Time is a one-way road: events race forward with no U-turn allowed. The arrow of direction is governed by entropy — a measure of disorder, which only grows in the Universe, like a traffic jam at rush hour. You can clear one intersection, but the overall congestion only gets worse.
Even the wildest “detours” — black holes and wormholes in curved spacetime — won’t let you drive the wrong way. Scientists applied the method of global entropy accounting (Global Entropy Transport) and proved: these objects just shuffle disorder from one pocket to another, like tidying one closet but leaving the whole house a mess, while the total chaos in the Universe keeps growing.
The striking conclusion: the entropy of a typical black hole is billions of times greater than that of an ordinary star — these monsters are veritable warehouses of disorder. The arrow of time is as solid as asphalt: even fanciful wormholes can’t make it show the way to the past.
The entropy of a black hole depends on the area of its surface (event horizon), not its volume — this discovery by Jacob Bekenstein gave rise to the idea of a holographic Universe.
In Greg Egan’s novel ‘Schild’s Ladder,’ the characters try to cheat thermodynamics, but the arrow of time remains relentless.