When you’ve read Analog as long as I have — and I date back to the days when it was named Astounding — you develop a real fondness for some of the primary players. That’s one reason I’m glad to hear the good news about John Cramer’s time travel experiment, which has received enough private donations to be pursued. Cramer’s ‘Alternate View’ columns have been running in the magazine since 1984, covering everything from cosmology to space drives and quantum mechanics. I’ve always admired his clear, straightforward style.
A physicist at the University of Washington, Cramer caught the attention of the press in recent months by discussing his hopes of testing the idea of quantum retrocausality. Here we’re in the domain of what Cramer calls the Transactional Interpretation, in which the processes of quantum mechanics involve waves traveling both forward and backward in time. His experiment, which may begin as early as next month, will test whether photons can communicate in reverse time.
The notion, absurdly reduced, is this: Entangled photons seem to be able to affect each other no matter how widely separated in time or space, the so-called Einstein-Podolsky-Rosen paradox that illuminates the bizarre nature of quantum mechanics. Do a measurement on one and it has an immediate effect on the other. Cramer is testing whether this ‘spooky action at a distance’ is the result of communications that move backwards and forwards in time.
I won’t run through the experimental apparatus again since we’ve covered it before, both in Of Time Travel and Funding and in an article called Backwards in Time? Each contains links to further background for those interested. But what pleases me is that this is the kind of experiment — relatively inexpensive, highly controversial and fraught with implications — that seems ideal for philanthropic rather than government funding. It’s a pleasure to see such money flowing, even though a broad consensus in the scientific community seems to hold that Cramer is wasting his time and other people’s money.
The Seattle Post-Intelligencer wrote up the funding story on the 12th and provided this quote, noting the consequences of failure:
Cramer said it’s possible that the primary goal of his experiment could fail and yet still produce something of value. Some new subtlety about the nature of entanglement could be revealed, he said, even if the photons don’t engage in measurable non-local communication. The “disentanglement” itself, he said, could be quite revealing.
“It wouldn’t be as nice as a positive result, but it would certainly be interesting and publishable,” Cramer said. If there is an interesting negative result or a half-positive result, he said he will buy more precise equipment to see if he can tease out what’s happening. Cramer has all the money he needs for this phase, but he hopes to see a second phase.
Cramer, whose credentials include work at the Brookhaven National Laboratory’s Relativistic Heavy Ion Collider and Europe’s CERN particle physics installation as well as his time at the University of Washington, has received more than $35,000 from people who read about his ideas on the Internet. The cash has flowed in from artists, scientists, business people, and space enthusiasts like Walter Kistler, founder of Kistler Aerospace. More traditional sources like NASA’s Institute for Advanced Concepts and the Defense Advanced Research Projects Agency had already turned down Cramer’s proposal.
What next? We’ll see whether the Transactional Interpretation receives any support in the experiments soon to be launched. Meanwhile, have a look at one of Cramer’s ‘Alternate View’ columns called A Farewell to Copenhagen?, in which he discusses a quantum test called the Afshar Experiment, and provides background on the competing Copenhagen and Many Worlds Interpretations. No one knows what will come next out of his laboratory, but anything connected with time travel seems to have caught the eye of Net watchers, so we’re sure to hear about it quickly.