Figure 1: A series of great conjunctions and trigons from Kepler’s book “De Stella Nova in pede Serpentarii” (1606)

The Star of Bethlehem – a mystery (almost) resolved?

The star of Bethlehem, which led the wise men from the East to the newborn Jesus Christ, is perhaps one of the most iconic stories of the New Testament in the Bible (Matt 2:1-13). The story has been depicted in countless artistic representations throughout the last 2000 years and is retold every year in Millions of places around Christmas time. However, what actually is the “star” in this story told by the evangelist Matthew? An interdisciplinary team of scholars involving astronomers, historians, and theologians, gathered at the University of Groningen, The Netherlands to address this question. Here I give a personal summary of what I learned at this conference. Reference to the speaker is given by names of the speakers in square brackets (see also Disclaimer at end and note the reference to the proceedings).

Figure 1: A series of great conjunctions and trigons from Kepler’s book “De Stella Nova in pede Serpentarii” (1606)

Figure 1: A series of great conjunctions and trigons from Kepler’s book “De Stella Nova in pede Serpentarii” (1606)


Opinions on the nature of the story are widespread and range from it being an accurate description of historic events that took place around the birth of Jesus Christ to it being a purely literary invention by Matthew as part of early Christian propaganda. Needless to say that the attitude towards Matthew is not necessarily uncorrelated with ones own personal beliefs and socialization and hence discussing this story is not always free of emotions.

However, even for those considering the story pure fiction, it may be worthwhile uncovering whether this story reflects events and motives being on people’s minds at the time. For the astronomer, the question is more down to earth: Was Matthew describing an actual astronomical event that happened around this time? And if so, which one? Suggestions for possible astronomical candidates are plentiful: comets, (super)novae, variable stars, planetary conjunctions, and – yes – even UFOs (though we will not spend any time on the latter suggestion here).

The great conjunction

Most of these events were quickly discounted: comets are usually bad omens and variable stars are hard to see with naked eyes. Chinese records show no supernova during the timeframe in question [B. Schaefer, R. van Gent]. Moreover, the story itself does not give the impression that the event was particularly spectacular, such that the star was easily recognizable for everybody.

Was it perhaps an astrological conjunction? This idea had been revived in recent years by M. Molnar in his book “The Star of Bethlehem: The Legacy of the Magi” (preceded by Voigt 1911). It was this particular book that was most intensely scrutinized at the workshop.

Center stage in this theory takes a great conjunction of the most prominent planets: Jupiter and Saturn. Such a “great conjunction” actually occurs roughly every 20 years successively in three different zodiacal signs, after which it returns – slightly shifted – to the original zodiacal sign. After 3-4 of these trigons (Figure 1) the conjunction shifts to the next set of three zodiacal signs (i.e., after 10 conjunctions per zodiacal sign) only to return after some eight hundred years to start a new circle with Aries (the Ram), the first of the signs.

It was, in fact, Johannes Kepler who observed in 1604 a supernova that occurred right in such a great conjunction, while the eight hundred year cycle was restarting. He noticed that a previous cycle had started around 7-6 BC and made a connection to a putative birth date of Jesus Christ at 5 BC [O. Gingerich]. He also wondered, based on the very unusual sighting of a nova, i.e. a “new star”, whether it was that great conjunction in Aries which actually spawned it. The likelihood of finding a Supernova, occurring every few hundred years, right in such a special conjunction is exceedingly small, yet today we understand that Supernovae are simply random stellar implosions of distant stars that are completely uncorrelated with our solar system. 

Molnar’s theory

Molnar reminded everyone that one should read the sky like an ancient astrologer and not judge it by what we would consider exciting or spectacular today. He goes on to argue that in those days Aries was the zodiacal sign associated with Judea. Hence, when the sun and the moon accompanied the great conjunction in Aries at a certain date in 6 BC, in particular when the moon occulted the regal planet Jupiter in the early morning during his helical rising, it would have made for a very unusual horoscope that signaled the birth of a new king in Judea. The great conjunction itself was visible for a good part of a year, where it would move across the sky, stop, return for a while, stop again and then move further. 

The reason for this behavior is the structure of our solar system, where the Earth rotates on a smaller and faster orbit around the sun than Jupiter and Saturn. While the Earth moves in a direction towards Jupiter and Saturn, both planets will advance forward. However, as the Earth catches up with them – leading to a triple conjunction of the two planets with Earth – both, Jupiter and Saturn, look like they are moving backwards (Figure 2).

Figure 2: Coin from Antioch showing a ram looking at a star. Drawn in yellow is the path of Jupiter and Saturn relative to the fixed stars in 6 BC (Figure taken from M. Mollnar's webpage.). One nicely sees the stopping and reversal of the planetary motion, caused by the Earth orbit being faster than those of Jupiter and Saturn.

Figure 2: Coin from Antioch showing a ram looking at a star. Drawn in yellow is the path of Jupiter and Saturn relative to the fixed stars in 6 BC (Figure taken from M. Molnar’s webpage). One nicely sees the stopping and reversal of the planetary motion, caused by the Earth orbit being faster than those of Jupiter and Saturn.

According to Molnar, the stopping and retrograde motion of the conjunction would naturally explain the path of the star described in Matthew “And behold, the star that they had seen when it rose went before them until it came to rest over the place where the child was” (Matt 2:9). Indeed, all astronomers at the meeting [P. Barthel, B. Schaefer, D. Hughes] agreed that no astronomical object, other than planets, would “go before” someone and then “rest” in one location.

Scrutinizing the theory

Hence, it seemed prudent to investigate the various aspects of that story and its historical context in greater detail. For example, what was the relevance of astrology at the time, does the text use astrological terms, would a horoscope be recognized as predicting a royal birth, and would that make someone jump on a Camel to conduct a long journey? Was Aries indeed the sign of Judea and what are the Magi really?

