[time-nuts] gnat sizing

[Magnus Danielson]

Lux, Jim (337C) wrote:
> 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.
> Task Manager, SOMD Software Defined Radios
> Flight Communications Systems Section
> Jet Propulsion Laboratory
> 4800 Oak Grove Drive, Mail Stop 161-213
> Pasadena, CA, 91109
> +1(818)354-2075 phone
> +1(818)393-6875 fax

Jim?

I know we had a go at some homebrew beer at work this evening, but I 
must confess you go on in a different scale. Do you pull this party 
trick often in the office?

Did you ever contemplate over the lack of a comic strip editor in the 
office?

Cheers,
Magnus