What advances in technology has the Hubble telescope given us?
Uhh... I'm sure manufacturing Hubble, it advanced technology quite a bit. If nothing else, creating such a large mirror has tons of applications in glass and mirror/lense refinement. And Hubble's replacements are to investigate Dark Energy/Matter both. What we could harness if we understand what they are, if they exist, is beyond imagination. The practical uses once we A discover dark energy and matter, and then begin to understand it? A force that acts against gravity leading to the expansion of the universe, which Hubble helped discover, is scary to think about under human control, and what technologies could come from it.