Ancient astrology

Fist of all, astrology was indeed widespread and an integral part of ancient society. One would miss many important of nuances of the time if one were to ignore this. Already 700 – 400 BC Mesopotamian astronomy was well developed with detailed records of planetary motions over centuries. By 400 BC mathematical tools were developed that allowed reasonably accurate predictions of the sky for any day of the year. Astrological systems developed and were used for multiple purposes, like casting an individual’s horoscope, predicting the fate of future events, or choosing the proper date for an expedition or a journey. This went so far that tables existed which correlated planetary conjunctions with weather and market prices. However, horoscopes were typically not cast in advance to predict the birth of a person or a king but only their death [M. Ossendrijver, A. Jones, S. Heilen]. 

In general astronomers and astrologers were two different professions – one who would observe and one who would interpret it. An astrologer would not really observe the stars, but merely use astronomical tables to calculate a horoscope. Nonetheless, both occupations were clearly tightly interwoven [K. von Stuckrad]. Still, in general it seems rather unlikely that an astrologer would have suddenly looked at the sky, discovered an interesting conjunction and rushed to Judea because of this.

Astrological language in Matthew?

So, does Matthew actually use astrological terms in his story? Molnar’s interpretation is that Matthew did not want to tell us that the star went in front of the Magi, but that he simply used commonly known astrological terms about planetary motion. The term “ἐν τῇ ἀνατολῇ” (en te anatole, at the rising) in Matt 2:2 indeed has an astrological connotation and can refer to a helical rising, i.e., a rise just before sunrise or at least a morning rising [A. Jones, A. Panaino]. On the other hand, “astér” is really a single star and can neither be applied to a conjunction or a comet. Identification as a single planet is possible though, but with difficulties [A. Panaino]. Within the Molnar theory one could perhaps argue that it was only Jupiter that was visible in the early morning and hence the regal planet could have been called “his star”. Overall, Matthew fails to consistently use proper astrological terms [S. Heilen], potentially because of ignorance.

Relating zodiacal signs to Judea?

So, what about the zodiacal signs: Does Pisces or Aries really refer to Judea, thereby giving a clue for the Magi where to go? Here the Molnar theory hits some opposition. It is indeed true that certain zodiacal signs were assigned to countries, however, in the traditional astrological systems of the time it would have been much more likely to associate Aries with Persia or Syria, while Judea was simply too insignificant to be included here explicitly. Only with the revision of Ptolemy later, can we see Judea being associated with Aries [J. Steele, S. Heilen].

As an interesting side remark, Heilen pointed out that the countries mentioned in the story of Pentecost in Act 2:9-11 rather closely follow the list of countries associated with zodiacal signs. This in itself suggested to me, that astrological themes are in fact being used in the New Testament – not judging whether the authors were aware of it or not.

Astrology in Jewish society

Indeed astrology played a much larger role in Jewish circles then one might have thought. While officially the Jewish religion would have nothing to do with it, astrological practices and knowledge were prevalent also in the ancient Jewish society. In particular king Herod the Great seemed well versed in astrology, engaging in discussions with the Roman emperor about it [von Stuckrad]. Moreover, van Stuckrad suggests that the great conjunction occurring in a new house most likely would have made Herod even more nervous than he already was. Known as a paranoid tyrant who was afraid of being overthrown, he slaughtered his two oldest sons in 7 BC and some 300 military leaders. In that respect the slaughter of the innocent (Matt 2:16) – estimates range from 7-40 children – would not be surprising, but is also not recorded elsewhere[1].

In fact, a great conjunction in a new sign had appeared already when the Hasmoneans rose to power in Judea in 126 BC and hence to an astrologically mind the return of this event could create serious unrest. Von Stuckrad also claims that similar astrological arguments played a role in the propaganda surrounding the Bar Kokhba revolt 132 AD.


Figure 3: A royal birth horoscope? The sky at sunrise April 17, 6 BC – all planets, sun and moon cluster around Aries (from M. Mollnar, “The Star of Bethlehem  - The Legacy of the Magi”, p. 97)

Figure 3: A royal birth horoscope? The sky at sunrise April 17, 6 BC – all planets, sun and moon cluster around Aries (from M. Molnar, “The Star of Bethlehem – The Legacy of the Magi”, p. 97)

A royal horoscope?

Molnar presented a particular horoscope for April 17, 6 BC (Figure 3), which looks impressive indeed. All planets, sun, and moon cluster around Aries. While some claim horoscopes can be interpreted literally at will [A. Adair], experts on ancient horoscopes reaffirm that this is only possible to a certain degree – there are, for example, simply good and bad horoscopes. An emperor with a good horoscope (e.g., Hadrian) would proudly use it for his purpose, while emperors with a particularly bad horoscope (Nero), would rather not make a big fuss about it [S. Heilen, K. von Stuckrad].

An issue to be considered is still whether all details of such a constellation as on April 17, 6 BC would have been actually visible in the morning– Saturn was probably invisible in the morning hours. Hence, some aspects of it can really only be calculated. Still, S. Heilen pointed out that indeed the constellation on April 17, BC would have made for a rather powerful horoscope for a royal birth. In particular, the fact that the Sun is preceded by “spear bearers”, i.e. the other planets marching in front of the sun (Figure 4), would be a rather telltale signature. Still, birth horoscopes would typically only be produced after the birth of an emperor.

Figure 4: The Sky as seen from Jersualem on April 17, 6 BC at 4 am in the morning. Venus, Saturn, Moon, and Jupiter march as “spear bearers” in front of the rising sun (made with “Stellarium”).

Figure 4: The Sky as seen from Jersualem on April 17, 6 BC at 4 am in the morning. Venus, Saturn, Moon, and Jupiter march as “spear bearers” in front of the rising sun (made with “Stellarium”).

