Talk:Retrocausality

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	Retrocausality has been listed as one of the Natural sciences good articles under the good article criteria. If you can improve it further, please do. If it no longer meets these criteria, you can delist it, or ask for a reassessment.
Article milestones Date Process Result December 18, 2006 Articles for deletion Kept December 27, 2006 Articles for deletion No consensus June 23, 2007 Good article nominee Listed February 27, 2008 Good article reassessment Kept Current Status: Good article

	Philosophy Portal This article is within the scope of the WikiProject Philosophy, which collaborates on articles related to philosophy. To participate, you can edit this article or visit the project page for more details.
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Additional information: Related task forces (core areas): Metaphysics Related task forces (major fields): Philosophy of science

	Portal This article is within the scope of WikiProject Physics, which collaborates on articles related to physics.
GA	This article has been rated as GA-Class on the assessment scale.
Low	This article is on a subject of Low importance within physics.
Help with this template Comments: edit – history – watch – refresh Contents 1 Regarding my assessments 2 Main Article 3 Discussions and editing 4 Proper sources 5 Original Research 6 Things to do 7 Rewritten article is much better than the previous stub 8 Positrons 9 Top-down Cosmology 10 Addressing pseudoscience 11 Progress evaluation for GA 11.1 GA review 11.2 GA pass 12 Tag removal 13 GA Sweeps (Pass) [edit] Regarding my assessments Low-importance: Part of a few viable physics concepts, such as CTCs and the modeling of antimatter as retrocausal, but hardly a topic that demands immediate attention by any means. Start-class: I've done most of what I can ... the absorber theory stuff is a cast-off substub of a section, and I don't know where to look for more. I'm not sure how much further discussion on CTCs, Roman rings, etc. belongs here and not at their articles. Another couple sets of eyes from the Project won't hurt. And, of course, the philosophy/social discussion section its a separate beast, although I'd like to think I've given it the same measure of attention. --Serpent's Choice 06:34, 7 January 2007 (UTC)

[edit] Main Article

Okay, so this article obviously needs a lot of work. I'm glad that somebody started it though, since it didn't exist until recently. The general summary, even, is inaccurate though. Retrocausality doesn't ignore cause and effect, it suggests that there may be waves capable of traveling in any temporal direction. Particularly, a particle could emit a wave that moves both forward and backward in time, and as the wave moves back, the 'signal' connects with the waves of another particle, thus linking two otherwise unrelated particles in the present (and potentially explaining why two particles at any distance from each other can appear to be 'coupled').

At any rate, I am not a scientist and do not have a whole lot of spare time and energy on my hands, which is why I hadn't started the article myself. Anyone else out there keeping track of this?

Additionally, while to my knowledge no experiments have been done to test this yet, there is at least one experiment that has been proposed and may be tested sometime next year. Heading the experiment is Professor John G. Cramer from University of Washington, Seattle, who was recently featured in this New Scientist article. Professor Cramer's daughter, Kathryn Cramer, responded to the article and posted a note she says he wished to pass along:

As implied in the article, I have recruited an atomic physics experimentalist (Warren Nagourney) and we have decided to do at least the first stage of the experiment. I now have a LiIO3 non-linear crystal on order that will be needed to do this. We will begin the experiment in a couple of months when the argon-ion laser owned by the UW Atomic Physics group becomes available (sometime around December to February).

All this information would probably be helpful in the main article, but I've never actually started an article myself before, so anyone have any suggestions or things to add? --'Kash 18:21, 20 October 2006 (UTC)

Okay, I updated the article from it's original incarnation, to include what might make a decent introduction. I mentioned just enough to not get into detail, and also lightly address the common arguments I've seen about it. I might try getting back to it sometime in the near future if others don't tackle it first, but I think that's all for today. --'Kash 00:09, 21 October 2006 (UTC)

[edit] Discussions and editing

Someone recently edited the main article to add "(not true but cant be assed to explain but read Newscientist What's done is done… or is it? * 28 September 2006* Patrick Barry* Magazine issue 2571)." A notation like this belongs in the discussion page, not in the main article, so I have removed it.

