On Under-determination in cosmology

TL;DR

This paper examines how modern cosmology faces under-determination of hypotheses by data, highlighting issues with data collection limits and the use of the cosmological principle, especially concerning the early universe.

Contribution

It offers a philosophical analysis of under-determination in cosmology, focusing on observational constraints and the role of the cosmological principle in theory choice.

Findings

Cosmology's data is limited to what a single observer can collect.

The cosmological principle is used to address under-determination but is philosophically contentious.

Discussion includes the early universe, raising questions about times before one second after the Big Bang.

Abstract

I discuss how modern cosmology illustrates under-determination of theoretical hypotheses by data, in ways that are different from most philosophical discussions. I emphasize cosmology's concern with what data could in principle be collected by a single observer (Section 2); and I give a broadly sceptical discussion of cosmology's appeal to the cosmological principle as a way of breaking the under-determination (Section 3). I confine most of the discussion to the history of the observable universe from about one second after the Big Bang, as described by the mainstream cosmological model: in effect, what cosmologists in the early 1970s dubbed the `standard model', as elaborated since then. But in the closing Section 4, I broach some questions about times earlier than one second.