Forensic Astronomy28 JANUARY 2020 • SKY & TELESCOPE
in a court of law. He went to the church and redrew the
profi le of the shadow as shown in the photo. Working with a
professional surveyor, he then measured the distance south,
west, and upward to the roof corner that cast the shadow.
He incorporated his collected measurements with data on
latitude and longitude, ran trigonometric equations, and
determined the exact position of the Sun in the sky at the
time the photograph was taken. A quick check in an astro-
nomical almanac yielded the moment the photo was cap-
tured on May 22nd. As Rigge entered the courtroom on that
fateful December day, just a week after meeting Yeisner, he
knew exactly when the photograph was taken. He announced
without hesitation to the judge and 12 jurors that it was
captured between 3:20.5 and 3:22.5 p.m.
Rigge had just blown up the prosecution’s case. The police
had discovered and defused the bomb at 2:50 p.m. Rigge’s
testimony meant the witnesses were claiming to have seen
the defendant carrying the bomb after it was already safely in
the hands of the police — a clear impossibility. The witnesses’
testimony had to be thrown out. With no direct evidence to
bolster their case, the prosecution was left with a hung jury.
The struggle, however, wasn’t over for Rigge and the
defense team. The prosecution pressed for a retrial. In the
three months before the return to court, they attempted to
intimidate and discredit Rigge. The lead detective and sup-
posed victim visited Rigge’s offi ces at Creighton repeatedly,
trying to persuade him to abandon Yeisner’s cause. At one
point, they even presented a doctored photograph to Rigge, in
an attempt to catch him in a contradiction.
Rigge saw through the doctored photograph, and held his
ground, like pioneering astronomers before him. He insisted
that he had no interest in the guilt or innocence of Yeisner’s
client. But as an unbiased and professional scientist, he wasA line from the tip of a shadow through the tip of the
object that casts it points directly to the Sun. By defi ni-
tion, it’s local apparent solar noon when the Sun is on the
meridian, due south as seen from the North Temperate
Zone. The Sun’s hour angle (distance west of the merid-
ian) determines the time of day, and its declination (dis-
tance north or south of the celestial equator) determines
the time of year, or date.
To pin down a moment within a year, you need to
know both the date and time. Ironically, it’s quite easy to
measure the time, the less signifi cant of those numbers,
because the Sun’s east-west motion results primarily
from Earth’s rotation, roughly ¼° degree per minute, as
users of non-tracking telescopes know to their sorrow.
When measuring the time of photographs, Rigge was
essentially using the structures in the photos as giant
sundials, and a fi rst-rate sundial is indeed accurate toZenithWESNSun on May 22
2:54 local solar time...equinox
es
6 p.m.3 p.m.
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ice...^wintersolsticeconfi dent that the testimony on which the case hinged was
incorrect, and he wasn’t going to be bullied. When the second
trial began in March 1911, however, the prosecution was
ready for him.
The lead prosecutor began to attack Rigge’s methods and
science in general, offering sarcastic asides to the jury duringpIn a 1904 Scientifi c American article, Rigge proved that this photo
was taken on May 2, 1893, at 3:06 p.m. Central Time. The position of the
shadow on the window casing gave the time and narrowed the date to
either May 2nd or August 11th. The state of the grass proved that it was
May, and the clarity of the air and position of the weathervane matched
meteorological records for 1893.Shadow Science
GREGG^ DINDERMAN^ /S&T