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This article was nominated for deletion on 2006-12-18. The result of the discussion was No consensus, and the article has been rewritten since nomination - no prejudice against renomination if the article still has not addressed concerns.

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Start	This article has been rated as Start-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 6.1 Rewritten article is much better than the previous stub 6.2 Positrons 6.3 Top-down Cosmology 6.4 Addressing pseudoscience [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)