The Infinite-Wear Argument: Why Physical Objects Can't Survive a Bootstrap Loop
A self-consistent time-travel loop that carries a physical object forces that object to age on every pass through the loop. Because the loop has no first iteration, the wear compounds without bound, so the object would arrive already destroyed. This is a common informal argument for why a {{bootstrap paradox}} can carry information but not durable matter.
Consider handing your past self a key, which that past self later carries back to give to you, closing a causal loop. For the loop to be self-consistent, the key you hand back must be identical to the key you received. But a physical object that travels the loop ages slightly on each circuit. Since a closed loop has no "first" pass that the wear could start from, any wear that accumulates on one circuit must already have accumulated on every prior circuit. The result is unbounded degradation: the key should arrive already worn to nothing. This reasoning suggests two possible conclusions. Either the Novikov self-consistency principle forbids the loop outright as physically impossible, or the only thing a loop can stably carry is something that does not degrade, namely information. A musical score or a string of digits can be copied perfectly with no cumulative wear, which is why information loops feel cleaner than material ones. But information is not a perfectly clean escape, because in practice it always rides on a physical substrate, paper, neurons, or storage media, all of which degrade. Truly substrate-free information might evade the wear problem, but it is not obvious such a thing can actually be handed to someone. A maintained material loop can work only if it is embedded in a larger non-looped economy that supplies fresh objects and absorbs degraded ones, which means it is no longer a truly closed loop. See The Conservation-of-Information Objection: Why Actionable Knowledge Eats Its Own Origin for why even pure information loops raise a separate puzzle.