Who are the Magi?

Another important discussion revolved around the wise men, i.e., the Magi, in the story, who were coming from the East of Judea. Are they really astrologers? Apparently the term could be used in a more derogative sense as sorcerer, however, in the biblical story the Magi seem to enjoy a rather high reputation. These Magi would then be part of caste of priests who played an important role in the ceremonial life at the Persian court, but who where not particularly known for engaging in astrology [A. Panaino]. Astrology was developed in Mesopotamia (Babylon) and widely used in the Hellenistic world, but not so much in Persia. Within the framework of the story, the Magi should be rather seen in their role as “king makers” who would be responsible for initiation rites of a new Persian king [A. de Jong]. On the other hand, it was pointed out that the biblical Daniel could also be considered as being a Magus [A. Panaino] – a story that played out in Babylon, where astrology was practiced after all.

In that respect it is interesting to look at parallel stories in history. Around the time of the writing of the story, one particularly noticeable event was a visit of Tiridates I of Armenia in 66 AD to Rome in order to worship emperor Nero and to be crowned as king. Magi as sign of his royal status and representatives of Zoroastrianism accompanied him and they would bow for Nero as well and present gifts. The word used to describe this act (prokunesis) is actually the same as used in the story of Matthew describing the wise men worshiping Jesus [van Kooten]. It could be that this event, which was still fresh on the mind, played into the writing of the story. Another parallel could be in more distant history: Alexander the great, after having conquered Persia and taking possession of the capital was greeted ceremonially by Magi who presented him with gifts of gold and frankincense – quite similar to Matt 2,11 [M. Ossendrijver].

Messianic expectations at the time

Finally, an important background of the story is the mindset of people around this time. Molnar claims a growing expectation for a Messiah in Jewish society, that would have made King Herod even more nervous and would have amplified or even inspired astrological claims to the same effect. Of course, there was not just one fixed Messianic idea at the time, but a multitude of them and it is hard to judge whether the expectations were really growing or just prevalent throughout the time [M. Popovic].

At least the Roman historians Josephus, Suetonius, and Tacitus make extensive reference to Messianic expectations and prophecies in Judea in their writings. Josephus refers to a well-known oracle that a Messiah would rule over the world and which he identified with the Roman emperor Vespasian. Tacitus mentions that the Jews believed a ruler from their country should rule the world and Suetonius claims that this oracle was known over all the Orient[2]. Strangely enough, it is very difficult to identify this uniquely with any of the biblical prophecies (e.g., Numbers 24:17 or Dan 7:13-14). What would make people apply them to their current period: other omens, horoscopes? Nonetheless, Suetonius clearly refers to an oracle of the God of Mount Carmel [J.-W. van Henten].

The theme resurfaced when Nero was presented with astrological predictions, in fact based on the association with Aries (actually preceding Ptolemy), that he would lose his power and regain it in Judea. After Nero’s death this led to widespread rumors and fears that he was still alive and would return from there [G. van Kooten]. Hence, it seems quite likely that oracles and prophecies about a Messiah as a new King of the Jews were known and probably widespread at the time.

Fact or Fiction?

So, what can we conclude from all of this? The most frequently stated conclusion drawn by scholars from the humanities was that the story is a pious fable, i.e. a literary fiction made up by Matthew himself to spread early Christian propaganda that Jesus was the new King and savior of the world. Consequently, astronomers would not really have any business in this matter. Moreover, some members of the audience questioned repeatedly why one would take this story serious at all and spend any time on it, while others rose in its defense.

Personally, I tried to play the part of an objective judge in this matter, trying to rid myself of pre-existing bias and enter this workshop with a rather open and perhaps even naïve mind. So, I was equally accepting that the story could be completely made up or was actually an accurate description of events that took place around the birth of Jesus Christ. It seemed that not everyone was willing to consider the latter position as a possibility.

As the workshop went on, I became fascinated and stunned by the elaborate picture of the ancient world that emerged from the combination of all the presentations. On the other hand, I grew somewhat disappointed when asking myself the question: Where is the data that confirms some of the conclusions? How unique is it really? Is the conclusion, e.g. pious fable, really born out by the presentation?

Contradicting biblical time lines

A theologian [A. Merz] working on the historical Jesus probably made the strongest argument in favor of the literary fiction interpretation. After all Matthew was the only Evangelist to report the story of the wise men. Moreover, stories from the childhood of Jesus are naturally less reliable than stories from his public life, which were witnessed by many more people, some of which would still be alive at the time of writing of the Gospels.

Merz pointed out that the time scales for the childhood of Jesus given in Luke and Matthew seem incompatible. In Matthew the family stays in Bethlehem for some time and then flees to Egypt, while in the gospel of Luke (2:39) Jesus’s family seems to return to Nazareth right away after having finished the required rituals at the temple. While both Luke and Matthew talk of a birth in Bethlehem followed by a youth in Nazareth, Luke misses the detour as fugitives to Egypt. Also, the local census of Quirinius, mentioned in Luke, was in 6/7 AD, while an Empire-wide census of Augustus took place in 8 BC, which, however, only involved Roman citizens. Both, Luke and Matthew, claim that Jesus was born during the reign of Herod, who died probably 4 BC (close to a lunar occultation).

Moreover, the bible reports that his own family initially did not accept him as King (Mk 3:21) and even labeled him being “out of his mind” when he started preaching. This they might not have done had they witnessed the worshiping of Jesus as a King by the Magi. Of course, one might argue that Jesus’ understanding of kingship was probably rather different from that of his contemporaries and family. Jesus’ unorthodox behavior might have in any case been very confusing and scary for his mother – independent of whether she really was expecting Jesus to rise to a leadership position in Judea.

Other speakers mentioned as arguments for the fable interpretation mainly certain potential inconsistencies and ample motives that conveniently served to reinforce early Christian messages. On the other hand, some inconsistencies are not too surprising after 60-80 years of oral tradition and a motive in itself does not yet make a crime.

