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An Otago researcher has found - 2000 years after it was
built - that the ancient Roman temple known as the Pantheon may
play the role of a colossal sundial.
The temple in Rome, completed in 128 AD, is a cylindrical
chamber topped by a domed roof with a skylight in the top
that lets through a dramatic shaft of sunlight.
But New Scientist reported Otago University's Professor
Robert Hannah - an expert in Roman art, "archaeo-astronomy"
and ancient calendar systems - has discovered the Pantheon
may have been more than just a temple.
Prof Hannah has just published a book, Time in
Antiquity, with a case study of the Pantheon.
He shows that for the six months of winter, the light of the
noon sun entering through the skylight, or oculus, traces a
path across the inside of the domed roof. In summer, with the
sun higher in the sky, the shaft shines on to the lower walls
and floor.
At the two equinoxes, in March and September, the sunlight
coming in through the hole strikes the junction between the
roof and wall, above the Pantheon's grand northern doorway.
A grille above the door allows a sliver of light through to
the front courtyard - the only moment in the year that it
sees sunlight if its main doors are closed.
Prof Hannah has shown this was no coincidence, because
smaller hollowed-out domes were made in Roman times to act as
a type of sundial to show the time of year.
He said that by marking the equinoxes, the Pantheon was
intended to elevate emperors who worshipped there into the
realm of the gods.
Prof Hannah's book also analysed of the development of
sundial technology, and their science, as well as other means
of measuring time, such as water clocks.
