Light: visible or invisible?

[StringJunky]

1 minute ago, Tub said:

If it isn't too far off-topic, i'd like to ask how we " see " dreams: obviously reflected light is not involved so there can't be any photons to be detected, and is it still the visual cortex that is involved? Can anyone enlighten me? ( Sorry ! ).

In the same parts of the brain that you 'see' wakeful stuff; the input during sleep is from memories and other senses.

[Tub]

Just now, StringJunky said:

In the same parts of the brain that you 'see' wakeful stuff; the input during sleep is from memories and other senses.

Thanks, SJ.

[StringJunky]

7 minutes ago, Tub said:

Thanks, SJ.

You still absorb information from your surroundings whilst asleep from tactile, olefactory and audio sensors which can be used as parts of a dream narrative.

[studiot]

2 hours ago, studiot said:

 

I'm listening ?

 

But you don't seem to be saying anything ?

I'm sorry to hear of your water shortage in Cape Town, is that the reason for your lack of loquacity?

 

But since someone likes my model, I will press on to address the actual OP about visibility v invisibility.

My first post here, but now residing in the spin off thread, I indicated that the situation is more complicated that at first meets the eye (pun intended).

This complexity extends to the question of visible v invisible and occurs, regardless of where we conside the seat of vision to lie.

Consider this

One of the standard tests for colour blindness consists of a series of pictures made from dots of two colours, with a field of dots of one colour containting an embedded symbol of dots in the other colour.

In the series the colours approach each other until the symbol is 'invisible' to all humans.

In the more contrasting earlier pictures the symbols are visible to some humnans but not others.

Yet all humans receive all the light reflected off all the dots.

[Strange]

9 minutes ago, studiot said:

One of the standard tests for colour blindness consists of a series of pictures made from dots of two colours, with a field of dots of one colour containting an embedded symbol of dots in the other colour.

In the series the colours approach each other until the symbol is 'invisible' to all humans.

In the more contrasting earlier pictures the symbols are visible to some humnans but not others.

Yet all humans receive all the light reflected off all the dots.

That's an interesting example. Although the difference is in whether the eyes respond to the light of that colour or not.

A contrasting example is people with synesthaesia who see numbers as different colours - they are measurably quick at finding a particular number from a crowded page of numbers because the different colour makes it stand out. But that colour is entirely generated in the brain, not from the eye.

[Furyan5]

2 hours ago, Tub said:

If it isn't too far off-topic, i'd like to ask how we " see " dreams: obviously reflected light is not involved so there can't be any photons to be detected, and is it still the visual cortex that is involved? Can anyone enlighten me? ( Sorry ! ).

Don't be sorry for asking a question. In this case it's actually very relevant. 

Usually our eyes detect light and send electrochemical impulses to our brains visual cortex. Here our brain creates a representation/simulation of the outside world, based on those impulses. The world you see is actually this internal representation. It even has a representation of you in it. 

Have you ever used 3D goggles while playing a game? If you hold your hand up in front of you, during the game, you see a virtual hand in front of you. The only difference between that virtual reality and our internal reality, is that we can't take our goggles off. Our whole life we only see this simulation. 

Now, when we dream, our brain is creating images, not from impulses from the eyes, but impulses from our imagination. It looks and sounds the same, because it occurs in the same part of the brain. 

2 hours ago, studiot said:

 

But you don't seem to be saying anything 

 

Is seeing something of zero-size logical?

 

16 hours ago, MigL said:

 

On the other hand my left eye 'sees' perfectly well, and focuses an image on my retina and its detector rods and cones. However the information cannot get to my brain because glaucoma damaged my optic nerve; and I 'see' nothing.

Your eye "sees" light, but you "see" nothing. My camera "detects" light but sees nothing. 

Oh wait, my camera "sees" light. Lol

 

Edited January 27, 2018 by Furyan5
Clarifying

[studiot]

4 hours ago, Strange said:

That's an interesting example. Although the difference is in whether the eyes respond to the light of that colour or not.

A contrasting example is people with synesthaesia who see numbers as different colours - they are measurably quick at finding a particular number from a crowded page of numbers because the different colour makes it stand out. But that colour is entirely generated in the brain, not from the eye.

 

I'm sorry I don't know enough about the detail for the mechanism of colour blindness or people with mixed up senses to comment.

Quote

Furyan5 said:-

5 hours ago, studiot said:

 

But you don't seem to be saying anything 

 

Is seeing something of zero-size logical?

 

I'm sorry I fail to the the connection to anything I have said.

What has zero size and is it visible or invisible?