Additionally, I have a subscription to New Scientist, have read that article, and no emperical observations of retrocausality have yet been made. The article discusses an experiment designed by Professor John G. Cramer, as mentioned above, and this experiment has not yet been performed. --'Kash 22:41, 27 October 2006 (UTC)

[edit] Proper sources

Per Wikipedia:Requests_for_arbitration/Pseudoscience, Acceptable sources, none of the sources given here are reliable for the purposes of an article on a scientific topic. The article either needs to be deleted, changed to address the topic from a mass media perspective, or supported by proper references for a scientific article per ArbCom, such as textbooks or articles in reputable peer-reviewed journals in the appropriate field. With the current sources, it is not possible to write a verifiable (WP:V) article on the topic as a scientific or philisophical concept. --Philosophus ^T 06:59, 19 December 2006 (UTC)

[edit] Original Research

Original research does not belong on Wikipedia. Furthermore, the notion of retrocausality is proved false in most modern physics textbooks. This is never mentioned in the article. Also, if retrocausation were possible, we would have memories of the future. Clearly that is not the case.

[edit] Things to do

Assuming this survives AFD in its current form...

• On the philosophy side:
  • A citation for Hume's definition of causality would be nice.
  • Some discussion on how retrocausality related to predestination/free will would be great, but will need a source. I didn't find one.
  • Should there be any discussion of "hard" time travel here, rather than just the wikilink to the article? Should we have include a {{main|time travel}} with a quick summary, as currently done with tachyons in science?
• On the science side:
  • The blurb on Feynman's positron model badly needs expansion.
  • Should any more tachyon information be included, given that tachyons are generally interpreted not to induce causal violations in time-like systems?
  • Did I miss anything that is/was actually legitimate science?

--Serpent's Choice 14:57, 25 December 2006 (UTC)

I would also work on the introduction. Right now, it seems to imply that such phenomena actually exist. --Philosophus ^T 20:15, 26 December 2006 (UTC)

Agreed, and altered. The mid-AFD article quick-fix is rarely the final draft, and I'll admit to having written a fairly slipshod lede at first. However, I do want to discuss the wording of the denial-of-reality. "Generally discounted" is a weaker denial than I might give similar concepts, but there are enough open questions regarding CTCs in heavily deformed space that I'm reticent to drop the bar on it any harder in the lede. I'm ambivalent about my current "no observation ... has been confirmed" wording versus a similar "has never been observed" -- is the Crough/Clay superluminal "cosmic ray" significant (and directly applicable) enough to contraindicate the simpler phrasing? Serpent's Choice 06:11, 27 December 2006 (UTC)

[edit] Rewritten article is much better than the previous stub

I'd argue that the new version by Serpent's Choice is a big improvement! I'm concerned about one particular sentence:

"However, no observation of retrocausality has never been confirmed, and the concept is generally discounted by both modern philosophy and mainstream science"

I'd argue for dropping that sentence, even though I agree with it. We should make clear that retrocausality is not scientifically confirmed, but a sentence like that is hard to give direct citation for. The fact that retrocausality is *not* mainstream should be evident to any reader who reads the whole article carefully. The alternative, which might be very laborious, is for the editor to find another published commentator who actually states 'No observation of retrocausality has ever been confirmed..', and then cite that comment. EdJohnston 05:43, 28 December 2006 (UTC)

I actually added that sentence in response to the concerns of Philosophus, above, who felt that the lede at the time (which is as it is now, minus that line) came too close to implying that retrocausality was an observed or recognized phenomenon. I know what a morass the fringe/pseudoscience/speculative/etc. material has been of late, so I've tried to tread lightly around the wordings -- although I'm not really any happier with that phrasing. Any suggestions for more compelling prose that resolves Philosophus's admittedly legitimate concern? Serpent's Choice 05:55, 28 December 2006 (UTC)

