The Journal of Portfolio Management published an unlikely article in 1986: “Is Time Travel Impossible? A Financial Proof.”
In it, California economist Marc Reinganum notes that anyone with a time machine would have an enormous incentive to manipulate investments and futures markets, using his knowledge of the future to amass huge profits.
If this were possible at all, it would be happening on such a large scale that interest rates would be driven to zero.
So the fact that we see positive interest rates proves that time travelers don’t exist.