Articles from the Institute Letter

Additional articles from new and past issues of the Institute Letter will continue to be posted over time and as they become available.

by Nir Shaviv

Our galactic journey imprinted in the climate—when Earth’s temperature (red dots warm, blue dots cold) is plotted as a function of time (vertical axis) and as a function of time folded over a 32-­million-year period (horizontal axis), the 32-million-year oscillation of the solar system relative to the galactic plane is evident.

How might climate be influenced by cosmic rays?

In 1913, Victor Hess measured the background level of atmospheric ionization while ascending with a balloon. By doing so, he discovered that Earth is continuously bathed in ionizing radiation. These cosmic rays primarily consist of protons and heavier nuclei with energies between their rest mass and a trillion times larger. In 1934, Walter Baade and Fritz Zwicky suggested that cosmic rays originate from supernovae, the explosive death of massive stars. However, only in 2013 was it directly proved, using gamma-ray observations with the FERMI satellite, that cosmic rays are indeed accelerated by supernova remnants. Thus, the amount of ionization in the lower atmosphere is almost entirely governed by supernova explosions that took place in the solar system’s galactic neighborhood in the past twenty million years or so. 

Besides being messengers from ancient explosions, cosmic rays are extremely interesting because they link together so many different phenomena. They tell us about the galactic geography, about the history of meteorites or of solar activity, they can potentially tell us about the existence of dark matter, and apparently they can even affect climate here on Earth. They can explain many of the past climate variations, which in turn can be used to study the Milky Way.

The idea that cosmic rays may affect climate through modulation of the cosmic ray ionization in the atmosphere goes back to Edward Ney in 1959. It was known that solar wind modulates the flux of cosmic rays reaching Earth—a high solar activity deflects more of the cosmic rays reaching the inner solar system, and with it reduces the atmospheric ionization. Ney raised the idea that this ionization could have some climatic effect. This would immediately link solar activity with climate variations, and explain things like the little ice age during the Maunder minimum, when sunspots were a rare occurrence on the solar surface. 


What do quantum interference, flocking of birds, Facebook communities, and stock prices have in common?

Many natural and social phenomena may be viewed as inherently computational; they evolve patterns of information that can be described algorithmically and studied through computational models and techniques. A workshop on the computational lens, organized by Avi Wigderson, Herbert H. Maass Professor in the School of Mathematics, highlighted the state-of-art and future challenges of this interaction of computational theory with physics, social sciences, economics, and biology.

Hassan Ansari (right) with Sabine Schmidtke

When Sabine Schmidtke and Hassan Ansari, an Iranian national, met more than a decade ago in Tehran, Ansari was a ­student of the traditional religious system in Qum and Tehran (the “Hawza”). Ansari had read Schmidtke’s doctoral thesis The Theology of al-ʿAllāma al-Ḥillī (d. 726/1325), which was translated into Persian and published in Iran in 1999. Schmidtke’s scholarship changed Ansari’s approach to Islamic sources and was one of the reasons why he became ­interested in historical studies on Islamic theology. “The historical approach is not only useful, it is necessary,” says Ansari. “I talk now as a Muslim scholar. We need to have this kind of historical studies to change our approach to our own intellectual and legal tradition and its holy texts.”

What makes Ansari a particularly exceptional scholar is his combination of Western and traditionalist Islamic training. In the “Hawza” in Qum and Tehran, he successfully completed the very highest level of study for the rank of Ayatollah, in the Shi‘i ­clerical system. He also has studied Islamic and Western philosophy and Islamic intellectual history at universities in Tehran, Beirut, and Paris. “Hassan’s command of the sources is extremely wide-­ranging,” says Schmidtke, “and he combines this with the very best ­historical-critical approach to the subjects and texts he is dealing with. He is an intimate connoisseur of manuscripts, Arabic and Persian, and the spectrum he covers is immense.”


By Robbert Dijkgraaf

Light connects us to the very beginning of the uni­verse. The first light was emitted roughly 380,000 years after the Big Bang, when matter was no longer closely tied together and light could escape. This radiation was detected for the first time fifty years ago this year.

Light is the great unifier. John Wheeler, the beloved Princeton physicist, used to draw the universe as a big capital U with a little eye on one leg, signifying that we, human beings, are the eyes of the universe looking back at itself. The universe after many, many billions of years formed human life on planet Earth, and we use light to observe and understand the universe. 

The growing understanding of the nature of light through the centuries is the perfect metaphor for science: it is an eye-opener. Almost 350 years ago, Isaac Newton, as a young man, put a prism in a beam of light and unraveled its various colors. This was the beginning of a long story. Around the year 1800, the astronomer William Herschel was the first to measure the temperature of light. He made the startling discovery that the rainbow does not stop at red, but actually continues, invisibly, as infrared light, which we cannot see but can feel as a sensation of warmth. 

What is light? Physics has a simple answer: an electromagnetic wave. Exactly 150 years ago, the Scottish physicist James Clerk Maxwell discovered the laws that describe these waves. I have a T-shirt with these equations and the text “And then there was light.” If only Maxwell had patented his equations! It would be enough to finance all research in the world.


By Sara McDougall

William of Normandy

The language of illegitimate birth reveals a rich, complex vocabulary.

Early this December, newspaper headlines made the sensational claim that recent DNA evidence had called into question the legitimacy of the British monarchy: scientists had identified what is known as a false-paternity event. Genetic analysis of the remains of King Richard III of England and his modern-day descendants indicated the possibility that Richard’s mother, grandmother, great-grandmother, or great-great-grandmother had a child with someone other than her husband and successfully passed that child off as her husband’s son and heir, thus corrupting the royal patriline with less-than-royal blood. 

If a scholar of medieval law can be permitted to reassure a reigning monarch and her family, I would like to suggest that their dynastic claim to the throne remains safe. Medieval England by the time of Richard III had developed strict rules against allowing illegitimate children to inherit from their fathers, particularly royal or noble titles, but English law also maintained quite a generous presumption of paternity.

As long as it was remotely possible that the mother’s husband could have conceived the child she presented as his, that child’s right as heir could not be challenged.

That does not mean that illegitimacy raised no problems in the Middle Ages. It most certainly did. But the various ideas of illegitimate birth held by people in the Middle Ages were not necessarily the sorts of problems that we think of today. This year, I have the privilege of investigating the history of ideas of illegitimate birth, and the exclusion of bastards from royal succession, in the former institution of the great scholar of kingship Ernst Kantorowicz, and in the company of brilliant friends and colleagues who have repeatedly challenged and inspired me since my arrival in September.

As I am finding, analysis of the language of illegitimate birth reveals a rich, complex vocabulary used to indicate something less than fully legitimate birth. Terminology included both new and old words, plucked from ancient sources or transliterated from medieval vernacular languages. We find this terminology in the widest range of medieval sources, used to describe contemporaries, ancestors, and biblical and even mythological figures. Definitions vary over time and space, but also depending on the context, the kind of source, and, of course, authorial intentions.