light. FFS.

Edit: I changed "nothing else" to "nothing less"

Edited February 8, 2018 by koti

[John Cuthber]

 

14 hours ago, Eise said:

It means that every attribute that applies to the superset, also applies to the subset. Now an attribute of macro objects is: can be seen by shining light on it. But this does not work for light. So light is not a subset of macro objects (even in this context).

Nice strawman.

Light is a thing.

So "light" is a subset of "things".

If I had said that light was a "macro object" - whatever that may be- you would have a point.

I didn't.

You haven't.

 

 

14 hours ago, Eise said:

Do they mean exactly the same with the words 'see'?

Nobody said they did.

However, both are legitimate uses.

So I really can see light .

So it's really not invisible.

 

[Eise]

10 hours ago, John Cuthber said:

I presume you don't, because you are steadfastly ignoring the fact that- in this thought experiment, without my glasses I don't see any goddamned apple.

Ah, Really missed that. Just to be sure that I understand you: the Enterprise is flying in your direction, and without glasses you are seeing badly. So what do you see1: a blurry blue object. And that is because you see2 blue light. (I know what I am saying: I have glasses since primary school...).

You are also consistently ignoring the fact that seeing macro objects is a different process as seeing light. It seems to me you are arguing that only see2 counts as seeing. But that doesn't fit to the daily use of the word 'seeing', in which we most of the time talk about seeing macro objects.

8 hours ago, John Cuthber said:

Nice strawman.

Light is a thing.

So "light" is a subset of "things".

If I had said that light was a "macro object" - whatever that may be- you would have a point.

I always meant macro objects when I wrote about 'things'. But if you want, I am flexible. So slightly different:

We have the set of things. Now one can divide this set in subsets based on all kind of differences. One difference: there are things we see can because they reflect light, e.g. cars, houses and apples. On the other side there is one thing we can see because it enters the eye: light.  The first category we can see1, the second category we can see2. (Didn't you say somewhere that 'we only see light'?)

23 hours ago, Eise said:

Do they mean exactly the same with the words 'see'?

8 hours ago, John Cuthber said:

Nobody said they did.

Then why do you have so much trouble that I clearly distinguish between the two meanings???

8 hours ago, John Cuthber said:

However, both are legitimate uses.

Of course. I repeatedly said it: no serious, real problem is solved by making this distinction. But one can make this distinction, and again, when somebody explicitly asks the question if light is visible, it should immediately ring a bell that this difference in use exists. So the correct way to answer such a question is to point to the two different uses of the word 'seeing', and that the answer depends on which meaning you give to the word seeing. If you imply both, then of course you see light and macro objects.

And again you are contradicting yourself: on one side you argue that we only see light; on the other you say that both meanings are legitimate. So what is it?

 

9 hours ago, koti said:

All we can see is light - nothing less, nothing more - only light.

Then you must conclude that the daily use of 'seeing', in the sense of 'seeing houses, cars and apples' is the wrong meaning. Say the OP would have asked if it is true that we cannot see macro objects, would you have agreed with him, because we in fact only see light?

On 08/02/2018 at 8:29 AM, Eise said:

Again: it is obvious that we all agree on the physical basis of seeing macro objects on the one side, and light at the other side. If we see light, it means the light enters the eye. If we see macro objects, the objects do not enter our eye. On the other side: we see cars because they reflect light, but we cannot see light that does not enter the eye, light does not reflect or emit light. Do we agree so far?

9 hours ago, koti said:

No, I disagree with the above, it is wrong

I only described physical facts here. So what is wrong?

[koti]

2 hours ago, Eise said:

 

Then you must conclude that the daily use of 'seeing', in the sense of 'seeing houses, cars and apples' is the wrong meaning.

Absolutely not, I do not have to come to this conclusion. In fact it would be a ridiculous conclusion, we see macro objects (or any other object) only due to light emitting or reflecting off of them and  there is no other means of seeing for humans. That is the only meaning of „seeing”, there is only one way of „seeing” for humans.

[Eise]

2 hours ago, koti said:

In fact it would be a ridiculous conclusion, we see macro objects (or any other object) only due to light emitting or reflecting off of them and  there is no other means of seeing for humans. That is the only meaning of „seeing”, there is only one way of „seeing” for humans.

But this implies again that we do not see light... Really, the only way out is to acknowledge that the word 'seeing' has two meanings (at least).