Middle ground – considering the early church

So, is it pure fiction indeed or literal transmission of historic events? Personally, I suspect the truth lies somewhat in the middle. It seems unlikely to me that the story, even if handed down via Jesus’ mother and her relatives, would not have undergone reinterpretations and misunderstandings, certainly if one considers that Mary most certainly did not undergo any higher-level training in astrology or politics.

On the other hand, the idea that Matthew would sit down and completely make up a fabulous story to spread his propaganda also does not make sense to me. This interpretation, though making a historian’s life simple, smells more of a post-modern view of a powerful church that is perceived as deeply corrupted. After all, the early church was different from what it was in the middle ages: no palaces, no power, and people longing for a distinctly less corrupt way of life. A purely fictitious story in order to produce well-polished propaganda as a marketing company might produce it today, does not really fit to the ethical standards of the early church. In fact, the Gospels do not shy away from reporting conflicting views and seemingly contradicting stories.

Most importantly, the early church was rather diverse from the start, as is evident still today from the four different Gospels and many letters from different writers. While there was no Internet yet, the ancient world and also the early church were still highly connected and diverse. Debates in search for truth took place between the various fractions of the movement and there certainly existed something that one today might boldly describe as “peer review”. Someone known to regularly make up stories would have lost credibility among his peers rather quickly. When the evangelists report events that seem fantastic to us today and which they obviously did not witness themselves, like the “zombiecalypse” [A. Adair] in Matt 27:52, they might simply retell stories as they were being told on the street. Also Tacitus reports not lesser miraculous events around the destruction of the temple (see footnote above).

At the very least, I would therefore suspect that such a story reported by Matthew had been around already for a while in some Christian circles and hence did not come as a complete surprise to his readers. Hence, there is reason to search for a historical and astronomical nucleus of the story after all. In the following I will therefore try to summarize what I consider a reasonable scenario that can emerge from choosing such an approach.

The star of Bethlehem – what to make of all this?

In the last years of the reign of Herod the Great a number of things culminated: Herod grew increasingly paranoid over his fear of loosing power. Ubiquitous prophecies of a new Messiah or King of the Jews certainly amplified those worries. Given the relevance of astrology, it seems not unlikely that certain astrological constellations would have made these expectations even timelier.

To picture this, we just need to think of the fascination of the Woodstock generation with the alleged new age of Aquarius or the worries associated with the last great conjunction in Aquarius 1583 which was supposed to herald apocalyptic changes and even triggered a papal bull. Astrological topics might therefore have been the talk of the street at the time.

Horoscopes were not cast just for fun to predict the birth of a particular person and they were somewhat time-consuming to calculate, hence one should not expect that horoscopes were produced for every day and hour to predict the potential birth of a king in another country. On the other hand, horoscopes were produced every day in large numbers throughout the entire Orient for all kinds of other purposes – not only for the past, but also to address the future. The great conjunction – in various levels of proximity – was most certainly known and was directly visible for a long part of an entire year.

It therefore seems unlikely that the advent of this potentially powerful conjunction went completely unnoticed and was not a popular topic at ancient Cocktail parties. Whether this really implies the particular constellations pointed out by Molnar were recognized in advance is less clear, but perhaps also irrelevant from a larger point go view.

This electrifying mixture of a mentally unstable ruler, Messianic prophecies, and various astrological omens coupled to potentially emerging ideas that a Jewish ruler shall rule the entire world would also not have gone unnoticed in neighboring countries. Certainly, against the background of the traumatic experience of Alexander the Great, who came virtually out of nowhere and conquered an entire empire, Persian and Mesopotamian kings probably watched carefully the development in the region. 

In that respect the question whether Aries is to be associated with Judea, Syria, or Persia, might have been secondary. The sole thought that a horoscope could have predicted the advent of a “new Alexander the Great” somewhere in the region would have been scary enough for anyone in power there – independent of where that new ruler is born. It might then simply have been the buzz going around in Jerusalem that attracted the attention of foreign dignitaries.

Would it then be unusual that official or unofficial delegations, perhaps involving Magi and/or other higher-ranking officials, occasionally or even regularly visit surrounding capitals, such as Jerusalem, for gathering intelligence, exchange notes, or simply to foster economic and political relations?

In fact, the account of Matthew does not really explicitly state that the star was the sole reason that made the Magi engage in their journey – it is mainly popular lore that has established this link so firmly in our minds. The Magi could have been one of many regular delegations in the Orient, carrying with them a long mission list – investigating the potential astrological prediction of a new king might have been just one item among many.

What made these Magi perhaps stand out was that they dared to approach Herod directly about the prophecies of the newborn king and the astrological signs right at or before the peak of his “slaughter period“. Such a question might have had rather unhealthy consequences for any other, less prominent visitor. The question likely scared the heck out of Herod who quickly assembled his entire cast of Chief priests and scribes. It is them who educated the foreign visitors about Jewish prophecies (Micah 5,2), which suggest that the new ruler would emerge out of Bethlehem. One could even provocatively wonder whether it was the Magi’s appearance that ultimately pushed Herod over the edge.

Given that Bethlehem was a rather small village not too far away, the Magi could easily have paid a visit to this place – an event that would not have made the history books, but certainly would have stuck in the mind of the few locals there. Deciding thereafter not to return via Jerusalem was probably a beneficial intuition worth of wise men.

Obviously, I just made up a story here. There is no way I can prove that this is the correct order of events that actually took place – other interpretations are certainly possible. However, taking all the information provided at the workshop about the historical context and not dismissing Matthew’s account a priori, the story seems by and large quite reasonable to me and I do not see why one is forced to postulate a literary invention.

