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

I know this subject will strike many of you as a little strange, for which I apologise in advance. I'm just dying to know whether I'm the *only* person who has noticed the following:

1. If there is something moving at fixed regular intervals (e.g. a flashing indicator on a car, or the second hand on a clock), then *sometimes*, when you happen to glance round and look at it, the first cycle of movement appears *much* longer than all the subsequent ones. It's as if your brain starts off with a racing clock rate (maybe because you just looked round, and are busy focussing), which then settles down once it's got its bearings. Inverting this timeframe gives a slow initial pulse followed by all the rest at normal speed.

2. If you are lying in bed in a dark room and there is light coming under a door, but there is an obstacle *almost* in the path of the light (wow, this is hard to describe), then you can sometimes be in a position where you can only see the light when you look directly at it. As soon as you look slightly away (moving only your eyes), it goes dark. I think this is because the pupil of your eye is actually on the surface of a rotating sphere (your eyeball), so even though you don't move your head, the point in 3D space at which information is collected by each of your eyes is actually changing - so the new position is in the shadow of the obscuring object.

Anyone else experienced either of these? By the way, one of my eyes also sees more red than the other, but that's another story..

P.S. I am human (I think)

There was a piece on World Service Radio about the "sticking second hand" phenomenum. Some science bod was interviewed who had worked it out. I can't remember the precise details of it, but I think you're not far off - it's some sort psychological and image retention thingy...

The clock in the office I'm writing this from has its second hand permanently stuck, so whenever you glance up at it you think your brain has timed out altogether.

I've definitely noticed the sticking second hand thingie a lot. To risk sounding like a smart-ass, it's a timing thing. If you look at the second hand during the middle of a "tick", it moves faster than you think it will.

Personally, I don't mind the second hand going wacky. But if the minute hand goes kaflooey, I'm calling the Time Cops and filing a complaint.

With regards to one of your eyes being redder than the other, I sometimes find that when reading a book a night I lie on one side with one eye closed and the book flat on the bed. After a while I'll get uncomfortable from being in the same position for too long and I'll open my other eye. It's only then that I realise that when looking out of the eye I had closed, everything has a green "tint" to it, while when looking out of the eye I'd had open, everything has a red "tint" (I can't think of a better word) to it. Is this what enables us to see through 3-D glasses? Is this what you're on about? Am I making any sense whatsoever? Answers on a postcard...

What you're experiencing there is the brain's natural ability to cope with different 'colour temperatures'. Put simply, different types of light affect the actual colours reflected by objects. If you've ever had to adjust the white balance on a camcorder you'll have seen this. Sunlight is more blue than light from a light bulb, which is yellow in comparison. Flourescent lights actually give off a green tinge.

In order for you to be able to recognise that things remain the same actual colour regardless of the light source (within limits, of course) the brain compensates for the overall balance of light coming into the eye. So a piece of white paper always looks white to you, even if the colour is actually yellowish.

When you've been reading with one eye closed, the brain hasn't been compensating for that eye, so when you open it, it sees different colours. The signals from each eye are being balanced differently, and you're seeing the differences as green and red.

This is nothing to do with 3D glasses, by the way. They work by filtering out one half of a stereoscopic image, so each eye only sees the image it is supposed to see. Trouble is, it doesn't work too well for colour pictures, so they developed another method, still in use today in many IMAX cinemas, which uses polarised lenses which only let through light travelling in a particular plane.

Woah...and you have certificates for this kinda stuff?

Yes I have noticed the red/green tints. My right eye has the red tint. I'm sure this helps us with depth perception, and maybe color perception. Do color blind people have the same "tints"?

another thing to take into account for the red, is that we have (i'm begining to get into unfamiliar territory, just the learning channel info here, corrections are welcome) rods and cones in our eyes, if i remember correct, rods allow us to see dark stuff, and cones allow for bright stuff. either way, the dark seeing ones see red better, cos in the dark, reds are easist to pick out. it may just be that you have more rods or cones in one eye. as for adaption, that is one of the many areas in which the human eye far excedes any camera. witha standard camera, pics taken under flourescent lights, will indeed have a green/yellow tinge. under merc vapour they will be yellowy, and under tungsten, it will be almost orange. using a filter will correct this (on a camera) by forcing the camera to look through and equal and opposite colour. our eyes, on the other hand, correct themselves. for instance, i wear glasses that have a blue tint to them (very subtle, but i liked the way james bond's looked in the new film). when i wear them, nothing looks unusual, but when i take them off, everything looks slightly yellow, but within a few seconds, it all looks normal again. our eyes are wonderful.

Have you ever stared at a wallpapered wall, lets say covered with a floral pattern in a dark red and white shade, and noticed that your eyes kept on cycling between pale green colors and black? Seriously, this happens to me whenever I stare at a certain wall in my house.

