seed speed

[Thomas G. Lammers]

At 09:59 AM 01-23-98 EST, Robin Panza wrote:

>The 60 MPH number reminds me of a wonderful zoological equivalent, the Deer=
 Fly
>(yes, I know there are many deer flies), which goes something like 914 MPH.
>Adrian Wenner tracked this down and found the origin, someone's published=
 (in a
>scientific journal, although I don't remember where) musing on how the
>DF appears ("oh, about x yards away") and passes ("not more than a second
>later").  Someone responded that, if one uses these figures, it means the=
 fly
>travelled 914 MPH, which is ridiculous.  The first author then pointed out
>that, rather than belittle the claim, we should be admiring the athletic
>ability of this wondrous insect!  Others joined the fray, pointing out the
>intense air pressure on the fly's head at that speed, experimenting with a
>fly-sized pbject on the end of a string (how long the string x how many
>rotations per minute giving the speed of the object), and so on. =
 Eventually,
>people decided not to waste any more time on it, but the figure (914 MPH)=
 had
>gotten into the literature and, to this day, you can find graphs of speeds=
 of
>animals with the Deer Fly leading the pack at 914 MPH.

I guess this gets into the larger concept of scaling.  We often see similar
gee-whiz statements about the proportional strength of insects.  You know:
"If you had the proportional strength of an ant, you could lift six
gazillion tons."   (That's why comic book superheroes like Spider-Man and
Ant-Man were so strong, because they retained the proportional strength of
their eponymous insects).  But the point is, that things are NOT fully
proportional at different scales.  An ant DOESN't lift six gazillion tons,
it lifts a couple grams.  The fact that the ant itself only weighs a
fraction of a gram is pretty much irrelevant.  The magnitude of the
difference is small at that scale.  It lifts a few more grams than it itself
weighs.  That's a world of difference (and scale) away from lifting several
tons more than you weigh.  Ask any engineer.

The deerfly may indeed be doing the equivalent of 914 mph [such precision!
-- 915 was beyond the pale?], though I doubt it; that's a one-second quarter
mile (1400 feet per second), something Don Garlits would be proud to claim.
The point is, even if the figure were accurate, the deerfly would  never
sustain that pace  for either 914 miles nor for an hour.  Its like the ads
for toy cars and airplanes that advertise "scale speeds of over 200 mph!"
It just isn't that impressive when you actually see it.

Percentages are always apt to be misleading.  The boss gives you a 25% raise
in salary.  Whether you are now wealthy or still just average depends on
what that translates into in dollars or shekels or zlotys.  THAT's what we
spend; not percents.   A 25% increase would not put me into a Rolls or a
Porsche, but Bill Gates could probably buy Disney World with the same
increase in annual income.


Thomas G. Lammers
  =20
Classification, Nomenclature, Phylogeny and Biogeography
of the Campanulaceae, s. lat.
                                   =20
Department of Botany                            =20
Field Museum of Natural History =09
Roosevelt Road at Lake Shore Drive      =20
Chicago, Illinois 60605-2496 USA

e-mail:    tlammers at fmnh.org
voice mail: 312-922-9410 ext. 317
fax:                312-427-2530

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