ASTRONOMY IN HISTORY
Sun, Moon, and Tides at Caesar’s Invasion of Britain in
55 BC
Donald W. Olson, Russell
L. Doescher, and the Texas State Honors Students
Sky & Telescope, August 2008
Audio Link
NPR All Things
Considered “Scientist Looks To
Stars For Answer On Caesar” July 26, 2006
Texas State University|SAN MARCOS
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Tide
and time: Re-dating Caesar’s invasion of Britain
Julius Caesar landed an invasion fleet on the shores
of Britain in 55 B.C., expanding the boundaries of the so-called “Known World”
and inadvertently sparking a dispute between historians and scientists for
centuries to come.
Now, a
team of astronomers from Texas State University-San Marcos has applied their
unique brand of forensic astronomy to the enduring controversy surrounding the
precise location of Caesar’s landfall, concluding that the historically
accepted date for the event--Aug. 26-27, 55 B.C.--is incorrect. The Texas State
team’s proposed new date of Aug. 22-23, 55 B.C., reconciles all the conflicting
evidence and offers both sides of the debate some measure of vindication in the
process.
Texas
State physics professors Donald Olson and Russell Doescher, along with
University Honors students Kellie N. Beicker and Amanda F. Gregory, publish
their findings in the August 2008 edition of Sky & Telescope
magazine.
O
Caesar, Where Art Thou?
“Most
history books say Caesar’s landing date was Aug. 26-27 and he sailed to the northeast
of Dover to land on an open beach near Walmer and Deal,” Olson said. “That
cannot be correct. The afternoon tidal streams could not have carried his fleet
to the northeast on that date.”
The
origin of the debate, ironically, lies in the strongest historical evidence:
Caesar’s first-hand account of the landing and ensuing campaign, which mentions
the phase of the moon and chronicles in considerable detail information
regarding time of day, landmarks and distances traveled once his fleet reached
the famed white cliffs near present-day Dover. Caesar’s narrative describes
how, once the winds and tides were favorable, the fleet sailed seven miles
along the coast before finding a suitable beach to put ashore. Unfortunately,
the actual direction the fleet sailed
is one detail Caesar omitted, and in that single oversight lies the bone of
contention.
Because
of specific coastal and inland land formations referenced by Caesar, historians
such as classics scholar Thomas Rice Holmes and archaeologist Charles Francis
Christopher Hawkes have long maintained that the fleet sailed northeast along
the British coast, coming ashore near the present-day town of Deal. The terrain
to the southwest, they argue, simply does not match Caesar’s descriptions. On
the other hand, men of science such as Astronomer Royal George Biddell Airy and
Admiralty Manual of the Tides
coauthor Harold Dreyer Warburg insisted a northeast voyage was impossible since
at the historically accepted date and time of Caesar’s landing the tidal
currents would be flowing strongly to the southwest--carrying the Roman fleet
in the opposite direction from Deal.
Deal
or No Deal?
The
Texas State researchers traveled to Britain in August of 2007 to study the
problem first-hand. In a fortuitous set of circumstances, the equinox and lunar
cycle coincided to closely replicate the tidal conditions Caesar
experienced--such an alignment wouldn’t occur again until 2140. Extensive
on-site research including the collection of tide gauge data, GPS tracking in a freely-drifting
boat and a host of other factors confirmed that the tidal currents
indicated a landing site southwest of Dover, while the topographical evidence
supported a Roman landing at Deal.
The
first break in unraveling the mystery came via an obscure account of the
landing by Valerius Maximus, a Roman writing in the 1st century A.D. In
Valerius’ work Memorable Deeds and
Sayings: Of Courage, he recounts one Roman soldier’s bravery as the tide
was falling during the fleet’s landing. The tide, however, would be rising
during the fleet’s landing if the date of Aug. 26-27, 55 B.C. were correct.
The
second break came from historian Robin G. Collingwood, who in 1937 identified a
probable transcription error in a sequence of dates relating to Caesar’s
landing, essentially rendering one of the Roman numerals for four (IIII)
instead of seven (VII) or even eight (VIII). Applying Collingwood’s revisions
to Caesar’s landing changes the date to Aug. 22-23--and reconciles all the
previously conflicting evidence.
“If
that’s the case, then everything falls into place,” Olson said. “Three things
fall into place: the topography matches the ancient descriptions; it matches
with respect to the direction of the tidal streams; and it matches with respect
to the water level.
“Our
new result is, essentially, the old result--we’re taking the Roman fleet up to
Deal and the open beach, but what you read in the history books, that it was
Aug. 26-27, that cannot be correct,” he said. “The scientists were right about
the tidal streams, and so were the historians about the landing site. With our
new result, our new date, everything is reconciled.”
CLICK HERE FOR IMAGE GALLERY: CAESAR’S INVASION OF BRITAIN
-30-
By the light of the
moon
Tim Radford on Donald Olson, the astronomer
cracking historical secrets with the aid of celestial bodies
Wednesday July 2, 2008
Thank heaven for
scientists who never mind their own business. Prof Donald Olson is an
astronomer at Texas State University who has, for more than a decade, taken on
a summer job as a historian. You may have heard him on Radio 4, delivering an
update on his latest research: the date and place of Julius Caesar's momentous
landing on the coast of Britain in 55 BC.
According to Olson, who
reports on his intellectual adventures for Sky and Telescope magazine, there has
always been an argument about quite when and where this happened. Caesar
himself had no Ordnance Survey map, had sketchy local knowledge, and of course
expected a lot of resentment from the locals. But he described, in book four of
the Gallic Wars, the white cliffs of Dover, and a detour to find a more level
playing field for the grim game ahead.
