Wikipedia:Reference desk/Archives/Science/2012 December 15

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December 15

Volitional Consciousness

Is there any scientific way to test for volitional consciousness? Futurist110 (talk) 09:08, 15 December 2012 (UTC)

Before you can decide on a test, you first must be clear on what it means. Volitional consciousness is not a term with a standard meaning - it doesn't mean the same thing to everybody, nor can its' meaning be extracted from looking up a dictionary (not from my dictionary anyway). To some it means the ability to focus one's consciousness on a particular subject/object/topic, and exclude everything else. That is certainly testable - get someone to concentrate on something, and try to distract them. It is a fundamental property of animal behaviour that, at various levels, stimuli are ignored. For instance, while typing this post, I am mostly ignoring the fact that my leg is itchy. I am totally unware of my heartbeat, and the birds in the tree outside my window. Another meaning, stemming from the writings of Ayn Rand (http://en.wikipedia.org/wiki/Ayn_Rand), is about whether or not we have free will, or are really pre-programmed automatons. This is a problem of semantics, is closely related to whether a machine can be conscious, and is a controversy/philosophical question as old as the study of cybernetics. (http://en.wikipedia.org/wiki/Cybernetics). It cannot be resolved. It cannot be resolved because becuase the term artificial intelligence/volitional consciousness cannot be precisely defined without asserting that it can be synthesised in a machine.

This is a not uncommon question on Reference Desk. I suggest that the OP, and anyone else tempted to add anything, does a search on the terms in Ref Desk archives first, or if not satisfied by my answer.

There's been a vast amount of words written on this, a topic that those of us who studied cybernetics at university have long learnt to ignore - somewhat like the US Patent Office would like to ignore folk who think they have invented perpectual motion machines. Floda 124.178.177.9 (talk) 09:39, 15 December 2012 (UTC)

This is a rather odd question. The term is not used in biology. The only place I have come across it is in the writing of Ayn Rand, who says "man is a being of volitional consciousness", by which she only means it's up to you whether you choose to focus on something or not. The OP could help out be explaining where he got the term, and what he thinks is meant by it. μηδείς (talk) 17:39, 15 December 2012 (UTC)

you mean one persons volitional consciousness is another's yellow banananess?66.87.80.4 (talk) 01:43, 16 December 2012 (UTC)

I mean the definition of the term as stated by Ayn Rand, specially the ability to focus on something and exclude everything else, but also the ability to change one's moral code, which humans are capable of doing but (at least most) animals are unable to do. Humans can think about their moral code and change it if they feel necessary, whereas the moral code of animals (generally) doesn't change over time. Futurist110 (talk) 20:29, 15 December 2012 (UTC)

Well there's a huge body of work in the cognitive sciences surrounding how attention and focus operate in various contexts (part of the problem is that these general terms are not really adequate to describe all of the many different ways in which the brain regularly reacts in prioritizing both incoming stimuli and ordering the mental constructs of "thought", however you define it. In other words, its a hard subject to treat all in one go here. At the same time, don't be in a hurry do put too large a distance between humans and all other animals in this regard. There's a problem in that morality is not an empirically quantifiable term in this context, though we are starting to develop a robust understanding of the neural mechanisms underpinning morality. But animals also have complex social and behavioral qualities that are largely neurologically innate but which experience (such as trauma or domestication, for example) can greatly influence. Now, you can always make the argument that they do not "choose" to change their outlook as such, but can you prove that you do? Empirically, how can you say for sure that you aren't being deterministically guided into that change of perspective and that your sense of choosing it and guiding your own moral code aren't just a part of the process? You can't ever have any degree of certainty on that issue really, because the observations would be made by part of the same framework of mechanisms that is being acted upon, your mind. And outside observers have very limited tools to make that assessment. The sense of choice could very well be just a sideffect of the relatively complex (in relation to most other animals) nature of how we respond to our environment and the resulting variation in how we react to stimuli. Snow (talk) 22:10, 15 December 2012 (UTC)

