Light: visible or invisible?

[koti]

Retina which is a light sensitive tissue in the human eye captures light in the ~390nm-700nm wavelength region.
Light present in the tissue = "seeing" Lack of light present in the tissue = no "seeing" Light in the 390nm-700nm length is visible to humans. Light in other wavelengths is not visible to humans. There's really not many issues which are simpler than that.

Edit: It doesn’t matter if the light is straight from a source or is being reflected off of something, as long as it lands in your retina we see it. Issues arise when discussing perception of what we see (color) but there is absolutely no issue as to the fact that we see light in the visible spectrum.
 

Edited January 30, 2018 by koti

[Furyan5]

3 minutes ago, studiot said:

 

You can easily turn this line of argument on its head

First let us agree that the car is a toy car so that we can perform the experiment in a darkened room.

a) Remove the torch.

b) Paint the car with electroluminescen paint.

c) Connect the car to a suitable electric source via a switch.

In the darkened room can you see the car?

d) Close the switch.

 

What do you see?

You say "I can see the car"

You do not say "I can see the light from the car"

You see the car because it emits it's own light. Again, light, allows you to see the car.

 

However now look sideways at the car so you can't directly see it.

You can see a glow from a light source.

You mean, you see dust in the air because it's illuminated by light from the car? That's all glow is.

 

 

[koti]

Just now, dimreepr said:

No, the defect prevents us from perceiving, the eye can see but the brain doesn't know it can. 

Here we go again with the semantics. I would say that "seeing" is the final product of the capture/processing process, the capture process (retina) is not seeing but its really a pointless discussion. All this doesn't change the fact that light in the visible spectrum is very much visible to humans. 

[studiot]

29 minutes ago, koti said:

Then the defect prevents us from seing. This isnt about defects.

 

But you are the one who defined seeing as the capture of light by the retina.

I was specific in my example that that capture happened correctly ie without defect.

Yet the subject said "I see nothing".

 

That is why I say it's complicated and requires context, which has to be supplied by the utterer.

Edited January 30, 2018 by studiot

[koti]

1 minute ago, studiot said:

 

But you are the one who defined seeing as the capture of light by the retina.

I was specific in my example that that capture happened correctly ie without defect.

Yet the subject said "I see nothing".

 

That is why I say it's complicated and requires context, which ahs to be supplied by the utterer.

Aparently its easy to fall into a trap when overthinking things  

To put it simple and short, the answer to the OP is: „Yes, light in the visible spectrum is visible to humans” 

My way of thinking is this: If a cable linking the sensor to the CPU in a camera is broken it means that the cable is broken not that the camera cannot „see” 

[studiot]

8 minutes ago, koti said:

Aparently its easy to fall into a trap when overthinking things  

To put it simple and short, the answer to the OP is: „Yes, light in the visible spectrum is visible to humans” 

My way of thinking is this: If a cable linking the sensor to the CPU in a camera is broken it means that the cable is broken not that the camera cannot „see” 

 

But we use the phrase " the camera cannot see" to cover both situations (and many more besides)

Which brings us back to context and complexity.

 

Here is an example you might appreciate.

I state

 

1 + 1 = 0

You contest this

and we could argue back and fore because I did not supply the context " in Boolean algebra"

Edited January 30, 2018 by studiot

[koti]

3 minutes ago, studiot said:

 

But we use the phrase " the camera cannot see" to cover both situations (and many more besides)

Which brings us back to context and complexity.

 

Here is an example you might appreciate.

I state

 

1 + 1 = 0

You contest this

and we could argue back and fore because I did not supply the context " in Boolean algebra"

I get it. I just prefer to refuse to dig deep into contexts when faced with a trivial question like the OP. Unless the OP specifies otherwise which he didnt the context is trivial.

[swansont]

2 hours ago, geordief said:

I was wondering something similar myself. When we look directly back at a beam of light (such as a torch) are we actually "seeing" the filament/source   ? (buried in the glare)

A filament is a macroscopic object. It has a shape. I ask about a vapor because the individual atoms are too small to discern with the naked eye.

[koti]

1 hour ago, koti said:

Retina which is a light sensitive tissue in the human eye captures light in the ~390nm-700nm wavelength region.
Light present in the tissue = "seeing" Lack of light present in the tissue = no "seeing" Light in the 390nm-700nm length is visible to humans. Light in other wavelengths is not visible to humans. There's really not many issues which are simpler than that.

Edit: It doesn’t matter if the light is straight from a source or is being reflected off of something, as long as it lands in your retina we see it. Issues arise when discussing perception of what we see (color) but there is absolutely no issue as to the fact that we see light in the visible spectrum.
 

Somebody gave me down vote for the above. Could that someone explain what is wrong with the above post?

