Fine-Tuning, Complexity, and Life in the Multiverse

TL;DR

This paper explores how fundamental physical constants influence the emergence of cosmic structures and life, discusses multiverse models with varying physics, and considers the scientific validity of multiverse hypotheses and anthropic reasoning.

Contribution

It analyzes the impact of physical constants on cosmic evolution and proposes models of a multiverse with different physical laws, advancing the scientific discussion on multiverse existence.

Findings

Physical constants critically affect star and planet formation.

Multiverse models may include multiple big bangs and varied physics.

Anthropic reasoning might be necessary if a multiverse exists.

Abstract

The physical processes that determine the properties of our everyday world, and of the wider cosmos, are determined by some key numbers: the 'constants' of micro-physics and the parameters that describe the expanding universe in which we have emerged. We identify various steps in the emergence of stars, planets and life that are dependent on these fundamental numbers, and explore how these steps might have been changed, or completely prevented, if the numbers were different. We then outline some cosmological models where physical reality is vastly more extensive than the 'universe' that astronomers observe (perhaps even involving many 'big bangs'), which could perhaps encompass domains governed by different physics. Although the concept of a multiverse is still speculative, we argue that attempts to determine whether it exists constitute a genuinely scientific endeavor. If we indeed inhabit a multiverse, then we may have to accept that there can be no explanation other than anthropic reasoning for some features our world.