Quantum mechanics is weird. For some that is probably not news, but as those people read on they may see it is even weirder than they thought. Researchers at the University of Vienna (paper) have determined that superposition, a phenomenon that allows one particle to exist in multiple states in space, should also for a particle to exist in multiple states in time.
A fundamental concept for everyday life is 'cause and effect.' What the researchers have found though is that causality need not be so definite in the Universe, so even if A causes B and B causes A, A and B can be in a superposition. The scenario the researchers use to describe it is a message being left in a room by Alice or Bob. Whoever enters the room first leaves the message for the other (A causes B or B causes A), but the actual decision of who enters the room first can be in a superposition. This means both messages can be in the room at the same time, and at least partly readable by the 'first' person to enter the room.
This superposition in the fourth dimension (time) could prove very useful for future studies of quantum mechanics and perhaps the linking of quantum and classical mechanics. Personally though, I'm wondering when someone is going to use this to answer the obvious question: which came first, the chicken or the egg?