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

David Awad

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.

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

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.
Paper Structure (14 sections, 2 theorems, 3 equations, 1 figure)

This paper contains 14 sections, 2 theorems, 3 equations, 1 figure.

Table of Contents

  1. Introduction
  2. What General Relativity Permits
  3. Existing Empirical Tests
  4. Our Contribution
  5. The Prediction Market Argument
  6. Setup
  7. The Arbitrage
  8. Causal Sensitivity and the Feedback Problem
  9. On the Transaction Cost Assumption
  10. Relationship to Reinganum (1986)
  11. No One Had the time to attend Hawking's Party
  12. The Many-Worlds Escape Hatch
  13. Empirical Evidence
  14. Conclusion

Key Result

Proposition 1

Under Assumptions ass:tt--ass:microstructure, the equilibrium price of every prediction market contract on a causally inert event equals $P(t) = 1$ if $E$ occurs and $P(t) = 0$ if $E$ does not occur, for all $t$ from market inception to resolution.

Figures (1)

  • Figure 1: Stylized price paths for a prediction market contract on an event that ultimately occurs. The blue (solid) line shows the typical observed path: interior probabilities that converge to $1 as information arrives. The red (dashed) line shows the price path implied by single-timeline backward time travel: immediate collapse to $1 at market inception.

Theorems & Definitions (3)

  • Proposition 1
  • proof
  • Corollary 1