Those seeking a non-spiritual interpretation of that biblical story can still easily resort to an oral tradition about foreign notables, inspired by ancient prophecies and modern astrology, visiting the the small village of Bethlehem. This would have being talked about still decades later among family and friends and or other groups and could have served as the nucleus of the story told by Matthew.

The interpretation of the star who “rose in the East”, “went before them”, and “stood still”, ultimately makes sense within the framework of planetary motion, even if not every terminology is perfectly correct.

The more I learned about the wise men, the more emerged the story of Matthew as a masterpiece of Biblical writing that not only transports theological meaning, but that is also able to condense the historical context into a few sober lines – very different from the miraculous story that I had still in my mind from childhood memories.

Whether the Magi actually visited and worshiped the young Jesus Christ in Bethlehem falls outside the realm of this scholarly discussion. Statistically such a coincidence seems unlikely, but then, someone born 2000 years ago who still claims more than 2 billion followers today must have experienced some statistically unlikely events anyway. Math does not help here to draw a conclusion.

Ignoring any theological debates, an explanation of the star of Bethlehem in Matthew 2, as a great conjunction in 7/6 BC makes perfect sense to me. That holds even true if one considers –  what I am not convinced of – the story to be a literary invention. Whether there is enough detail to reliably derive a particular date from the historical nucleus, such as Molnar did for the birthday of Jesus Christ, is certainly debatable.

In summary: when asked about what the star of Bethlehem in Matthew 2:2+9 actually is, I would join some fellow astronomers and confidently state that “Jupiter” has become my personal front-runner since last week – despite the visible groaning of some historians and theologians at the conference about this conclusion.

DISCLAIMER: This is a personal summary of the talks and discussions presented at the Star of Bethlehem workshop in Groningen, which I did not do on behalf of the organizers, but just for my personal pleasure. I have given conference summaries before, but then only for astronomical conferences. While I tried to be as objective as possible, my summary will naturally be selective and filtered by my own personal biases. It will also contain errors in understanding and may not always properly represent the opinions and statements made by those I quote in the text. In fact, all references are made to the oral presentation of the speakers, as I understood them. Full references and authorized statements from the authors directly will be available only once the papers appear in the printed version of the book. This text here should be seen as a living document that may be updated once I am made aware of actual errors or if I have changed my mind, based on better arguments.

The final conference proceedings will be published by Brill Academic Publishers (Leiden/Boston), edited by G. H. van Kooten and P. Barthel.


[1] van Kooten mentions in this respect a story told by Suetonius (“Lives of Caesars”, 2.943) about Augustus, where a similar massacre of children for similar reasons was barely avoided.

[2] Interestingly Tacitus also refers to visible signs that preceded the destruction oft the Jewish temple, such as the opening oft the temple door, illumination oft the temple, and sounds. [J.-W. van Henten]. One is reminded oft the dramatic death of Jesus described by Matthew (27, 51), where the curtain to the temple was torn.


Chronology table

Figure 5: Chronology of events and calendars around the year 1 AD, produced by Rob van Gent [Utrecht]. An updated and improved version will be published in the conference proceedings.

Figure 5: Chronology of events and calendars around the year 1 AD, produced by Rob van Gent [Utrecht]. An updated and improved version will be published in the conference proceedings.

The Story of The Visit of the Wise Men

(Matthew 2:1-13, English Standard Version)

Now after Jesus was born in Bethlehem of Judea in the days of Herod the king, behold, wise men[a] from the east came to Jerusalem, saying, “Where is he who has been born king of the Jews? For we saw his star when it rose[b] and have come to worship him.” When Herod the king heard this, he was troubled, and all Jerusalem with him; and assembling all the chief priests and scribes of the people, he inquired of them where the Christ was to be born. They told him, “In Bethlehem of Judea, for so it is written by the prophet:

“‘And you, O Bethlehem, in the land of Judah,
    are by no means least among the rulers of Judah;
for from you shall come a ruler
    who will shepherd my people Israel.’”

Then Herod summoned the wise men secretly and ascertained from them what time the star had appeared. And he sent them to Bethlehem, saying, “Go and search diligently for the child, and when you have found him, bring me word, that I too may come and worship him.” After listening to the king, they went on their way. And behold, the star that they had seen when it rose went before them until it came to rest over the place where the child was. 10 When they saw the star, they rejoiced exceedingly with great joy. 11 And going into the house they saw the child with Mary his mother, and they fell down and worshiped him. Then, opening their treasures, they offered him gifts, gold and frankincense and myrrh. 12 And being warned in a dream not to return to Herod, they departed to their own country by another way.

Bing bang inflation – the biggest science news of the century that wasn’t

Dust rather than big bang – map of the Milky Way dust distribution made with the Planck satellite (ESA)

A few months ago the world was stunned by an announcement from Harvard University of what seemed to be the biggest science news of the century: the BICEP2 experiment proved that right after the big bang our universe underwent a rapid phase of cosmic inflation. This finding became front-page news all around the world. Now it seems clear that this statement cannot be upheld, as the European Planck satellite has published a paper indicating that the authors significantly underestimated contributions from dust in our Milky Way. A new science scandal? Not really, but some lessons can be learned.

So, what has happened? BICEP2 measured very accurately the properties of radio signals from the primordial fireball of our universe generated 380,000 years after the big bang. In particular, they measured the polarization – the direction of oscillation of the radio waves – of this cosmic background radiation with unprecedented  precision. The observed pattern of polarization on the sky, so called B-modes, seemed to fit predictions made for the inflationary model. In this model the rapid expansion of our baby universe would produce ripples in spacetime that propagate as gravitational waves through the cosmos and leave their imprint in the fireball radiation.

