do decaying neutrons travel between universes?
According to string theorists, our universe is just one of many in an otherwise infinite cosmos and that all the different universes don’t just sit quietly in a vacuum, but actively interact with each other when space and time bend and fold to create the right conditions for different forces and particles to jump between them. While the exact number of all these cosmoses is pretty much impossible to estimate with any certainty, evidence for just one or two other universes would provide a very solid pillar for string theory and the multiverse hypothesis in general. And to that end, cosmologists have been looking at such anomalies as the mysterious dark flow, measuring the various oddly shaped blotches in the CMBR, and using some very creative mathematics to picture universes imploding into black holes to catch a hint of another universe acting on our own. But since all of the macro observations collected so far have been rather far from definitive, a team of physicists based in Belgium decided to scale their search down to the subatomic level, measuring the decay rates of neutrons trapped with well established techniques for studying their motion, then hit with a laser for good measure.
Basically, the idea is that neutrons should decay at a certain rate as they bounce around trapped in magnetic fields or by gravity, and imperfections in how these fields contain them usually result in a slightly faster rate of decay than expected. But while most of the accelerations in decay rates would be due to the containment, an infinitesimal number of these decays may be caused by the neutrons switching universes. Mind you, this will happen only a handful of times during an experiment but the math says that it can happen, and it has in a few previous experiments they’ve reviewed. What’s even more interesting, they could affect the probability of such flips between universes by using a laser in the neutron trap, usually known as a bottle. After firing very precise and carefully monitored pulses at decaying neutrons, the physicists say, they should see a slight increase in how many neutrons departed for another universe using a fairly straightforward formula derived from the math they used to arrive at the conclusion that neutrons can switch cosmoses. Sounds fairly straightforward. Trap a few quadrillion neutrons, chill them to temperatures found on the icy moons of the outer solar system to slow them down a little, then fire a few laser pulses and see whether their decay rate increases ever so slightly.
Still there’s the nagging question of how exactly this experiment would prove that the neutrons are not simply decaying but switching universes. If anything, it sets up a situation very similar to an episode of The Big Bang Theory in which Sheldon chides Leonard’s work for being “extremely derivative” to which the slighted Leonard replies “at least I don’t have to make the particles go through 27 dimensions just to make the math work.” And as usual, Sheldon counters with “well, they’re there” to complete his circular argument. The dimensions exist because the math says they exist, much like the neutrons are supposed to decay into another universe as the math shows they could, rather than by an observation extending into another cosmos to make sure they took the trip and exited the universe. Of course their trip would also raise the question of what compensates for the sudden loss of neutrinos. Even at a rate of ten per quadrillion, an occasional exodus from this universe would add up fairly quickly when we consider how small and plentiful they are. We’d need a exouniversal neutrino to make the same journey a missing neutrino in our cosmos would’ve made but since every universe can easily end up with different laws of physics and there’s no law that requires similar universes to be side by side, we now have to consider even more radical mathematics to describe the entire inter-universal ecosystem.
Doesn’t this all seem like a whole lot of assumptions and considerations for a phenomenon we can’t verify in the real world? On what basis would we say that seeing an increase in the decay rate of neutrinos points to a subatomic trip between universes rather than a correlation between certain intra-universal phenomena and a faster decay rate for the particles? As the physicists acknowledge, we really can’t. We can only see if we could observe the correlations they calculated to see if they hold up in the next few decades. And that brings us to an illustration of the big problem with some of the more exotic branches of theoretical physics. We can test if they come up with formulas fitting observational models and confirm whether the math works out. But we just can’t test whether such mathematical conveniences as hidden dimensions or other universes really exist using an extremely speculative model showing correlation while making a leap to causation. Physics cranks who very loudly decry math as a secret codex of wily scientists, use such speculations to justify their own musings, no matter how outlandish. This doesn’t mean that theoretical physicists should abandon their work to silence cranks, of course, but they should remember that the rubber has to meet the road at some point, and floating in the realm of esoteric mathematics often doesn’t translate into real world physics for many reasons…
See: Sarrazin, M., Pignol, G., Petit, F., Nesvizhevsky V. (2012). Experimental limits on neutron disappearance into another braneworld arXiv: 1201.3949v1