• Our article on the neuroscience of free will gives a pretty comprehensive discussion of the topic. Looie496 (talk) 19:10, 15 December 2012 (UTC)

Thank you. I'll make sure to look at it. Futurist110 (talk) 20:29, 15 December 2012 (UTC)

• But Rand's point is not that one can or should focus on one thing to the extent of blurring out all other things. Rather, she is concerned with whether you raise or lower your level of thinking when faced with a problem. How do you react to 'cognitive dissonance'? (Although that is not a term she used herself.) Do you make more of an effort to understand a thing, or to evade understanding it? Here are some excerpts from her writings on the topic of focus, http://aynrandlexicon.com/lexicon/focus.html, but be aware that the additions by Leonard Peikoff of her 'cult' are posthumous. As for the voluntary part, Rand is not arguing that people have some mystical freedom to break the laws of physics and do other than what they as bodies actually do, just that the essence of moral responsibility on the individual level traces down to whether one does or does not choose to think. Self-blame or self-esteem accrues to the effort you make to understand or react rationally to a given issue. μηδείς (talk) 20:59, 15 December 2012 (UTC)

promising technologies in natural resource management

promisin technologies in natural resource management — Preceding unsigned comment added by 39.54.24.59 (talk) 15:39, 15 December 2012 (UTC)

That's pretty vague. Can you give us additional information about your homework assignment? ←Baseball Bugs ^{What's up, Doc?} carrots→ 15:46, 15 December 2012 (UTC)

See desalination, solar power, wind power, geothermal power, tidal power, and wave power, to start. StuRat (talk) 16:12, 15 December 2012 (UTC)

CNS vs PNS

Damaged or severed nerves of peripheral nervous system can regrow. But damage to the central nervous system is not repairable. Why? --PlanetEditor (talk) 16:42, 15 December 2012 (UTC)

Think of replacing cells in the CNS like replacing the damaged hard disk on a computer. On the computer, you lose whatever was on the hard disk. The same seems to be true of the central nervous system. That is, you lose the network of connections which represent the "intelligence" stored there. I suppose we could be designed to start from scratch in such cases, and learn to walk again, etc. However, evolution didn't favor this capability, since it rarely would have been an option for an adult to start over like that, they would have starved to death first. StuRat (talk) 16:52, 15 December 2012 (UTC)

Your assumption is not correct. The CNS also gets repaired, although in a different way than the PNS. See neuroregeneration. OsmanRF34 (talk) 17:36, 15 December 2012 (UTC)

• When nerves of the PNS are damaged and regrow, the neurons (cell bodies) in the spinal cord that give rise to those nerves do not die -- they stay alive and grow new axons. When the spinal cord is damaged, the same thing happens in the initial stages -- the surviving neurons start to regenerate their axons -- but scar tissue forms at the site of the injury and blocks the path of the new axons, so that they can't reach their targets. For damage to the brain the story is more complicated -- the processes depend on the exact nature of the damage. Looie496 (talk) 19:03, 15 December 2012 (UTC)

Lower vertebrates like amphibians and fish are capable of CNS regeneration. Lack of such an ability is a feature of only mammals and birds. The reason why it was lost is not known but is likely related to lack of need. Indeed, serious CNS injuries in mammals and birds are almost always lethal without outside help (regeneration takes time). However only humans can help each other. So, it simply does not make sense to regenerate CNS. Ruslik_Zero 19:14, 15 December 2012 (UTC)

Thank you guys for the explanation. --PlanetEditor (talk) 03:30, 16 December 2012 (UTC)

Can you blame someone for appearing to be lazy?

