December 2016

Rabbi Abraham Zacuto and the Astrolabe

The Age of Discovery of the Portuguese Jews

Story and photos by Jaq Greenspon

The synagogue of Tomar, housing the Museu Luso-Hebraico Abraham Zacuto, located at 73 Rua Dr. Joaquim Jaquinto.


Portugal has had a somewhat complicated history with its Jewish population, particularly dating back to the late 15th century, when, let’s face it, most of Europe was having complications with its Jewish populations.

Here’s the way it worked: The Spanish, under the newly reinstated Christian monarchs, King Ferdinand and Queen Isabella, figured Judaism, as a religion, was no good and so, on March 31, 1492 decreed that within four months, by July 31st of that same year, all the practicing Jews had to convert to Christianity. Previously, when the Moors, a heavily Muslim population, had been in charge of the Iberian Peninsula (basically Spain and Portugal) the Jews had the status of “People of the Book” and were treated with tolerance, if not respect. Because of this, Jews immigrated in the area and flourished, their communities being places of culture and learning. The conquering by the Christian kingdoms changed everything. Ferdinand and Isabella issued the Alhambra Decree, which stated that you either became a Christian or you had to leave.

Let’s be real here. Spain in 1492 was not unique in Europe. In fact, it wasn’t even unique in Spain. This overall expulsion had been a long time in coming, mind you, as the Christian kingdoms slowly worked their way through the peninsula kicking out the Moors, who had been there for about 700 years. In fact, about 100 years earlier, in June of 1391, a mob attacked the Jewish community in Seville, killing 4000 people while the rest converted to Christianity in an effort to spare their lives. This action was repeated several times across Spain, with synagogues being desecrated and converted into churches; men, women and children being killed with bodies tossed carelessly into the streets, until, finally, in mid-August, the destruction stopped and the Jewish communities were almost utterly destroyed.

Many of the survivors of these horrors had “converted” and were living as Marranos or Conversos, Jews who were practicing their religious faith in secret. Which brings us back to Ferdinand and Isabella, who hated the thought of “Crypto-Jews” in their midst and set about to expell or convert (for real this time), the remaining Jews in Spain. Which takes us right back to that March day in 1492 when the Alhambra decree was put into effect. This decree, by the way, was eventually rescinded in December... of 1968. It took nearly 500 years before Jews would be allowed to pray openly in Spain again. By the end of 1492, nearly 200,000 members of the community had converted while up to 100,000 (experts differ on the number, putting a floor at 40,000 and a ceiling at 100K) had fled – a large number of these Jews simply crossed the border into Portugal, where they would be tolerated…if they could pay for their proposed haven.

Even paying their way into relative safety in the new country didn’t last long, as a mere eight months later, the same King John II who had made the original deal, back tracked on it and declared a sentence of slavery on any Jews (read: refugees) in the region. This was rescinded after John II’s death by his successor, King Manuel I, who briefly returned freedom to the Jews, only to once again change his mind (due to political pressure) and compel conversion or suffer expulsion of the remaining Jews in the country. Not to be outdone, however, Manuel added his own proviso that any Jews leaving Portugal had to do so without their children. Hell of a guy, really.

Of course, one of the good things to come out of these horrendous acts is that a Spanish scientist, who also happened to be devoutly Jewish - to the point of refusing conversion - by the name of Abraham Zacuto found himself in Portugal after being expelled by Spain in 1492. By this point, Zacuto, born in 1452 to a family of minor nobility, had already distinguished himself as an astronomer, publishing what would become one of his primary works, the Bi’ur Luhot, an easy to read almanac of astronomical movements of the (then known) 5 planets, the moon and the sun. Although originally written in Hebrew, it was translated almost immediately into Latin as The Perpetual Almanac, the publication of which (along with a Castillian counterpart) was one of the first books published using the moveable-type press in Portugal. This work was instrumental in freeing ships from either following the coast lines or copying well known routes already charted. In effect, it opened the seas to enable new discoveries and really start the age of exploration.

Here’s the thing: scientific achievement and innovation comes from all over and regardless of the fact no one in Spain actually liked the Jews, there were certainly reasons to keep them around. Zacuto was one of them. Christopher Columbus had used Zacuto’s charts on his famous voyages (once, as the story goes, had even used them to, Twain-like, predict an eclipse and threaten the safety of celestial bodies if he and his crew weren’t treated with respect). But like butterfly wings in Shanghai affecting surf conditions in Hawai – or something like that – you never know how one action will affect another and Zacuto leaving Spain gave him the opportunity to become an astronomer in the court of King John II of Portugal. His work there continued under King Manuel, who wanted to mount his own voyage of discovery like his Spanish neighbors had done.

The man for the job was Vasco da Gama. Da Gama knew what he wanted to do and sought funding from John II, who was enthusiastic, but a bit gun shy about actually putting plans into motion. King Manuel had more gumption and thought it was a good idea, but wasn’t sure if da Gama was the man for the job. Abraham Zacuto thought he was and lobbied Manuel hard to allow da Gama to set off for India (or wherever else the winds might take him).

