Orchid XP v3 wrote:
>>>> Why do you think that those frequencies are far above 50 Hz?
>>>
>>> My engine *idles* at several thousand RPM...
>> The significant character here is 'M'
> 
> Hmm. What is 2,000 RPM in Hz? 33 Hz? That's interesting...
> 
>>>> What sound does your motor make? Can you find the base frequency on 
>>>> your keyboard?
>>>
>>> Surely that's just the resonant modes of the exhaust system and the 
>>> chasis?
>>>
>> Whatever it is, that is what you see. If it moves faster than 50 Hz 
>> you either see it not moving at all or, viewed in the right direction, 
>> as a semitransparent surface.
> 
> AFAIK, the retina sees the "integral" of incident light over time, 
> roughly. 
Not really
> So I'm not sure why an object moving fast enough would appear 
> to stop moving. Become invisible, perhaps, if it's small enough...
> 
>> If you can prove that you can see something moving at, say 200 Hz, I 
>> have a couple of friends working on the retina that would be most 
>> interested in such a physiological anomality. ;)
> 
> How about my tuning fork? That says "440 Hz" on it, and I can see that 
> vibrating plainly enough... ;-)
Again the question is if you see the 440 Hz or a much lower frequency 
wobble. The ends of the fork should be a little wider and a little 
transparent. Anyway I think what you see is that it is moving, not the 
movement itself.
> 
> (Oddly though, it doesn't seem to make much audible sound, despite the 
> ends of the fork traversing really quite some distance. I can only 
> surmise that it doesn't move the air around very much or something...)
> 
Perhaps otherwise it would loose energy too fast and the tone would die 
out quickly.

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