Cassini – Science the Church and a Gnomon

As the Cassini Saturn probe prepares for its final few orbits before being de-orbited into the planet, it’s worth considering who it was named for – the C16th Italian astronomer Giovanni Cassini. These days the Vatican collaborates with the European Space Agency and NASA on space science. Even the Vatican Library uses an image file storage system developed by NASA – it was a system originally designed for radio astronomy.

 

But it is worth remembering that the Church has often had an uneasy relationship with science. Galileo Galilei was tried in 1633 for heresy by the Inquisition and was sentenced to formal imprisonment – one of the Church’s ‘oops’ moments – later commuted to house arrest.

In 1582, when Galileo was just 18, Pope Gregory revised the calendar, as the Julian calendar developed under Julius Caeser was getting embarrassingly out of step with the solar year (it lacked leap years). But the introduction of the more accurate Gregorian calendar that we use today, presented a new problem. The major Feast Days needed some re-calibration. The most difficult one was Easter – a so-called Moveable Feast – and a pretty important one to the Christian faith. It was supposed to fall on the Sunday following the first full moon after Spring Equinox (20 March). While today we just look it up on Google or wait for Facebook to remind us, it was a bit more complicated back in the C16th. You see, the problem was that the Church followed the lunar year, while everyone else followed the solar year, and they don’t quite match up. It was time to find some astronomers who hadn’t yet been executed for heresy, and who would admit to being astronomers… no pressure then.

Genovese astronomer Egnazio Danti (cosmologist to Cosimo de Medici I) was called to Bologne to work with Pope Gregory’s Calendar Commission to help determine accurate dates for the Spring Equinox – and by extension, Easter. He constructed a Gnomon – a sight line – inside the Basilica of San Petronio in Bologne and cut a hole high in the wall to allow the sun to shine through onto the gnomon. This was used to determine the path of the sun at certain times of the year, and help with measuring the lunar cycle too. But less than 100 years later, some renovations designed to expand the Basilica meant that the wall with the hole for the sun was removed (oops)… So in 1655, a mere 20 years after Galileo’s death, Giovanni Cassini was brought in to design a new gnomon in the same church. His ambitious plan was to build a much longer gnomon for more accurate observations. His ulterior motive was to prove Galileo’s observation that the Earth went around the sun, not the sun around the earth – this time without getting into trouble with the Inquisition.

So what has this to do with travel? You can still see Cassini’s gnomon today in the Basilica of San Petronio in Bologne. But if you are visiting Rome you can find another Gnomon – it’s worth checking out the floors in some of these churches, and look for an angled line in bronze running across the floor… There’s also one at the Church of San Sulpice in Paris (pictured below) – made famous by the movie of Dan Brown’s ‘The Da Vinci Code’.

Church of St Sulpice Paris

The C16th Basilica of Santa Maria Degli Angeli in Rome was dedicated as a Basilica in 1920 by Pope Benedict XV in 1920. But from the outside, it doesn’t look much like a church at all. Curiously, it was built inside the ruined Frigidarium of the Roman baths of Diocletian (ca 300AD), thus preserving a significant part of the ancient Roman building into the modern age.

 

Basilica of Santa Maria degli Angeli

The church itself was designed by none other than Michelangelo. So, from a simple ancient Roman exterior, you enter into a magnificent Renaissance church of breathtaking scale – one of the world’s largest.

Basilica of Santa Maria degli Angeli

But I had heard that it held one more surprise. A gnomon. The gnomon here was copied from Cassini’s design. Pope Clement XI commissioned the astronomer Francesco Bianchini to construct the Gnomon. Bianchini was Secretary of the Calendar Commission, and h chose the Basilica of Santa Maria degli Angeli because of the stability of its Roman walls and foundations, and because of its height and large internal space. Bianchini improved on Cassini’s design by allowing for the observation of stellar transits – even in daytime.

Basilica of Santa Maria degli Angeli

Here you can clearly see the sun approaching the meridian line.

The pinhole occulus through which the sun shines is located high on the wall, and to give it a clear path, part of the entablature and the capital of the pilaster – designed by Michelangelo – was cut away – perhaps a metaphor for the tension between art and science and the church! I have added an arrow to show where the sun enters.

