Re: Using the sun to send a message

From: Ian Stirling (root_at_mauve.demon.co.uk)
Date: 10/04/04 

Date: 04 Oct 2004 16:21:05 GMT

In sci.physics The Ghost In The Machine <ewill@sirius.athghost7038suus.net> wrote:
> In sci.physics, Ian Stirling
> <root@mauve.demon.co.uk>
> wrote
> on 02 Oct 2004 12:58:09 GMT
> <415ea5e0$0$42246$ed2e19e4@ptn-nntp-reader04.plus.net>:
>> In sci.physics Uncle Al <UncleAl0@hate.spam.net> wrote:
>>> Skybuck Flying wrote:
>>>>
>>>> Hi,
>>>>
>>>> Seeing all the bull*** in this newsgroup or maybe sci-fi... or maybe
>>>> future technology I thought I add some of mine hehehehe.
>>>>
>>>> My idea is to use the SUN as a way to send a message to aliens ;)
>>>>
>>>> We build a big shield around the sun. And then we can turn it on and off
>>>> like a lamp.
>>>
>>> Won't work. Shield reaches equilibrium temp and emits. Who is going
>>> to launch it, NASA? Ha ha ha.
>>
>> Do the numbers before you laugh idiotically.
>> A shield around the sun at the diameter of the earth would reach
>> around 0C.
>>
>> (there are engineering difficulties.)
>
> For starters -- where would the actual mass come from? Also, the
> shield will have to be in orbit around the Sun, at least during
> initial construction.
>
> If we were to generate a Dyson sphere out of pure iron -- I've no
> idea what thickness would be required to resolve all of the
> stresses and strains -- Uncle Al's observation will come true;
> the shield will have to (eventually) throw out as much energy as the
> Sun generates, lest things get overwarm inside. Of course the
> actual spectrum may be slightly different. I'm not sure what

Radically different.
If you put it at earth orbit, it's a blackbody of 270K or so, not 2700.
At mercury orbit it's around 400K or so (not done numbers).

Would be a distinctly odd source.
No emission/absorbtion lines, surface temperature under a brown dwarf,
but anomolous luminosity.

If the sun is a black body, and so is the shell, then temperature
goes as the inverse second power of radius.

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