Once the voyage was approved, Zacuto offered private tutelage to da Gama and his captain, a Jew by the name of Gaspar, in how to use not only the charts and tables he had come up with, but also a metal astrolabe of his own invention, designed to be used at sea (rather than the wood ones which had been in practice, designed to be used on land and were notoriously inaccurate). These changes, and these charts, allowed da Gama to discover trade routes to places as diverse as India and Brazil.

Unfortunately, with King Manuel’s turn coat proclamations, Zacuto once again found himself on the run. This time leaving Europe altogether and, along with his son, heading for Africa and a brief respite in Tunisia, where he was welcomed into the flourishing Jewish community…before threat of Spanish invasion caused him to move to Turkey with a huge number of other Jewish immigrants and refugees. While in Tunisia, though, Zacuto wrote another book, this one, called the Sefer Hayuhasin, on the history of the Jewish people from the beginning of time right up to Zacuto’s present day – about 1500. His death (it’s disputed, either 1515 or 1520) probably came during a pilgrimage to Jerusalem during Passover, which allowed him to be buried, per his wishes, as close to Jerusalem as possible.

With all of this background in my head, I found myself up early on a Wednesday morning in Lisbon, heading for a train to take me to Tomar, a small, picturesque town about 90 miles northeast of the capital. Tomar has been around for a while and in fact a roman city, Selium, can be found under the current city’s foundation (this is why the oldest church in town is located in the “new” section and not the “old” section – the foundations are from that Roman period). It is overseen by a 12th century Templar castle, built on a hill in the center of town. Eventually, with the dissolution of the Templars, it became a monastery and a stronghold, useful in defeating the Moors.

And in 1492, with the addition of a large number of refugee Spanish traders and artisans, Tomar became home to a thriving Jewish community, one which built a synagogue to house their daily and weekly worship.

That synagogue still stands and that was my destination that morning. It’s not a hard place to find. The tourist map you get for free at the information office has it clearly marked and in case you get lost, there are signs reading “Sinagoga” on the side of the roadway leading to it. Even with all that, it’s not what you’re expecting.

For example, when one gets off the train in Tomar and steps out of the station the old town stands before you. Above you, though, is that Templar castle which became a church. There’s no missing it. Ahead of you, is the spire of another church, this one is the Church of São João Baptista, which makes up one side of the central town square. Easy to spot, east to recognize. All over Europe, churches are like that. They are big and flashy and ostentatious

The synagogue of Tomar, however, not so much. It’s located at 73 Rua Dr. Joaquim Jaquinto, which is a perfectly nice, if rather narrow, cobblestone street, lined with homes. The only thing giving number 73 away as anything different is the Mogen David above the green door made from what looks to be flocking and blue Styrofoam balls. To be fair, that’s not the original door. The original, which naturally faced east, can still be seen inside the building, but the actual passageway has been blocked by more recent construction.

Inside, the reconstructed interior holds the Museu Luso-Hebraico Abraham Zacuto (the Abraham Zacuto Portuguese Jewish Museum), housing Judaic artifacts from around the world, including a torah donated from California. The room itself, for that’s all it really is, is unique in that it has four columns supporting the gothic arched ceiling and in the upper corner, perfectly preserved, is the ancient method of sound amplification. Between the columns stands a bimah of sorts, decorated with the accouterments of a service in progress.

The synagogue was built between 1430 and 1460 but had outlived its initial function, obviously, by 1497, when King Manuel issued his convert, flee or die edict. From that point, the building changed hands and purposes several times, from being used as a prison, to being used as a church to even being a hay loft. By 1921, nearly 500 years after it started life, the building was declared a national monument, but all that meant was it couldn’t be destroyed. It took Samuel Schwarz, a Polish engineer, to finally negotiate the purchase of the building and then, using his own finances and wherewithal, restore the building to the status it’s in now. Schwarz, who is known today more for his discovery of crypto-Jewish families living in Belmonte, Portugal, donated the building to the country in 1939 on the condition it become a museum. Ironically, in exchange for this donation, he and his wife were granted Portuguese citizenship which, more than likely, saved their lives during World War II.

Today, the museum is run Teresa Vasco, a delightful woman who speaks no English but is thrilled to show off the collection. She speaks her Portuguese slowly, in hopes of you understanding her, and you know what? If you’ve got a basic understanding of Judaism, you actually get most of what she’s saying. For what you don’t understand, there are brochures in several languages, including English and Hebrew, and a small souvenir counter in front of where she sits offers ephemera like a set of four books -marks, complete with pictures and information about the museum, for €.50.

With fewer than a dozen Jews still living in the city of Tomar (and less than 2000 in the country – although after Brexit, the number of British Jews seeking Portuguese residency and citizenship is on the rise), it’s more important than ever that the museum’s stated purpose, to try “to establish a museum and library on the history of the Jews in all the nations of the world,” be fulfilled. They’re charting a new course, to bring the history of the Jews together in one place, so it makes sense that Abraham Zacuto, who was responsible for the age of discovery, who has a crater on the moon named after him, who wrote one of the first Jewish histories, and who was a Portuguese resident, is their namesake.


Abraham Zacuto

A planispheric astrolabe from the workshop of Jean Fusoris in Paris circa 1400, on display at the Putnam Gallery in the Harvard Science Center.

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