““The objective world simply is, it does not happen,” wrote mathematician and physicist Hermann Weyl in 1949. From his point of view, the universe is laid out in time as surely as it is laid out in space. Time does not pass, and the past and future are as real as the present. If your common sense rebels against this idea, it is probably for a single reason: the arrow of causality. Events in the past cause events in the present which cause events in the future. If time really is like space, then shouldn’t events from the future influence the present and past, too?”
“mathematically, entanglement in time is identical to entanglement in space, and we have no qualms with information traveling in all directions across space.”
“To think about this problem, consider the most prosaic of objects: a popsicle stick. The stick will bend or buckle, depending on the pressure you apply to both ends. Now imagine a popsicle stick whose ends are separated in time, rather than in space. The same logic should apply: What happens to the middle of the stick will depend on the situation at each end. For entangled particles, the endpoints happen to be in time. At one end is the moment they were created next to each other in the laboratory, and at the other end is the moment when they are far apart and a measurement is taken. Their behavior at some intermediate time depends on information flowing from both past and future.”
“As with so much else in quantum mechanics, this concept of retrocausality is limited in scope. Only in certain circumstances can we see the future influence the past. Although individual particle processes can move backward or forward in time, the universe as a whole is skewed in the forward direction, because its past endpoint was highly ordered, and its future endpoint is highly disordered. Our mortality is this asymmetry in microcosm.”
“So is our sensation of time’s passage and, by extension, of free will. We have the feeling that the past is fixed because we have records of it, created as the universe slid from its highly ordered origins toward a messier future. We have no such records of the future. In fact, you could define the future as “that we know not of.” And one of the many things we don’t know about the future is what we ourselves will do in it. We acquire this knowledge only in the act of living. Our decisions might be preordained, but we still have to go through the paces, and that is what gives our volition meaning.”
“One of the most developed retrocausal models is the so-called transactional interpretation developed by physicist John Cramer of the University of Washington. According to Cramer, every event sends out a wave propagating both forward and backward in time, connecting the measurement of a particle with its earlier preparation, but canceling out at other locations in spacetime. But even this picture, Wallace says, is just “a sketch of ideas.” There remains no complete model for retrocausality.”
“Retrocausal models have forced physicists to reconsider long-standing taboos. In affording a role for future events in the present day, it joins a line of thought stretching to Plato and Aristotle. They argued that nature, like man, is organized around final ends and goals. Just as the purpose of the baker is to bake, the purpose of the raindrop is to fall, and of the seed to grow into a tree. These so-called teleological approaches fell out of the scientific mainstream when Newton and his contemporaries proved that you could predict the future of natural objects using only present circumstances. There was no explicit role for the future, or need for it. With retrocausality, physics may be forcing a very old idea back into the conversation.”