Rainbows

[tomgwyther]

Would I be right in think that:

1. In order for a rainbow to exist; it must be observed

2. There are as many rainbows as there are people looking at rainbows.

 

The reason I ask is this. A while ago I was at my mothers house, her lounge has an extensive view over the Solent. (Solent: a straight of ocean between the Isle of Wight and main land England)

I was stood at the window, while she was sat on the couch, about 6' away. We both observed a rainbow.

She asked

"You have a better view of that rainbow than me, how far round does that rainbow go? How big is it? my view is obscured by the window frame."

"From my point-of-view, I can see both ends of it touching the horizon, but then your observation of half a rainbow is equally valid." I replied.

"How can that be?" she said "Surely you have a better view of the rainbow as you're stood nearer the window."

I then went on to explain about Water droplets, 30 degree angles, spectra, refraction etc etc and that the people on the beach in front of the house would have a different view of the rainbow, which would be equally as valid as our own.

 

This episode eventually led me to the conclusions (1&2) above. So, are they correct?

 

 

I've included this slightly appalling picture in an attempt to illustrate the two view points.

Edited November 4, 2010 by tomgwyther

[Moontanman]

Would I be right in think that:

1. In order for a rainbow to exist; it must be observed

2. There are as many rainbows as there are people looking at rainbows.

 

The reason I ask is this. A while ago I was at my mothers house, her lounge has an extensive view over the Solent. (Solent: a straight of ocean between the Isle of Wight and main land England)

I was stood at the window, while she was sat on the couch, about 6' away. We both observed a rainbow.

She asked

"You have a better view of that rainbow than me, how far round does that rainbow go? How big is it? my view is obscured by the window frame."

"From my point-of-view, I can see both ends of it touching the horizon, but then your observation of half a rainbow is equally valid." I replied.

"How can that be?" she said "Surely you have a better view of the rainbow as you're stood nearer the window."

I then went on to explain about Water droplets, 30 degree angles, spectra, refraction etc etc and that the people on the beach in front of the house would have a different view of the rainbow, which would be equally as valid as our own.

 

This episode eventually led me to the conclusions (1&2) above. So, are they correct?

 

 

I've included this slightly appalling picture in an attempt to illustrate the two view points.

 

I think you are correct, everyone sees a different rainbow, your rainbow is unique to you and therefore as real as anyone else's.

 

I think this is interesting

 

http://en.wikipedia.org/wiki/Rainbow

 

A rainbow spans a continuous spectrum of colours; the distinct bands are an artifact of human colour vision. The most commonly cited and remembered sequence, in English, is Newton's sevenfold red, orange, yellow, green, blue, indigo and violet (popularly memorized by mnemonics like Roy G. Biv). Rainbows can be caused by other forms of water than rain, including mist, spray, and dew.

 

or this, I've seen the moonbow effect many times but not a glory.

 

http://en.wikipedia.org/wiki/Glory_(optical_phenomenon)

[swansont]

I think it's fair to say that the (double) refraction of water does not depend on whether there is an observer.

[tomgwyther]

So postulate #2 is demonstratively true, whereas postulate #1 is somewhat subjectively true.

That is, the conditions for the appearance of a rainbow would all be there except for the observer whom is necessary for the rainbow to exist.

[Rilx]

The postulates can be united to

"There are as many rainbows as there are observers looking at rainbows".

 

Rainbows are characteristically subjective experiences. The "objective spectrum" created by refraction includes all wavelengths of sunlight, which is astronomically larger than any animal can see. Besides, even though the phenomenon of refraction don't depend on observers, colours exist only in the minds of observers.

[dragonstar57]

The postulates can be united to

"There are as many rainbows as there are observers looking at rainbows".

 

Rainbows are characteristically subjective experiences. The "objective spectrum" created by refraction includes all wavelengths of sunlight, which is astronomically larger than any animal can see. Besides, even though the phenomenon of refraction don't depend on observers, colours exist only in the minds of observers.

but the rainbow is there regardless of the presence of an observer

[tomgwyther]

"There are as many rainbows as there are observers looking at rainbows"

 

This is as I suspected. in that, as opposed to a table or tree, which does exist irrespective of the presence or absence of an observer. A rainbow or other similar phenomena needs a conscious observer in order to be diagnosed as a rainbow... In order to exist.

[Sisyphus]

This is as I suspected. in that, as opposed to a table or tree, which does exist irrespective of the presence or absence of an observer. A rainbow or other similar phenomena needs a conscious observer in order to be diagnosed as a rainbow... In order to exist.

 

But a table or a tree also need an observer in order to be "diagnosed" as a such. The atoms of a table are objective. The fact that those atoms constitute a "table" is subjective, a classification of the human mind.