We both say 'I see an apple' and 'I see light', but the process as a whole is not the same. In the first case reflection is necessarily involved, in the second it isn't. But don't you agree that is just a question of semantics? Do you think we disagree on any physical process involved in seeing?

[studiot]

4 hours ago, koti said:

Absolutely not, I do not have to come to this conclusion. In fact it would be a ridiculous conclusion, we see macro objects (or any other object) only due to light emitting or reflecting off of them and  there is no other means of seeing for humans. That is the only meaning of „seeing”, there is only one way of „seeing” for humans.

If this were true then how would you account for the fact that two humans can look at something and 'see' two different things?

 

This fact is much used in optical illusions.

[koti]

1 minute ago, studiot said:

If this were true then how would you account for the fact that two humans can look at something and 'see' two different things?

 

This fact is much used in optical illusions.

Because their brains parse light differently based on knowledge, experience and dozens of other factors.

[studiot]

1 minute ago, koti said:

Because their brains parse light differently based on knowledge, experience and dozens of other factors.

 

So there is more than one way of seeing for humans.

 

Edited February 9, 2018 by studiot

[koti]

2 minutes ago, studiot said:

 

So there is more than one way of seeing for humans.

 

No. In the context of seeing or not seeing light - No. What happens in somebodies brain when parsing light which was fed into it is outside of the scope of the OP question. Light is visible.

56 minutes ago, Eise said:

But this implies again that we do not see light... Really, the only way out is to acknowledge that the word 'seeing' has two meanings (at least).

We both say 'I see an apple' and 'I see light', but the process as a whole is not the same. In the first case reflection is necessarily involved, in the second it isn't. But don't you agree that is just a question of semantics? Do you think we disagree on any physical process involved in seeing?

Im pretry sure we are not in disagreement on the physics (Ive seen your posts in physics, you are not impaired as to knowledege in physics) I might be wrong though, maybe you do not know how image is being created in human eye and brain, you tell me.

[dimreepr]

Just now, studiot said:

 

So there is more than one way of seeing for humans.

 

 

No, we can only see the light that enters the eye but there is more information than we can perceive because we don't possess the real-time processing power to do so; so the brain guesses to fill in the gaps. Much like a radio can detect all the stations/transmissions but can only play one station at a time.

[studiot]

2 minutes ago, koti said:

No. In the context of seeing or not seeing light - No. What happens in somebodies brain when parsing light which was fed into it is outside of the scope of the OP question. Light is visible.

Quote

 

I have a question about light. We all know that we see objects because they reflect light into our eyes. But we never see the actual light. So my question is why can't we see light. Or can we in fact see light. If so, how?

 

The OP presumably had a reason for that statement, though we will never know what that reason was.

So no, it is not outside the scope of the OP at all.

 

'Seeing' is a complicated process, as is 'invisibility/visibility' and they not the same thing.

I can see with my eyes a certain something that is invisible , but I cannot see it in my minds eye in my brain.

 

 

Just now, dimreepr said:

 

No, we can only see the light that enters the eye but there is more information than we can perceive because we don't possess the real-time processing power to do so; so the brain guesses to fill in the gaps. Much like a radio can detect all the stations/transmissions but can only play one station at a time.

We can overcome this by looking at a static picture for as long as we need.

Again this is still the basis of many optical illusions.

[dimreepr]

4 minutes ago, studiot said:

We can overcome this by looking at a static picture for as long as we need.

Again this is still the basis of many optical illusions.

 

And radios are susceptible to heterodyning.  

[studiot]

7 minutes ago, dimreepr said:

And radios are susceptible to heterodyning.  

Go on ?

[koti]

52 minutes ago, studiot said:

 

The OP presumably had a reason for that statement, though we will never know what that reason was.

So no, it is not outside the scope of the OP at all.

 

His question was can we or can we not see light which the answer to is a yes we can. His statement that "we never see actual light" is false. Look at the emitter below which I just took a picture of...its in very low mode below 2 lumens to take see the emitter in the photo. In one of the pictures the emitter is on in the other its off. Can you guess which is which? If you can, you can in fact see the photons being emitted straight from the source of light. 

[CharonY]

1 hour ago, koti said:

What happens in somebodies brain when parsing light which was fed into it is outside of the scope of the OP question. Light is visible

The process of "seeing" requires brain activity if we define it as being able to "see" objects. I.e. it is the reconstruction of an object based on patterns sensed by the photo-reactive cells.

