Editing Kardashev scale (section)

=== The technology ===
{{Further|Stellar engineering|Megastructure}}This parameter is one of the most undetectable in the Universe due to the fact that solid matter structures are at low temperatures and emit weak radiation. Their luminosity, which is difficult to observe, also makes it impossible to observe them with telescopes. Likewise, we cannot detect them by their [[Gravity|gravitational effects]].<ref name="Kardashev-1971" /> On the other hand their existence can be detected by analyzing the [[wavelength]]s between 8 and 13 microns, corresponding to surface temperatures of 300 K. A hypothetical [[Dyson sphere]] could thus be detected,<ref name="Carrigan Jr.-20102"/> provided that the observation is made from space. Locally, the significant dip in luminosity that would result from a giant Dyson sphere (or "Fermi bubble") would allow the detection of a Type&nbsp;III civilization.<ref name="Carrigan Jr.-20102"/>

A [[megastructure]] like a Dyson sphere could be the result of a technology based on [[Self-replicating machine|self-replicating probes]], as those imagined by [[John von Neumann|von Neumann]]. A Type&nbsp;III civilization would indeed have the means to disperse a significant number of these spheres throughout the galaxy, which would have the effect of attenuating the light emitted by the galaxy.<ref name="Calissendorff-2013" /> Kaku also considers this to be the most efficient method of colonizing space. For example, a galaxy 100,000 light years in diameter would be explored in half a million years.<ref name="Kaku-2007" /> [[Paul Davies]] has suggested that a civilization could colonize the galaxy by scattering miniature probes, no larger than the palm of a hand, using [[nanotechnology]]. This thesis is realistic, he explains, because it is obvious that the technology is becoming increasingly miniaturized and proportionally less expensive.<ref name="Kaku-2007" />

Type&nbsp;II megastructures would be easier to detect. This would be the case of a [[Dyson sphere]] used as a "[[stellar engine]]",<ref name="Badescu">{{Cite web |last1=Badescu |first1=Viorel |last2=Cathcart |first2=Richard B. |title=Space travel with solar power and a dyson sphere |url=http://www.astronomytoday.com/exploration/solartravel.html |url-status=live |archive-url=https://web.archive.org/web/20230415102053/http://www.astronomytoday.com/exploration/solartravel.html |archive-date=2023-04-15 |access-date=2023-08-22 |website=www.astronomytoday.com}}</ref> as well as the contribution of heavy elements.<ref name="Carrigan Jr.-20102"/> Similarly, "Shkadov thrusters", which would produce a lateral thrust of 4.4 [[parsec]]s on their star by reflecting solar radiation through a structure made of mirrors, would be observable objects. This device would break the symmetry of solar radiation and counteract [[Gravity|gravitational forces]], allowing a Type&nbsp;II civilization to move its home solar system through space.<ref>{{Cite journal |last=Shkadov |first=L. M. |date=1987 |title=Possibility of controlling solar system motion in the Galaxy |url=https://ui.adsabs.harvard.edu/abs/1987brig.iafcR....S/abstract |journal=38th Congress of the International Astronautical Federation |bibcode=1987brig.iafcR....S |archive-date=2023-08-22 |access-date=2023-08-22 |archive-url=https://web.archive.org/web/20230822180535/https://ui.adsabs.harvard.edu/abs/1987brig.iafcR....S/abstract |url-status=live }}</ref><ref name="Badescu" /> Drake and Shklovski have also considered the possibility of "seeding" a star (Stellar salting) by artificially adding extremely rare elements such as [[technetium]] or [[promethium]]. Such an intervention in a star's composition would be detectable.<ref name="Carrigan Jr.-20102"/>

It is still possible that humanity could discover traces of lost Type&nbsp;I, II, or III civilizations. The search for material traces of such civilizations (e.g. Dyson spheres or stellar engines), an "interesting alternative" to the conventional SETI program, lays the foundation for a "[[Xenoarchaeology|cosmic archaeology]]" according to Richard A. Carrigan. Efforts to detect intelligence markers in the atmospheres of [[exoplanet]]s (such as [[freon]], [[oxygen]], or even [[ozone]], residues of biotic activity according to [[James Lovelock]]'s research)<ref name="Carrigan Jr.-20102"/> are one of the most promising avenues. A civilization watching its star die (as a [[red giant]], for example) could have tried to prolong its existence through megastructures that should be detectable.<ref name="Carrigan Jr.-20102"/> The possible traces could be nuclear remnants, to be sought within the [[Stellar classification|spectral types]] going from [[A-type main-sequence star|A5]] to [[Main sequence|F2]] according to Whitmire and Wright.<ref>{{Cite journal |last1=Whitmire |first1=Daniel P. |last2=Wright |first2=David P. |date=1980-04-01 |title=Nuclear waste spectrum as evidence of technological extraterrestrial civilizations |url=https://dx.doi.org/10.1016/0019-1035%2880%2990253-5 |journal=Icarus |volume=42 |issue=1 |pages=149–156 |doi=10.1016/0019-1035(80)90253-5 |bibcode=1980Icar...42..149W |issn=0019-1035}}</ref> It could also be a change in the [[Natural abundance|isotopic ratio]], due to a stellar engine, or an unusual spectral modulation in the composition of the star.<ref name="Carrigan Jr.-20102"/>