h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

About the "you can only see it when you're not lokking at it" phenamenom:

I have a computer in my room. It has, like many other computers, some LEDs on it. When I'm in bed, I sometimes by accident line myself up so that these LED appear to be on the border of somthing that would obscure the LEDs. When I look at the LEDs, I can see them. When I look nearer to the middle of the obstruction, I can't see them. If I move slightly so that I can't see the LEDs when looking straight at them, then when I look farther away from the obstruction, I can see them. I don't know why this happens, I just wanted to record my experiences with this problem.

Hooloovoo and Jim Lynn, have got it about spot on. I'm colour-blind with the most common red-green deficiancy (it's real name if you're interested is "Protanopia" - I don't know the others.) and it is about not being able to distinguish between particular colours rather than actual 'blindess' to them. For me I often confuse purple and blue, it is as if the red element of the purple isn't there and it just looks blue. However, that said, The Green light on traffic signals looks white, as if there were no colour there at all! (And yet the grass is still green), not that it mattered any great deal, when I was young i just learnt them by sequence.

There is a guide entry on this if you want more information.

Clive

P.S About the Universe being lazy, is that like a kind of anti-entropy?

Clive

I quite frequently experience the amalgumated stuff effect when gettign out of bed during the middle of the night or nearly waking up at about 6 in the morning, I tend to see piles of clothes (which is what my bedroom floor generaly consists of!) folded in certain ways and imuminated by the moon or light from my bedside table develop features and stare at me, i'm not joking.

the other thing that sometimes happens is if a room is dimly lit then sometimes I see objects out of the corner of my eye wich then when I turn my head to look disappear, I don't believe in ghosts but it may be a similar thing that causes people to report ghost sightings.

someone mentioned the fright caused by a 'foreign' arm after laying on it untill it is asleep, there is actually a rare neurological disorder which results in one side of the body becoming alienated from the other. People suffering from this disorder are unable to always recognize for example their left hand or arm as belonging to themselves so when the guilty appendage assaults them in someway,say by removing something from their pocket or unexpectedly reaching for their face the person becomes frightened or agitated and on some occasions this has resulted in acts of self mutilation as they attempt to protect themselves from themselves.
There is a wonderfullly entertaining book written on the subject of strange and rare neurological disorders written by prominent neurologist Dr Oliver Sacks in which he describes many of the more peculiar and humours patients he has treated. Picadore publishes the book its called 'The man who mistook his wife for a hat.'

reminds me for some reason of Phineas Gage.

The seeing/not seeing effect when rotating the eye *is* caused by the effective lateral movement of the pupil, just as if you moved you head.

There are two odd optical effects I've observed :

a) Fix your gaze on a distant (~6m/20ft) object. Hold a piece of card vertically a few inches in front of the eyes so that the top edge is just under the field of vision, and move it up and down, into and out of your line of site. I find that the area of the distant object just above the (out of focus) card edge appears to be squashed upwards slightly as the card moves upwards. This seems to happen even if I fix my vision solidly on the object in question, so it doesn't seem to be caused by movement of the pupil.
If I'm either looking past a nearer (1m/3ft) object, and focussing on the distant one, or if I'm focussing on the edge of the closer object, the closer object doesn't seem to move at all.


b) (At least for the mildly myopic / astigmatic among you). Sit in a darkened room without your glasses or contact lenses about 3m/10ft from a piece of hifi gear or similar which has a small LED or fluorescent display.
Trying to focus on the display with one eye covered, I find that rather than a blurred blob for each digit, I see a central dark area, surrounded by a ring formed of definite multiple copies of the display, of different intensities, but all reasonably sharp. (Imagine that you made a rubber stamp of the correct image, and then repeatedly stamped it with different pressure whilst moving the stamp slightly between each stamping.) If I concentrate on one of the two or three brighter images, I can clearly read the digits. The ring of blurred images is several times wider than the actual display. Some of the components of the ring seem blurred, but if I concentrate on them, I get the impression that they are made of multiple sharp fainter copies

If this was simply a matter of focussing, shouldn't any initial point source of light be spread out into some kind of circular or elliptical disc, rather than what would appear to be a a few points around a ring? Are the multiple images some sort of image-processing artifact arising from interactions between the hardwired line-detector nerve groupings on the retina, or are there actually many multiple images of the same small object really being projected onto my retina by my substandard optics?
Moving my gaze from one portion of the ring of images to another has little effect on the shape or position of the ring.