The actions on the retina itself is insufficient to see objects. It is only able to sense photons (or rather the absorption of photons by pigments). To use Eise's example, photons hitting retina would be the perception of light (see2, I believe) and reconstructing these patterns would be another definition of "see". Even colour perception is an ensemble activity and requires higher wiring. A disruption in the wiring would allow you to see light (or rather, perceive brightness differences) but could destroy the ability to perceive colour and/or objects.

[koti]

20 minutes ago, CharonY said:

The process of "seeing" requires brain activity if we define it as being able to "see" objects. I.e. it is the reconstruction of an object based on patterns sensed by the photo-reactive cells.

The actions on the retina itself is insufficient to see objects. It is only able to sense photons (or rather the absorption of photons by pigments). To use Eise's example, photons hitting retina would be the perception of light (see2, I believe) and reconstructing these patterns would be another definition of "see". Even colour perception is an ensemble activity and requires higher wiring. A disruption in the wiring would allow you to see light (or rather, perceive brightness differences) but could destroy the ability to perceive colour and/or objects.

Thanks CharonY, although I am well aware of everything you wrote, it is well written. This has no merit in my opinion in answering the simple OP question. Color perception is a tricky subject for example and Ive spent quite some time researching it for work but whether we can or cannot see light - common. None of the processes mentioned in your post can take place without light entering the eye. Arguing the semantic side of „I can see pitch black darkness therefore light is not all I can see” is just silly in my opinion.

[dimreepr]

1 hour ago, studiot said:

Go on ?

These plants clearly see, no other definition required.

What we see is a different question.

[CharonY]

The discussion goes in circles because it is down to semantics. But considering the rest of the discussion one can make a the distinction that they can only see light (i.e. differences in brightness) but are unable to see objects. Or, as has been mentioned, we perceive light directly (on the retina) but need additional information (and mechanisms) to perceive objects.

As most have conceded, that is a meaningless distinction in terms of OP, but it is pretty much one of the distinctions that spawned these nine pages. Obviously, we always need the former to be able to do the latter. But if we wanted to make a distinction, we could.

 

Edited February 9, 2018 by CharonY

[studiot]

19 minutes ago, dimreepr said:

These plants clearly see, no other definition required.

What we see is a different question.

I posted an encouraging "go on" because I couldn't make a connection to the extract from my post which you replied to.

 

I am now even more mystified than ever by your response.

 

58 minutes ago, CharonY said:

The process of "seeing" requires brain activity if we define it as being able to "see" objects. I.e. it is the reconstruction of an object based on patterns sensed by the photo-reactive cells.

The actions on the retina itself is insufficient to see objects. It is only able to sense photons (or rather the absorption of photons by pigments). To use Eise's example, photons hitting retina would be the perception of light (see2, I believe) and reconstructing these patterns would be another definition of "see". Even colour perception is an ensemble activity and requires higher wiring. A disruption in the wiring would allow you to see light (or rather, perceive brightness differences) but could destroy the ability to perceive colour and/or objects.

 

Well that is only one definition of 'seeing' and contrary to the Scientific Dictionary definition, coinciding with the usage by the John Cutherber camp.

However I am glad you joined the fray because I was hoping to ask someone who knows vastly more bioscience than I to pass comment on creatures which are born blind but have eyes which they later develop sight in.

 

1 hour ago, koti said:

His question was can we or can we not see light which the answer to is a yes we can. His statement that "we never see actual light" is false. Look at the emitter below which I just took a picture of...its in very low mode below 2 lumens to take see the emitter in the photo. In one of the pictures the emitter is on in the other its off. Can you guess which is which? If you can, you can in fact see the photons being emitted straight from the source of light. 

 

 

I have always stated that there is more than one usage of see.

Yes I agee we can see light. One distinct usage

I also agree with those who say we can see objects, in the sense of a Cahron Y's reconstruction. Another distince usage

I can also see difficulties with both those usages in certain circumstances, if either are presented as the only definition.

 

That is why I have constantly maintained

 

"It's complicated"

 

and provided numerous examples.

 

Here is one for optical illusions.

What do you 'see' ?

 

 

[dimreepr]

3 minutes ago, studiot said:

I am now even more mystified than ever by your response.

 

OK, sorry, forget the radio reference, just reply to my latest post in the context of the OP "Is light visible"? of course it is despite what you think you see.