contrary to reason or common sense; utterly absurd or ridiculous.
“a preposterous suggestion”
Synonym absurd, ridiculous, foolish, stupid, ludicrous, farcical, laughable, comical, risible, etc.
The Latin origin of the word implies putting “the cart before the horse”. That the future (pre) can precede the past (post). That causality is violated. We philosophise about causality but we all accept it in our lives as the way things are. Something happens; we want to know why. The requirement that cause precedes effect also drives many scientists’ prejudices against accepting precognition, divination or déjà vu experiences as real. When Daryl Bem published his paper Feeling the Future, in which he presented experimental results that showed most people have the ability to perceive events a few seconds before they occur, the paper was met with a barrage of criticism. Several scientists reworked his data in various ways to try to make the effect go away. (For a history of the criticism, see Larry Dossey’s article, Why are scientists afraid of Daryl Bem.)
Recently, causality is being questioned again by theoretical physicists such as Mathew Leifer at Chapman University in Orange, California. The reason for the renewed interest, is that particle entanglement, and Bell’s Inequality already threw causality into question. If, as per Bell’s Theorem, particles can affect each other simultaneously despite being separated by large distances, then already we can no longer talk about which particle affects which. Where is the cause, and where the effect?
The idea of retro-causality (the cart before the horse), is as old as Newton’s Laws. Nothing in Newtonian physics says that a smashed glass cannot reassemble and become whole, like a movie played backwards. But we don’t expect it to happen, and Boltzmann thermodynamics explains why. However in the quantum world where weird things happen, retro-causality may happen after all.
It’s an appealing notion in that it helps understand Bell’s Inequality where two entangled particles apparently remain in touch, despite their separation. The reality may be that one particle sends a message back in time to the second particle about its quantum state, and the second particle responds, so as to appear to be instantaneously affected. In 2010 Huw Price, proposed that that because quantum processes are time-symmetric, nothing requires the flow of time to be unidirectional. Retro-causality would then be inevitable. It would solve quantum paradoxes such as the behavior of entangled particles. However, due to a flaw in his argument, few physicists took the idea seriously. More recently Leifer and Mathew Pusey resolved the issue in Price’s argument. In a paper published in the Proceedings of the Royal Society, they showed that retro-causality must be an integral part of the quantum theory, if the quantum theory is to be time-symmetric.
For the moment, the papers all involve theoretical arguments to explain some of the more bizarre aspects of the quantum theory. They imply that on the quantum level, the future can affect the past. Does this have any bearing on Daryl Bem’s experiments? It might, by providing a mechanism that would make his results more palatable. If the human brain’s activity, as many neurologists are inclined to think, involves quantum computing, then it might also involve retro-causal processes. The future may already be there, influencing the past, at least on a quantum level. How those affect the world we know and experience is another question.
Perhaps Daryl Bem’s results will turn out not to be so preposterous after all.