The detection of the cosmic background radiation had already generated two Nobel prizes (1,2), so the third one was now just a question of time.   The press officers of the participating institution did their job and made sure this message would not go unnoticed. Rumors spread conveniently before the press conference via Facebook and Twitter and a heart-wrenching youtube video was posted showing how the good news was delivered to Stanford’s Andrei Linde, one of the fathers of the inflationary model.

The news was almost instantly accepted as fact. This worried me a little bit, given that  there are so many difficult steps from the actual experiment to the final conclusion. In a previous blog I discussed these worries and the role Facebook and Twitter play nowadays in science communication. Moreover, everyone – including myself – was expecting that inflation was true anyway, which made it easy to embrace the results right away. However, as the scientific misconduct cases of Schön and Stapel have demonstrated, wishful thinking is where things can go wrong most easily in science.

Moreover, for some the finding even seemed to be some kind of an epiphany, delivering the long-sought support of the multiverse theory. After all, if the universe can spontaneously self-inflate, this might have happened countless times already with other universes elsewhere.

Indeed, Andrei Linde himself likes to motivate his scientific talks with the ultimate divine question: Our present universe shows an incredible level of fine-tuning – how can that be? Either, he says, the universe was created by God, or, there is a countless number of different universes spawned by his inflationary model – and God is not necessary. Unfortunately, it is not entirely clear whether that causal connection is correct and whether God agrees with it but, nonetheless, the bar is set very high.

So, at the peak of the hysteria, this was the point where it was time to grab a cup of tea, wait, and let the scientific method take its course.  Indeed, doubts surfaced whether the authors of the study, had properly quantified all other – non-cosmological – effects that could have contributed to their measured signal. The community noticed that the paper in question had not yet been peer-reviewed by a major journal. In addition, the BICEP2 team was anticipating results of a European satellite project, Planck, that could scoop them. In fact, the Planck collaboration was in possession of much better data on emission from dust in our Milky Way, that could potentially confuse the cosmic background signal. Hence, the BICEP2 collaboration, not yet having access to the data, scanned a preliminary dust map from a conference presentation of Planck and used this to estimate the magnitude of the effect – not a good idea.

Quickly, Flauger, Hill & Spergel showed that the dust contribution was so uncertain, that the BICEP2 results could be insignificant. And indeed, in the final published version of the BICEP2 paper the claim for detection of inflation was softened. Now it was still up to Planck to determine how strong the dust contribution really was. As it seems now, the dust contribution is in fact much higher than estimated by BICEP2. Hence, at the end of the day there is very little left to support the strong the claim that inflation has been discovered.

So, what does that mean? Well, the experimental finding of BICEP2 is not questioned, however, rather than looking at the face of God – as Nobelprize winner G. Smoot called it – BICEP2 might have just looked at the dusty outskirts of our own Milky Way.  Cosmic inflation might still have happened, but currently there is no experimental evidence for it.

Planck and BICEP2 now work on a joint paper, trying to combine their data, so maybe, with a more careful analysis a cosmological signal can still be found – or not.

What are the consequences now? Does one need to retract the BICEP2 paper? Well, the published version was a bit more careful and acknowledged in the end, that dust could spoil their results. So, factually there is probably no ground to retract the paper itself. Will the authors be in trouble? Not necessarily, but they’ll probably have some interesting discussion ahead of them. At least the paper is already quoted close to 700 times within half a year. Hence, formally this will contribute positively to their citation records. On the other hand, most expert committees will know how to put this in perspective. Is the scientific method in danger? Actually also not – peer review via journals, conferences,  and twitter has worked remarkably well in this case. Has the BICEP2 team jumped the gun? Absolutely! The “only thing” that was blatantly wrong in this story was the press release (and a few other bits of the media campaign that were a bit over the top).

For scientists it remains a difficult question when to publish results. Science is after all a competitive field. Most scientists seek truth, but if you are too late, someone else may get the fame and the precious grants. It would be naive to ignore these factors.

So, what can we learn from this? Are press releases bad? Not necessarily – they are good entertainment, but they are not always good science.

There is no reason to reject the entire body of scientific knowledge, but the next time you see a press release about a groundbreaking discovery, sit back, take a cup of tea, and exercise some random acts of skepticism – it will sort itself out. 

Science in the era of Facebook and Twitter – get used to it

Science in the era of Facebook and Twitter - a whirlwind of hypes and likes.

Science in the era of Facebook and Twitter – a whirlwind of hypes and likes.

“Science is wrong, most of the time” – I am not sure who said that first, but I am sure someone did so well before me. This is a banality for those who do science at the forefront of our knowledge, yet sometimes it seems very difficult to also accept that view in the public discourse. Well, in the days of Facebook and Twitter it is plain obvious to everyone.

As an active astrophysicist I had to reflect on this, while a number of big and small events were accumulating.

It all started with a press conference at Harvard where astronomers announced that they found evidence for cosmic inflation. This news quickly spread over the entire world via Twitter and Facebook and it was hailed as spectacular evidence for the big bang by the regular press. Just  a few weeks later people aren’t so sure anymore. In fact, I personally think that the measurement is impressive but insignificant at this stage (due to foreground uncertainties that are impossible to quantify right now – but, I too could be wrong, of course).

This morning the SWIFT telescope announced a new gamma-ray source in the nearby galaxy Andromeda, that was picked up by news sources, Twitter, and Facebook well before most scientists did. That source would have been very interesting indeed. Alas, it turned out not to be there. That fortunately happened so quickly that neither print media nor TV could report it. Clearly, in the past there were other major false alarms that (astro)physicists remember, such as the announcement of faster-than-light neutrinos, life on Mars, or cold fusion (which actually occurred in prehistoric times).

So, what is going on? Does science lose its credibility? At least that was a question I was asked by our university news paper in connection with an ongoing debate here. My answer was that we – scientists, media, and general public – need to learn how to handle science in the era of social media. It is not as it used to be. Scientists are no longer the almost omniscient divine beings that, thanks to their unchallenging wisdom, hover well above the ground that absorbs normal mortals.