Perhaps you could go through the list of authors in the AAAS symposium, and check whether any of *them* reported actual experiments on retrocausality, by themselves or others. If not, then you could summarize the drift of what they said. Like: 'No author at the recent symposium.. knew of any actual experiments..' The phrase 'generally discounted', while very likely true, is hard to cite adequately for WP:V. Also, trying to generalize about modern philosophy is like trying to bottle a cloud. EdJohnston 17:07, 28 December 2006 (UTC)

Made another shot at fixing the lede into something acceptable that doesn't seem to give excessive implication of plausibility. Serpent's Choice 07:43, 2 January 2007 (UTC)

[edit] Positrons

Feynman later employed retrocausality to provide a proposed model of the positron. In this model, electrons moving backward in time would appear to possess negative electric charge. Further understanding of antimatter has rendered this model largely obsolete.

Electrons moving forward in time have negative electric charge, don't they? Should the above sentence say "positive" or was the suggestion that electrons are moving backward in time? --Hitchhiker89^talk 19:35, 31 December 2006 (UTC)

Indeed, and now fixed. Somehow the claim that I "missed a sign change" in my math seems weak in a text article. =) Serpent's Choice 04:08, 2 January 2007 (UTC)

[edit] Top-down Cosmology

Although I've run across a few web references to Hawking's "top-down cosmology" as retrocausality, I'm inclined to consider them in error and not include them here. Hawking's proposal is clearly a revised anthropic principle, but nothing inherent in that concept actually alters the past. Serpent's Choice 07:42, 2 January 2007 (UTC)

[edit] Addressing pseudoscience

To what extent is it appropriate or necessary to include coverage of pseudoscientific theories on this topic (as described at WP:FRINGE), such as those presented in Journal of Scientific Exploration? Serpent's Choice 09:38, 21 January 2007 (UTC)

I think there would have to be a lot of discussion of the pseudoscientific topic in mainstream circles, as described in WP:FRINGE#Examples. ("including but not limited to scientists, scientific journals, educational institutions, political institutions, and even the United States Supreme Court"). This mainstream discussion would need to be documented in mainstream references. EdJohnston 21:46, 21 January 2007 (UTC)

Well, I took a shot at it. Other than one reference to the Journal of Scientific Exploration, my journal sourcing was exclusively from BMJ and Foundations of Physics. It could probably do with at least one more pair of eyes for quality concerns, nevertheless. Serpent's Choice 06:10, 22 January 2007 (UTC)

[edit] Progress evaluation for GA

Retrocausality SCORES IN KEY AREAS
Legality	A	A	A	A
Neutrality	A	A	A	A
Writing	A	A	A	A
Sources	A	A	A	A
Citations		B	B	B

The only problem I see in this article is that some paragraphs are missing citations. The writing is no doubt readable, and it flows very nicely. For a subject that doesn't attract an organized countermovement, you would expect that much in the GA, on top of neutrality, which I believe has been achieved here. The sources are no problem. Overall this is a good article. However, let someone else have the final say.◙◙◙ I M Kmarinas86 U O 2¢ ◙◙◙ 03:59, 11 June 2007 (UTC)

I have added a few more references throughout and cleaned up some wording. The only paragraphs without citations at this time are brief passages that serve as organizational introductions to fully-cited subsections. Serpent's Choice 21:10, 12 June 2007 (UTC)

[edit] GA review

Hi! OK, no big objections here after the first read. There are some things that need clarification I believe, or could be elaborated upon to make the article more accessible. In detail:

In the 1950s, Michael Dummett wrote in opposition to such definitions, stating that there was no philosophical objection to effects preceding their causes.[6] This argument was rebutted by fellow philosopher Anthony Flew[7] and, later, by Max Black's "bilking argument".[8] A more complex discussion of how free will relates to the issues Black raised is summarized by Newcomb's paradox.

To better understand how sentences 2 and 3 relate: what is the bilking argument? (which issues raised black?)

Jan Faye

There's no wiki link, maybe it would help to say s.th. Jan Fay, a philosopher of the University of Ulm, Germany, or something

CTC arise from some exact solutions to the Einstein field equation.

