[ExI] The Universe is disappearing

[Anders Sandberg]

(Seems my original post got eaten by entropy; here is a repost)

The media are reporting it as evidence of the End of the Universe or the imminent heat death:
http://news.discovery.com/space/galaxies/universe-is-dying-galactic-survey-shows-150810.htm
http://arxiv.org/abs/1508.02076
Basically, the energy production is going down.

This  is unsurprising to anybody keeping up with star formation trends  (http://arxiv.org/abs/1202.3436). There is also a common view that  planet formation peaked way back, leaving Earth as one of the later  planets (still, there is a possibility that because of gas infall there  will be enough of a long tail of future planet formation that makes us  early anyway: http://arxiv.org/abs/1508.01202 ).

Still, I wonder if this isn't good news for us intelligent creatures, for three reasons:

First,  high star formation also means high supernova and GRB rates; as  Cirkovic et al have argued, this might even have precluded the formation  of intelligent life until recently (and some people think it causes a  galactic habitable zone). 

Second, a lot of stellar energy  doesn't mean a lot of lifezones: the lifezone radius and width scales as  the square root of the luminosity, making it scale as mass to the power  1.75. But the lifespan of a star scales as mass^-2.5, so the total  "width-years" scales as mass^-0.75 - we get more space and time for life  among low-mass stars. Since lighter stars are more common than heavier  (along some power law distribution), we can conclude that while  luminosity often gets dominated by the young bluewhite stars most of the  habitability is produced among the dimmer ones (also, see  http://www.sciencemag.org/content/346/6210/732 - there may be a lot of  ejected dim stars between galaxies). Since the dim ones last long, the  total amount of lifezone may be going up.

Third, it also means  that less matter is burned into unusable radiation before we can get to  it and use it to produce life, intelligence and complexity. The  radiation losses are not that large if we can convert matter directly  into energy (a few percent tops), but if there is a tech ceiling  limiting us to fusion (direct or through Dyson shells) then we may want  to avoid having the stars go out too quickly. 



Anders Sandberg, Future of Humanity Institute Philosophy Faculty of Oxford University
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