[Madness]

Types of Advanced Civilizations: According to the Kardashev Scale

[Wilshire]

Fun to think about.

Couple of random thoughts:
A Dyson Sphere, despite being ridiculously resource intensive to construct (making it pretty much impossible), should one exist it would likely be equally impossible to see from Earth.
I believe that it was Kaku that I heard discuss why we haven't see type 1/2/3 civilizations in our endless search. That discussion is probably the most interesting part of this scale.

[TLEILAXU]

I've heard the opposite, i.e. that a dyson sphere would give off a specific spectral signature that would make it easier to detect.

[Wilshire]

I've heard the opposite, i.e. that a dyson sphere would give off a specific spectral signature that would make it easier to detect.

It would be a unique object that, if you could see it, it would be very obvious what it was.
But trick though, is that a dyson sphere is specifically designed to absorb 100% of the energy output of the star - light, heat, radiation, etc. It would be like trying to find a black 8ball in a pool of black ink. Once you found it, it'd be obvious that it was different, but until then it would be very difficult to find.

[TLEILAXU]

I've heard the opposite, i.e. that a dyson sphere would give off a specific spectral signature that would make it easier to detect.

It would be a unique object that, if you could see it, it would be very obvious what it was.
But trick though, is that a dyson sphere is specifically designed to absorb 100% of the energy output of the star - light, heat, radiation, etc. It would be like trying to find a black 8ball in a pool of black ink. Once you found it, it'd be obvious that it was different, but until then it would be very difficult to find.

From wikipedia

In Dyson's original paper, he speculated that sufficiently advanced extraterrestrial civilizations would likely follow a similar power-consumption pattern to that of humans, and would eventually build their own sphere of collectors. Constructing such a system would make such a civilization a Type II Kardashev civilization.[30]

The existence of such a system of collectors would alter the light emitted from the star system. Collectors would absorb and reradiate energy from the star.[2] The wavelength(s) of radiation emitted by the collectors would be determined by the emission spectra of the substances making them up, and the temperature of the collectors. Because it seems most likely that these collectors would be made up of heavy elements not normally found in the emission spectra of their central star–or at least not radiating light at such relatively "low" energies compared to what they would be emitting as energetic free nuclei in the stellar atmosphere–there would be atypical wavelengths of light for the star's spectral type in the light spectrum emitted by the star system. If the percentage of the star's output thus filtered or transformed by this absorption and reradiation was significant, it could be detected at interstellar distances.[2]

Given the amount of energy available per square meter at a distance of 1 AU from the Sun, it is possible to calculate that most known substances would be reradiating energy in the infrared part of the electromagnetic spectrum. Thus, a Dyson sphere, constructed by life forms not dissimilar to humans, who dwelled in proximity to a Sun-like star, made with materials similar to those available to humans, would most likely cause an increase in the amount of infrared radiation in the star system's emitted spectrum. Hence, Dyson selected the title "Search for Artificial Stellar Sources of Infrared Radiation" for his published paper.[2]

SETI has adopted these assumptions in their search, looking for such "infrared heavy" spectra from solar analogs. As of 2005 Fermilab has an ongoing survey for such spectra by analyzing data from the Infrared Astronomical Satellite (IRAS).[31][full citation needed][32] Identifying one of the many infrared sources as a Dyson sphere would require improved techniques for discriminating between a Dyson sphere and natural sources.[33] Fermilab discovered 17 potential "ambiguous" candidates, of which four have been named "amusing but still questionable".[34][full citation needed] Other searches also resulted in several candidates, which are, however, unconfirmed.[35][36][37]

[Wilshire]

Given the amount of energy available per square meter at a distance of 1 AU from the Sun, it is possible to calculate that most known substances would be reradiating energy in the infrared part of the electromagnetic spectrum.

I was thinking visible spectrum but obviously I forgot that there are many, many other spectra that we can observe with instruments lol.
I admit to have been thinking of it functionally like trying to see a blackhole - this would be far easier.

Or it would be, unless of course the hypothetical Type II civilization that can make a Dyson Sphere (I think that the wiki there points out how difficult and probably unreasonable making one would be). also has as-of-yet-discovered (by humanity) supermaterials that don't waste energy by radiating all kinds of waste all over the place.
Honestly, if you're going to go through the trouble of making a DS, you're going to want to capture all that energy and use it for something useful. Its not too crazy to believe that this might be the case.

That said, I fully admit I wasn't thinking about this in my earlier post. Clearly, using something other than the visible spectrum makes my original point entirely moot, and now I'm off into the land of science fiction. Thanks for the clarity