 

But this discussion is more metaphysical than I think it needs to be. The objective reality of the rainbow is that light is double refracted as it passes through droplets of water. As a result, nearby points in space will be bombarded with photons not in the usual mixed up way, but receive them from slightly different directions depending on the wavelength of each photon. None of that requires an observer.

 

The statement "I see a different rainbow than you" is still true in more ways than "I see a different table than you," though, because the rainbow referred to is the light itself, and different light is entering your eye than mine. The same is true when looking at a table, but in that case you're not talking about the light entering your eye, but rather the object that the light entering your eye allows you to deduce the existence of. "I see a different rainbow than you" is more equivalent to "I see a different image of a table than you," which is true, because your perspective is different. You could say, however, that you are both looking at the same water droplets.

[swansont]

Perhaps another way of looking at this (as it were) is that a rainbow is a phenomenon rather than an object. In order to observe the phenomenon, you have to be in a certain area for the light to refract and get to you, while that is not true in the same way for viewing a physical object. But the phenomenon is occurring regardless of whether there is an observer.

 

I think the "I see a different image of a table than you" comparison is good.

[michel123456]

At the risk of sending this thread in another direction: the same, and worse, goes for the image in the mirror. If you look in a mirror not in front of you, but at an angle, in such manner that you can see another person, a friend of yours, you will see the image of your friend upon the mirror, and your friend will see your image upon the same object at the same time. Which of the image is "real"?

Edited November 5, 2010 by michel123456

[Rilx]

Sisyphus, swansont, michel123456, with all respect, I think you are barking up the wrong tree.

 

What I'm saying is that colours don't exist in the nature. They are born in our brains. Our visual system selects those wavelengths from the refraction of sunlight which we are evolved to detect ("see"). It is only a small part of the objective phenomenon of refraction spectrum, which includes "all" wavelenghts. Other animals see different rainbows, if any.

 

Colours we see don't systematically correspond any electromagnetic wavelenghts, as can be seen in visual illusions. Instead, their function is resolution.

 

[Sisyphus]

I don't disagree with you, Rilx. Similarly, you could say that the image of a table doesn't exist in nature. However, the patterns of photons that the brain processes as table or rainbow do exist in nature. "Color" as such is subjective - the light that causes us to see color is not.

[Rilx]

But refraction does not build any pattern of photons which would objectively correspond the rainbow we see. It refracts all wavelenghts similarly whether they belong to human visual spectrum or not. This flat row of refracted wavelenghts enter our retina, and our photoreceptive cells select the wavelengths which will - not until then - form the pattern we experience as a rainbow.

 

Images of tables or other physical objects don't behave this way. Corresponding patterns of photons exist before they enter our eyes. Actually we don't usually care too much of the exact color of physical objects. But rainbows are nothing but light, colours are all they are.

[Sisyphus]

But refraction does not build any pattern of photons which would objectively correspond the rainbow we see.

 

Sure it does. The photons incoming towards a given point will be sorted by wavelength, coming from slightly different directions.

[Rilx]

I try to invent a good example to enlighten my viewpoint.

 

I'd also appreciate if some others thought this problem.

[tomgwyther]

The table and the tree retain their properties without them being looked at. For example, i can close my eyes and observe or measure a table by reaching out and touching it, it still has all the tabley qualities I would expect.

the same would be true of the two people looking at each other in a mirror at 45 degrees; they could close their eyes and touch, hear or smell each other.

A rainbow needs to have a lens, a retina and a brain to exist. the conditions for a rainbow may be present, but the appearance of a seemingly three dimensional object in the sky is not.

[Sisyphus]

The table and the tree retain their properties without them being looked at. For example, i can close my eyes and observe or measure a table by reaching out and touching it, it still has all the tabley qualities I would expect.

the same would be true of the two people looking at each other in a mirror at 45 degrees; they could close their eyes and touch, hear or smell each other.

A rainbow needs to have a lens, a retina and a brain to exist. the conditions for a rainbow may be present, but the appearance of a seemingly three dimensional object in the sky is not.

 

That's why I think it's more analogous to the image of a table. The atoms of the table are there whether anyone is looking at it or not, and so are the water droplets refracting light and "sorting" it by wavelength. But in order for the image of the table to exist, it needs photons bouncing off of it, through a lense, and onto a retina, and that effect needs to interpreted in a brain for an "image" to exist.

 

One way it is different is that our brains tend to interpret "table data" fairly accurately, to judge there is a solid object of so and so size and shape, which is a conclusion similar to what other observers will arrive at. While the "rainbow data" causes an illusion that makes it seem* like there is a three dimensional solid object at some particular location in the sky, that an observer at a different location will disagree with completely.

 

*"makes it seem" as in, if you interpret sensory data the same way you interpret it while looking at a table, you will arrive at this conclusion