Light: visible or invisible?

[koti]

44 minutes ago, studiot said:

 

What do you 'see' ?

 

 

Me and dimreepr arguing about religion

[John Cuthber]

On 2/9/2018 at 7:07 AM, Eise said:

I always meant macro objects when I wrote about 'things'.

Then, by a neat "begging the question" argument, light isn't a visible thing because it's not a thing. However the thread isn't about "thing-ness" i's a bout "see-able-ness".

More fundamentally, I see you have finally come round to my way of thinking.

 

On 2/9/2018 at 7:07 AM, Eise said:

On the other side there is one thing we can see because it enters the eye: light.

Light is a thing we can see, ergo it is not invisible.

On 2/9/2018 at 7:07 AM, Eise said:

...is a different process as seeing light...

If there is a process of seeing light then light is visible.
QED.

Also, you seem to have missed the context of my comment that you only see light.

On 2/22/2016 at 7:41 PM, John Cuthber said:

Unless we are talking about the idea of "close your eyes and imagine a hippo- how many legs does it have" as seeing, then there's no sensible debate here

The only thing you see is light.

The blue apple that you insisted that I saw only exists in my head- it's like the hippo.

Same for the optical illusions.

And the same is true of the view you have of the world. If you look at a landscape only a ting bit in the middle is actual in proper focus. Almost all of what you "see" is formed in your brain from what you expect to see.

Is this gorilla invisible?
http://www.theinvisiblegorilla.com/videos.html

 

Edited February 10, 2018 by John Cuthber

[Eise]

On 09/02/2018 at 6:08 PM, CharonY said:

The discussion goes in circles because it is down to semantics.

That really seems the case. The problem that I seem to have, is that it looks like I am presenting some alternative physics. I don't. 

On 09/02/2018 at 6:08 PM, CharonY said:

But if we wanted to make a distinction, we could.

Exactly. That is all I am pointing out: that one can make this distinction. Not that one should. 

Hi John,

Let's make an example again. You are standing in a totally dark room with an absolute black wall, the air is dry and there is no dust. There are two dividers in the room, leaving an opening. Behind the left divider stands a laser, behind the right divider stands an absolute black absorber to which the laser light is directed. No light is leaking out. Behind the opening also stands a chair.

Now you stand in front of the opening:   

                       chair
                                         x
     Laser --->                       absorber
                                         x

xxxx Divider xxxxx              xxxxx Divider xxxxxxx





                      you

Do you see the laser light?

Now you take a flash light, and shine it through the opening. You see the chair, but do you see the laser light? Can you see the laser light in this situation? So is light visible if you look at it? ('At it' is not the same a looking into the beam). 

[John Cuthber]

Been there; done that.

That's the same issue as the coast of China. I can't see it because I'm not in the right place so I'm not looking at it. Obviously, I need to clarify what that means for you.

There is no pathway for light from the coast of China to reach my eyes (because there is stuff in the way) and there is no way for light from the laser to reach my eyes (because it's going in the wrong direction..

 

For the sake of simplicity, I'm ignoring scattering of light by air.

On 2/12/2018 at 7:23 AM, Eise said:

it looks like I am presenting some alternative physics. I don't. 

No it looks as if you are saying that something you can see is invisible.

I guess you can call that semantics, but only if you more or less ignore the accepted definition of the words.

(you sometimes choose to put numbers on the word "see" to show that- like many English words- it has slightly different meanings depending on context)

[Eise]

12 hours ago, John Cuthber said:

For the sake of simplicity, I'm ignoring scattering of light by air.

Yes, please. Otherwise I must pump out all the air from the room, and put you into a astronaut suit...

12 hours ago, John Cuthber said:

That's the same issue as the coast of China. I can't see it because I'm not in the right place so I'm not looking at it. Obviously, I need to clarify what that means for you.

There is no pathway for light from the coast of China to reach my eyes (because there is stuff in the way) and there is no way for light from the laser to reach my eyes (because it's going in the wrong direction..

If you were as close to China's coast as to the laser, you would surely see it. But you see1 the coast, but you do not see1 (or see2!) the laser beam in the room.

12 hours ago, John Cuthber said:

I guess you can call that semantics, but only if you more or less ignore the accepted definition of the words.

I already said a dozen times that the distinction is pretty artificial.

12 hours ago, John Cuthber said:

(you sometimes choose to put numbers on the word "see" to show that- like many English words- it has slightly different meanings depending on context)

Exactly. So we agree that 'to see' has slightly different meanings. Then why do you not agree that if we rigorously distinguish the two meanings, reduce the meaning to only one of them (see1 = seeing macro objects because they reflect or emit light), that it does not apply to light itself (see2 = seeing light because it enters the eye).

