[ExI] extropy-chat Digest, Vol 148, Issue 11

John Clark johnkclark at gmail.com
Tue Jan 26 18:42:42 UTC 2016

On Tue, Jan 26, 2016 at 6:26 AM, Anders Sandberg <anders at aleph.se> wrote:

​> ​
> Actually, the Webb telescope is radiating a lot of IR in most directions.
> It is only the the business end that is cold.

I don't see why that would be. A parabolic dish will focus the IR light
hitting the dish from the outside but it won't focus the blackbody IR
emitted by the dish itself due to its temperature. from a distance a dish
should look indistinguishable from a disk provided they were both at the
same temperature and size and they were both silver, or if they were both
black. With the Webb the outside
 will be reflected and will heat the detector at the focus and thus
creating more blackbody IR that the  distant observer will see, although I
concede at a
*slightly* longer wavelength.  So OK it would look slightly cooler because a
the business end
​ ​
the detector would be in the distant observer's
 line of sight and at other directions it would no
​t be​
, but I think the reflected IR would be far weaker than the blackbody IR.
​ So they'd be *almost* indistinguishable. ​

​ John K Clark​
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