On 8/18/2015 12:15 PM, Brian Howie wrote:
In message , George Cornelius
writes
Still, I would be curious as to whether that 50% rule - if it is
accurate at all (does a laser beam hitting a black body have to
reflect back 50%?) - applies to a microwave downlink.

If it's a true black body it's all absorbed , and either conducted away
as heat or re-radiated at the temperature of the black body at
different wavelengths

A better laser analogy is a set of lenses and a focussed fibre-optic
between them. It's possible to arrange this to be nearly 100% efficient.

Brian


It is my understanding that interstellar space (between galaxies) is
about as good a black body as can be obtained. If a source is directed
into that space, I very much doubt a return could be detected by mortals.