How the World Was Formed

 « Why is there something rather than nothing ? »

We may never be able to fully answer this question posed by Gottfried Leibniz. To a physicist, this conundrum boils down to the origin of matter in our universe.

After the period of expansion that followed the Big Bang, matter and antimatter appeared and then annihilated each other. In a process that we still don’t understand, matter seems to have prevailed over antimatter. This emerging matter formed our visible world.

What more could we tell Leibniz?

Physicists who adhere to the standard Big Bang model believe that the evolution of the universe is adiabatic and reversible.

It is entirely conceivable that our universe does not exchange heat with the outside, even in expansion, but thermodynamicists reject the idea that the universe is reversible. Once matter is created, the second law of thermodynamics comes into play along with time, and entropy begins to grow. Time, which points in the direction of increasing entropy, drives the universe inexorably toward its future. There is no turning back.

This is the law of nature.

• Entropy, the ratio between the quantity of heat exchanged with the outside (zero, in theory, in the standard model) and the temperature (frighteningly high), is therefore almost nil because the dissipation that comes with entropy does not yet exist in the initial world, which is perfect. It’s absolute order.

• Subsequently, irreversibilities of all kinds produced by the dissipation of energy due to collisions between all sorts of particles lead to increased entropy in the entire closed universe system.

How the Planets Were Formed

When the universe was nascent, its initial molecules were uniformly distributed, with low entropy. Agitation at the molecular level from the high temperatures led to irreversible phenomena. Entropy increased.

But these mass-containing molecules were attracted to each other due to gravitational pull. They grouped together in organized clusters, causing a local decrease in entropy that was largely compensated for by energy dissipation that produced an overall increase in entropy throughout the universe.

The Origin of Motion

The question of the origins of motion has haunted mankind since the beginning of time.

The enormous temperature imbalance between the initial universe and the outside (about which little can be said) caused the universe to expand abruptly.

Much later, astronomers sought to explain the movement of the planets through determinism, that is, based on the assumption that the planetary system is predictable, stable, and therefore fully understood. This made it possible to establish the laws of classical mechanics.

The Rise of Chaos

Studying the general equations for planetary motion, Henri Poincaré showed that the calculations are inextricable. He called the solar system stability in question, and laid the foundations for chaos theory.

The motion of the planets may appear stable for tens or hundreds of millions of years before losing stability and becoming chaotic.

Most phenomena in nature are non-linear, even though we often approach them using linear equations. It follows, then, that systems in nature are not deterministic.

Gravity (or, since the advent of general relativity, the curvature of space-time) renders equations for motion non-linear and introduces chaos into the solar system.

Boltzmann’s Statistical Thermodynamics

In seeking the source of entropy at the molecular level, Boltzmann proved that it is impossible to track the movement of molecules in detail due to their overwhelming number. It is this lack of predictability, this uncertainty, that gives time a direction.

Boltzmann showed that the degradation of energy, as measured by entropy, is related to disorder at the molecular level.

Creating Order Out of Growing Disorder

Thermodynamics teaches us that disorder may increase, but nothing prevents orderly areas from being formed locally at any given moment, as long as an equal or greater amount of disorder appears in another part of the system. This is permissible under the second law of thermodynamics.

Prigogine’s Dissipative Structures

A more advanced lesson in non-linear thermodynamics is the creation of order in dissipative systems moving away from their initial equilibrium. Irreversibilities lead to disorder but can also lead to order.

These ordered structures generally occur after first undergoing bifurcation and chaos.

Prigogine, in particular, focused on these self-organized structures, which occur in times of great disequilibrium. He called them dissipative structures, thus marrying the concepts of order and disorder. They are maintained by interacting with their environment and weaken after a while before disappearing entirely.

Shannon’s Information Theory

Clausius introduced entropy on a macroscopic scale, and Boltzmann explored it on the microscopic and statistical levels. Information theory, founded by Claude Shannon, demonstrates the relationship between quantities of information and entropy.

A system’s entropy measures both its disorder and our ignorance of the microscopic behavior of the system. By learning more information about the system, we decrease the system’s entropy. When we know all the information there is to know about a system, it has zero entropy, and it is in a state of absolute order.