What is Retrocausality: Definition and 23 Discussions

Retrocausality, or backwards causation, is a concept of cause and effect in which an effect precedes its cause in time and so a later event affects an earlier one. In quantum physics, the distinction between cause and effect is not made at the most fundamental level and so time-symmetric systems can be viewed as causal or retrocausal. Philosophical considerations of time travel often address the same issues as retrocausality, as do treatments of the subject in fiction, but the two phenomena are distinct.

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  1. A

    I The question of retrocausality

    Hello all. There is the essence of the experiment in this link: https://en.m.wikipedia.org/wiki/Delayed-choice_quantum_eraser You can see the essence of the original experiment under this text. Excerpt from the text: By using a coincidence counte, the experimenters were able to isolate the...
  2. entropy1

    I Does determinism exclude retrocausality?

    Suppose the system under examination is fully deterministic. Does that imply that effects follow causes and not precede them? For instance, if in this system Alice would respond to event X with A, but, if instead of X event Y would have happened, with B, does that mean she has no choice between...
  3. K

    I New paper by physicists Ken Wharton and Nathan Argaman on Retrocausality

    I found this a very interesting article: Retrocausality may sound like science fiction, but it might be the best way to explain certain features of the quantum world, as detailed in a major new paper by physicists Ken Wharton and Nathan Argaman. Published in Reviews of Modern Physics, Wharton...
  4. entropy1

    B Does retrocausality follow from logic?

    I can't remember where this subject came forward in my topics, so I created a new topic. Suppose that: If X happens, we observe A, and: If Y happens, we observe B. Could we then say: If we observe A, Y did not happen, and: If we observe B, X did not happen, if we apply this to...
  5. entropy1

    B Exploring the Possibility of Retrocausality and Acausality in Quantum Mechanics

    Does the definition of locality in the QM sense include the prohibition of retrocausality?
  6. N

    I What time structure supports info moving backward in time?

    This of course is speculative, but IF faster-than-light travel (or wormhole tunneling or some other exotic means) was found to be able to communicate information from the future to the present, what would that indicate about the structure of time? Some might argue that indicates a block-type of...
  7. entropy1

    I Correlation setup between past and present

    Suppose A is an ensemble of measurement events in the past. Suppose B is an ensemble of measurement events in the present. Suppose there is a correlation between A and B that stays the same over time. Suppose we can manipulate the outcomes of B (for example by choosing the orientation of the...
  8. J

    I The Role of Causality in Primary and Secondary Physics

    With reference to the Delayed wheeler choice thought experiment. I.E. deciding to detect the photon either from one side or the other side of a galaxy that has obscured the which way path of the photon emitted from a distant galaxy "behind" the "gravitational lensing galaxy". Also...
  9. Buzz Bloom

    I A new approach: retrocausality in QFT

    I looked at the other threads that have discussed retrocausality, but a scan of the article https://phys.org/news/2017-07-physicists-retrocausal-quantum-theory-future.html?google_editors_picks=true seems to take a new approach. The paper also gives two references. Proceedings of The Royal...
  10. T

    I Possible retrocausal events and time paradoxes

    Does the universe allow retrocausal events to happen as long as there are no time paradoxes?
  11. thenewmans

    Retrocausality interpretations for fermions

    This question is about experiments involving entangled electrons or any other fermion for that matter. I’ll get to that in a sec. I’ve been interested in understanding interpretations that have retrocausality. (TIQM by Cramer, Wheeler–Feynman absorber, time symmetric by Price) It’s easy to...
  12. thenewmans

    B What’s the difference between TIQM and Time Symmetric QM? (a

    I have a few questions about interpretations that use retrocausality. I only know of 2. 1. TIQM - Transactional Interpretation of QM by John Cramer 1986 https://en.wikipedia.org/wiki/Transactional_interpretation 2. TSQM - Time Symmetric QM by Huw Price...
  13. W

    B Explaining to middle and high schoolers the alternatives to retrocausality

    I run a maker space and it has taken a dive into physics recently. I have 2 students doing a quantum entanglement experiment from SciAm and the Spooky Action at a Distance website. And, we have done a simple quantum eraser with polarized light. All I can tell them is that "physicists say"...
  14. N

    B New retrocausality experiment ?

    It seems that this was published last year on IJQF http://www.ijqf.org/wps/wp-content/uploads/2015/12/TooLate.pdf "In the EPR experiment, each measurement addresses the question “What spin value has this particle along this orientation? We propose a new setting where the question is...
  15. Q

    B Does retrocausality only apply to subatomic particles?

    It seems that historical events are the same every day. If the future affected the past wouldn't history books change everyday by themselves? Is it possible that history does actually change but we don't realize it because our memories change too?
  16. entropy1

    Bell-state entanglement swapping and retrocausality

    I thought there were already some posts about this, but I can't find them.:frown: In this article of Anton Zeilinger et al. they perform an experiment which suggests FTL or retrocausal influence. Alice and Bob both produce their own polarisation-entangled photon pair, both send one photon of...
  17. SpaceKidd_N7

    Delayed Choice Quantum Eraser: Am I missing something here?

    Hello everyone, I actually have three questions: 1. Am I missing an important detail in my understanding of how the delayed choice quantum eraser experiment is done? 2. How does one account for what takes place in the experiment without using the concept of "retrocausality" (effect before...
  18. Hybrid

    Is Retrocausality inherently deterministic?

    I'm a "lurker" of this forum and decided to create an account because I was curious as to whether Retrocausality implies a determinate, or indeterminate view. I'm posting this thread as a derivative from the discussion taking place in the quotes down below from the following thread...
  19. M

    Superposition and retrocausality

    Hello guys, I made this analogy for double slit experiment. I would like to share this idea and I would like to hear your opinions and ideas. Thank you. I apologize for any typos or bad grammar, I am not native english speaker. Here it is: Analogy for wave collapse I am using term KNOWER...
  20. J

    Huggins Displacement Theory and Retrocausality

    I was looking at the Wikipedia entries on Time Travel and the Grandfather paradox and noticed a paragraph on the so-called Huggins Displacement Theory. I haven't been able to find the source although I assume it's originator was the Victorian astronomer Sir William Huggins. Does anyone know of...
  21. J

    Retrocausality solves QM problems?

    Retrocausality solves QM problems?? Does retrocausality successfully solve the problems of QM? This recent paper seems to claim it does. http://arxiv.org/abs/1001.5057 Comments, anyone? Also what is the relationship of retrocausality and collapse? TIA Jim Graber
  22. J

    What is the Controversy Surrounding Retrocausality?

    i looked it up on the wiki page and was a little hard for me to understand.
  23. O

    Quantum Entanglement and retrocausality

    Recently, an experiment in the Canary Islands demonstrated that messages could be sent using Quantum Entanglement over a distance of 144km. Since I took courses in both Relativity and Quantum Mechanics, this confuses me, since the presence of distance between the two locals would cause...