Failure is part of the scientific enterprise. It is good that some scientists stick their neck out and dare to claim something. However, it is equally good that other scientists try to chop these heads off – with counter arguments. That is proper science and cherished academic tradition. Scientific truth is not the outcome of a single Eureka moment but of a long sociological process and hence it is subject to all human deficiencies.

This is no news and has been said many times before, but scientists, media, and general public tend to forget too often. Well, social media reveals that just too clearly.

In the past most scientific debates would take place in academic circles and results would only gradually diffuse into the general public. Now the information transfer is instantaneous – often not filtered by journalists, who can only follow the wave rather than steer it.

Is that a problem? It may seem so in a society where science seems more and more optional and becomes part of the entertainment and political circus. The consequence: science is becoming defensive.

In subjects like climate change, vaccination, evolution, but also more ethics-related issues such as stem cell research, there is either a vocal minority or sometimes even a silent majority of the general public that questions scientific positions. Moreover science is big business for large institutions and groups. That raises suspicions and the scientific credibility comes under pressure. Every additional false discovery, immediately amplified by social media, may shatter that credibility further.

So, what to do? Shall we dig in and stop sharing our latest finding with each other and with the public? Or shall we stop making claims and just publish highly polished results?

The latter is, in fact, something that big science collaborations have adopted as their working model and it may become the model of the future. Too much money is at stake.

However, I prefer honesty. Let’s simply get used to the fact that science can be wrong – and that scientists can be wrong – without dismissing immediately the entire body of scientific knowledge. Scientists should not be made afraid of making claims and also not be made afraid of being wrong. Being wrong is as much part of our job as is losing part of being a football player. I am convinced, if scientists are less arrogant and more honest about the inner workings of science, credibility will naturally prevail in the long run.

However, we probably need to develop an etiquette on how to communicate science results and how to involve the public in the scientific process these days.

For example, announcements like that of a sudden outburst of a cosmic source need to get out as soon as possible to the community, so others can react before the flare is over. In the case mentioned above, the SWIFT team did nothing wrong. They communicated their result as they usually do: swiftly and properly. The event turned out to be a glitch; that is not normal but can happen. Any media reporting on such events has to make its own choice: either be too late to report or report on something that is premature. To make this call hire and train good science journalists and do not be afraid of correcting your story if it goes wrong.

Very different, however, is the story of the Big Bang result. It was presented in a press conference as “first direct evidence of cosmic inflation” accompanied by a rumor-based social media campaign. Nobel prize winners were invited to be present at the data release and soap-opera style reality TV movies about potential Nobel prize winners went viral. The authors of the paper asked for the media and social media attention, they got what they asked for, and they will have to carry the consequences – potentially together with the rest of the community if it turns out to be wrong.

The paper in question had not been submitted to a journal and was not yet refereed by  experts, but instead it was released to the entire world together with a very bold claim.

Many colleagues hailed that as a major step towards openness and a transition from traditional publishing  methods to modern swarm intelligence and social media based interaction. I think that is crap – or at least naive.

The procedure was primarily adopted in order to beat others (e.g., Planck), to secure a dreamed-of Nobel prize for whoever, and perhaps to secure tenure and other jobs for collaboration members. Does anyone really believe none of these thoughts played any factor in this story? Science can be a fierce competition and our Harvard colleagues certainly know very well how to play that game.

So, may I suggest three options on how to proceed:

1) If you want to use the web to referee your work, then do so, but be defensive.  Make clear that this are preliminary results, subject to discussions. Let the process take its course and then have a press release summarizing the conclusion at the end. Any ensuing media frenzy is their problem – let the media and the web find a way to deal with the process and get used to it.

2) Or, have it refereed thoroughly and traditionally and then have a press release or even a press conference organized by your institution, following some clear ethics rules. In case of an extraordinary claims, editors of journals should be very careful in selecting a number of very different referees, rather than be very quick. Still, be humble in your claims as author.

3) Finally, you can release it to the media before submission, but then make clear that this is just one possible explanation, an interesting hypothesis, a contribution to the discussion. The media needs to learn to understand and report that properly. Certainly, refrain from press conferences,  emotional youtube videos, etc. in this case.

Which method you choose (I have chosen 2 and 3 already) also depends on the enormity of the result. If you really have Nobel-price winning results (which I haven’t had yet), then Method #2 is perfectly fine – you will get it in any case. If you don’t, also the biggest press campaign will not get you one.

Above all, let’s make clear that science is an ongoing discussion. It can benefit a lot from social media interaction with each other and the public. However, that automatically requires honesty, less agitation, more understanding from the public, and a sense of humility among us scientists. In the end, however, it makes us vulnerable – whatever we do. We also need to learn to live with that.

Photo of your vote? Show respect to democracy, don’t do it!

A little while ago, I wrote my first blog on why I was very unhappy with the massive wave of pictures taken by voters of their own ballot paper together with their face in the voting booth –  called “stemfie” in NL. This later actually made it into the court of law.

I was upset, because in my mind the “stemfie” violates one of the most fundamental principles of our democracies: the secret vote. With Germany’s history in the back of my mind – and the lessons learned from it – I care deeply about democracy. Like everywhere in life, some basic principles have fundamental effects on where a society will go and they should not be up for fun and jokes. It is therefore no surprise that the “stemfie” is explicitly illegal in other countries.

Indeed, recently a foundation for the protection of civil rights and Lucas Kruijswijk went to court to prevent this from happening again. I thought their lawyer, Douwe Linders, had written a piece that is worthwhile reading. (And that is not just, because they actually used my blog as inspiration and quoted it there … :-).