Basilica of Santa Maria degli Angeli

The church also houses a Foucault pendulum which demonstrates the earth’s rotation through the pendulum’s elliptical swing.It was invented by French scientist Leon Foucault, who first demonstrated it in 1851 at the Paris Observatory – it now resides in the Museé des Arts et Metiers in Paris.

Basilica of Santa Maria degli Angeli

The pendulum weight is in the form of a globe as though pushed with a giant hand. Metaphors for force were quite literal! As you can see below

Basilica of Santa Maria degli Angeli

So, from a C16th astronomer seeking to solve the Church’s problem with Easter through detailed observations of the Sun, to a spacecraft providing detailed observations of Saturn we can glean nearly five centuries of the Church’s relationship to science and the arts by visiting a two-thousand year old Roman bath house renovated by Michelangelo in Rome. And all this, from noticing a strange geometric pattern on the floor of a church! It does pay to look down sometimes!

Rome – The Trevi Fountain and an ancient aqueduct

Just about everyone who travels to Rome tosses a coin or two into the Trevi Fountain (Fontana di Trevi) – myself included! Legend has it, that if you throw a coin into the fountain over your opposite shoulder, you will return to Rome. Such rituals have their roots way back thousands of years before Christianity, whereby valuable items were tossed into water sources to keep the water gods happy. Today it serves a charitable purpose. Around €3,000 or US$3350 a day is tossed into the fountain. In 2016 around US$1.5m went into the fountain, our own coins among them. The money is collected each night and given to a charity that supports homeless and destitute families through a special supermarket. And yes it’s against the law to remove money from the fountain.

Trevi Fountain

But the Trevi fountain is special in part because of the water that supplies it. In fact, there has been a fountain on this spot since 19BC and even today it is still fed by the Virgo Aqueduct built by Agrippa. It was the only one to survive intact into modern times as it mostly ran underground. Today, most of the water is recycled for environmental reasons, but the source is still the ancient aqueduct.

The fountain lies at the intersection of three roads – Tre Vie – or Trevi as it has come to be known today. There is a legend that when the Roman engineers were seeking a fresh water source, a young woman took them to a spring around 13kms from the city. The aqueduct was named in her honour as the Aqua Vergine, or Aqua Virgo. This legend is depicted in a bas-relief. The aqueduct fed the Agrippa baths for 400 years near the present site of the fountain.

Trevi Fountain

The Trevi Fountain we see today was commissioned by Pope Clement XII in 1730. He held a competition for the design which was initially won by Alessandro Galilei – a Florentine and relative of the astronomer Galileo Galilei. But there was a great public outcry that a Florentine had won, forcing a re-vote finally won by Nicola Salvi.

The main figures are Oceana riding on a shell chariot drawn by two horses, each led by a Triton. One of the horses is calm, the other tempestuous showing the changeable moods of water.

On either side are niches depicting Abundance pouring water from an urn, and the other depicts Salubrity, holding a cup with a snake drinking from it.

Trevi Fountain

The top is crowned with the Papal insignia showing the beehive hat and the crossed keys of St Peter over a plaque with a dedication to Pope Clement XII.

Trevi Fountain

Water is essential for life. Ancient Rome’s 11 aqueducts ensured enough water flowing into the city to provide for more than a million inhabitants. But Rome’s great strength was also its vulnerability – dependence on water supplies brought from 13kms away. The aqueducts were critical infrastructure. Most of them were carried on massive stone pylons that could be destroyed by war or earthquake. While there were springs within the city boundaries, the water was brackish. And water from the Tiber carried disease. But there was good fresh spring water just a few kilometres away in the Anio mountains. With the destruction of the surface aqueducts, the population of Rome declined rapidly, leaving a residual population among the ruins of Rome’s great civilisation.

Gradually Rome was rebuilt achieving greatness once again in the Renaissance and into the modern world. The Trevi fountain is one of the few working survivals from ancient Rome – a reminder that a good water supply is necessary to sustain us, and that sometimes our greatest strength can also mask a fundamental weakness.

Whether you are inspired by films like La Dolce Vita or Roman Holiday, or you are drawn to the fountain for the artwork or just to toss in a coin hoping to secure your return to Rome, it is worth thinking about the water that supplies it, and consider where our own water comes from.

 

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