Modern Cosmology: Assumptions and Limits

Physical cosmology tries to understand the Universe at large with its origin and evolution. Observational and experimental situations in cosmology do not allow us to proceed purely based on the empirical means. We examine in which sense our cosmological assumptions in fact have shaped our current cosmological worldview with consequent inevitable limits. Cosmology, as other branches of science and knowledge, is a construct of human imagination reflecting the popular belief system of the era. The question at issue deserves further philosophic discussions. In Whitehead’s words, “philosophy, in one of its functions, is the critic of cosmologies”. (Whitehead 1925)

💡 Research Summary

The paper examines how modern physical cosmology is shaped by a set of underlying assumptions that arise from both empirical constraints and human imagination. It begins by outlining the observational and experimental limits that define the domain of cosmology: data are confined to the post‑big‑bang era, to regions within our cosmic horizon, and to phenomena that can be captured by current telescopes and detectors. Consequently, many aspects of the early universe, the pre‑inflationary epoch, or speculative multiverse scenarios remain beyond direct verification.

To make progress under these restrictions, cosmologists adopt foundational premises such as the cosmological principle (large‑scale homogeneity and isotropy) and the universal applicability of General Relativity. These premises are not derived from raw data alone; they are chosen for mathematical tractability, historical precedent, and philosophical comfort. The author argues that such choices embed the cultural and intellectual milieu of the era into the scientific model, effectively making cosmology a construct of human imagination as much as a description of physical reality.

The analysis juxtaposes two philosophical stances: scientific constructivism, which views cosmological models as human‑made narratives that organize observable phenomena, and scientific realism, which maintains that observations reveal an objective external reality independent of our concepts. Rather than declaring one position superior, the paper suggests that modern cosmology operates at the intersection of both: models are provisional approximations to an underlying reality, continuously refined through empirical testing and philosophical critique.

A central theme is the role of philosophy as a “critic of cosmologies,” echoing Whitehead’s claim. Philosophical scrutiny exposes hidden premises—e.g., the assumption of spatial flatness justified by inflationary theory—and prompts re‑examination of the standard ΛCDM model. While ΛCDM successfully accounts for the cosmic microwave background, large‑scale structure, and supernova distance measurements, it leaves unresolved the nature of dark matter and dark energy, the initial conditions that gave rise to inflation, and the deeper reasons for the observed fine‑tuning of cosmological parameters.

The paper concludes that the limits of modern cosmology are inseparable from the assumptions it adopts and the technological capabilities it possesses. Advancing beyond these limits requires two parallel efforts: (1) a transparent articulation and critical assessment of the foundational assumptions, and (2) the development of new observational techniques—such as next‑generation gravitational‑wave detectors, 21‑cm cosmology, and high‑precision surveys—that can probe previously inaccessible regimes. By fostering ongoing dialogue between scientists and philosophers, the field can move toward a more comprehensive and less anthropocentric cosmological worldview, acknowledging that the quest to understand the universe is as much a cultural and philosophical endeavor as it is a scientific one.