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!

Paris – the final pack for the Camino

Arriving back in Paris after a two-day visit to Northern France to see some friends, it is time to get serious for the final pack. We will be sending a bag on to Santiago de Compostela with our smart clothes, so we will only have the bare essentials for the backpacks we’ll take on the Camino de Santiago (French route).

Camino pack

We repacked several times, weighing the packs each time, only to find them still too heavy, so we repacked again.

See here for my packing video made before we departed from Australia.

With the third re-pack it is uncomfortably apparent that my DSLR camera is just too heavy – it weighs almost 1.5kg in its bag. So it’s hard decision time. Reluctantly, I have to admit that my 10kg backpack is right on the limit – and that is without water – or the camera! So, with the decision made, I packed the camera in the send-on bag and resolved to work on my iPhone camera skills.

With that decision made, and the packs as light as we could manage, it was time to get some sleep – to be ready for an early check-out and a short walk to the Montparnasse railway station.

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INDEX – If you wish to follow our journey from the beginning, or jump in to any of the Camino posts,
here is a link to the index page – which can also be found in the navigation bar at the top of this blog

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Rijksmuseum – The well-stocked kitchen

The Well-Stocked Kitchen – painted 1566

In 1566, the painter Joachim Beukelaer warned us about the dangers of Facebook, Pokemon-Go and distractive technologies. Perhaps not literally, but he illustrates the point beautifully in his painting: The Well-Stocked Kitchen. In this painting, we are drawn first to the kitchen maids in the foreground, then to the abundant display of food.

The Well Stocked Kitchen

All of this is designed to show us how easily we are distracted from perhaps the more significant scene deep in the background – which is a representation of Christ visiting Martha and Mary. But of course our attention has been drawn by the brighter colors, the shiny objects, the sensual world, and it would be easy to miss the figures in the background and their significance.

Modern sources of distraction

So too, today, we are easily distracted by the latest car, the latest smart device, the most colourful and shiniest of toys. All of which can easily blind us to more basic human values, and the actual world around us. How often do we see people sitting together deeply engaged in text communication with other people, far removed.

Now, there may be good reason for such behaviour at times – when we simply can’t be physically present with our significant other, or perhaps there are urgent arrangemements to be made, that simply can’t wait until after our companions have departed.

Perhaps our attention is so arrested by the succulent artichokes and onions and meaty delicacies embodied in a 60+ Hertz refresh-rate on our screens, that we fail to notice our companions have each fallen silent and that they too are gazing and tapping like urgent woodpeckers on their smart devices in deep communication with others not physically present.

There is clearly a place for such technologies. The challenge is to know when to switch them off and foreground those who willingly share their presence with us despite the lure of the endorphin-inducing screen – or a well-stocked kitchen.