Can we "effectivize'' spacetime?

TL;DR

This paper examines the limitations of effective realism and effective field theories in physics, especially in the context of quantum gravity, highlighting challenges in understanding spacetime.

Contribution

It critically analyzes effective realism and EFTs, revealing their shortcomings in providing a realistic theory of spacetime within quantum gravity.

Findings

Effective quantum gravity does not offer a realistic spacetime theory.

EFTs face interpretative dilemmas regarding classical spacetime references.

Challenges arise in applying EFTs to fundamental questions about spacetime.

Abstract

According to \textit{effective realism}, scientific theories give us knowledge about the unobservable world, but not at the fundamental level. This view is justified by the well-received \textit{effective-field-theory} (EFT) approach to physics, according to which our best physical theories are only applicable up to a certain energy scale and expected to break down beyond that. In this paper, I explain the motivations for the EFT approach and effective realism and their benefits. I also raise new challenges for this approach. Applying effective realism to \textit{effective quantum gravity} (EQG) reveals its shortcomings: EQG does not give us a realistic theory of spacetime even within its scope of validity. It also exposes a general interpretative dilemma faced by all EFTs concerning their indispensable references to classical spacetime beyond their scope of validity.