And who's zed?

Zero and infinity are very different from one another. For example, as numbers get smaller, they get closer to zero. But as numbers get larger, they do not get closer to infinity.

A very large number is no closer to infinity than a very small number.

Another way of stating the red/blue and dark/pale contrasts:

High frequency is the opposite of low frequency,

and

High amplitude is the opposite of low amplitude.

Bono:Talent

That is a very interesting series of posts, Pinhedz, and am going to have to take a little more time to fully appreciate what you are saying.
But here is my initial reaction: You seem to defining 'Opposite' by direction.
I say: Big and Little- Big can be infinitely Big, Little can be infinitely Little.
Negative Infinity and Positive Infinity- It's still infinity.
Colours: We are limited in the colours we are able to percieve. But I don't see any reason to believe that 'they' end in either direction.
So, these examples are only points on a spectrum. Pick a point in space: You can't move either up or down from it you can only move away.
If I had asked for the Opposite of +23 and you said: -23; I could understand the mathematicians categorization. But they aren't really Opposites except in an equationally sort of way.
Zero is Zero. It is infinitely Zero. 'Infinity' may move Away in every and all directions including through, and up, and down, and around Zero.
Maybe I will think of a better way of explaining myself later. I just completed building a 40 ft swinging walk bridge across a spring branch and I'm a little worn out.

A few points for when you've recovered:

Quote:

You seem to be defining 'Opposite' by direction.

-- No, I say I there's more than one way to define it, and we haven't picked one.

Quote:

I say: Big and Little- Big can be infinitely Big, Little can be infinitely Little.

-- I said that, too (in fact, that was my answer to your question).

Quote:

Negative Infinity and Positive Infinity- It's still infinity.

-- They are still opposites on a number line.

Quote:

Colours: We are limited in the colours we are able to percieve. But I don't see any reason to believe that 'they' end in either direction.

-- They don't have to end for frequency or amplitude changes to be in opposite directions. But the theoretical limits would be zero frequency (infinite wavelength) at one end and zero wavelength (infinite frequency) at the other end.

Quote:

So, these examples are only points on a spectrum. Pick a point in space: You can't move either up or down from it you can only move away.

-- I be hard-pressed to name an opposite for a color. If you took two laser beams of the same color--but 1/2 wave-length out of phase so that they interferred destructively, the result would be no light at all. You could call those two beams opposites in the same sense that you could call matter and anti-matter opposites.

Quote:

If I had asked for the Opposite of +23 and you said: -23; I could understand the mathematicians categorization. But they aren't really Opposites except in an equationally sort of way.

-- If you had asked me to identify the opposite of +23 or the opposite of -23, I think I would have been stumped (but I might come up with something anyway).

Quote:

Zero is Zero. It is infinitely Zero. 'Infinity' may move Away in every and all directions including through, and up, and down, and around Zero.

-- You can say that about an origin point, but on a number line there are only two directions.

There is no mathematical or scientific answer to the question "What is the opposite of zero." So any answer to the question should really start with a statement about what we mean by opposite. I suggested a few ways to define it, one of which allows an answer (e.g., big vs little), while the other precludes an answer (e.g., positive vs negative).

_________________
I don't do it for the money, babe. I do it to entertain people.-- Susan Boyle

Moving away from something in a different direction doesn't negate something that moves in a seemingly other direction.

Your example of the two exact same colours intersecting 1/2 a wavelength out of synch is interesting. If light is both a wave and a particle I wonder if the waves of one version of the same colour interfer with the particles of the other, and vice versa. I will have to think about that.
But we can both agree that if the two versions negate one another, we are left with zero.

Nah, I don't think that is the end. I asserted that there wasn't a clear definition of the term 'Opposite'. That the definitions of that term are muddle headed. That each and every one of those definitions are mere constructs. Abstractions. That they don't hold up under scrutiny.

You said that opposite is a convention. Also: "I think to prove the existence of 'Opposite' we need two fixed points absolute and diametrically opposed to one another."

By that, I assume that you mean to prove the existence of "Opposite" in nature.

But to me, your critierion for "proof" in nature is just your convention for defining opposite.

Using your convention, I would have to say that zero and infinity do not negate each other. I could not even call infinity a fixed point, because for any fixed point, you can always name another that is bigger, or farther, or whatever.

But, there could be a different convention (albeit not yours) that treats "big" and "little" as opposites (even though they don't negate each other). Under such a convention, I could argue that zero and infinity are opposites.

Positive and negative charges will neutralize each other. But I can't call charges "fixed points."

I do think that is the best we can do. Man is the measure of all things. These things mean what we say they mean. The term 'Opposite' can apparently mean most anything. 'Zero' is somewhat more fixed. 'Infinity' is completely unhinged but strangely enough, also fixed.
But what do you think of my idea that in any two intersecting beams of light, the waves of one interfere with the particles of the other, and vicer versar?

Sorry, I posted my above post before I read your previous post. Aren't the terms 'positive' and 'negative' also Directional?