# The Top-Down Complexity

## TL;DR

This paper explains the growth of complexity in the universe as a causal process driven by thermodynamics and cosmological expansion, linking physical laws to biological complexity.

## Contribution

It presents a holistic, physics-based framework connecting cosmology, thermodynamics, and biological systems to explain complexity growth across scales.

## Key findings

- Complexity increase aligns with the second law of thermodynamics.
- Growth of complexity is driven by cosmological expansion.
- Free energy rate density governs local complexity growth.

## Abstract

The rising complexity of our terrestrial surrounding is an empirical fact. Details of this process evaded description in terms of physics for long time attracting attention and creating myriad of ideas including non-scientific ones. In this essay we explain the phenomenon of the growth of complexity by combining our up to date understanding of cosmology, non-equilibrium physics and thermodynamics. We argue that the observed increase of complexity is causal in nature, stands in agreement with the second law of thermodynamics and has it's origin in the cosmological expansion. Moreover, we highlight the connection between the leader of complexity growth in localized areas of space with free energy rate density, starting from the largest scales towards the smaller ones. Finally, in the light of recent advances in non-equilibrium statistical mechanics, our belief in the causal structure of modern scientific theories is transferred to biological systems. On relevant scales, adaptation and complexity growth follows a similar pattern, in which free energy rate density is provided by an external electromagnetic radiation. The presented, holistic approach, arms us with predicting power about variety of attributes of complex systems and leads to a chain of successful explanations on all scales of the Universe.