This person just don't have the right neurotransmitters in his brain, and a pill can cure that. The same seems to apply to people who are too aggressive. We cannot blame them, in the same way that we cannot blame diabetic patients, they are just suffering from it. OsmanRF34 (talk) 18:18, 15 December 2012 (UTC)

Since that line of reasoning leads directly to the conclusion that you can't have any attitude toward anybody, clearly there must be something wrong with it. In my view what is wrong is that you are using an incorrect "theory of blaming". Looie496 (talk) 19:19, 15 December 2012 (UTC)

This, of course, makes it a Humanities refdesk question, not a science one. In the meantime, I would argue that while you may not wish to "blame" someone for being lazy, you will choose to employ people who will do the work that you are employing them to do, not those who will (or might) not. Equally, if you are raising or teaching a child who acts in a lazy way, you may choose to experiment with different ways of altering this behaviour. --Demiurge1000 (talk) 19:12, 15 December 2012 (UTC)

Define "lazy". If you mean someone without any energy, or who is content to spend time sitting down rather than standing, maybe the person concerned has a hormone deficiency or other medical problem. Or someone who doesn't feel the need to do what other people thinks they should do, well then I think the person with the problem is not the "lazy" person but the people who judge them. --TammyMoet (talk) 19:33, 15 December 2012 (UTC)

The truth is that most things humans do are not purely due to a medical issue or 100% free will, but some combo of those factors. I tend to only accept that a behavioral problem is 100% medical if I see some strong evidence, like a brain tumor. StuRat (talk) 19:43, 15 December 2012 (UTC)

Well, unless you believe in a nonphysical mind, every behavior you see is a result of brain activity, so whether you call it "medical" doesn't really make much difference. The existence of this difficulty is widely recognized, but there is no consensus on how to resolve it. My personal view is that the concept of blame is intrinsically dualistic, and that any attempt to apply dualistic concepts to information about the brain leads to hopeless boggles. Looie496 (talk) 00:44, 16 December 2012 (UTC)

But we do need to resolve it, such as when someone commits a crime and claims it's not their fault due to a medical condition that "made them do it". StuRat (talk) 03:50, 16 December 2012 (UTC)

I remember a joke where a murderer defends himself by claiming it was his hands that committed the murder, not him. So he should not be given punishment. The judge then sentenced the murderer's hands to life imprisonment saying the person can stay with his hands if he wish so. --PlanetEditor (talk) 04:29, 16 December 2012 (UTC)

I believe removing the hands of a thief was a traditional punishment. That philosophy could really discourage would-be rapists. :-) StuRat (talk) 19:04, 16 December 2012 (UTC)

Redolent of the "pound of flesh" debt in The Merchant of Venice. Portia knew what she was talking about when she argued, successfully, that nowhere in the agreement was there any mention of blood. -- Jack of Oz ^[Talk] 23:30, 16 December 2012 (UTC)

You can blame them, however, it doesn't mean that it is either morally acceptable, or justifiable. Laziness, is a morality concept. The question is essentially, "Is it moral to accuse another of having an inferior sense of morality?" Unconstructive criticism is a socialy destructive behaviour. Plasmic Physics (talk) 01:28, 16 December 2012 (UTC)

I'm an example. I have Asperger's, I have poor initiative and I appear lazy. Even so, I would happily lend a hand a stranger who needs it, all they need is ask. Plasmic Physics (talk) 01:39, 16 December 2012 (UTC)

So, you knew all along that it's possible to blame anyone for anything. As for the real question, what's moral to one person is immoral to another, and there is no one "correct" morality. The question has nothing to do with science, and a reference desk cannot advise you about this. -- Jack of Oz ^[Talk] 01:54, 16 December 2012 (UTC)

That there is no "correct" morality is a philosophical view, the other contesting view is that there is an absolute, held by some religions. You are correct though, this question is better suited to the humanities desk. Plasmic Physics (talk) 02:25, 16 December 2012 (UTC)

I believe that the question does have something to do with science. It relates to how our scientific knowledge about the brain can be used. Looie496 (talk) 02:45, 16 December 2012 (UTC)

So, you're considering how the subject's freedom of choice is affected by their psychological condition? Plasmic Physics (talk) 03:06, 16 December 2012 (UTC)

Neuroscience of free will. --PlanetEditor (talk) 03:28, 16 December 2012 (UTC)

