On 2/2/2012 2:02 PM, p.kinsler@xxxxxxxx wrote:
FrediFizzx<fredifizzx@xxxxxxxxxxx> wrote:
No. It does not prove E and B fields are causing each other.

It seems to me that you are confusing "something that works" with a proof
of
a theorem.
I'm glad that the Yee-Algorithm gives accurate and repeatable results.
That does not mean that it represents reality.

No need for that. It proves, however, that E and B
can cause each other without giving wrong results.

Sorry, but it does no such thing. There is no causality proven
there. It is just a mathematical trick to help solve certain
EM problems.

Leaving aside whether any numerical algorithm might prove something
about the physical world, I would say that the Yee-Algorithm /defines/
the causality of any numerical simulation it is used in.

Exactly. The algorithm specifies how E and B are
obtained, and for each of them this is done by using
the other at a slightly earlier time. In that sense
one of them causes the other at a slightly later time.
My point is not that this proves that reality works
this way (as Fred seems to think) but it proves that
reality _can_ work this way!

In the algorithm, this way of working does not lead
to inconsistencies, no numerical instability, and it
even gives results that completely agree with
measurements! This refutes quite a number of arguments
used against the notion of E and B causing each other.
Whether Fred does not understand this, or simply does
not want to understand this, is not clear to me. But
his reply is not an objection to my statement.

Thus, descriptions of causality (or causal mechanisms, if you prefer)
certainly exist, even if you wish to debate their existence or validity
in other contexts (such as in the physical world or in physics).

And FDTD merely being used to solve "certain EM problems"? That's a bit
like saying English is a linguistic trick used by "certain humans" to
communicate.

O, those people P.G. Wodehouse wrote about?!

--
Jos
.

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