What is a Watt???

[Derek]

Hi All,
Just a brief note that I hope is easily understandable...

Watt = Joule per second.
I think this is the crux of the matter, in that, this is what causes the confusion.

It could easily be rewritten as
amount (Watt) = amount (Joule) over a certain time (second).

To describe a flow one needs amount AND time, so a Watt does not describe a flow, but a Joule per second does.
In short without time one merely has an amount.

Watt per square meter, W/m2, could be rewritten as
Amount (Watt) over a specified area (square meter).
This does not include time, so therefore can not describe a flow.
This is why a W/m2 is a power or pressure figure.

If one is dealing with black bodies however then a W/m2 is effectively a substitute for flow
because all the parts are "equal" black body surfaces...

So, that means all K&T and GH is explained as ALL black bodies.
They could not possibly work for gray bodies, because for gray bodies (ie the real world)
a W/m2 is merely a power figure ONLY,
the amounts of the flows are unknown...