• In a criminal case, a claim of temporary insanity is an affirmative defense, which requires the defendant to admit he committed the act, but was not morally culpable, due to self defense or organic illness or the like. The burden of proof in these cases is voluntarily on the defense, counter to StuRat's implication. μηδείς (talk) 03:26, 18 December 2012 (UTC)

• What implication ? StuRat (talk) 19:49, 18 December 2012 (UTC)

People can be bred to be lazy, via recumbent DNA. :-) StuRat (talk) 04:57, 20 December 2012 (UTC)

Aura (paranormal)

Saw a camera at a holistic fair which purports to photograph an aura. How does it work? Kittybrewster ☎ 18:29, 15 December 2012 (UTC)

The technical side of photographing auras is explained at Kirlian photography. OsmanRF34 (talk) 18:35, 15 December 2012 (UTC)

Here's a critique of the technique [1] and another [2]. Mikenorton (talk) 18:40, 15 December 2012 (UTC)

Absent spiders

I have several places in my house which seem to get spider webs, yet have no actual spider present. Do spiders place webs in multiple places and travel between them, looking for anything that was snagged ? StuRat (talk) 19:57, 15 December 2012 (UTC)

Could it just be that the spiders are really small and thus hard to spot (even those that look quite large when walking can disappear when they tuck the legs in)? Or that the spiders are lurking in cracks in the wall (or the shadows, or whatever) near the web? I have seen them do this before, but I don't think that spiders (outside of cartoons) actually choose to spend a lot of time hanging around in the middle of their own webs where everyone (birds included) can see. --Kurt Shaped Box (talk) 20:21, 15 December 2012 (UTC)

Yes, there are plenty of spiders that hang out on the edge of their web and will hide when they sense a possible predator, and not all are very large either. μηδείς (talk) 20:39, 15 December 2012 (UTC)

I wonder to what extent spiders pay attention to us as we approach, considering the scale difference? Do they even recognise us as living things? I know that sometimes it's possible to walk right up to a web with the spider in it and not have it react to you at all. Can't say that I've ever actually noticed this, or even looked for it - but I'd imagine that the reaction would be vastly different (i.e. flight response) if something like a Starling or Thrush approached. --Kurt Shaped Box (talk) 01:57, 16 December 2012 (UTC)

I've noticed that different insects and arachnids react very differently to the presence of people. Spiders generally seem to completely ignore me, right down to lowering right down on me as I type at the computer, only to be immediately squashed. Centipedes, on the other hand, run like hell as soon as they spot me. StuRat (talk) 02:22, 16 December 2012 (UTC)

The large spiders in my cellar seem to be more wary. They will ignore me until I intend to catch them, then will suddenly run and hide. I've pondered on whether this is some kind of telepathy, but suspect that they have the ability (like most animals and birds) of inferring intention from eye movements. On the other hand, I find it difficult to believe that a spider's brain has this level of sophistication. Perhaps there is a simpler reflex response developed as a result of predation by birds. Dbfirs 10:24, 17 December 2012 (UTC)

Yes, it might be as simple as when they first feel vibrations or might depend on the rate at which your position closes on them. StuRat (talk) 00:18, 18 December 2012 (UTC)

I tested both of those and they are indeed factors, as is change in light, but I thought I'd detected a separate response. Are spiders' eyes (and associated signal processing) sufficiently sensitive to detect direction of gaze in a predator? Dbfirs 08:12, 18 December 2012 (UTC)

That seems well beyond spider intelligence, to me. StuRat (talk) 08:16, 18 December 2012 (UTC)

I agree that a spider will not have the cognitive processing required to infer intention in a predator (as many birds and mammals do), but could it be a lower-level instinctive response? Dbfirs 09:00, 19 December 2012 (UTC)

I doubt they can even detect eyes, much less which way they are looking, but rather just see a large, moving, warm object. This type of thing I think of as associated with higher animals, like birds and mammals. Tigers, for example, won't normally attack if you are facing them (presumably an evolutionary adaptation from many being speared when attacking people from the front). StuRat (talk) 21:18, 19 December 2012 (UTC)

