If entropy is increasing, where is it coming from?

The question of where entropy comes from as the universe relentlessly marches toward greater disorder has puzzled scientists and philosophers since the concept emerged in the 19th century. According to the second law of thermodynamics, the total entropy—a measure of disorder or randomness in a system—can never decrease over time in an isolated system like our universe. But if entropy is always increasing, what is the ultimate source of this cosmic disorder?

The answer lies in the primordial conditions of the universe itself. Observations indicate that the Big Bang began in an extraordinarily low-entropy state, with matter and energy distributed with remarkable uniformity—a highly ordered configuration that defies statistical probability. This ultra-ordered starting point established an immense gradient between the universe's initial state and its thermodynamic equilibrium. The subsequent 13.8 billion years have essentially been an inexorable process of the universe redistributing this stored order into ever-greater disorder.

Every physical process contributes to this entropic cascade. When stars fuse hydrogen into heavier elements, they transform concentrated nuclear energy into diffuse heat and radiation. When galaxies collide, their neatly structured spiral arms dissolve into chaotic stellar streams. Even on Earth, burning fossil fuels converts organized chemical energy into randomized thermal energy and greenhouse gases. On quantum scales, the collapse of wave functions during measurement represents another irreversible process generating entropy. According to renowned cosmologist Sean Carroll, “Entropy increases because we’re moving away from a very special low-entropy past toward a generic high-entropy future.”

The ultimate driver appears to be gravity’s paradoxical role in the cosmic story. While gravity can create localized order (like planets and stars), it simultaneously drives the universe toward greater overall disorder by enabling irreversible processes. Black holes, gravitational wave emissions, and the expansion of spacetime itself all funnel energy into forms that increase universal entropy. Current theories suggest the final state will be “heat death”—a cold, dark cosmos where energy is perfectly distributed and no thermodynamic work remains possible.

However, this cosmic narrative contains profound exceptions where entropy appears to reverse locally. Life on Earth temporarily defies entropic decay through complex biochemical processes powered by solar energy. But these local instances of order come at a cost: plants and animals export entropy to their surroundings, maintaining internal organization while contributing to the universe’s overall disorder. The total entropy balance sheet continues to grow.

As experiments at CERN’s Large Hadron Collider probe the earliest moments of creation and telescopes map the accelerating expansion of spacetime, scientists continue refining our understanding of entropy’s origins. Some theories propose that quantum gravity effects near the Big Bang may explain the initial low-entropy state, while others suggest our universe might be part of a larger multiverse system. Whatever the final explanation, the arrow of entropy remains the fundamental signature of our universe’s unfolding story—a relentless reminder that all complex systems, from dying stars to melting ice cubes, participate in the great thermodynamic leveling that began with the first cosmic breath.