This is such a cool paper!

One of the neat ideas it communicates is that the longer we wait, the less of the universe we can access:

  Delay - Galaxies lost
  1 million years ~ 0.02%
  10 million years ~ 0.2%
  100 million years ~ 2%
  1 billion years ~ 20%
  10 billion years ~ 80%
  150 billion years ~ 99.9999997%

Or this,

"For example, dropping matter into black holes via their accretion disks converts 5.7% of its rest mass into light, which far exceeds the efficiency of the thermonuclear reactions which power stars, and might be a much more efficient way to gain access to the mass-energy stars contain (though it clearly comes with its own engineering obstacles)."

"A related question is not how much matter (or energy) could be reached, but what is the greatest amount a civilisation could secure in one gravitationally bound location, so that it could be used for some unified long-lasting project during the time of isolation"

Maybe we can pinpoint where advanced alien civilizations would be based on an understanding of their energy needs.

Spoiler alert on Hubble Extreme Deep Field photo: "This image thus spans the edge of our affectable universe, with most of the places it shows being forever beyond our reach. "

I find all of this incredibly beautiful.