There are forms of SETI besides the listening-for-interesting-signals kind.  Looking for large-scale artifacts also exists:<p><a href="http:&#x2F;&#x2F;home.fnal.gov&#x2F;~carrigan&#x2F;infrared_astronomy&#x2F;Fermilab_search.htm" rel="nofollow">http:&#x2F;&#x2F;home.fnal.gov&#x2F;~carrigan&#x2F;infrared_astronomy&#x2F;Fermilab_s...</a><p><a href="http:&#x2F;&#x2F;www.space.com&#x2F;24269-how-to-search-for-alien-civilizations.html" rel="nofollow">http:&#x2F;&#x2F;www.space.com&#x2F;24269-how-to-search-for-alien-civilizat...</a><p>I find these fascinating: let&#x27;s consider the branching tree of ways civilizations might grow and then look for evidence for leaves on that tree.