yes, maybe it's an optical illusion. like blattsalat described it or maybe similar to 3d drawings of a stair where you can choose to see it going up or down.

i have never seen these lights in reality though...

I think it's an optical illusion too, perhaps our brain really is too slow? The weird effect is the biggest when looking at an airstrip in the dark. I guess, that flashes and darkness really mess up our 'I see a flash'-depth interpretation somehow hahaha.

Cheers

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I think our brain sees the light as a different object when it is on or off. While it is on, the light seems to move up on your 'screen', then it goes off ('dissapears') and goes on again: 'reapears' (if it would continue to move 'up' at that speed) at the position of the next light.

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I guess, Excessus is right.
This means, it is the sort of optical illusion of
turning wheels in movies that ello mentioned*:
static pictures interupted by darkness
which are re-connected by the brain to get a continuous movement.
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*- the wheels which seemed to turn back while they turn fast forward -

About the wheels, that's only true for anything recorded I think hehehe.

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Only in a movie. You never see them turn backwards in real life.

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I've got a remote controlled model helicopter and when the blades start spinning you never see an optical illusion of them 'turning backwards in slowmotion', this must either be a standard movie effect or the effect of simply recording something and playing it back with a limited (lower) amount of frames per second ...

As for the phenomenon, it's pretty interesting. Perhaps the brain is fast enough to see two different lights 'arrive' at different times, but I think the 'auto correction' of the brain would mess things up.

When I think of it, if our brain would be able to see or notice two lights arrive at different times, wouldn't this cause a gigantic smearing effect for all lights we see, because it would imply that we could actually see the lightbeams? So I think our brains are not that fast, or it may 'over correct' what we see when 'interpretating'.

Cheers

Ok, I'll reveal the solution of the riddle.

A position-dependent flash sequence can have two reasons. The simplest one is that it's a very old airport with rotating beacons for the runway lights. All beacons rotate synchroneously, so their light beams always have the same angle. Therefore when looking at the runway sidewards from a distance, they all flash at the same time. However when an aircraft approaches the runway or takes off, the beacons are seen in slightly different directions by the pilot, so their light beams become visible in sequence.

However, our airport doesn't use rotating beacons but xenon flashes. Still, you see them flash in sequence even when they all light up at the same time. The reason is indeed the optical effect mentioned by Blattsalat. Our optical nerves react faster on a bright flash than on a dim flash, so close lights are seen a little earlier than far-away lights. Although the flashes appear to have the same brightness, it's an optical illusion - a flash close to us has in fact four times the brightness than a flash in twice the distance. For a similar reason, when you see street lamps suddenly go on in the evening, you have the impression that they are switched on in sequence.

BTW, this was a small hypothetical airport - big commercial airports use non-flashing runway lights and lights that flash in a real sequence _before_ the runway.

the phenomenon with the turning wheels or ther spinning objects apearing to turn the wrontg way only apears at a specific speed this is when the wheel has turned almost completely since the last frame of the movie and so the brain percieves it as moveing backwards, it then apears when the wheel has done almost two rotations since the last frame and so on. it is because film is a seriese of pictures whereas in real life we see the continual stream of movement so dont notice it.

has to do with strobic effect and the mechanics in how our eyes work ( we don't see continuously, but in 'frames' just like a movie or video game)

the wheel effect has to do with the "scanning" frequenz of our eyes/brain =~ 24frames a second

if the wheel turns exactly the angle of one spoke in one frame our eye cant recognize if its turning forward or backwards. similar to what happens if you post 2 screenshots next to each other where one wheel has turned just the ammount of one or a multiple of the spoke angle. (the wheels match on each other so does our brain "see" it as well)

if now the wheel turns just a little bit less then the distance of the single spokes it seams to turn backwards.

this would work with a flip-book as well or your monitor: imagine a point at the very right of the screen. Now with every frame the point moves 100% of the direction. the result would be nothing - a still standing point.
if the point now only moves 99% of this direction per frame, it will start to move slowly from the right side to the left one till it appears on the origin again.

now its up to you to figure out what happens at 10% or even at 50%

phew, way to much text for something so unimportant like this
especially if you put some spin-wheels on your car

sreehc

our eyes don't have a scanning frequency or a shutter like a film/video camera.

i think sometimes wheels themselves can work like a camera shutter. for example if you look through openings of the rims at something moving behind them or if some reflection on the chrome only happens at a certain angle which changes while overtaking the vehicle or something like that. then your eyes receive light flashes at a certain frequency and a strobe effect occurs.