Traveling to the planets takes big money and we’ve been part of the squabbing over where NASA money in particular ought to be allocated. But what about projects that take small money? The term is relative, of course, but John Cramer (University of Washington) thinks $20,000 should suffice to run his experiment in time travel, and with NASA’s Institute for Advanced Concepts now shutting down, he’s having a hard time raising it. This Seattle Post-Intelligencer story has more.
We’ve looked at Cramer’s work before, but a brief summary is in order. It involves Einstein’s ‘spooky action at a distance,’ the so-called Einstein-Podolsky-Rosen effect. Quantum entanglement seems to mean that two entangled particles influence each other no matter how far distant in space. That action appears to be instantaneous, which introduces the paradoxical outcome of suggesting that something can communicate faster than the speed of light.
Einstein, of course, would say that’s flat out impossible. Quantum theorists, for their part, have come up with ways of explaining entanglement that don’t involve communication, but Cramer disagrees. He believes that communication does occur but involves movement both forwards and backwards in time. To test the proposition, he would send entangled photons along fiber-optic cables of different lengths, causing the one taking the longer path to be delayed.
Because the photons are engangled, a measurement of one as a particle or a wave determines what happens to the other. Cramer wonders whether he can’t use this effect to make a signal arrive before it was sent. Here’s a description of his idea that the San Francisco Chronicle reprinted from New Scientist:
[Cramer's] extra twist is to run the photons you choose how to measure through several kilometers of coiled-up fiber-optic cable, thereby delaying them by microseconds. This delay means that the other beam will arrive at its detector before you make your choice. However, since the rules of quantum mechanics are indifferent to the timing of measurements, the state of the other beam should correspond to how you choose to measure the delayed beam. The effect of your choice can be seen, in principle, before you have even made it.
Note the ingenuity of the experiment, its elegant simplicity, and its modest budget. This test of what Cramer calls the transactional interpretation of quantum mechanics could tell us whether particle interactions do indeed move both backward and forward in time, a phenomenon known as retrocausality. If they do, we’ve taken a step forward in working out what could one day become the unification of quantum mechanics and relativity. “In 20 years, nobody has been able to tell me why this can’t work,” says Cramer.
With government funding unlikely, the case for cutting-edge experiments funded by philanthropy is stronger than ever. The key here is that the kind of money the Tau Zero Foundation and others will need to raise for a given project isn’t necessarily vast. We’ve already seen that players like Elon Musk and Paul Allen are committed to using part of their personal fortunes for the advancement of space exploration. As the Foundation begins to explore the philanthropic terrain, keep your fingers crossed that less expensive projects like Cramer’s will soon find a receptive audience.