md65536

Sounds okay to me. But I am an idiot! "You'd be in the future" doesn't quite make sense but I think you mean that Earth's clocks will have advanced some huge amount relative to yours. You age normally; Earth ages extremely quickly.* I think this is correct because from Earth, if we saw you get near a black hole we'd see your clocks slow down. So suppose we spent a century watching your clock age a day, and then you were able to return to Earth. Neglecting travel time (including related special relativistic effects), you'd have experienced ageing a day while Earth aged a century. You're correct in that if you remain wholly inside a local frame of reference (not spaghettified where some parts of you will age differently than others) then you experience local time passing at a "normal" rate. ---I doubt this is possible with an extreme example like this. * Actually I don't know where you'd measure Earth's advanced ageing. If you were receiving timing signals from Earth the whole time, would you receive them in rapid succession while hanging out near the black hole? Or would Earth appear to age rapidly as you escaped the black hole?

Seen on a statistical level --- after the fact? If you look at the statistics perhaps they suggest that information travelled faster than light, but if you have no way of extracting that information until afterwards, then it is impossible to use that information to affect events retrocausally. To be honest I don't understand the variation. My weak understanding of the first variation comes from going through dumbed down details. "Statistical" usually means based on some connection between a lot of individual data, and a single datum may tell you nothing. If you want to control the outcome of a single photon event, information regarding that event is only available later, I think. Even if later it seems like somehow it was "known" by something ahead of time, there is no theoretical way to exploit that information at the photon's source.

Thanks for the links. Actually I don't know what my point was. http://en.wikipedia.org/wiki/Beam_divergence says that all beams diverge, proportional to wavelength and inversely proportional to smallest beam diameter. I'd mistakenly thought a narrower beam (with a waist limited by Planck length?) could be aimed more precisely. My poor understanding of QM is the same. Even for an extremely large very close target, the photon could miss, meaning it would essentially shoot out perpendicularly to the beam, if the photon is moving in the general direction of the target at all. I would assume then that there's also a tiny chance that the photon would travel backward away from the target. Actually these questions come from thinking about "what the universe would look like to a beam of light", which I know is not really a valid question because light doesn't "see" or experience anything. But if all beams diverge, and there is the possibility of a photon going anywhere, then from the source it's not possible to know for certain which way a single photon will go. The single photon, travelling as a wave, also diverges. In a sense it might be thought of as travelling in all directions at once. A'ight now I've fully digressed into "Speculations" territory, but I was looking for a rationale for the idea that the universe isn't squashed in one direction to light, but all directions. I don't think that the universe is squashed into a plane according to light, but into a point. Anyway... if a laser's divergence could be minimized with a large enough beam "waist" and a small enough wavelength, then the beam could be aimed precisely on a small and distant target, but the individual photons could still go anywhere, I guess with decreasing probability with increasing precision.

Suppose you fire a photon from some ideal source to a target point on a flat surface 1 m away. Suppose that the smallest distance from the target that you can theoretically hit, with probability P, is epsilon. Is P < 1 for any finite epsilon? Is there a remote chance of missing a target no matter how big it is? Is epsilon related to the Planck length? Is it related to the photon's wavelength? If the target were moved to say 10^100 m away, would epsilon be scaled by a factor of 10^100?

Does your first link not satisfactorily answer it for the second version of the experiment? From http://en.wikipedia.org/wiki/Delayed_choice_quantum_eraser: "The total pattern of signal photons at the primary detector never shows interference, so it is not possible to deduce what will happen to the idler photons by observing the signal photons alone, which would open up the possibility of gaining information faster-than-light [...] The apparatus under discussion here could not communicate information in a retro-causal manner because it takes another signal, one which must arrive via a process that can go no faster than the speed of light, to sort the superimposed data in the signal photons into four streams that reflect the states of the idler photons at their four distinct detection screens. In fact, a theorem proved by Phillippe Eberhard shows that if the accepted equations of relativistic quantum field theory are correct, it should never be possible to experimentally violate causality using quantum effects"

I agree but I think the same things can be said of a lot of different conspiracy theories. All of the psychology, confusion, suspicions etc of conspiracy theories in general apply here (including the straw man of grouping all conspiracy theories together). I'd like to see a lot of things investigated openly, including UFOs. I'd be interested in knowing what Bush Sr. etc. knows about the subject.

