At 09:42 7/07/99 , James Nix wrote: > There's an interesting chapter in Paul Davies' "About Time" >(Touchstone 96', Ch 13 "Experimenting with Time") on human reaction time. >The message/impulse may only take .01 sec to get to the brain but to react >takes a little longer. It also varies from person to person. Reaction time >can be less in performing "automated" and repetitive tasks, and a .1 >reaction time is common. The >"now" we experience is estimated at .04 secs. (Paul is at the University >of Adelaide, maybe Tony can get him to add something to the discussion?) I do know Paul Davies e-mail and snail mail addresses, but he is no longer directly connected with University of Adelaide, though still living here. He has never been an exprimentalist. When I did physics 1 ( 101 for North Americans) in 1960, The reaction time experiment for hand eye system was an experiment we did. It served 2 purposes, an exercise in processing measurements with simple statistics[ means, standard deviations, SD of mean, and to show one about reaction time itself. From memory my eye/hand reaction time was about 250 milliseconds. Last year in a visit to Science Museum in Kensington,London, i tried ( and corrected) a similar experiment it was comming out more like 330 milliseconds. Shows the effect of 38 yearson the human physiology! Tony Beresford Of course for using a stopwatch for satellite tracking consistency (smaller standard deviation) is more important than a smaller absolute value. There is of course some systematic error because the start is by hand/eye co-ordination and the the stop is by hand/ear co-ordination in my most used visual tracking technique.