I'd quickly explain what CTCs would imply. I know that's at the CTC article, but for a better understanding of the following sentences, it seems necessary. I'd propose to add s.th. like "A CTC is a world line of an object returning to origin, which would seem to imply at least the theoretical possibility of retrocausality and timetravel."

proposed an alternative theory.[25] University of Washington physicist John Cramer presented the design for an experiment to test this theory at an American Association for the Advancement of Science symposium, subsequently receiving some attention from the popular media,[26][27] although the experiment has never been performed as of 2006.

please clarify. the idea proposed relates to the tachyon idea, I think? add the basic idea of the proposal (taken from the src: "Cramer's approach to explaining entanglement is based on the proposition that particles at the quantum level can interact using signals that go both forward and backward in time") to better connect this proposal with the following paragraph regarding tachyons.

In popular culture

Can you elaborate on the example given? if you cite example, why not explain how retrocausality (or time-travel) works in Hogan's novel.
I haven't really looked at the other GA criteria yet (WP:MoS, images, sources), at a first glance everything seems fine, that's why I decided to focus on the prose. Good work by the way :) I will return shortly to check the other criteria, but as of now, I'd probably just put it on hold to because of the minor issues raised above. Well, read you soon I hope! Johnnyw talk 11:25, 18 June 2007 (UTC) After reading it a second time, the only things that spring to mind are

• "prayer healing" should probably not link to "prayer" but to "Faith healing", right?
• maybe mentioning in the lead that the concept is used in popular culture is justified?

Well, all in all, I'll put in on hold for now (image, sources seem OK). Hope to hear from you soon :) Johnnyw talk 15:50, 20 June 2007 (UTC)

I have defined the bilking argument, identified Faye more clearly, added a gloss for CTCs, and provided more substantial revision of the section on Cramer, including a discussion of another experiment in the field. I've also improved or expanded wikilink targeting throughout. How's it looking? Serpent's Choice 17:09, 21 June 2007 (UTC)

Very nice, good work. Could you take another look at the "in popular culture" proposal I made above to see if my remark is justified? And on a side note: I am receiving visitors until the beginning of next week and probably won't be able to take another look until Tuesday. So don't worry if I am not responding to any changes until then — if you worry about what else to do, you could compare if you missed out on any other proposals I made above, as I said, I don't have time to double-check right now myself, sorry for that! And: thanks for your work on this topic! Best wishes, Johnnyw talk 17:29, 21 June 2007 (UTC)

[edit] GA pass

Fair enough, looking good, thanks for addressing the issues I mentioned above. The article passes of course. I'd wish to see a bit more of info in the popular culture section, since it only covers literature right now: A short mentioning of other forms of media and a quick explanation of the idea used in the Hogan's novel would be desirable. Well, that's it: congratulations and thanks for your work. --Johnnyw talk 11:33, 25 June 2007 (UTC)

[edit] Tag removal

I removed the current-events tag from this article. Although there is some ongoing research into the topic (Cramer, et al.), that is true of all topics in science. There is no "current event" in this field in the typical sense: no sudden breakthrough (or expectation of one), no major event that would lead researchers or readers to expect that in a day's, week's, or month's time the content of this page would be different. The alternative would be to tag nearly all pages about science topics with the current-events tag, but I am reasonably certain that does not follow from current practice and procedure. Serpent's Choice 03:36, 16 June 2007 (UTC)

[edit] GA Sweeps (Pass)

This article has been reviewed as part of Wikipedia:WikiProject Good articles/Project quality task force. I believe the article currently meets the criteria and should remain listed as a Good article. The article history has been updated to reflect this review.

Some minor suggestions for improvement, outside the GA review process:

• I thought this sentence in the "As physics" section intro encroached on NPOV: "In general, models that appear to permit retrocausality or time travel are often thought to possess mathematical artifacts or to simply be conceptually flawed." It should be sufficient to discuss the theories and let the weight of evidence for each side speak for itself.
• There's a brief allusion to Costa de Beauregard's alternative theory of quantum entanglement—it would be nice if a brief explanation of this theory was included.

-- jwanders^Talk 23:58, 27 February 2008 (UTC) [edit]