[Tub]

3 hours ago, Furyan5 said:

 

Usually our eyes detect light and send electrochemical impulses to our brains visual cortex. Here our brain creates a representation/simulation of the outside world, based on those impulses. The world you see is actually this internal representation. It even has a representation of you in it. 

 

 

 

 

Thanks for your reply, Furyan5; this would explain the old phrase: " It's all in the mind ". Relating to the OP, then, is it reasonable to say that " visible " light  is white, reflected light of a certain frequency detectable by the eye, while " invisible " light , such as UV and IR,  is unreflected light of a frequency above or below our visual spectrum, and that " visible " light strikes the eye as a blanket of white, ( Studiot mentioned a sort of " whiteout "), until the eye, acting as a prism, sorts the different frequencies into separate colours - or is that done later by the brain? 

 

3 hours ago, Furyan5 said:

Now, when we dream, our brain is creating images, not from impulses from the eyes, but impulses from our imagination. It looks and sounds the same, because it occurs in the same part of the brain. 

 

 

 

Shakespeare, in " The Tempest ", famously wrote: "... We are such stuff as dreams are made on.. ". ( Act 4, Scene 1 ). Seems he was right.

[John Cuthber]

4 hours ago, Furyan5 said:

Is seeing something of zero-size logical?

I'm not too fussy about whether it's "logical" or not but in principle, I can set up an experiment to let you see it happen.

Electrons have no measurable size, yet they scatter light.

[Furyan5]

2 hours ago, Tub said:

Thanks for your reply, Furyan5; this would explain the old phrase: " It's all in the mind ". Relating to the OP, then, is it reasonable to say that " visible " light  is white, reflected light of a certain frequency detectable by the eye,

This definition is fine, as long as you realize that the light itself is not visible. It's the brains interpretation of lights wavelength  (which we perceive as color) and it's intensity (which we perceive as brightness). 

while " invisible " light , such as UV and IR,  is unreflected light of a frequency above or below our visual spectrum, and that " visible " light strikes the eye as a blanket of white, ( Studiot mentioned a sort of " whiteout "), until the eye, acting as a prism, sorts the different frequencies into separate colours - or is that done later by the brain? 

It's done, later in the brain. Everything we see is done in the brain.

 

Shakespeare, in " The Tempest ", famously wrote: "... We are such stuff as dreams are made on.. ". ( Act 4, Scene 1 ). Seems he was right.

I prefer the poem by Emily Dickinson.

The brain is bigger than the sky,

For put them side by side,

The one, the other will contain,

With ease, and you beside.

 

2 hours ago, John Cuthber said:

I'm not too fussy about whether it's "logical" or not but in principle, I can set up an experiment to let you see it happen.

Electrons have no measurable size, yet they scatter light.

You should be fussy about it being logical. If we can't see electrons with the naked eye, how can we see light?

[John Cuthber]

2 minutes ago, Furyan5 said:

This definition is fine, as long as you realize that the light itself is not visible

That's a circular argument.

3 minutes ago, Furyan5 said:

If we can't see electrons with the naked eye,

If they are brightly enough lit, we can.

[Furyan5]

5 minutes ago, John Cuthber said:

That's a circular argument.

How is that circular? Claiming light is visible because it's called "visible light" is circular reasoning. 

If they are brightly enough lit, we can.

You actually believe that? We can see electrons with the naked eye if they are brightly lit? Do you have any evidence to support this extraordinary claim?

 

[John Cuthber]

What extraordinary claim?

Scattering of electromagnetic radiation from electrons is well documented,

[beecee]

9 hours ago, Furyan5 said:

Except for your last sentence, you're right. We see the OBJECT that reflects the photons. Seeing objects provides us with an evolutionary advantage. Our eyes DETECT photons. 

Therefor we do see light and your philosophical pedant is just that.

[John Cuthber]

30 minutes ago, Furyan5 said:

 

Things may go better if you learn to use the quote function properly.

[MigL]

I really didn't think this would need an explanation...

'Seeing' is the brain's interpretation of information it gathers from certain detectors ( usually the eyes ). The detectors work by ( usually ) interacting with EM radiation.

Whether something is 'visible' or 'invisible' depends on the ability of the information, the EM radiation, to get to the detectors, the eyes.
This can be due to the path ( something may be in the way ). the intensity ( its too dark, I can't see anything ), or the type of information ( some animals can 'see' infrared, we cannot ).

The point I'm trying to make is that light, or photons, are the information carriers. And while we 'see' by interacting with the information carriers, a photon itself cannot transmit any information about itself ( it would need to radiate light ) for us to be able to 'see' it.
I.E. photons are invisible.

 everything else is semantics.