Other prey (especially that with horns) can also injure tigers so there has been longer for evolutionary adaptation, though I suspect that tigers also have some cognitive processing of risk. Perhaps my observations of spiders have been contaminated with some confirmation bias. I might try some more experiments when I have time. Dbfirs 11:13, 20 December 2012 (UTC)

If you're willing to part with the info, your geographic location will have considerable influence on the answer to this question. There are any number of spider species which are prone to abandoning their webs or lairs if conditions are not quite right (a quick change in temperature or humidity are often sufficient to do the trick) or if they simply have not had luck snaring prey and there are still others that have relatively short lifespans and may have simply died before you spotted them. However, I believe there are relatively few species which will try to maintain several completely independent webs concurrently and travel between them. There are of course many species which are nomadic and spin smaller webs to assist in hunting as needs demands. Snow (talk) 22:27, 15 December 2012 (UTC)

Detroit. This is inside, so the heat and humidity are certainly OK for spiders. StuRat (talk) 22:31, 15 December 2012 (UTC)

Thinking about this further, it doesn't really take that long to spin a web. You might only have like, two or three spiders in your house if they move around a lot and try different locations for their webs as Snow mentions... --Kurt Shaped Box (talk) 01:51, 16 December 2012 (UTC)

Kurt is almost there. Spiders aren't completely stupid. If one spins a web, gets some good meals, then not so many, maybe that means he's now got most or all the prey insects in that area. Then he'll go somewhere else and make a new web.

You'll find that, in general, critters like spiders that aren't very good at detecting humans detect their prey by detecting vibration via their legs, in contact with the gound or in contact with their web. Their nervous system is tuned to detect the amplitudes, cycling, and frequencies that their prey makes. Critters like certain centipedes, cockroaches, etc that readily detect humans and scurry away real quick have sensors that detect air currents. When a human comes near, or even just his hand, he displaces a lot of air, so the critter detects that something huge is coming his way.

I've seen an exquisite demonstration of the tuning of a spiders' nervous system. One spun a web across the external rear vision mirror of my car. No sign of the spider, but I figured he was hiding between the mirror and the cowling. I poked the web - nothing happened. I got in the car and started. Vibration from the idling engine did not affect the spider. I set off down the road - the wind distorted the web quite a bit. No sign of the spider. I stopped at an intersection. A fly landed on the web. Instantly the spider ran out, grabbed the fly, and ran back inside again.

Wickwack 121.221.224.223 (talk) 02:47, 16 December 2012 (UTC)

Webs don't last long. Once they get dusty they are more visible to you than a new web, but no longer effective. Some species build a new web every day.--Shantavira|^{feed me} 06:53, 16 December 2012 (UTC)

I've removed webs from the exact same spot 2 days in a row, with no sign of a spider (beyond the web) on either occasion. StuRat (talk) 19:34, 16 December 2012 (UTC)

Spiders may just hide outside the web, trying to be unconspicuous for prey. Also, when spider waits outside the web rather than on it, the web has more area to grab the prey. Brandmeister^talk 23:00, 16 December 2012 (UTC)

Relativity

So technically my left eye observes a different reality than my right, right?66.87.80.4 (talk) 23:47, 15 December 2012 (UTC)

No. Evanh2008 ^{(talk|contribs)} 23:50, 15 December 2012 (UTC)

If you turn your head so that there is a finite relative velocity between your eyes, or if you are lying on your side so that one eye is at a gravitational potential difference between the eyes. Count Iblis (talk) 00:24, 16 December 2012 (UTC)

That is how I thought of it I was slowly shaking my head side to side and looking at the rv mirror deco swinging 66.87.80.4 (talk) 01:24, 16 December 2012 (UTC)

Yes, due to the relativity factor of simultaneity. Plasmic Physics (talk) 00:45, 16 December 2012 (UTC)