He did not give a precise
date ("only a small part of the summer was left") but he was
particular about the time he saw the hostile cliffs ("about the fourth hour
of the day"), about how long he waited ("until the ninth hour"),
and the distance he had to go ("about seven miles"). He also
mentions, a bit later on, that on his fourth day in Britain as an illegal
immigrant the cavalry reinforcements from Gaul were delayed by a storm, a full
moon and an unusually high tide.
Such clues were enough to
give scholars a crack at dating the invasion. Just as astronomers can predict
future full moons, so they can confidently time them far in the past. So, they
calculated, Caesar saw Dover but turned northeast and sailed around the South
Foreland and landed at either Walmer or Deal on August 26 or 27. Latin scholars
might have been happy with this conclusion, but hydrographers and astronomers
were not; they calculated that the tides would be running the wrong way at the
ninth hour of those days and take Caesar to the south-west.
So the team from Texas
made the Julian date with destiny their summer assignment. They read all the
texts, checked the tidal patterns, turned up in Dover in August 2007 just when
the equinox and lunar cycle coincided to replicate the tidal conditions that
Caesar reported, and figured that the problem could be sorted by assuming an
easily-made clerical error by someone who copied the original manuscript. If
so, time and tide would have been just right for a landing at Deal on August 22
or 23. Case closed - possibly.
This is arcane science
applied to ancient history, and it makes both subjects lively. To get a more
complete picture of the problem, Olson and his colleagues and students had to
read Dio Cassius, and study Valerius Maximus, a chronicler from the first
century AD. They had to consult classicists and archaeologists, match the
Julian and Gregorian calendars, examine the verdicts of Victorian astronomers
and naval hydrographers and use global positioning satellites to measure their
own progress around the Channel coast.
They also had to
understand Roman time measurement (there were always 12 hours between sunrise
and sunset so the hour had to be elastic, according to season), and of course,
they had to put themselves, and the readers of Sky and Telescope, in the
position of an invasion force, ironclad and sword-wielding, on a hostile
strand.
Olson has been
illuminating history and brightening the skies in such ways for many years. He
stared at Van Gogh's White House at Night, identified the evening star, and
used its position to track down not just the original house but the exact day
and hour at which Vincent must have begun his painting. He found a reference to
Tycho Brahe's 1572 supernova in Hamlet ("the same star that's westward of
the pole") and he dated a freak tide (Brittany, December 19, 1340)
mentioned in Chaucer's The Franklin's Tale. He used astronomical experience to
provide new information about Edvard Munch's The Scream and Van Gogh's 1889
painting Moonrise.
He proposed a revised date
for the battle of Marathon in 490 BC - from which the modern Olympic endurance
test takes its name - reasoning that if experienced 20th century runners don't
collapse and die, then why would Pheidippides the fateful messenger fall dead
as he delivered the news? That bit of research involved poring over Herodotus
and Plutarch, a fresh look at the lunar cycle and a bit of juggling with the
Spartan and Athenian calendars, to provide an intemperately hot August date
(with the extra risk of heat stroke) for the battle that saved Athens from the
Persians, rather than a milder September one. And of course, with a showman's
eye for timing, he cracked the question in 2004, the summer of the Athens
Olympics.
Do any of these things
matter? Yes, because they provide another way of making sense of the world
around us. Olson is not the only such adventurer: one Italian physicist
reported in the journal Nature that the great poet Dante had described, 350
years in advance, the Galilean principle of invariance (check it out in Canto
XVII of Inferno, the bit where Dante and Virgil board the monster Geryon for an
aerial tour of one circle of hell).
Other scientists have tried
to crack the secrets of Damascus steel (remember the bit in Walter Scott's The
Talisman where Saladin slices a cushion in half?) and recreate the beer that
ancient Egyptians might have quaffed and explain the fall of the walls of
Jericho (not so much Joshua's trumpet, more of a timely earthquake), and even
conjecture the conditions on planet Krypton that would select for the
superhuman musculature of Superman.
All these are games with
science: attempts to apply rigorous reasoning to events that are either one
step away from myth or even complete nonsense.
But why not? To enjoy the
story of Caesar and the storming of Deal (or Walmer) you now have to think
about the moon and the tides and the cliffs of Dover bristling with
spear-carrying warriors and the slow progress around the South Foreland to that
awful moment when, with a heavy shield, a spear and a sword, you have to splash
through the water onto a strange land, under attack from a fierce foe painted
with woad. It adds a dash of excitement to the mathematics you had to learn to
calculate gravitational forces, and it colours the leaden classroom memory of
translation from Caesar's Commentaries.
In the supermarket of
scholarship, this is the kind of value-added thinking that brings the punters
in: buy astronomy, and get a turning point in history for free; choose a slice
of Roman imperial adventure and feel the wind in your face and the tide racing
up the English Channel.
EducationGuardian.co.uk © Guardian News and Media Limited 2008
LINKS
Texas State University Honors
Program
http://www.txstate.edu/honors/
Don Olson, Physics Department, Texas
State University
http://uweb.txstate.edu/~do01/
Marilynn Olson, English Department,
Texas State University
http://www.english.txstate.edu/people-contacts/faculty/olson.html
Christopher Olson, JD, Hawaii
Lawyer, Oahu Lawyer, Oahu, Hawaii
http://hawaiiattorneyonline.com/