Penn State with evident relief. There, postdoccing his way through some respectable electron spin work led to a faculty position. He was now safely worrying various III-V compounds into yielding up their transport coefficients. Gordon saw him at meetings and they had an occasional drink together, sharing wary conversation.
He eavesdropped on gossip about revival of the Orion spaceship idea, and new work by Dyson. Then, as Gordon was fetching another sandwich and talking to a reporter, a particle physicist approached. He wanted to talk over plans for a new accelerator which had a chance of producing a tachyon cascade. The energy required was enormous. Gordon listened politely. When a revealing skeptical smile began to spread over his face, he forced his lips back into an expression of professorial consideration. The high-energy types were struggling to make tachyons now, but most outside observers felt the effort was premature. Better theory was needed. Gordon had chaired several panels on the subject and had grown thick-skinned about new, big-money proposals. The particle physicists were addicted to their immense accelerators. The man who has only a hammer to work with finds that every new problem needs a nail.
Gordon nodded, looked sage, sipped champagne, said little. Though the evidence for tachyons was now overwhelming, they did not fit into the standard ongoing program of physics. They were more than simply a new species of particle. They couldn’t be put on the shelf beside the mesons and hyperons and kaons. Before this physicists had, with the instincts of accountants, decomposed the world into a comfortable zoology. The other, simpler particles had only minor differences. They fit into the universe like marbles in a sack, filling but not altering the fabric. Tachyons didn’t. They made new theories possible, kicking up the dust of cosmological questions by their mere existence. The implications were being worked out.
Beyond that, though, were the messages themselves. They had ceased in 1963, before Zinnes could get extensive confirmation. Some physicists thought they were real. Others, forever wary of sporadic phenomena, thought they must have been some fortuitous error. The situation had a lot in common with Joe Weber’s detection of gravitational waves in 1969. Later experiments by others had found no waves. Did that mean Weber was wrong, or that the waves came in occasional bursts? It might be decades before another flurry could settle the question. Gordon had talked to Weber, and the wiry, silver-maned experimenter seemed to take the whole thing as a kind of inevitable comedy. In science you usually can’t convert your opponents, he had said; you have to outlive them. For Weber there was hope; Gordon felt his own case was forever uncheckable.
The new theory by Tanninger certainly pointed the way. Tanninger had put tachyons into the general relativity theory in a highly original way. The old question that came up in quantum mechanics, of who the observer was, had finally been resolved. Tachyons were a new kind of wave phenomenon, causality waves looping between past and future, and the paradoxes they could produce gave a new kind of physics. The essence of paradox was the possibility of mutually contradictory outcomes, and Tanninger’s picture of the causal loop was like that of the quantum-mechanical waves. The difference came in the interpretation of the experiment. In Tanninger’s picture, a kind of wave function, resembling the old quantum function, gave the various outcomes of the paradox loop. But the new wave function did not describe probabilities—it spoke of different universes. When a loop was set up, the universe split into two new universes. If the loop was of the simple killing-your-grandfather type, then there would result one universe where the grandfather lived and the grandson disappeared. The grandson reappeared in a second universe, having traveled back in time, where he shot his grandfather and lived out his life, passing through the years which were forever altered by his act. No one in either universe thought the world was paradoxical.
All this came from using tachyons to produce the standing-wave kind of time loop. Without tachyons, no splitting into different universes occurred. Thus the future world that had sent Gordon the messages was gone, unreachable. They had separated sometime in the fall of 1963; Gordon was sure of that. Some event had made Renfrew’s experiment impossible or unnecessary. It could have been the Ramsey-Hussinger press conference, or putting the message in the safety deposit box, or the Kennedy thing. One of those, yes. But which?
He moved among the crowd, greeting friends, letting