Could this second effect have something to do with diffraction at the pupil? - it's so pronounced, I would have thought whatever causes it would have a serious effect on my vision generally, but with glasses on, my eyesight is definitely above average.

Hmm.. that's all very interesting, and I understand perfectly, having been an amateur cinematographer at college - but I don't think it applies here. The thing is, even after both my eyes have been open for some time, I can close one and see more red than when I close the other. The effect is barely noticeable indoors, but in full sunlight it is unmistakeable. I often experience it when looking at grass (the normal type, not the type you smoke!!) because of the green content. Perhaps I should have said "one of my eyes sees less green than the other"..

That's exactly it!! And I'm convinced it's because your pupil is a hole in a moving hemisphere (yuor eyeball), and therefore the light collection point is not fixed, even when your head is stationary (if that makes any sense)...
[EXCITED MODE OFF]

Wow! I'm impressed with all that detail, Potholer! I'm intrigued by the multiple images thing. I agree that you should see each point as a ring, were focussing the only problem. I feel that you may be correct about the images being generated by irregularities in your optics.

Funny you should mention that.. I once fell asleep with my hands on my chest (which I hardly ever do). I then had a dream about being in a gang about to rob a bank. I was sitting in the front of the van, and had to turn around to get my bag from the back. One of the guys in the back grabbed me by the wrists, menacingly. I then distinctly remember waking up, and then realising that someone was still restraining my hands! After a second or two I realised what had happened - my hands were on my chest, and had 'gone to sleep'. However, this was not the full story, as it was *not* the usual 'pins and needles' - I could move my arms normally after a few seconds.
A few days later someone told me the answer. It seems that we have a mechanism somewhere in the base of the brain that disconnects the motor cortex from the spinal column during dream sleep - presumably so that we don't thrash about too much (obviously doesn't always work, judging by some people ). Sometimes this mechanism doesn't disengage straight away when we awake, and this is why I was unable to move my arms for a few seconds.
Spooky, eh?

WOW

I wanted to thank everybody for all their contributions - as a relative newcomer to h2g2, I can't tell you how gratifying it was to get such a tremendous response - and all of it fascinating reading too!

Thank you!

I just remembered another example for this light-under-the-door thing: Close one eye and look with the other straight ahead. Then position your index finger (or pencil or whatever) on the side of your face where your closed eye is, so that you can barely see it past your nose with your open eye (important: remember to look straight ahead!). When you turn your open eye now towards your finger, it disappears behind your nose!

Egad! It works!

I have noticed both of these things, as a person who is unemployed generally thinks too much for his/her/it/their own good.

1) It's not just with clocks. Watch a film you've never seen before, or not in a while, without a watch or anything to keep time. It will seem to drag on forever. Then, watch the same spot of film again, preferrably with a friend, and it will seem to go much quicker. I believe it occurs thusly: the brain, during a new situation of any type, has to process a lot of information. Therefore, it either slows itself down, or seems to slow itself down because it is so active, and therefore can't spend any time thinking about nude ladies or the football match as it would prefer. The next time the experience occurs, the brain is able to fill in the blanks (after realising that it has already stored a paradigm of the situation) a bit and therefore has more time to spend in "idle," to put things into a multiprocessing or automotive perspective. The same effect can be seen on the first day of a new job. The day generally seems to take a lot of time, especially if it is spent meeting new people, learning new machines or filling out a lot of difficult forms. The second day, when everything is pretty much the same, goes by much faster, or seems to. I realise this is pretty much the opposite of Einstein's classic explanation of relativity, but then again he wasn't interested in psychomechanics so much. I would append it thusly: "If you sit with a pretty girl for an hour and it feels like a minute, it's time to find a new girl."

