Science in a Very Large Universe

TL;DR

This paper discusses how our predictions about the universe depend on a probability distribution over our possible locations within a very large universe, combining physical theory with assumptions about our typicality.

Contribution

It introduces the concept of the xerographic distribution as a way to incorporate our assumed typicality into cosmological predictions.

Findings

The probability of data replication increases with universe size.

Predictions depend on the choice of xerographic distribution.

Combining theory with typicality assumptions enables testable predictions.

Abstract

As observers of the universe we are quantum physical systems within it. If the universe is very large in space and/or time, the probability becomes significant that the data on which we base predictions is replicated at other locations in spacetime. The physical conditions at these locations that are not specified by the data may differ. Predictions of our future observations therefore require an assumed probability distribution (the xerographic distribution) for our location among the possible ones. It is the combination of basic theory plus the xerographic distribution that can be predictive and testable by further observations.