White hole siphons are megastructure-scale energy generators built by Type 4 entities. They use white holes which are the time-reversed counterparts of black holes which cannot be entered, only exited.
White hole siphons are built around primordial white holes (left over from the Big Bang) or are artificially induced by "inverting" a black hole using a Closed Timelike Curve, preventing entry of light and matter.
The negative entropy fountain[]
While black holes consume matter and increase entropy (information scrambling), white holes spew out matter and light with effectively negative entropy.
- The white hole continuously ejects "virgin" matter and photons that have no correlation with the outside universe.
- The siphon is a Dyson sphere built around the white hole, that captures this highly ordered, low-entropy energy.
- By introducing this low-entropy matter into a dying universe, the civilization can locally reverse the Heat Death, effectively winding back the thermodynamic clock of their galaxy.