Vertex Eisenstein
Gallente
The Dead Parrot Shoppe Inc.
Brutally Clever Empire
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Posted - 2007.08.23 16:10:00 -
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Edited by: Vertex Eisenstein on 23/08/2007 16:17:23
Edited by: Vertex Eisenstein on 23/08/2007 16:16:35
Edited by: Vertex Eisenstein on 23/08/2007 16:13:08
 Quote:
The human bran can generally detect and react to 1/4 of a second intervals.
Of course it can, that timeframe is far too slow. The shortest interval visually detectable (the flicker fusion frequency) is usually about 16Hz (62.5 ms). This is for a white light strobe though. For moving images 30Hz flicker is sometimes detectable, hence TVs operating at 60 or 70 Hz and mains AC current operating at 50Hz. If mains current cycled slower the lights would appear to flicker.
I'm pretty sure this is a function of the photoreceptors rather than the visual cortex, although I'm guessing a bit here. The evidence that makes me think this is the fact that a strobes have a colour illusion associated with them, whereby the flash has a colour tint depending on frequency. This is due to the different latencies of the 3 species of cones in the retina. If the processing pathways were the culprit then the variation if receptor latency shouldnt cause this effect.
Someone else said this guy was wrong because of reaction times, but that is a different problem - here we need to know the shortest possible time able to be observed, which is a perceptual thing, and so not a function of the motor system.
As an aside, leaving vision out of it, the brain can detect much shorter intervals than those able to be seen. The bearing sound is coming from is largely calculated by the time difference between detection at one ear and the other - the intraaural time difference. The maximum ITD is 0.63 milliseconds, that is when a sound originates from 90 degrees. Humans can discriminate to within about 3 degrees of azimuth so we can certainly detect times MUCH smaller than this. Of course ITD is not the only factor involved, but it is the most important.
Apologies for the wall of text, but I'm very very bored...
edit: assuming the 16Hz flicker fusion figure, I get 4 million M/s as the speed required to cover 250Km in that timeframe. I may be wrong though - I'm a biologist not a physicist!
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