"Capt RB" wrote in message
...

"Edgar" wrote in message
...

No I haven't. You are confusing _into_ and _onto_.
Your beam of light only goes onto a square foot. Nothing can go into
something that only exists in two dimensions.



The concept of divergence (used in geometrical calculus) is a measure of
any
type of flux crossing a surface as the enclosed volume goes to zero. As
the
limit is taken, the enclosed volume shrinks to zero faster than the
surface
area. The divergence is a measure of flux crossing a surface of zero
enclosed volume.

In the case of a beam of light entering an enclosed surface, the
divergence
would be zero as the light source is external to the enclosed volume. The
total flux entering and leaving the surface (even if it is flat consider
both sides) is zero.

I said that in considerably fewer words...

A sphere does exist in two dimensions, for instance in both angle and
radius.

No , it does not exist in two dimensions since it is a solid shape and has
volume.

Only two dimensions needed to define the surface or volume.

No, that is not right. You only have to define one thing, namely the radius
of a sphere, not any angle, but the radius itself means nothing unless you
add to the definition the word _sphere_ , which is by definition a three
dimensional shape since the radius is not limited to just the x and y
coordinates.

Not all coordinate systems are cartesian or orthogonal

Can't comment on that. those two are enough for me..