Why the Future Is Not Trading: Causally Inert Events as a Test for Time Travelers

TL;DR

This paper uses prediction market data to empirically argue against the existence of single timeline backward time travel, showing that market prices do not behave as would be expected if such time travel were possible.

Contribution

It introduces a novel empirical test for backward time travel using prediction market behavior, sharpening previous economic arguments without physical experiments.

Findings

No degenerate prices observed in large datasets

Prediction market behavior is inconsistent with single timeline time travel

Causally inert events do not influence market prices

Abstract

We present an empirical argument against the existence of single timeline backward time travel using the price behavior of prediction markets. If rational agents could travel backward in time, binary prediction contracts would converge to degenerate prices (0 or 1) immediately upon market formation. We observe no such behavior across large datasets of resolved contracts. This yields a directly falsifiable prediction and sharpens prior economic arguments while avoiding reliance on physical experimentation. The argument requires only the existence of a single profit motivated agent in the future capable of interacting with markets along a closed timelike curve intersecting the market's spacetime location. We further argue that such agents would have no incentive to conceal trades in causally inert events, where outcomes are independent of market prices, implying that any such activity would be visible in aggregate price behavior. While many worlds interpretations evade this test, we argue that only single timeline models are empirically falsifiable, and prediction market evidence is inconsistent with their existence.