Theoretical physicists from the University of Vienna have released a statement that challenges our understanding of physics. In it they claim that according to quantum mechanics there are conceivable “situations in which a single event can be both, a cause and an effect of another one.”
The radical idea rests on the concept of superposition; where a particle can be in two places at once. The team from Vienna have shown that the causal order of events could be in superposition. This is impossible in classical physics, where there is a causal order of events to all phenomena. This sort of throws our whole concept of time off. The team’s example is of two people leaving messages in a room on separate occasions. Alice walks in the room, erases a message on a pad of paper and leaves her own. Afterwards, Bob does the same. He is able to see what Alice wrote, but Alice is not able to see what he wrote because he wrote his message after her. But if Alice and Bob have a “quantum system” to ascribe their message on…
…they can end up in a situation where each of them can read a part of the message written by the other. Effectively, one has a superposition of two situations: “Alice enters the room first and leaves a message before Bob” and “Bob enters the room first and leaves a message before Alice”.
“Such a superposition, however, has not been considered in the standard formulation of quantum mechanics since the theory always assumes a definite causal order between events”, says Ognyan Oreshkov from the Université Libre de Bruxelles (formerly University of Vienna). “But if we believe that quantum mechanics governs all phenomena, it is natural to expect that the order of events could also be indefinite, similarly to the location of a particle or its velocity”, adds Fabio Costa from the University of Vienna.
This merely proposes the idea that a causal order of events isn’t a necessary part of nature. According to the team the real search is for an instance of the superposition of causal orders in nature and where to look for it. Regardless, just the idea can mess with your whole reality. It certainly shines a new light on our concept of time. The team’s paper will be published in this weeks “Nature Communications”.