[time-nuts] Visual clock comparison

Chris Albertson albertson.chris at gmail.com
Sun Apr 19 14:23:35 EDT 2015

I think the question really was "How close must two visual clock
displays be to be perceived as being exactly in sync?".  Some people
(but not me) can see a 1/10 second difference and to me a one second
difference is obvious.  The answer is likely between 1.0 and 0.1
seconds.  But if you add a "tick" every second then the 1/10 second
difference is very easy to hear but most people can't hear a 1/40th
second difference.

I think using coincident clock faces would make it easy to see any
arbitrary difference.  All you need to do is measure the distance
between the centerlines of the two second hands.  If you used a
microscope that could track the hands you could in theory see very
tiny differences.

On Sat, Apr 18, 2015 at 9:17 AM, Mark Sims <holrum at hotmail.com> wrote:
> The problem is the human visual system only processes one object at a time.  You can't look at and compare two separate items simultaneously.  You could minimize the effect by placing one clock face directly in front of the other with like only the 12:00 positions visible (or two LEDs next to each other).  That way the two second hands can be perceived simultaneously.
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Chris Albertson
Redondo Beach, California

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