But we can go on endlessly. If you still do not agree, I think we should agree to disagree.

 

Edited February 14, 2018 by Eise

[John Cuthber]

2 hours ago, Eise said:

If you were as close to China's coast as to the laser, you would surely see it.

 

Not if I was facing in the wrong direction

Not if there was something in the way

Not if it was dark

 

All of these things would mean that light from China didn't reach my eyes.

Similarly the fact that the light from the laser doesn't reach my eyes is the straightforward reason why I can't see it.

2 hours ago, Eise said:

Then why do you not agree that if we rigorously distinguish the two meanings.

If we change the meanings of words then we can make anything "true", but it isn't helpful. 

However, if we use the conventional meanings 

"invisible" means something you can't see and

you have already agreed that we can see light (albeit that you seem to think we need to stick a number on the word "see").

So, since light is something can see, and things you can see are not invisible, light is not invisible.

2 hours ago, Eise said:

I already said a dozen times that the distinction is pretty artificial.

The meanings of words are entirely artificial and thus the distinctions between them are too- but, as long as we stick with the accepted meanings we can communicate.

If we stop using  words for their "accepted" uses then fish handstand juice blue circuit.

[Eise]

21 minutes ago, John Cuthber said:

If we change the meanings of words then we can make anything "true", but it isn't helpful. 

I agree with that. But I only fleshed out that there is a physical difference between seeing macro objects and seeing light. For the first I need light (by reflection or by the macro object emitting light itself), for the second other light is not useful to see it, and light also does not emit light. Both processes are described by the same word 'seeing'. So the meanings are there, in the daily use of the word. I did not add a completely new meaning. I just made an artificial distinction between these two meanings. In this light it is possible to understand and react on the OP. You can be sure, without such questions as in the OP, I never make this distinction.

26 minutes ago, John Cuthber said:

If we stop using  words for their "accepted" uses then fish handstand juice blue circuit.

You take the words from my mouth...

 

[John Cuthber]

6 minutes ago, Eise said:

seeing light.

Once again- since you can see light, it's visible and there's nothing more to say about it.

[koti]

6 hours ago, Eise said:

...if we rigorously distinguish the two meanings, reduce the meaning to only one of them (see1 = seeing macro objects because they reflect or emit light), that it does not apply to light itself (see2 = seeing light because it enters the eye).

See1 = See2. In fact there is only one „see” unless black butter skate oven. 

Edited February 14, 2018 by koti

[John Cuthber]

Well, according to this remarkably well informed site.

https://randomwordgenerator.com/

"dance example similar mosquito sympathetic work out accompany pound spontaneous important"

But I'm sure you knew that already.

[koti]

16 minutes ago, John Cuthber said:

 

https://randomwordgenerator.com/

 

I like that, good for facebook conversations.

[Eise]

3 hours ago, John Cuthber said:

Once again- since you can see light, it's visible and there's nothing more to say about it.

If you want. 

33 minutes ago, koti said:

See1 = See2

You see a car because it enters your eye?

34 minutes ago, koti said:

In fact there is only one „see”

I see.

[koti]

21 minutes ago, Eise said:

 

You see a car because it enters your eye?

 

That's not a valid question in my opinion.

[Eise]

31 minutes ago, koti said:

That's not a valid question in my opinion.

Why?

I don't think so. The answer of course is 'no'. But light you see when it enters your eye.

[koti]

55 minutes ago, Eise said:

Why?

I don't think so. The answer of course is 'no'. But light you see when it enters your eye.

Its not a valid question because whatever you see is due always and only to photons hitting your retina. It doesn’t matter whether you look at a car, through a telescope at a body 600mln light years away or at an atom of helium through a scanning electron microscope. I just don’t see the alternative definition of „see” which you are trying to convey here.

Edit: The electron microscope is a bad example, its a different method of observation through bombarding the specimen with particles and getting a result in a detector.

Edited February 14, 2018 by koti

[Eise]

1 hour ago, koti said:

. I just don’t see the alternative definition of „see” which you are trying to convey here.

I am not trying to to convey a new definition. I try to clarify the question of the OP.

[koti]

On 22.02.2016 at 6:24 PM, The_Believer1 said:

Hello friends!

 

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?

 

8 minutes ago, Eise said:

I am not trying to to convey a new definition. I try to clarify the question of the OP.

The question whether light is visible or invisible is trivial. On top of it the above contains a false premise that "we never see the actual light"

 

[dimreepr]

5 minutes ago, Eise said:

I try to clarify the question of the OP.