[studiot]

38 minutes ago, koti said:

I get it. I just prefer to refuse to dig deep into contexts when faced with a trivial question like the OP. Unless the OP specifies otherwise which he didnt the context is trivial.

 

Those who bring a closed mind to the discussion table can gain no benefit from the discussion and may even antogonise others, even if they are right.

 

1 minute ago, koti said:

Somebody gave me down vote for the above. Could that someone explain what is wrong with the above post?

Twasn't me guv, honest.

[koti]

4 minutes ago, studiot said:

 

Those who bring a closed mind to the discussion table can gain no benefit from the discussion and may even antogonise others, even if they are right.

 

Twasn't me guv, honest.

What can I say, you're right. As for the downvote, stop explaining yourself or I'll really think its you

[geordief]

27 minutes ago, swansont said:

A filament is a macroscopic object. It has a shape. I ask about a vapor because the individual atoms are too small to discern with the naked eye.

Has the other "philosophical" thread gone for good? I thought it made sense to split the subject...

 

 

[swansont]

1 hour ago, geordief said:

Has the other "philosophical" thread gone for good? I thought it made sense to split the subject...

That one was locked because a certain someone would not refrain from insulting people. Posts in this thread that were of philosophical or neurological nature have been removed,

[geordief]

2 minutes ago, swansont said:

That one was locked because a certain someone would not refrain from insulting people. Posts in this thread that were of philosophical or neurological nature have been removed,

I am sure the subject will crop up again some time...

[beecee]

6 hours ago, Furyan5 said:

So, it's invisible, unless it hits your eye directly. And if it hits your eye, you see the source of the light. Visible light is the light which allows us to see. 

 

What doesn't hit your eye is never seen in any circumstances. Afterall the eye is the organ that enables us to see and works by receiving and recognising the part of the EMS that is visible to the eye. 

That's physics...that's how the universe works.

[koti]

39 minutes ago, beecee said:

That's physics...that's how the universe works.

Apparently Riddick’s universe works differently. 

[John Cuthber]

On 1/29/2018 at 12:52 PM, Furyan5 said:

 

The eye is nothing but an antenna. 

It would be better if you didn't base your argument on things that are factually incorrect.

"It should be apparent by now that the retina does not just collect and transduce information about light. The signal that is transmitted to the brain has already gone through multiple stages of processing before it even enters the optic nerve."
From

http://courses.washington.edu/psych333/handouts/coursepack/ch13-Information_processing_in_retina.pdf

 

 

[StringJunky]

9 hours ago, koti said:

Aparently its easy to fall into a trap when overthinking things  

To put it simple and short, the answer to the OP is: „Yes, light in the visible spectrum is visible to humans” 

My way of thinking is this: If a cable linking the sensor to the CPU in a camera is broken it means that the cable is broken not that the camera cannot „see” 

Seeing is a process that involves all the components; remove one and it is blind. Seeing needs a brain to create/record the impression of the image and it needs everything else to get the image to it. In short, there is a minimum number of interdependent components needed for the process of seeing to occur.

Edited January 30, 2018 by StringJunky

[swansont]

11 hours ago, StringJunky said:

Seeing is a process that involves all the components; remove one and it is blind. Seeing needs a brain to create/record the impression of the image and it needs everything else to get the image to it. In short, there is a minimum number of interdependent components needed for the process of seeing to occur.

From a physics standpoint that's all a black box. As was implied earlier, one must assume the detection system is working. Otherwise you're just being obtuse and fishing for loopholes.

 

 

[John Cuthber]

On 30/01/2018 at 2:18 PM, swansont said:

A filament is a macroscopic object. It has a shape. I ask about a vapor because the individual atoms are too small to discern with the naked eye.

As I pointed out , the sodium vapour in a street lamp is blue, but what you see is yellow.
So the yellow you see isn't the "source", it's the light you see..

 

If you look at an apple, it's red.

If you look at an apple that's on a spaceship moving towards you very fast, you see it as a different colour, say blue.

The apple hasn't changed, but the light has.

How can anyone argue that you can't see light, when you can see the colour change?

On 29/01/2018 at 2:54 PM, Furyan5 said:

But by now I'm sure the answer is obvious. Like it or not.

Furyan out.

Yes, it's obvious.

You can see light- that's why you can see the colour change. It's why you can see the yellow light from a blue thing (so it's not  a matter of "seeing the source".

 

[Eise]

10 hours ago, John Cuthber said:

How can anyone argue that you can't see light, when you can see the colour change?

That is simple: you see the colour of the apple change. Not of the light itself.

