Symposium on unidentified flying objects: hearings before the Committee on Science and Astronautics, U.S. House of Representatives, Ninetieth Congress, second session, July 29, 1968.

140
One
figure
shows
the
appearance
of
one and
two
foot
birds*
as
they
might
appear
on
a
16mm
frame
taken
with
a
3"
telephoto
lens
-
f/16
at
a
distance
of
1,200',
at
3,000'
and
at'3,300'.
Many
of the
images on
the
"Utah"
film
have
an
angulardiameter of
0.001,
2
radians
(some
as
large
as
0.001,16
radians),
thus
they
mightbe
interpreted
as
one
foot
(wing
span)
birds
at
600'
to
800',
two
foot
(wing
span)
birds
at
1,200'
to
1,600'
or
three foot
(wing
span)
birds
at
2,400'
to
3,200'.
At
these
distances,
it
is
doubted
if
birds
would
give
the
appearance
of
round
dots;
also
they
would have
been
identifiable
by
the
camera
if
not
visually.
However,
actual
movies
of
birds
in
flight
would
have
to
be
taken
to
completely confirm
this
con-
clusion.
The
following
type
of
gulls
have
been
know
to
fly
at
times
over
this
locality:
California
Herring
Gull
(a
common summer
resident),
Ring
-Billed
Gull
and
the
Fork
-Tailed
Gull,
see
Reference (4).
The
images are
probably
not
those
of
balloons
as
their
number
is
too
great
and
the
phenomenon
of
flaring
up
to
a
constant
brightness
for
several
seconds,
and
then dying
out
again cannot
well
be
associated
with
any
known
ballon
observations.
Certain soaring insects—notably
"ballooning spiders"
(References
(5)
and
(6)
)
produce
bright
-moving
points
of
light.
The
author
has
witnessed
such
a
phenomenon.
It
is
produced
by
Sun
reflections
off
the streamers
of
silken
threads
spun by
many
types of
spiders.
Caught
by
the
wind,
these
streamers
serve
as
a
means
of
locom6tion
floating
the
spider
high
into
the
air.
They
occasionally
have
the
appearance
'of
vast
numbers
of
silken
flakes
which
fill
the
air
and
in
some
recorded
instances
extend over
many
square
miles
and
to
a
height
of
several
hundred
feet.
The
reflection,
being
off
silk
threads,
is
not
as
bright
as
diffuse
reflection
from
a
flat
white
board.
Thus no
flaring
of the
images
could
be
expected.
The
author
noted that the
sections
of
the
"web"
that
reflected
measured
from
1
/
4
"
to
1
/
2
"
for
,the
largest
specimens.
Thus
the
images might
be
attributed
to
ballooning spiders
at
distances
of
50
to
100
feet.
However,
these
web
reflections
ordinarily
show
upon
only
against
a
rather
dark background
and
it
is
doubted
if
their intensity
would
be
great
enough
to
produce the
in,tense
UFO
images
against
a
bright
sky.
Besides the
above remarks,
pertinent to
the
actual
images,
several facts
can
be
gleaned
from
the motion
of
objects.
The
observations
are not
apt
to
support
the
supposition
that
the
objects
were
conventional
'aircraft
as
the
maneuvers
are
too
erratic,
the
relative
acceleration's
probably
ruling
out
aircratf
at
distances
of
over
five
miles.
Several observers familiar
with the
appearance
of
chaff
have
seen
the
film
and
concluded that
the
persistence
of
the nontwinkling
constellations,
their
small
quantity,
and
the
reported
absence
of
aircraft
oberhead
makes
chaff
unlikely.
Furthermore, the
single
object
passing across
the
field
of view
would
be
most
difficult
pe
explain
on
the
basis
of
chaff.
These
same
remarks would
apply
also
to
bits
of
paper
swept
up
in
thermal
updrafts.
The
relative
ahgular
velocity
might
be compatible
with
soaring
bird
speeds at
distances
of
lesSkthan
one
mile,
the angular
velocity
of the
single
object
could
be
attributed
to
a
bird
within
about one thousand
feet.
There
is
a
tendency
to
pan
with
a
moving
object—not
against
it—
so the
velocities
in
the
table
probablyrepresent
a
lowet bound.
The
motion of
the
nbjects
is not
exactly
what
one would
expect
from
a
flock
of soaring
birds
(not
the
slightest
indication
of
a
decrease
in
brightness
due
to periodic
turning
with
the
wind
or
flapping)
and no cumulus
clouds
are
present
which might
betray the presence
of
a
strong
thermal
updraft.
On
the other
hand
the
single
object
might
represent
a
single
soaring
bird
whichbroke
away
in
search of
a
new
thermal—quite
a common
occurrence
among
gulls—see Reference (7).
That
the
air
turbulence necessary to
account for
their
movement
if
they
werenearby
insects
(even
the
single object's
motion!)
is possible,
can
be concluded
from
examination of Reference (8).
However,
if
the
objects
were nearby
spider
webs
the lack of observed or photographed streamers
is
unusual.
Furthermore,the fact that
they were
visible
from a
moving
car for several
minutes
is
hard
toreconcile
with
localized insect
activity.
The
phenomenon
of atmospheric mirages, Reference (9), might
conceivably
account for the images.
Such a
hypothesis
is
hampered by the
clear
weather
con-ditions
and
the
persistence
and
clarity
of the images. Also
no "shimmering" canbe
detected
and
the motion
is
steady.
Again the object
which breaks
away
wouldbe
difficult
to explain.
*The
dimensions
refer to
wing
spread.
The
actual exposed white area of
a
bird is
usuallyless
and depends upon the perspective
of the observer.
This
difference
has been roughly
accounted for in the data given, however,
if
the body were the principal reflector
the
,
distance given should be reduced by a
factor of
2
or 3.