It's a boolean question, what's to clarify? 

[John Cuthber]

2 hours ago, Eise said:

You see a car because it enters your eye?

Nobody said that, and you should know better than to try a strawman attack.

 

2 hours ago, Eise said:

The answer of course is 'no'. But light you see when it enters your eye.

Congratulations, you have demonstrated that a car is not the same as light.

Now all you need to do is find someone who was wondering about that question. Please, don't let us delay you in your search- elsewhere.

[Eise]

15 hours ago, John Cuthber said:

Nobody said that, and you should know better than to try a strawman attack.

This is what Koti said:

19 hours ago, koti said:

See1 = See2

These are my definitions. And see2 means 'seeing because it enters the eye', which of course is only valid for light. So it is not a strawman at all: it is a conclusion following from the definitions of see1 and see2 and Koti's proposition that these are the same.

15 hours ago, John Cuthber said:

Congratulations, you have demonstrated that a car is not the same as light.

Thank you. But saying of two things they are the same (or not) is always under a point of view. The point of view here is how we see things. We see cars because they reflect light, and we see light because it enters the eye. That is the difference this thread is about.

15 hours ago, John Cuthber said:

Now all you need to do is find someone who was wondering about that question.

Just the OP. Nothing more. You can google yourself. You will find some similar questions and reactions.

15 hours ago, koti said:

The question whether light is visible or invisible is trivial. On top of it the above contains a false premise that "we never see the actual light"

Well, yes, more or less. But the OP noticed a difference between how we see light and how we see macro objects.

15 hours ago, dimreepr said:

It's a boolean question, what's to clarify? 

That only two answers are possible, does not necessarily mean that the question is easy. And many posters here answered with 'it is a question of semantics', or 'depends on how you define seeing' (not just me!) So even if a question has yes/no character, it does not mean that one of these answers suffices. To give a terrible example: 'do humans have free will?' It is a yes/no question, but discussions about it are furious. Still appearing books and articles about it. And the answer might in the first place be the same as here: 'it is a question of semantics', or 'depends how you define free will'.

 

Examples:

On 22/02/2016 at 6:46 PM, swansont said:

So a lot of this depends on what you mean by "seeing" light.

On 26/01/2018 at 8:41 PM, studiot said:

I agree we need a working definition of seeing and in order to have that we need a working model of the process

On 26/01/2018 at 10:19 PM, MigL said:

Maybe we need to define what visible and invisible means instead.

On 27/01/2018 at 9:19 PM, MigL said:

everything else is semantics.

On 28/01/2018 at 2:52 PM, swansont said:

Slippery and especially so when nobody defines their terms.

On 29/01/2018 at 12:02 PM, swansont said:

Depends on how you've defined the terminology. (...) Stop pretending that everyday language has such precise definitions. It doesn't.

 

 

 

 

 

Edited February 15, 2018 by Eise

[Area54]

I haven't read the entire thread, but I incline to CharonY's remark that this is a semantic debate. That made me wonder, can we feel touch?

If you reflect on what that means - and i haven't figured it out - it might lead you to a similar conclusion. If it does nothing for you please excuse the interruption.

[koti]

1 hour ago, Eise said:

This is what Koti said:

”See1 = See2”

Cute strawman Eise. I thought you were better than that. 

[Eise]

46 minutes ago, koti said:

Cute strawman Eise. I thought you were better than that. 

Explain why this would be a strawman. You use my definitions. How else should I understand this?

52 minutes ago, Area54 said:

That made me wonder, can we feel touch?

That is not the same, that is a pleonasm. Something like 'it costs expensive': one should say 'It is expensive' or 'it costs much'.

52 minutes ago, Area54 said:

I incline to CharonY's remark that this is a semantic debate

Yep. 

 

Edited February 15, 2018 by Eise

[Area54]

28 minutes ago, Eise said:

That is not the same, that is a pleonasm. Something like 'it costs expensive': one should say 'It is expensive' or 'it costs much'.

You have missed the point. The meaning of an expression is contingent upon ones interpretation of the meaning and interrelationship of its components. When ambiguity as to these meanings exists contrary interpretations are possible. The inherent awkwardness/peculiarity of my phrase, can we feel touch, was there to provide an alternative example. It either works for the reader, or it doesn't.

[koti]

41 minutes ago, Eise said:

Explain why this would be a strawman. You use my definitions. How else should I understand this?

First you advertise your 2 definitions of seeing which I don't agree with and when I'm contradicting your line of thinking with my line of thinking you state that Im using your definitions. Its more of a "being a dick" fallacy than a strawman.

Edited February 15, 2018 by koti