Eclipses: a pump of curiosity?

Even though the wiring of the human brain evolved in an exceptional way, if novelty had remained below a certain threshold, early humans may not have received a sufficient trigger to begin forming the concept of reasons.

My accepted manuscript for the Proceedings of the International Astronomical Union Symposium No. 367, 2021, is available under the journal’s Green Open Access policy.

Earth in a spin

The Earth … has been spinning unusually fast lately. 2020 included the 28 shortest days since 1960.

Graph showing the length of days in 2020.Image:

Our story on the Earth’s quickening rotation is generating a lot of interest, from the Daily Express to Live Science to USA Today.

Update (17 January): There’s also coverage of the story in Spanish-language media, including an interview with BBC Mundo.

Screenshot from BBC Mundo

Visualizing the music of the spheres

We have known for thousands of years that the sky is full of harmonies and rhythms. Pythagoras called it the “music of the spheres.”

As part of the build-up to next week’s great conjunction, Steffen Thorsen (CEO of and I have written a piece for Sky & Telescope on the pattern of closer-than-usual approaches between Jupiter and Saturn.

Our team of programmers, astronomers, and enthusiasts at wanted to visualize the roughly 400-year rhythm of super-close conjunctions between Jupiter and Saturn. For fun, we created an algorithm to run through a mathematical model of Jupiter’s and Saturn’s movements over a 16,000-year period.

16,000 years of Jupiter-Saturn conjunctions

Image credits: Steffen Thorsen & Graham Jones, Sky & Telescope

Extraterrestrial intelligence and the Fermi paradox

The Milky Way and ESA's Gaia spacecraftThe Milky Way contains 100 billion stars. So where is everybody? (The spacecraft shown in this artist’s impression is one of ours: it’s ESA’s Gaia space observatory.)
Image credit: ESA/ATG medialab; background: ESO/S. Brunier

One of the highlights of IAUS 367 is Nikos Prantzos, from the Institut d’Astrophysique de Paris, on “the quest for extraterrestrial intelligence and the Fermi paradox”. He’ll be presenting a general overview of the topic, as well as an original analysis of the Fermi paradox in terms of the Drake formula — a framework for thinking about the number of technological civilizations within our galaxy.

Other highlights include Jay Pasachoff on “the science and the magnificence of observing total solar eclipses”, and Alex Young on “engaging the public through solar eclipses”.

IAUS 367 is a virtual symposium that was originally going to be held in San Carlos de Bariloche, Argentina. On 14 December a total solar eclipse will cross Chile and Argentina, about 125 km north of Bariloche. map of the total solar eclipse on 14 December 2020The (very narrow) dark red line shows the path of totality for the December 2020 solar eclipse. Areas covered by lighter shading will see a partial eclipse.
Image credit:

We’re planning to broadcast the eclipse on (It will be the second part of an eclipse season double-header that began with our livestream of the penumbral lunar eclipse on 30 November.)

Extending the Rare Earth hypothesis

Image credit: IAU

I’ll be presenting “Solar eclipses: A pump of curiosity for early humans?” at the International Astronomical Union Symposium 367 next month.

The symposium was originally scheduled to take place in San Carlos de Bariloche, Argentina, close to the path of totality for the 14 December solar eclipse. However, covid-19 restrictions mean it will now be an online event.

My poster session will extend the Rare Earth hypothesis to ask: does the Earth have some special ingredient that led not only to complex life, but to curious life?


Solar eclipses: A pump of curiosity for early humans?

Graham Jones, University of Shiga Prefecture

A central and unique feature of the human species is our desire for explanations. Where did our sense of curiosity come from? And why, on the current evidence, are we the only species in the Universe to possess this feature? Traditionally, these have been treated as separate questions; in this presentation, I will suggest a way to combine them into a single line of inquiry. I will also draw on the Symposium themes of cultural astronomy and solar eclipses to propose a speculative answer.