Looking up stuff from ajb's post I came across this: http://en.wikipedia.org/wiki/Conformal_Cyclic_Cosmology It sounds similar to your idea, including something about the singularity you could get by treating a black hole's eternity as a single instant... but the resulting big bang would be separate from "our" big bang---a separate causally disconnected universe or something. I much prefer this idea. I think that "looping back in time" leaves more questions and explains little. I would avoid thinking that anything breaks causality unless that is the only conclusion left. Or unless there was some evidence of a violation... which to me is akin to finding evidence that reality is inconsistent. But who knows. Decades ago some scientists considered the idea that for example all electrons have the same properties because they are the same single electron, moving forward through time and backward as antimatter, an astronomical number of times simultaneously. Anyway, still I think that if you can make sense of stuff moving or jumping backward in time, you'll find that the idea doesn't violate causality, or it doesn't correspond to reality.

He doesn't say it happened to him. He says the camera crew captured it and came into his office and told him about it. They had the film developed and through proper bureaucratic channels it was sent off to Washington and he doesn't know if anyone's seen it since. So he described what happened in detail, even though he was in his office. Then he describes the film being whisked away, without stating that anyone viewed the film at all. It might be reasonably assumed that he saw the film, but why wouldn't he mention that specifically? He then goes on to explain how saucer shapes are good for travelling through the atmospheres of other planets. I would say that's a logical fallacy of "begging the question", and suggests confirmation bias. Edit: After watching it again, I feel that the editing, interviewer, and narrator reduce the credibility a lot. They are clearly going for a desired effect, and not presenting unbiased info. If it was Picard, that might be a little more credible...

Also a crackpot here. I imagine that the problem here is not one of causality, but one of conservation of energy (mass). If all information were destroyed when entering a black hole, there might be no way of affecting the past and breaking causality??? I suppose you're implying that all of the energy from the big bang would come from stuff that falls into black holes during the lifetime of the universe? Wouldn't this mean that conservation of energy would require that all matter eventually falls into a black hole? (Possibly a big crunch.) I don't think that's going to happen; isn't heat death the expected end of the universe? Speaking of conservation of energy, when matter falls into a black hole, the black hole increases in mass accordingly. So say with our perception of time, that mass continues on in the black hole, I guess until the black hole evaporates. Are you suggesting that from some other perspective, our perception of, say, "forever" is a single instant... uh... in which mass somehow cycles between big bang and the mass' lifetime, including eventual swallowing by a black hole?

If I was the devil I'd convince people to wage wars in the name of God. I'd promote hatred, inequality, division... and again blame the other guy. If I were the devil I'd trick people into doing my work while believing they were on God's side. In other words if I were the devil I'd just keep right on doing what he's doing. If I were the flying spaghetti monster, I'd make Jean Dujardin win an academy award for best actor. It has a ring of truth to it. If you make up an imaginary being or effect or whatever, and then selectively "predict" (or postdict?) that it would cause some of what you've seen, and then use that as evidence that the imaginary thing exists, then it's easy to trick yourself and some others into thinking it has something to do with "truth".

Curious... but what kind of numbers are we talking about here? Mass in (F) will be gravitationally attracted to (D) anyway, but are you saying that (F) will actually levitate and be pulled upward by a force greater than g? How hot is as [Hot] as you can make it and how cold is as [Cold] as you can make it? Do you have photographic or video evidence of it? Thanks.

My apologies to Divagating the Future, for making her the subject of her own thread without a chance to respond. I hadn't realized that she was banned.

No. It's probably best that way; it would just feed my penchant for conspiracy theories!

Don't forget the "uncommon and sometimes flawed use of English" [emphasis mine], which I think is important because sometimes it doesn't seem to be about whether or not someone is speaking properly, but whether or not "they speak like us". My experience in this matter is that I've only seen some of the posts in question. I realize there are some posts that I wouldn't agree with and am not interested in, and I haven't bothered reading them. So all that I see is a few posts, that seem to me to be treated with harassment, disrespect, and unfairness. Now that I know that this treatment is due to other, unrelated posts that I haven't seen, that explains how such seemingly appalling replies are considered justified. I just have to realize that a reply to a post can be a reply to all the user's posts, which might be acceptable around here though it can lead to situations that are bothersome to me. (Even if it's not acceptable, I realize that I'm guilty of it too.) "Scum" is probably a gross exaggeration. I think that more likely if someone starts off sounding unprofessional, they have to bend over backwards digging out of a hole that is the assumption that they're stupid or a troll etc. The assumption that someone's post is less intelligent than it actually is, also makes it easy to misinterpret. I'm glad though that excitement is a goal of the staff. As a crackpot, I find depressing the sheer volume of knowledge I'd need to be more effective.

