[ExI] Fermi question, was is a FTL drive a dream

[Kelly Anderson]

On Sat, Dec 24, 2011 at 2:49 AM, Anders Sandberg <anders at aleph.se> wrote:
> On 2011-12-24 09:35, Kelly Anderson wrote:
>>
>> Uh, maybe dumb question here... but how would we tell a star was
>> dimmer unless we measured the brightness before and after the
>> civilization had created their Dyson swarm or whatever it was that
>> dimmed the star? Is there a way to tell it's dimmer than it should be
>> without having measured it's brightness before?
>
>
> Yes. Stars shine with (roughly) a blackbody spectrum, telling us their
> temperature. Normal stars fall into certain curves on the Herzprung-Russell
> diagram,
> http://en.wikipedia.org/wiki/Hertzsprung%E2%80%93Russell_diagram
> which relates their absolute magnitude (total energy output) to their
> temperature. If you Dyson a star it will become dimmer (less magnitude) but
> the temperature will be unchanged (same color): it will move straight
> downwards. So if you see a star outside the big clusters, that could be an
> indication of a partial Dyson shell.
>
> In addition, a Dyson shell will re-radiate the energy as deep infrared, so
> the next step is to check if there is a huge excess of cold blackbody
> radiation.
>
> http://home.fnal.gov/~carrigan/infrared_astronomy/Other_searches.htm

Thanks Anders and everyone else that answered this query... I figured
there would have to be some way of figuring this out. Astronomers
think so differently from me... I find it fascinating to read of their
approaches and exploits.

-Kelly