Arrow of Time Origin

The thermodynamic arrow of time — the observed fact that entropy increases toward the future and not the past — requires an explanation for why the universe began in a state of extraordinarily low entropy. In ΛCDM, the Big Bang singularity simply posits an initial state of extreme order without explaining its origin, and the Boltzmann brain problem haunts any infinite-time cosmology that attempts to treat low-entropy fluctuations as random. Successive Collision Theory provides a physically motivated low-entropy initial condition through the collision mechanism itself. When two large comoving pockets intersect superluminally, the kinetic energy of their relative motion is the source of entropy increase. Before the collision, each pocket is in a relatively organized gravitational state — matter distributed in structures that evolved over the preceding epoch of the parent timeline. At the moment of collision, this kinetic energy is thermalized into a photon-baryon plasma. The collision is an entropy-generating event that establishes a definite thermodynamic boundary: the pre-collision state (organized kinetic energy) is lower entropy than the post-collision state (thermalized plasma). This boundary is the cosmological arrow of time for our observable patch.

Crucially, this picture does not require the universe as a whole to have a low-entropy beginning. In eternal infinite spacetime, the global entropy is always effectively infinite and has no meaningful "beginning." The thermodynamic arrow experienced by observers within our patch is a local arrow established by the specific collision that created our patch — a directed event that deposited organized kinetic energy into a thermalized plasma, initiating a local entropy gradient that has been increasing ever since. Each collision event in the eternal universe creates its own local thermodynamic arrow for the debris it produces. The arrow of time in our observable universe is not a global cosmological fact requiring a finely tuned initial state — it is the local thermodynamic signature of the inelastic collision that created us, as natural and inevitable as the entropy increase following any energetic impact.