Take one of their examples: you are part of a football team in a small village, where everyone votes PVV (or SP, of SGP, or PvdA, or CDA, or VVD, or whatever), only you disagree secretly. They all vow to post their ballot on Twitter, because that is legal. Do you think everybody in this country would dare to stand up against his/her own club, say no, and vote differently? We have to protect whose who are weak and vulnerable to ensure a free and fair election. If a vote is only “voluntarily” secret, it is not really free and secret (as the practice in East Germany showed too well).

The court dismissed the case, but very clearly recocgnized the serious concerns raised. Nonetheless, “it is not forbidden” – as the minster and highly apreciated fellow Spinoza-prize winner, Ronald Plasterk, has explicitly told the public yet again. In fact, the media is even promoting it with such ridiculous articles as “Nine tips to make a perfect picture of your ballot“. The “Parool” could not have shown a more insensitive and clueless attitude towards democracy. At least in the UK, where a similar discussion is happening, the BBC reports states “The Electoral Commission fears (that) the craze for taking self-portraits on phones and posting them on social media threatens the secrecy of the ballot”. Indeed, an election with a wave of “stemfies” is in danger of being invalid.

So, my plea to anyone who cares about the long-term future of democracy: show respect, don’t take a “stemfie”!


P.S.: I was discussing the NL court ruling with Luca Kruijswik. My German thinking is: “you lost, so you lost”. However, he claims that the Dutch system is different (see below). I am curious to find out, whether that is just wishful thinking or Dutch reality.

L.K.: “Don’t worry, this verdict is a deep disgrace for our Ministry.

In most countries, success, failures, mistakes are valued high, especially in Eastern European countries.

In the Netherlands we care less about mistakes/failures/success, but more about honesty and loyalty to the case (whatever that
will be).

This has maybe to do with our dike builders. You build one dike for a whole community. Then it is more important that your neighbor, that maintains a piece of dike that also protects your property, is honest and loyal to the case. Any mistakes will be picked up by the group.

If you read the verdict, the judge said, you didn’t make a mistake, but you were not loyal to the constitutional values. This is a
total disgrace in our country. The Judge couldn’t make it more worse for the Ministry than this. Just correcting the situation was too simple. He wants the Ministry to do that.

Furthermore, we have 2 Professors in State Law that agree with the claim, so, one should not be worried about the outcome. In the plead of the State, it was stated that there will come a statement of the whole government. Such remark can only be made, if the Ministry of General Affairs (with Rutte as Minister) has confirmed this. This statement must take the verdict of the judge into account.
And the judge didn’t leave much space to come with another solution than to forbid the stemfie.”

The “stemfie” – How to ridicule the secrecy of free elections

Dutch local elections are over and the “stemfie” was the big winner. In large numbers would voters take a picture of themselves (“selfie”) with their readily filled-out ballot (their “stem”) in the voting booth. Most people think that is funny and even the leaders of national parties, like Alexander Pechtold of the D66 did so – after all the Dutch authorities formally declared this to be legal!

I am convinced this is not funny, in fact it is dangerous and illegal in a true democracy. The “stemfie” is ridiculing the secrecy and freedom of the vote.

When I say that, people look at me baffled as if I just proposed flying to the moon (Ok, I did that too in the past …). So, here are a few arguments why I think so strongly about that issue:

Social pressure of peers or government can eventually force you indirectly to make your vote public through a “stemfie”. That prevents you from freely making your choice. Pechtold could have still voted for his secret love VVD (or SP) and said afterwards in public that he voted D66. This freedom he does not have anymore. Next time he does NOT produce a stemfie people will wonder whether he really supported the local candidate at all. Pechtold can live with that, but he exercises peer pressure on all his other party members to forfeit their right to a secret vote as well.

In fact, the method to make secrecy optional was used in East Germany during the communist era to get the desired results. You would cast your vote “voluntarily” openly  and everybody who did not do so was marked down – so that led to 90% + results for the reigning government..
Hence, every election where you voluntarily can cast an open vote is not a secret election anymore and is invalid in my mind – even if you are living in a still functional democracy. Clearly Germans are more sensitive about this issue due to their history, but that does not mean one should ignored that experience elsewhere.
Moreover, if many people make their votes public in a documented way then also the votes of the few others are not secret anymore – especially in a local election with a few votes. An extreme example: If 5 people in one area  have voted for a certain party, which has 6 members, and those 5 people make their vote public with a photo, there is no way for person number 6 to argue that he too voted for that party. Also if in one small community 99 of 100 votes are made public, also the one remaining vote is not secret anymore. Even if the margins are not so tight, at some point the number of really secret votes may become uncomfortably small.
The freedom to vote against a party line or against social peer pressure in your neighbourhood is gone and people may be afraid to cast particular vote. Just the fact that people, may be afraid to be “caught” voting for or against a certain party – because everyone else took pictures – invalidates that election.
Note that stating who you voted for outside the cabin is perfectly fine. This is one of the few occasions where it is perfectly ok to be able to lie.
Another serious issue is that this makes it possible to buy or manipulate votes. If someone offers money for your vote or threatens you if you do not vote as desired, you could still vote differently in the secrecy of the cabin. If you can, however, document what you vote, this will quickly become part of the deal and the election is no longer free and fair for everyone.
NB: Of course, something similar can happen if you vote by letter at home. Hence, this is a concern and taking pictures of that ballot should be equally illegal. Moreover, you could probably still sneak in a different ballot in the envelope at home. This is not really possible in a public election booth.
In summary, allowing people to photograph themselves with their ballot in the cabin seriously undermines and invalidates any free and secret election. Moreover, you cannot demand from autocratic countries how to vote properly, if you yourself do not make sure you follow the rules strictly yourself and set the very highest standards.
In my mind the Dutch authorities have failed miserably in this regard and endangered the democratic process in the long run.
P.S.: Of course, the true low point of those elections happened after the voting booths were closed, which reminded me of a yet darker part of German history and sent me home shivering in my car…