2) Yeah, this happens to me all the time, I assume it's something to do with the way the eye perceives things in the periphery. Another interesting trick peripheral vision plays is that, since it is processed at effectively a different angle than you can possibly view things with your focal sight without turning your head (draw a diagram of the eye in relation to a perceived object if this seems confusing), you'll often see things out of the corner of your eye that you can't see, really, without moving your head about like a s*****c puppet. Which really annoys me -- what's the point of noticing something that you can't see properly without doing a whole lot of work?

surely the universe being lazy is just straightforward entropy. Since entropy is the tendancy toward the most energetically favourable state.

For me the film thing works the other way round. When I see a film for the first time, it goes by really quickly. When I see it again, it seems to drag on and on. My guess is that it's because the first time I watch it, I don't know what's coming next. When I watch it the second time, I can't be bothered to wait for the thing to happen.

I can get this feeling in a new film too. Sometimes, they set up a scene to let you know that 'something' is going to happen e.g. they linger on the countdown timer of the bomb, or show someone lingering on a street corner with a gun. I suppose this is meant to build tension. I find it has the opposite effect; when I see it, I then sit there just waiting for them to get that bit of the story out of the way. I don't *want* to know what's going to happen next. I want to be surprised!

I find books the other way round. The first time, it takes ages, because I have to read every word in order to take it all in. The next time, however, I know the broad thrust of what's happening, so I can sort of skim read i.e. I can skip the odd word or sentence if it's a bit boring. It's a bit like watching a film with your finger poised on the FWD button. So this time, the book takes less time!

A classic example of the universe being lazy can be found in volume 2 of the Feynman Lectures on Physics.

There is a whole chapter in there discussing the Principle of Least Action. Using this very simple "the universe is very lazy" idea, you can work out some wonderful equations describing trajectories and all sorts of stuff.

Great!

Maybe I should also mention that I've found that the 'new job' syndrome is the other way round for me too.

The first day is really quick, and thereafter it gets slower and slower and sslloowweerr...

One of us, my dear dasmegabyte, has got a strange brain! Our next task is to work out which one of us it is!

I think you should have said 'AT LEAST one of us...'

I notice the variable time effect frequently while potholing. The first time I encounter a particularly long or strenuous crawl underground, it seems to go on forever. On subsequent trips, it rarely seems anywhere near as bad. Crawls or awkward passages also often seem much longer on the way in than on the way out, though I suppose that's partly due to my having to keep at least half my energy in reserve for the return trip. On the way in, I have to be more cautious, on the return, I can really go flat out.

The same goes for repeatedly walking a tiring mountain track when ferrying supplies to a camp. Once I know the landmarks, I have small successes to aim for as I walk. That helps me to know both that I'm making progress, and (possibly more importantly) that I am still on the right track, so any energy I expend isn't wasted by going in the wrong direction.

Here's another piece of vision weirdness to ponder: have a person stand across the room from you, and then hold a book (or notebook, vinyl sleeve, chessboard, whatever) in front of you, vertically, between your eyes, so that said person can only be seen by one eye - say your left eye. If another person now suddenly waves his hand in front of your right eye, person #1 across the room will disappear! [note: this only works if it's someone *else's* hand waving, and not your own - I suppose the predictability of the movements of your own hand plays into the effect]

As to the dead arm thing... gods, that is alarming. I've only done it once - woke up and found an arm in my bed, which certainly didn't *seem* to be my arm... I actually jumped away from it for a second (come on, folks, it was like 3 AM, and I wasn't what you'd exactly call "awake"). Then for some reason I picked it up (what else is one expected to do with a mysterious alien arm in one's bed? Throw it out, I say!) and finally perceived it to be mine... sheeeeesh.

Grayswandir