# [ExI] BICEP2 and the Fermi paradox

Anders Sandberg anders at aleph.se
Thu Apr 10 22:22:05 UTC 2014

```Tomaz Kristan <protokol2020 at gmail.com> , 10/4/2014 11:18 AM:
> But is now the true year 2014, or a simulation of 2014 run in the year 4,982,944?

Is this the true year 4,982,944 with the simulation of 2014, or just a simulation of all that, run in the year 4,982,945?

I am not saying this (infinite) regression kills the probability of ancestral simulation going on. It weakens it.
Suppose the amount of available computing power grows exponentially as exp(t). To run a ancestor sim you need at least that much computing power, so in practice you will only run simulations that are a factor F smaller, that is, you have a choice of civilizations from the start of time T0 to T-ln(F) where T is the current real time. A sim of time t will potentially contain simulations earlier than t-ln(F), and so on.
So between T0 and T0+ln(F) there will be no ancestor sims. Between T0+ln(F) and T0+2ln(F) there will be simulations of the first interval. Between T0+2ln(F) and T0+3ln(F) there will be some simulations of the first interval (of which many more can be done, since they are so small), and some simulations of the second one (which may contain simulations of the first interval). In general, in interval N there can be X sims of interval N-1, FX simulations of N-1, F^2 X sims of N-2, or F^N X sims of interval 1. In addition, some of the late interval simulations contain simulations of earlier intervals.
So in this model, it looks like we should expect an ever increasing number of simulations of the earlier intervals, and that the ratio between the early to the late is going up exponentially. So this predicts that a random observer should predict he is in a simulation of an early interval.

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