Perhaps I am completely clueless here, but my understanding is that describing two observers as observing completely different realities is erroneous in the extreme. The same reality is observed, though the attributes ascribed to any given object may vary in different ways (relativity of simultaneity would be one of many causes for this). While all properly conducted observations are *correct*, none of them can be described as being objectively *true*, but that does not mean that there are multiple realities being observed. I guess the OP may be interested in Andromeda paradox. Evanh2008 ^{(talk|contribs)} 01:15, 16 December 2012 (UTC)

You could think of it as everyone sees the exact same reality - they simply disagree over where to point the xyz-t axes of spacetime. Someguy1221 (talk) 01:39, 16 December 2012 (UTC)

so my eyes are agreeing to disagree then, cool66.87.80.4 (talk) 01:47, 16 December 2012 (UTC)

Your first answer was sufficient, Evan. It's one reality sensed from two different vantage points an inch apart and integrated into one perception. μηδείς (talk) 01:40, 16 December 2012 (UTC)

Darn philosophical semantics. Plasmic Physics (talk) 02:28, 16 December 2012 (UTC)

Similarly, there are not multiple contracted universes nor does it ever contract when you turn your head sideways. Therefore, observer motion results in only an apparent "length contraction" of the universe, in contrast to the actual and very real contractions of, say, electrons. Opinions differ [3], but from my perspective, there is nothing about relativity that adequately explains the difference. -Modocc (talk) 05:23, 16 December 2012 (UTC)

Even without the effects of relativity, you eyes receive different images from different angles, and your brain combines these into the composite image of "reality" that you perceive. Relativistic effects are just the 4-D equivalent. Dbfirs 07:43, 16 December 2012 (UTC)

Sure the eyes differ, just as one can examine two sides of a coin, and as in the fable of the blind men and the elephant there are different perspectives. Moreover, there is one objective reality per scientific realism. But although it makes sense that actual length contractions occur locally, this differs from happening with respect to the entire map of the universe, and we have already discarded one model that included such apparent change: the apparent motion of the universe around the Earth, but only because we eventually understood why it was happening. There is always a distinction between apparent change due to changes in one's references and actual change, but relativity tends to blur the distinction because some length contractions appear to be real, but others are not. -Modocc (talk) 08:32, 16 December 2012 (UTC)

I don't understand your "some length contractions appear to be real" claim. If I observe a 100 cm rod from an oblique angle of 60 degrees, not knowing that I am observing obliquely, then it appears "contracted" to only 50 cm. Is this what you meant? It doesn't make sense to me that "actual length contractions occur locally". Dbfirs 09:04, 17 December 2012 (UTC)

By "appear to be real", I simply meant that I believe objects actually do contract... when these are physically accelerated, which is typical of localized phenomena. However, if one's measuring sticks and clocks are accelerated and are therefore physically altered by such acceleration, then there should only exist apparent contractions and frequency change with objects that were not accelerated. -Modocc (talk) 20:04, 17 December 2012 (UTC)

Ah, I see! You are talking about general relativity there. I suppose if the front and back of an object are in different inertial frames as a result of acceleration then a contraction could be considered real. Dbfirs 22:04, 17 December 2012 (UTC)

SR is considered to be adequate when gravity can be neglected, because GR arises when an inverse square law is introduced such that it produces the appropriate spacetime curvature. Its thus important to consider that accelerations occur even when the spacetime is flat. -Modocc (talk) 23:52, 17 December 2012 (UTC)

The main issue that comes up is that (in theory, to be pedantic) relativity means that there is no way to define "simultaneity" between the two eyes. There is no way to say that the two eyes see something at the same time or at different times except in one particular frame of reference. Of course, that frame of reference could be the one presumably shared by the two eyes (unless you're turning your head or something that gives them motion relative to one another). I won't even get into experiments you can do with entangled photons... Wnt (talk) 09:12, 16 December 2012 (UTC)