It all boils down to the difference between how we 'see' different things:

• We 'see' the macro objects around us, because light is reflected by them or they emit light themselves
• We cannot 'see' light because it reflects light or it emits light; we can 'see' light directly, if it hits the eye

So in the first point light is just the means to see the things around us. But using light to see light simply does not work. (What do you do in a hell lit room, with a very faint light source? Do you turn one more lights, or do you turn the room lights off? What the hell is that, something you see better in the dark?)

Furyan5 furiously pleads that the second meaning of 'seeing' does not count as seeing. If it would be an important philosophical topic (it is definitely not a physics topic!), philosophers would split up the two concepts of seeing with the help of two different words: one can 'see1' macro objects, and one can 'see2' light. And then try to solve the real problem behind it. In this case however, I do not see any real problem. We all agree more or less on the facts of seeing.

But it is a nice intellectual exercise: try to understand the opponent, find different concepts that can lurk behind the same word, and so try to light up the intellectual problem, see the root cause of the seemingly different views on the facts. In this case it really is nothing more than an intellectual exercise. ('Light' metaphors used intentionally...)

[studiot]

 

12 hours ago, John Cuthber said:

As I pointed out , the sodium vapour in a street lamp is blue, but what you see is yellow.
So the yellow you see isn't the "source", it's the light you see..

Thank you John for telling me something new I didn't know +1

So I investigated.

 

1 hour ago, Eise said:

That is simple: you see the colour of the apple change. Not of the light itself.

It all boils down to the difference between how we 'see' different things:

• We 'see' the macro objects around us, because light is reflected by them or they emit light themselves
• We cannot 'see' light because it reflects light or it emits light; we can 'see' light directly, if it hits the eye

So in the first point light is just the means to see the things around us. But using light to see light simply does not work. (What do you do in a hell lit room, with a very faint light source? Do you turn one more lights, or do you turn the room lights off? What the hell is that, something you see better in the dark?)

Furyan5 furiously pleads that the second meaning of 'seeing' does not count as seeing. If it would be an important philosophical topic (it is definitely not a physics topic!), philosophers would split up the two concepts of seeing with the help of two different words: one can 'see1' macro objects, and one can 'see2' light. And then try to solve the real problem behind it. In this case however, I do not see any real problem. We all agree more or less on the facts of seeing.

But it is a nice intellectual exercise: try to understand the opponent, find different concepts that can lurk behind the same word, and so try to light up the intellectual problem, see the root cause of the seemingly different views on the facts. In this case it really is nothing more than an intellectual exercise. ('Light' metaphors used intentionally...)

Eise, you didn't address John's very good comment.

 

But you clearly agree that 'see' has multiple meanings.

As a result I contend that it is encumbent upon the promoter to establish which one is to be used either by sufficient context or by a specific definiton at the outset.

[Eise]

1 hour ago, studiot said:

Eise, you didn't address John's very good comment.

What did I miss? If you imagine the observer, then what he will see1, is that the apple is blue. You see that because your visual system sees2 blue light, instead of red. Just shift the meaning of to see to see1 and I addressed John's argument.

Furyan5  used the words 'to see' and to 'to detect'. But that leaves his absurd sounding 'one cannot see light' standing. With my artificial difference between 'to see1' and 'to see2' it is always clear what I mean:

You can see1 macro objects, thanks to reflecting or emitting light. We cannot see2 macro objects.

We can see2 light, but we cannot see2 macro objects because they do not enter our eyes. 

Everything clear? 

[studiot]

36 minutes ago, Eise said:

What did I miss?

John asked a very good question about sodium, although this situation also applies to other materials.

Sodium is a greyish/white/silver metal as a solid, but in the gaseous phase it is blue if illuminated with ordinary light.

Under these conditions it does not give off any yellow light.

If the blue gas is then stimulated with electricity it then also gives of yellow light.

We no longer see the blue (although it must still be there) only the yellow.

But the sodium gas itself remains blue.

So we are seeing yellow light emitted by blue objects as a result of some electrical process.

[Eise]

15 minutes ago, studiot said:

ohn asked a very good question about sodium, although this situation also applies to other materials.

Sodium is a greyish/white/silver metal as a solid, but in the gaseous phase it is blue if illuminated with ordinary light.

Under these conditions it does not give off any yellow light.

If the blue gas is then stimulated with electricity it then also gives of yellow light.

We no longer see the blue (although it must still be there) only the yellow.

But the sodium gas itself remains blue.

So we are seeing yellow light emitted by blue objects as a result of some electrical process.

Ok, this is what John said:

17 hours ago, John Cuthber said:

As I pointed out , the sodium vapour in a street lamp is blue, but what you see is yellow.
So the yellow you see isn't the "source", it's the light you see..

What you see1 are two different things:

- a street lamp with a blueish content, by means of reflecting light

- a street lamp with a bright yellow content, by means of emitting light

But of course you see2 blue light in the first case and yellow light in the second case.