quantum causality remains an oxymoron
Countless poems, essays, and novels have ruminated on the inexorable forward march of time, how it slowly but surely grinds even the mightiest empires to dust and has an equal fate in store for the wealthiest of the wealthy and the poorest of the poor. But that only seems to apply if you are larger than a subatomic particle. If you’re an electron or a photon, time seems to be a very fungible thing that doesn’t always flow as one would expect and regularly ignores a pillar of the fabric of space and time: the fundamental limits imposed on the exchange of information by the speed of light. But some scientists were hoping they could bring the quantum world to heel with better designed experiments, arguing that because we have not observed single photons in an entangled system changing state faster than the speed of light would allow, calculating a cloud of them with advanced statistical methods, perhaps the noise drowned out the signals.
Well, Dutch scientists with the help of several colleagues in France decided to try test quantum entanglement using stable, heavy electrons entangled with photons so they could observe how the systems changed on stable particles, without worrying about decoherence. After managing to successfully entangle the system 245 times they collected enough data to plug into a formula known as Bell’s inequality, designed to determine if there are hidden variables in an experiment involving quantum systems. The result? No hidden variables could have been present while the spooky action of instantly changing quantum systems was reliably observed every time. It’s one of the most thorough and complete tests of quantum causality ever undertaken, and there have been a few murmurings of a potential Nobel Prize for the work. However, the paper is still under peer review and with the widespread attention to it, is bound to be scrutinized for flaws.
What does this mean for us? Well, it shows that we’re right about weird physics on a subatomic level happening exactly as counter-intuitively and inexplicably as we thought. But it also tells us that we can’t narrow down a simple conclusion and hints that some of the laws of physics might be scale variant, i.e. different depending on the size and scope of the objects they affect, and a scale-variant universe is going to make coming up with a unified theory of everything way more difficult than it already is because we now need to understand why it works that way. But again, this is science at its finest. We’re not trying to come up with one definitive answer to everything just by running enough experiments or watching the world around us for a long time, we’re just trying to expand how much we know to expand out horizons, finding answers and raising new questions which may be answered centuries down the road. Sometimes just knowing what you don’t know can be a big step forward because you now at least know where to start looking for an answer to a particularly nagging or difficult problem and where you will hit a dead end.