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Left and Right - Definitely defineable

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758954.  Tue Nov 09, 2010 6:31 am Reply with quote

Leith wrote:
I don't know the full story, but Daniel Dennett appears to touch on this in "Consciousness Explained":

Daniel Dennett wrote:
Many have noticed that it is curiously difficult to say just what properties of things in the world colors could be. The simple and appealing idea - still found in many elementry discussions - is that each colour can be associated with a unique wavelength of light, and hence that the property of being red is simply the property of reflecting all the red-wavelength light and absorbing all the other wavelengths. But this has been known for quite some time to be false. Surfaces with different fundamental reflective properties can be seen as the same color, and the same surface under different conditions of lighting can be seen as different colors. The wavelengths of the light entering the eye are only indirectly related to the colors we see objects to be.

It's certainly true that colours can appear very different in contrast with other colours (as an example see here).

However, if you communicated to an alien civilisation that our eyes perceive a pure light source emitting E-M radiation at a frequency of 650 nm as "red", then that would communicate the idea perfectly.

759565.  Thu Nov 11, 2010 8:32 pm Reply with quote

If the idea you are trying to communicate is the essence of the human concept of 'red', then I'm not sure I agree.

You'd be describing one way in which, under laboratory conditions, you could get most people to report that they saw a red colour. It's not even an experiment that our hypothetical alien correspondents could likely repeat, unless they have a strikingly similar biological make-up, culture and evolutionary history to us (and not necessarily even then).

Leaving aside the purely subjective qualities or our experience of red, that description says nothing of the role or utility of red in our lives - that it helps us recognize ripe fruit, fire and blood (and possibly offers delight or warning to shepherds?). It doesn't describe our behavioural response to red - that it can trigger associations of alarm, warmth or anger. These aspects of red seem to me to be at least as important as the medium that maps these properties of the world around us to our perceptions, perhaps even more so. That they are disparate and hard to relate or categorise simply reflects that red is a more complex and multi-faceted idea than we often give it credit for.

As for the medium itself, in daily life the colours we perceive are determined not just by the absolute frequency of incident light on one part of our retina, but also by the distribution of frequency and intensity of light across our whole field of vision. The effect of Colour Constancy can be used to produce illusions like the one you linked above, but in general it is a useful and important trait that allows us to associate colours with objects independently of the lighting conditions. Furthermore, in very low light our perception of colour in relation in light frequencies changes as rod cells take over from cone cells (the Purkinje effect).

Here's an interesting post of tchrist's that further illustrates the complex and indirect relationship between light frequency and colour: post 646784.

936307.  Fri Aug 31, 2012 12:56 am Reply with quote

If we define enough information for these aliens, they can know what *we* call right from left.

I'm not sure what exact graphics would show this, but its to do with the right-hand rule of magnetic fields (some others have touched on this, but I'm not sure they went this way.)

If: I can show which way a current flows (for instance by showing charge differential) in a wire

If: I can show the human left and right hand (that is, attached to the human) in a way to show the fingers bend only one way.

If: I can show the lines of magnetic lines of flux (and which direction they are flowing)

I can use the 'right-hand' rule to show that the human's right hand describes the direction of the lines of flux in terms of the current flow. Thus, I can define the right hand of a human (a human drawing), thus I show right from left.

... like I say, the drawings are a bit complex, but for instance the human drawing on the voyager disc could be used to show hands clenched and open (showing that they only bend the one way)... and... and its late...


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