On 30 November 2016, around 100,000 people all over the world logged online and played a video game. Together, they surely would have frustrated Albert Einstein.
Screenshot: The BIG Bell Test
The physics that governs the most basic aspects of our universe relies on maths that seems to work really well, but one concept, quantum entanglement, can seem downright upsetting.
Entanglement confounded Einstein because of the way it seems to instantly send information faster than the speed of light. Einstein thought perhaps there was some hidden variables that would explain the entanglement without superluminal travel - if you just knew more about a quantum system, you'd be able to predict the properties of two entangled particles.
But the new experiment lead by Morgan Mitchell from the Institut de Ciències Fotòniques in Spain, called the BIG Bell Test, demonstrated that, sorry Einstein, your idea wasn't right. Quantum mechanics is just weird.
The experimental test subjects were video game players, and all they needed to do was play a button-mashing game in an effort to be as random as possible.
Entanglement, what Einstein called "spooky action at a distance", describes things that are separated far in distance yet seem to be inseparable mathematically - measuring one seems to immediately impact the other. Scientists have been aware of these spooky correlations since quantum physics' beginnings, as early as 1935.
Let's start with how things work in the real world. Let's say you had an apple and an orange, put each into a different lunch bag, and sent each lunch bag off with one of two children in heading in different directions. If one kid opens the bag and sees an orange, she immediately knows the other kid must have an apple. Obviously, looking at the orange didn't cause the fruit in the other bag to become an apple.
If an outside observer knew literally everything possible about this situation, they could have guessed which fruit each kid had the whole time. That's how Einstein thought quantum physics should work.
But, based on work done by John Stewart Bell, that isn't how quantum physics works. If the oranges and apples followed the rules of quantum mechanics, then both bags would simultaneously contain both fruits before the measurement happens. On opening the bag, each fruit then assumes a definite identity, regardless of how far they are separated.
No information is passed faster than light, and regardless of how much you know about the fruits, you can never guess what's inside the bags before making your measurement. There are no hidden, yet-to-be-discovered facts to help you know what's inside the bags before you look.
A ton of experiments since then have proven this. These experiments rely on the fact that after multiple measurements, special correlations will appear that would only be possible if the particles took on that spooky communicating-but-not-really nature of entanglement.
Bell's experiments always require an entangled system in which there is significant space between the two entangled particles. But newer Bell tests also write rules that prevent the way you measure what's in the bag from biasing your results. In an oversimplification, it's kind of like only being allowed to measure the bag's contents using randomly-assigned orange-only or apple-only detectors.
But as we've said previously, it's nearly impossible to guarantee that something is actually random and isn't secretly being chosen by some hidden force.
Bell suggested early on that to overcome this problem, you could rely on the randomness of human free will. The BIG Bell Test does just that.
The game is a button-mashing game - you move forward through a landscape by smacking zero and one as randomly as possible in an effort to be unpredictable. There are bosses you try to beat by guessing what an "oracle" won't guess. It's very random. As Wired reports, the scientists enlisted participants through a large-scale PR campaign that included podcasts and recruiting students at schools.
The video game players' behaviour sent random numbers to measurement apparatuses at 12 labs on five continents that were performing their own tests of entanglement. The random data from the video game determined the settings on the measuring devices. These experiments all once again revealed the spooky correlations, providing more evidence that there are no hidden variables governing the outcomes of measurements of entangled particles.
Sorry, Einstein - turns out that quantum mechanics really is as spooky as you thought it was.
Entanglement will continue to be important for quantum communications, which scientists hope to use to send encrypted messages or to perform quantum computations, so scientists will continue to test its limits.
If you want to try out the video game, though, it's here.