Yes, one must take one's proper place even in the imaginary world of a puzzle. A lesser person cannot be imagined to have a superior car. A respectful puzzle with a proper attitude would display appropriate subordination. Admittedly, I was offended at the notion that I would drive a Corvette, at least in the presence of faster cars. I think it is a better puzzle if I am the one driving the faster imaginary car. But I think you're right though. I would guess that one might think that if another posted puzzle is incomplete, then this one might be as well. Perhaps an attitude of "my brain's better than your brain" so if I can't solve the puzzle, there must be something wrong with it. It's just a suspicion though... figuring out the post ratings is a puzzle in itself. I get the same answer.

Good puzzle. I voted it up, but I guess someone disagrees.

I disagree. I feel that in the spirit of what Divagating the Future describes as a forum, any post would be judged by the content of the post, and not by the user name, user profile, or even opinions expressed in other unrelated posts. I can tell that some users judge like this, where even the "wrong poster" can write a correct post. For some, any post by the wrong poster is automatically wrong. If this is more of a social group than a forum, then OP's point is valid. Many social groups are exclusive, and use excuses to justify the exclusion. It would be interesting if "science is a trial by fire" is being used as an excuse to be mean to outsiders. I have come to view highly rated posts as meaning they're considered correct and helpful. If it's just an indicator of popularity in the group, I'll treat it as such. It is good that this is a place to socialize, and not just a formal academic forum. I will lower my expectations of precision, professionalism, and inclusiveness. Edit: Err.. that is... I know it's an internet forum, and there are certain (lower?) expectations based on that, which I indulge in myself. But I also see the use of scientific principles, and the requirement that claims must be backed up with evidence, etc as things that elevate the forums above all that. I was hoping it was more of a modus operandi, rather than just an initiation test. Not "for outsiders, this is a thesis defense; for the "group", it's a club." I skimmed and cherry-picked, but I agree with you. In OP's case, a few unpopular posts, uncommon and sometimes flawed use of English (easily misinterpreted), and others' assumption that one is "scum until proven worthy", seems to have made it the majority of her experience.

I was about to erase that line from my post but now I have to instead take it back. Moments after writing it I discovered it was false. It was probably always false, but twisted in my mind. And then cargo-cult scientists like myself mimic the behavior and become the problem. Ideally, established fire-hardened scientists should be treated with fire, and newcomers should be treated lightly. However, I realize that most crackpots are not going to benefit from being humored, and a harsh treatment is often necessary. It must take great skill to know when harsh treatment is needed, and to respond to what is said instead of responding based on assumptions of the one who said it. No, just particular cases that I don't want to mention. My post involved venting, and was perhaps unfair and regrettable. In general the staff and experts' posts are fair and above average quality. Sometimes there are posts that are let pass or upvoted, but would be torn to shreds if they came from someone with a negative reputation. And vice versa. Edit: I guess I should say, bad posts are rarer among staff and experts. It's only the issue of "pats on the back all around" for all posts, good or bad, that seems to me to apply only to the established residents. It is a forum with an aristocracy.

Am I nobody? I agree with some of her points. There is a problem of people "patting each other on the back" in these forums. I see idiotic posts by crackpots, and then a cold, often harsh but usually fair rebuking by experts (science's "trial by fire", into which humiliation sometimes gets mixed in and mistaken for something good). --- Okay, that's fine. Crackpots need at least a reality check. I occasionally see idiotic posts by "experts" and staff, and no rebuking. I see idiotic posts voted up which I assume means they're considered "helpful". That's not fine. The "trial by fire" applies to all; it doesn't end once you've established yourself. I have not yet seen an expert admit to an error. I see hateful posts by some staff, sometimes harshly "correcting" others' posts that were correct in the first place. And then, the hateful posts are voted up by someone! Who does this?! That's not fine! That's unacceptable and it defiles the forums and has brought me to the verge of leaving in protest. It's got to the point where I can't always tell, by the content of or response to posts alone, the difference between a deluded crackpot and an expert. It is only a case of "a few rotten apples." I've seen a lot of good conversations and examples of astounding genius, and learned a lot (especially from swansont and Dr. Rocket in particular), but I've also come to view the forums as "the infallible insiders versus the worthless outsiders", where one must prove themselves or be treated with disdain. Sometimes it seems like there is missing a sense of understanding that everyone is ignorant in some way, and anyone might be a genius or an expert on something, and that we're all just people, with flaws and with feelings.

Correct. It struck me how different the two words sound, yet visually differ by only a little mark (depending on font I guess), so I made a riddle out of it. I looked up the word "rhyme" to make a clue, and it led to "correspond". To get back to rhyme may require a huge leap in lateral thinking, and might not be that good a clue.

Thanks No apologies necessary. If the details were easy to get, I would be able to explain it more easily.