I've got another one: When you step on an escalator that isn't moving for some reason (like being out of order, as most escalators at any given subway station seem to be), there is a short moment of discomfort and irritation. That happens even when you know that this escalator won't move and you think you are prepared for it.
As far as I know that's another neat little trick of our brain: it prepares unconciously for the coming situation (like standing on a moving escalator and having to keep balance). If something else than the expected happens, there is this moment of irritation.
Another example of this is, when you are sitting on a train that brakes to stop at a station. Usually, there's a short jerk when the train stops for good. If the train driver manages to stop the train without that jerk, you have a strange feeling and keep on expecting that jerk.

how about this one.
your playing a sport (i'll use volleyball as the example cos it happens to me most playing volley ball)
your going to dig the ball to keep it up, you tense for the dive, but at the last second you see a team mate already diving, so you stop. but for some reason your muscles refuse to calm down, it seems like the energy you sent to them has solidified. i really hate that.
another thing
not so weird but scary as crap. you fall asleep lying on your arm, so it looses circulation. then you roll over, semi-consious, and it lands on your chest. because it's asleep, your body only registers an unidentified arm on your body, so you freak out thinking there's someone else in bed with you, even though you distinctly remember going to bed alone.

I get that arm thing too and no matter how often it happens it still freaks me out.

Ans that one where you walk upstairs in the dark and for some reason your brain expects another stepat the top when there isn't one. You get a split second panic as you foot crashes back down to the right level, cos it feels like you've stepped off a cliff.

actually rods merely pick out light intensities - they also share neurones so you see dimmer things but with less acuity. the cones are four colour, and there are three types (r,g,b). green is the easiest to see, but red has the lowest frequency so it has less energy to burn out your sensitive night vision.
i get the tinting thing as well - i think it could also be something to do with the relative amounts of red,green,blue cones in each eye.

because I am short sighted when I am wearing glasses everything appears smaller. this means that at night when i have taken my glasses off everything is larger than I'm used to. because it's all dark (and I can't see as clearly) I am always walking into things that I think are further ahead because I expect them to be smaller. ouch!

on the subject of the light under the door, this is actualy caused by the small hairy toed elf called frank who lies down accross the door the moment you look away, he does this so that you start to notice things like this.

:-}

Apparantly some European countries use these poor defenseless elves as curency!

P.S it strikes me (like a large humming rock!) that not many people use the h2g2 at ten past two in the morning.

MULTI COLOURED SQUIRELS TO YOU!!!!

The basic essence of the universe is that everything is shy and lazy. Ever walked in on your cat while it is in the box? Ever seen a road maintenance crew that isn't on coffee, ever?

So taking into consideration the basic essence of the universe, when you suprise objects that are flashing at regular intervals you get one of two responses:

1. If no one else is looking they take a minute to get started because they have been laying about.
2. If others are watching the object and you start looking, the first glance causes them to have a brief moment of shyness. This self conciousness causes a momentary hesitation.

The dark room with the light coming under the door. Well there are numerous explainations. The most likly is that your eyes and every object in the room have conspired against your brain to keep from working. Kind of like putting in a repeating loop video tape in a security camera.

I know that this is all very technical.

About reading in bed:

It's already been said about the eye correcting for colour temperature, but I think the main point has been missed. If you read with one eye, and the other eye closed, then the closed eye is "seeing" a much redder colour. This is because of the blood in your eyelid. The brain corrects for this, and hence when you open your eye and the brain continues to compensate for the red light, everything looks a bit green instead.

The same effect occurs if you close both eyes, look towards a bright light for a few minutes (eg the sun when you are sunbathing), and then open them. Both eyes appear to have a green tint.


The eye:

Rods are sensitive to intensity
Cones are sensitive to colour.

Rods are much more sensitive than cones, and are used for night-vision. Hence, at night you can only see in black and white.


Colour blindness:

Has been mentioned on this forum before. What I want to know is what exactly *is* colour blindness? Can a colour blind person only see in black and white at all times, or do they see a different colour? For instance I look at grass and see the colour I call green. You look at grass and see the colour you call green. But that doesn't necessarily mean that we are both seeing the same colour.

There are a few types of colour-blindness. I belive the most common is red-green colour blindness. It happens because the eye is missing one of the sets of cones, so it can't differentiate between two colours (like red and green). It's not that you see in black and white, just that some colours will look the same to you, while to other people they'll look different.

Interesting fact - I once worked with a programmer whose job was to write the colour-display code, using complex dithering algorithms in 256 colour displays, and he was colour-blind, but since he did everything based on maths it was always spot-on so it rarely mattered that he couldn't always check the result visually.

I've had both the 'second hand effect' and the 'object disappearing when I move my eyes' thing.

The latter happened to me when I was a kid in bed. The bed sheet had got crumpled in front of me, and the wardrobe handle was only visible when I wasn't actually looking straight at it. Of course, after a few seconds I moved, and I couldn't get back in the exact position needed for the effect to appear again.

I tried asking a few adults about this (teacher included), and they all wittered on about "blind spots" which I knew was irrelevant.

I managed to replicate the effect with a piece of paper shoved in front of my eye.

On a similar subject, have you ever had the experience, particularly when you've just woken up, that you look at a bunch of objects in your room with only one eye, and the pattern of light formed by several objects is such that it looks like something else? You lie there thinking "I don't own any object like that!", and eventually when you open both eyes (or get a little less dopey), you realise that your brain had completely misinterpreted what it was seeing. And then it's really difficult to see it the *wrong* way.

I read about this phenomenon in a book recently, and I realised it had happened to me many times, but I'd never thought about it.