[studiot]

42 minutes ago, MigL said:

I really didn't think this would need an explanation...

'Seeing' is the brain's interpretation of information it gathers from certain detectors ( usually the eyes ). The detectors work by ( usually ) interacting with EM radiation.

Whether something is 'visible' or 'invisible' depends on the ability of the information, the EM radiation, to get to the detectors, the eyes.
This can be due to the path ( something may be in the way ). the intensity ( its too dark, I can't see anything ), or the type of information ( some animals can 'see' infrared, we cannot ).

The point I'm trying to make is that light, or photons, are the information carriers. And while we 'see' by interacting with the information carriers, a photon itself cannot transmit any information about itself ( it would need to radiate light ) for us to be able to 'see' it.
I.E. photons are invisible.

 everything else is semantics.

 

An interesting summary view and well worth considering (which I am doing at the moment).

Thank you MigL +1

[John Cuthber]

1 hour ago, MigL said:

a photon itself cannot transmit any information about itself

Really?

Does a violet photon not carry information about itself that differs from the information about itself that a red photon caries?

I grant you, it's tricky with single photons, but that's not what we see. We see streams of many photons.

If I can tell you what colour some light is, then that's because I can see it in much the same way that I can tell you what colour a car is- because I can see it.

[studiot]

54 minutes ago, John Cuthber said:

Really?

Does a violet photon not carry information about itself that differs from the information about itself that a red photon caries?

I grant you, it's tricky with single photons, but that's not what we see. We see streams of many photons.

If I can tell you what colour some light is, then that's because I can see it in much the same way that I can tell you what colour a car is- because I can see it.

Well spotted +1

[John Cuthber]

Thanks.

I don't think I will be putting it on my CV.
 

[studiot]

Well I guess that anyone interviewing you for a job would know that you were not the discoverer that violet photons were different from red photons.

[StringJunky]

1 hour ago, John Cuthber said:

I grant you, it's tricky with single photons, but that's not what we see. We see streams of many photons.

Apparently, our eyes can detect single photons better than chance. About 1 in 9. Only on the rods and just as brief flashes.

Edited January 27, 2018 by StringJunky

[John Cuthber]

2 minutes ago, studiot said:

Well I guess that anyone interviewing you for a job would know that you were not the discoverer that violet photons were different from red photons.

I'm not sure I'd want to admit to being in an environment where the fact that you can tell what colour light is- because you can see it- was ever actually under discussion

[studiot]

My Chambers dictionary of Science and Technology has

 

Quote

sight

Sensation produced when light waves impinge on the photosensitive cells of the eye.

So they are clearly of the opinion that the formation of the image on the retina consititutes seeing, not the model constructed in the brain from that "sensation".

Yet that sensation is no use without the collection and transmission of the signal to the brain - the owner of the ey is still blind without that.

Edited January 27, 2018 by studiot

[Furyan5]

1 hour ago, John Cuthber said:

Really?

Does a violet photon not carry information about itself that differs from the information about itself that a red photon caries?

Ummm, photons don't have

I grant you, it's tricky with single photons, but that's not what we see. We see streams of many photons.

If I can tell you what colour some light is, then that's because I can see it in much the same way that I can tell you what colour a car is- because I can see it.

 

2 hours ago, MigL said:

I really didn't think this would need an explanation...

'Seeing' is the brain's interpretation of information it gathers from certain detectors ( usually the eyes ). The detectors work by ( usually ) interacting with EM radiation.

Whether something is 'visible' or 'invisible' depends on the ability of the information, the EM radiation, to get to the detectors, the eyes.
This can be due to the path ( something may be in the way ). the intensity ( its too dark, I can't see anything ), or the type of information ( some animals can 'see' infrared, we cannot ).

The point I'm trying to make is that light, or photons, are the information carriers. And while we 'see' by interacting with the information carriers, a photon itself cannot transmit any information about itself ( it would need to radiate light ) for us to be able to 'see' it.
I.E. photons are invisible.

 everything else is semantics.

Exactly what I've been saying all along. Pity it isn't as obvious to everyone. 

1 hour ago, John Cuthber said:

Really?

Does a violet photon not carry information about itself that differs from the information about itself that a red photon caries?

I grant you, it's tricky with single photons, but that's not what we see. We see streams of many photons.

If I can tell you what colour some light is, then that's because I can see it in much the same way that I can tell you what colour a car is- because I can see it.

You really don't get it, do you? You see cars, because your eyes detect light. The color of the car depends on the type of light your eyes detect. You can't see light, because light doesn't emit light. If something doesn't emit light, it can't be seen.