I'll add two intermediate variations: Variation 0: As above, without the stuff from variation 1 or 2. What happens? I'll let it be taken for granted that (as I believe) the solution for the xkcd version also applies to this variation; All of the blue-eyed islanders leave on day N. Variation 0.5: As variation 0, with an additional rule: Any islander who knows what day she'll be leaving must immediately book a ticket off the island (ie. as far in advance as possible). The booking information is private; everyone may know that you're booking a ticket but no one else is able to find out what day you're booking for (unless by deduction). What happens? Alternate: Variation 1b: It is common knowledge that any islander who knows for certain (barring any unpredictable events including new outsider knowledge) what day they will leave, must announce it immediately, and tell everyone else what day they're leaving. What happens? No need to solve all the variations yourself...

Well now we're talking. I agree. After writing the reply below I've decided that my reply is a rambling nit-picking of details that is an unnecessary diversion from the point of the puzzle. ---- Many people will distrust division. One may rightly mention that division can be misused to incorrectly prove that 0=1. So if division---or induction---is being misused one need only point out the error. One need not "explain why division by 0 doesn't work" in order to use division. Yes, we must be careful not to misuse any mathematical or logical reasoning, but we only need to distrust it when we don't know how to use it properly and precisely. The induction proof for this puzzle "hides" the deductive reasoning that an islander might do, but that's okay because the puzzle specifically avoids the requirement that the islanders each think it through, with their magical logic abilities ("if there is some way by which someone can deduce their eye-colour, they will do so instantly."). So, yes, all that is needed is to be scrupulously careful. I think that a confusing trick in this puzzle is that we mix up what we as omniscient puzzle solvers know and reason about the situation, and what the islanders know and reason. And I think it also tricks a puzzle writer, as in the case here where OP has made it an assumption that since we know that all the islanders follow the rules, that the islanders themselves know that too. For the induction proof to be water-tight, it must not make any uncertain assumptions. The funny thing is, it is reasonable to argue that there's a flaw in the induction proof in this case (and with any other way of solving the puzzle)... The argument that if there was one blue, the other islanders would know the lone blue would deduce her eye color relies on the assumption that the islanders know that the other islanders know and obey the rules. WE know that they do, but we're meant to assume that it's common knowledge for the islanders. Of the 3 versions mentioned herein (OP's, wikipedia's, and xkcd's) I think that only the xkcd version is specified precisely enough that the intended solution need not rely on such assumptions about the islanders.

Yes... but once again that's not common knowledge. Read and understand the wiki entry on common knowledge (logic) and you should see why the existence of a blue-eyed islander is not common knowledge before the visitor's statement. ----- I'll try to explain this one more time and then I'm giving up, because I'm obviously failing at communicating anything effectively here. Consider a smaller case of 7 islanders: 3 blue, 3 brown, and me with unknown-color eyes. I see 3 blue. IF my eyes are not blue, then the 3 blue each see only 2 blue. They will think it possible that there are only 2 blue. If the blue that I see think that there are only 2 blue (which I know to be incorrect), they may think that each of those 2 blue see only one other blue. That is, the blue I see might think the blue they see might think there is only one blue... and that this sole blue might then see no blues and so might think that there are no blues. No one thinks that there are no blues. No one even thinks that anyone else thinks there are no blues. But it's possible to think that the blue I see think A: that there are only 2 blue, and B: that the 2 blue each think there is only one blue, and C: that the 2 blue each think that the one blue that they see thinks there are no blues. Once the visitor gives the common knowledge of the existence of a blue-eyed islander, it is no longer possible for me to assume that the 3 blue I see can assume that there are 2 blue who can assume that there is only 1 blue who can assume that there are no blue. The existence of 1 blue-eyed islander is only truly common knowledge on day 1. The existence of 2 is common knowledge on day 2, deduced from the common knowledge that if there was only 1 blue she would have determined her eye color and suicided by then. The existence of 3 is common knowledge on day 3, etc. I see 3 blue. On day 3 it is common knowledge that there are 3 blue. IF the 3 blue I see, each see only 2 blue and try to assume there are only 2 blue, they will deduce the contradiction and know that they have blue eyes. They will suicide on day 3. ELSE If they're still around on day 4 I know that there are at least 4 blue. I now know that my eyes are blue. Edit: Note that the whole time, it's possible to assume without contradiction that each of the 3 brown I see, each see only 2 brown and can assume that those 2 see only 1 brown, and can assume that the 2 can assume the one brown sees no browns. The existence of a brown-eyed islander is never common knowledge (unless we assume some additional amount of common knowledge about eye color that isn't specified in the puzzle).

"Faulty Cable To Blame For Superluminal Neutrino Results" http://science.slash...eutrino-results This story got a lot of people thinking. Was it really all for nothing? Edit: I guess I should mention that this isn't confirmed yet, and the article neither explains it very well nor cites sources.