Re: OT: Algebra help, please

Marjorie <dontusethisaddress@xxxxxxxxxxxxxxxxxxx> wrote:
Linda Fox wrote:
On Tue, 27 Jan 2009 23:46:05 +0000, "J. P. Gilliver (John)"
<G6JPG@xxxxxxxxxxxxxxxxxxx> wrote:
(I always thought the
distinction between indigo and violet somewhat artificial, too.)

I've never got that bit either.

Me neither. I think it's just a way of creating a seventh colour, as
seven is a propitious number and 6 is not. They could just as well have
made it "turquoise" or "lime".

Are there English traditions that don't include indigo? I wonder if
I remember my early education wrongly but I think I didn't really
learn seven but six rainbow colours, and I have a memory of noticing
that indigo was mentioned more in English than German sources. These
days of course such differences are blurring, but a Google search for
the German equivalent of "rainbow six/seven colours" comes out 38,500
vs 11,100 in favour of the six colours. Apparently the rainbow flag
used by the gay and lesbian movement has six colours while the one
used by the Italian peace movement has seven.

The German Wikipedia article on indigo says: "Newtons indigo / Indigo
was named by Isaac Newton as one of the 'seven colours' of the spectrum,
although what we really have is a continuum. He chose seven because
this matched the magical number of the then known planets, the seven
days of the week and such. [...] But as the human eye is comparitively
insensitive in this part of the spectrum, indigo is more perceived as
a nuance of violet or blue. Many colour metrics avoid this by placing
the boundary between violet and blue at 450 nm." (Indigo is between
425 and 450 nm, according to the article.)

Sebastian

.

Relevant Pages

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