Change as a Law of the Universe
Written by Isla Madden
All things in the Universe are forever becoming—the cosmos is not static. We perceive events in sequence, giving the impression that past, present, and future are distinct, when in reality they unfold together along the spacetime continuum. Unlike space—where we may move backward and forward—time is the current that carries us in one direction. Change is not incidental to time’s existence; it is its engine, binding each moment to the next.
In the mid-19th century, Rudolf Clausius observed that while energy is conserved, its capacity to do useful work diminishes over time. This principle was named entropy, from the Greek entropē (‘transformation’ or ‘turning’). Later, Ludwig Boltzmann showed that entropy quantifies the number of microscopic arrangements compatible with a system’s state. In an isolated system, entropy tends to increase, and the arrow of time emerges from this steady progression. The light cone diagram illustrates how the flow of time and the finite speed of light limit which events can affect one another, mapping the causal structure of spacetime.
While the second law of thermodynamics ensures that total entropy increases over time, local decreases are possible, enabling the emergence of stars, planetary systems, and ultimately, life. The Universe began in a state of exceptionally low entropy. In this far-from-equilibrium condition, tiny density fluctuations in the nearly uniform primordial matter underwent gravitational instability: regions with slightly higher density attracted more mass, collapsing to form the first stars and large-scale cosmic structures.
We are not separate from the nature of this process, but constituents of the changing cosmos itself. The atoms in our bodies were produced during stellar nucleosynthesis, dispersed by supernovae, and incorporated into the material which coalesced to form our Solar System. The interplay of order and disorder, expressed through the dynamics of entropy, has governed the unfolding of the Universe, and through these processes, we exist as integral components of its ongoing evolution.
The ancient Greek philosopher Heraclitus proposed his doctrine of constant flux, suggesting that the fundamental nature of reality is change: “πάντα ῥεῖ” (panta rhei); “Everything flows.” Everything in nature is subject to change: the energy that sustains our cells gradually dissipates as chemical gradients fade, and the Sun, upon which Earth’s life depends, will eventually exhaust its hydrogen fuel and evolve into a red giant. The Universe is in constant transformation, from microscopic biochemical processes to the largest cosmic events, and all structures exist only temporarily within this ongoing flow of energy and matter.