To give the OP some context here, the relativity of simultaneity follows from the relativistic postulate of light speed invariance. Because of validating experiments, the light speed invariance is considered exact and the experience of invariant simultaneity an approximation. With any pragmatic differences in the relative motion of the eyes, the eyes coincide with imperceptible differences in simultaneity according to relativity. --Modocc (talk) 16:28, 16 December 2012 (UTC)

The relativity of simultaneity has nothing to do with this question; please ignore those answers. What your eye perceives at a given moment is approximately the past light cone of the pupil. This does not depend on the velocity of the eye, only its position (and the current time). Any differences between what the two eyes see is due to different perspectives, differences in the light travel time (less than a nanosecond), aberration, and Doppler shift. None of these are specific to relativity. Aberration and Doppler shift depend on the velocity of the eye, but they only distort the image of the object; they don't change the reading on a clock. -- BenRG (talk) 21:26, 16 December 2012 (UTC)

No. Embed a miniature clock in each eye. These two clocks will differ in their readings if an ice skater is spinning and the head is held such that one eye is central to his/her axis of rotation. This is no different than any other relativistic exercise. -Modocc (talk) 21:49, 16 December 2012 (UTC)

I'm talking about clocks that you see out in the world, not clocks embedded in your eyes. -- BenRG (talk) 22:49, 16 December 2012 (UTC)

So? The OP was referring to differences between what each eye measures. Other clocks do not refute these embedded clocks and what one's brain registers with them. -Modocc (talk) 22:59, 16 December 2012 (UTC)

You're not making any sense. What I said is that the velocity of the eye doesn't affect the reading on any clock. What that means if that if you have two eyes at the same place at the same time, but with different velocities, they will see the same reading on any clock. This is just a basic property of locality: the eyes are in the same place so they are detecting the same light. This applies even to clocks inside the eyes, if it were somehow possible for both eyes to see one of those clocks. Of course, two different clocks (in the eyes or anywhere else) may not show the same time, but that has nothing to do with the original question. I don't see what you think it has to do with the relativity of simultaneity either, if that's what you were disagreeing with. -- BenRG (talk) 23:26, 16 December 2012 (UTC)

Ah... I must agree with the reality of your unwavering clock(s). :-) Of course, for the skater, the central eye ages quicker than the orbiting eye, and at this scale their brain occasionally resolves its twin eyes paradox with or without a jump in simultaneity? Interesting, no? -Modocc (talk) 23:59, 16 December 2012 (UTC)

What the Andromeda paradox (linked above) really shows is that the concept of the relativity of simultaneity is largely useless in practice. Small accelerations relative to Andromeda can change the "present time at Andromeda in your rest frame" by weeks in either direction, but they don't change the time of the events that you can see (or detect by other means). The "present time at Andromeda in your rest frame" has no relevance whatsoever to any measurement you can make, so it doesn't matter what it "does" when you accelerate. Instead of saying that there are a bunch of incompatible notions of simultaneity of distant events in special relativity, it's more accurate to say that there's no useful notion of simultaneity of distant events in special relativity. -- BenRG (talk) 21:47, 16 December 2012 (UTC)

"Small accelerations relative to Andromeda can change the 'present time at Andromeda...", changes the model's data points, but this apparently "doesn't matter" with regard to someone's local measurement? Perhaps, but if the concept is useful at small scales with small clocks and distances, it ought to be similarly useful at larger scales (which to validate would simply involve far longer elapsed times between events). -Modocc (talk) 22:53, 16 December 2012 (UTC)

Saying "there's no useful notion of simultaneity of distant events in special relativity" is like saying "there's no useful notion of equal x coordinates of distant points in Euclidean geometry". By "distant points" I really just mean distinct points. You can use Cartesian coordinates if you want, but it's important to understand what they do and don't mean. You can even define "a line's concept of equal-x-coordinate", as long as you understand that it's just something you made up and doesn't change any theorem of Euclidean geometry. -- BenRG (talk) 23:26, 16 December 2012 (UTC)