I'm from the SE of England, Brighton and Ipswich, and this is the measurement as I remember it from a very long time ago too Peter.
Steve - G8KVD <- that dates me just a bit & ZL3TUV 2009/8/23 Peter Vince <[email protected]>: > Maybe I was brought up in a more genteel part of West London, but the unit of > measurement I was brought up with was a > Gnat's Whisker. I don't think that was just my parents cleaning it up, as > that expression seemed pretty common. Sometimes > abbreviated to just "a gnat's", but it was definitely its whisker that was > understood. > > Peter Vince (G8ZZR, London, England) > > > On Wed Aug 19 22:49 , 'Lux, Jim (337C)' <[email protected]> sent: > >>I realize we are straying afar.. but inquiring minds may wish to know. >>Referring to "A handbook of the gnats or mosquitoes: giving the anatomy and >>life history of the Culicidae" by George > Michael James Giles, 2nd edition, 1902 (thank you google for digitizing this > book from the Stanford library) The forward > says that the second ed is much better than the first "...the result of a > couple of months of constant work with the > microtome." So I think we can consider this a reliable reference. >> >>Now I readily confess that this book seems devoted to only members of family >>Culicdae, and it's not clear that when > referring to gnat anatomy as an unit of measure whether these are the gnats > being referred to. The common name gnat > seems to be applied to many small (often biting) Dipterid Insects, and > Wikipedia seems to restrict the gnat terminology to > other families. >> >>It would appear that the rectum of the gnat is about 1/10th the diameter of >>the abdomen (there's a drawing of a transverse > section of the abdomen on page 91). If the page is about 6" wide (judging > from the type size, and the image of the checkout > card in the back page this is reasonable.. it's probably octavo size), then > the 100x drawing is 2" across, so that rectum is > .002 inches across (call it 0.05 mm, or 50 microns) . This is much larger > than the 1E-4 inches (2.5 microns) previously > cited, but well within the range for human hair diameters (given as 17 to 181 > micron in a variety of online sources, but a > much smaller range of 50-90 micron is cited in "Forensic Examination of > Hair", albeit for scalp, J. Robertson, Ed.) >> >>Now, to return to the original question of position accuracy for your timing >>receiver. Whether 50 microns will result in a > significant timing error? 1 nanosecond is 300 mm light time. 300 microns is 1 > picosecond, so that 50 micron position error > is down in the femto seconds.. >> >> >>James Lux, P.E. > > > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > -- Steve Rooke - ZL3TUV & G8KVD A man with one clock knows what time it is; A man with two clocks is never quite sure. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
