Story set in 2909. A Prognostication Machine which can look into the future beyond 50 years (but no earlier) predicts the destruction of the entire universe in about 1000 years. Evidently, a new movement in high-energy physics over the next 600 years leads to developments which ultimately lead to the creation of a machine which can siphon off energy from a parallel universe. As soon as the machine starts, something goes wrong and the energy from the other universe destroys ours.
A reporter, who stumbles on to the top-secret prognosticator complex, sees this future and then helps figure out by backward reasoning and some help from the prognosticator how the entire sequence started. The chain of events was set off by one John Fitz-Simmons, Sr., who, on Feb 9, 2909, stumbled into his future wife and exclaimed, “Well, I'll be a pie-eyed emu!”. Over time, the two get married and his son, learning of the phrase, interprets it as a mathematical equation (this is the mathematical rebus on which the story hinges). The “Tension Energy Dynamics Equation” is I = (b/a) * pi * i * e / mu , which is the symbolic equivalent of the pie-eyed emu phrase. All else follows conveniently.
One final twist you can see coming a thousand years away: The senior Mr. Fitz-Simmons is none other than the reporter himself (of course, the reporter does not know this and how his name changes form the last few lines of the story)