Sky & Telescope - March 2019 - 53

MARS DR AWING: THOMAS A . CAVE; FIGHTER ID CA RD: WIKI COMMONS

The history of astronomy is rife
with examples of the phenomenon that
cognitive psychologists call "expectation
bias." When William Herschel discovered Uranus in 1781, he initially mistook the pale green orb for an approaching comet. For several weeks he reported
that its diameter was steadily increasing
even though the apparent size of the
receding planet was actually decreasing.
Yet Herschel was the greatest observational astronomer of his era.
A cautionary tale of the interplay
of expectation and observation from
the annals of military history is worth
recounting here. Fifteen months before
the outbreak of World War II, an
experimental ﬁghter plane known as
the Heinkel He-100 captured the world
air speed record for Germany. Plagued
by overheating engines, a fragile cooling system, and a rash of landing gear
failures, the design was rejected by the
German Air Ministry in favor of the
Messerschmitt Me-109, which would
serve as the Luftwaffe's principal singleengine ﬁghter throughout the coming
war. The 12 He-100 prototypes were
relegated to the defense of the Heinkel
factory at Rostock on the Baltic coast.
Manned by factory test pilots, they
would never ﬁre a shot in anger.
In the spring of 1940 the German
Propaganda Ministry decided to put the
idle He-100s to good use. Re-christened
the Heinkel He-113, the aircraft were
painted with the insignia of ﬁctitious
squadrons and staged on several airﬁelds. Heinkel factory workers posed as
Luftwaffe pilots and ground crewmen
in a series of photographs that appeared
in German newspapers and magazines
to accompany the announcement that a
sleek new ﬁghter of unrivalled performance was beginning to enter Luftwaffe service.
The ruse was a resounding success. The British military intelligence

u During World War II
scores of Allied pilots
reported encounters with
the Heinkel He-113 despite
the fact that the handful of
prototypes were never used
in combat.

services warned pilots
and anti-aircraft gunners that they would
soon be encountering
the He-113. Within a
month Royal Air Force
pilots began to report
dogﬁghts with He-113s
over the English Channel. Some pilots even
contrasted the He-113's
appearance and performance with those
of the Messerschmitt
Me-109, the aircraft
they had actually encountered.
Pilots, anti-aircraft gunners, and
aircraft spotters on both sides received
extensive training in aircraft recognition. The ability to rapidly and accurately identify both friendly and enemy
aircraft was literally a matter of life and
death. Posters and ﬂash cards featuring aircraft silhouettes were widely
employed to foster the ability to recognize aircraft at a glance.
Although the He-113 did bear a
superﬁcial resemblance to the Me-109,
it had salient differences that should
never have eluded a trained eye. Yet

reports of encounters
with He-113s continued for years. It was
only after the war that
the British realized the
extent to which they
had been hoodwinked.
More than a twinge of
embarrassment may
account for the fact that
the Air Ministry's ﬁles
on the He-113 were only
declassiﬁed almost 30
years after the end of
the war.
How were such
highly trained observers repeatedly deceived?
The answer is really
quite simple - they
"saw" what they were
led to expect to see, just
like the host of observers who "saw" a
network of canals on Mars. The same
interplay of expectation and observation has no doubt contributed to the
controversial reports of the ashen light
of Venus and Transient Lunar Phenomena ("TLPs"). The story of the He-113
is worth recalling if only momentarily
whenever we look through a telescope.
As any trial lawyer will attest, eyewitness testimony can be very unreliable.
¢ Contributing Editor TOM DOBBINS is a
lifelong student of astronomy as well as
military history.

u These 1969 drawings by the well-known
optician and observer Thomas Cave demonstrates that skilled observers continued to
depict Martian canals until their existence was
conclusively disproved when NASA's Mariner
9 orbiter mapped the Red Planet from pole to
pole in 1971. South is up.
sk yandtele scope.com * M A RCH 2 019

http://www.skyandtelescope.com

Sky & Telescope - March 2019

Table of Contents for the Digital Edition of Sky & Telescope - March 2019