I will begin by considering the Rare Earth hypothesis, which states that the development of complex life depended upon a set of physical, chemical and biological circumstances that may be vanishingly rare within the Universe. I will extend this idea to open up a new line of inquiry: does the Earth have some special ingredient that led not only to complex life, but to curious life? I will speculate that solar eclipses may be such an ingredient.

We can confidently say that solar eclipses are not rare within the Universe. However, the ‘perfect’ total and annular eclipses we experience on the Earth, together with their mean frequency of once every few hundred years for a given location, may be exceedingly rare. Although these eclipses have no lasting effect on the Earth and its environment, they have an overwhelming effect on humans and human communities. I will tentatively propose that solar eclipses provided early humans with novelty on a scale large enough to help trigger the development of curiosity.

In effect, solar eclipses may have acted as a finely tuned ‘pump of curiosity’: if they occurred more frequently, they would not have provided sufficient novelty to stimulate the brains of early humans; if they occurred less frequently, they would not have provided enough stimuli to different communities, at different times, to kindle the first flames of curiosity.

This presentation will provide Symposium delegates with an opportunity to engage in fun speculation across a range of disciplines. To help generate discussion and debate, I will present comments from my interviews and correspondence with practitioners working in a variety of areas, including:

  • astronomy and physics – eg, Stephen Webb, author of «Where is everybody? Seventy-five solutions to the Fermi paradox and the problem of extraterrestrial life» (Springer, 2015)
  • exoplanet and exomoon research – eg, Cecilia Lazzoni, lead author of «The search for disks or planetary objects around directly imaged companions: A candidate around DH Tau B» (arXiv:2007.10097, 2020)
  • neuroscience and philosophy – eg, Daniel C Dennett, author of «From bacteria to Bach and back: The evolution of minds» (WW Norton, 2017)
  • primatology and anthropology – eg, Tetsuro Matsuzawa, editor of «Primate origins of human cognition and behavior» (Springer, 2001)
  • solar eclipses and human culture – eg, Jay Pasachoff, co-author of «Cosmos: The art and science of the Universe» (Reaktion Books, 2019).

Predicting solar flares

Solar flare

“The distribution of solar flares is similar to earthquakes: we have many small solar flares, and a big one is very rare. However, when a big flare occurs, the impact on our economy and society may be enormous. Satellites may be damaged, and the electrical power grid may be damaged over a very wide area. The only way to mitigate such kind of impact is with prediction.”

My latest piece for EarthSky is an interview with Kanya Kusano, director of the Institute for Space-Earth Environmental Research at Nagoya University — his team have come up with a way of predicting solar flares a few hours before they happen.

Kanya Kusano
Credit: Nagoya University

Where did our sense of curiosity come from?

The pump of curiosity in I-M

My recent article for I-M on solar eclipses and the Fermi paradox is now available online.

As Daniel C Dennett, a philosopher and cognitive scientist, has observed, searching for explanations is a central feature of our species. Where does our sense of curiosity come from? As an exercise in fun speculation, I propose it could have been influenced by two rare-earth factors.

The (extremely tentative) idea is that solar eclipses may have acted as a ‘pump of curiosity’ for early humans.

We can safely say that eclipses are not rare in the universe. But the perfect solar eclipses we experience on earth, where the moon and sun combine in spectacular fashion every couple of centuries or so, may be exceptionally rare. Even if these eclipses are one among many factors that led to the development of curiosity, it means that a key human trait is partly a consequence of two things that are nothing more than coincidences: the ratio of the moon’s and the sun’s diameters is the same as the ratio of their distances, and the moon’s orbit is tilted.

I’m currently working on a paper about the pump of curiosity, which I’m hoping to present at the International Astronomical Union Symposium 367 later this year. As part of my research, I’m grateful to a number of people who have generously shared their knowledge and expertise with me, including Cecilia Lazzoni, who might have found our first exomoon; Tetsuro Matsuzawa, who studies chimpanzees and the evolutionary origins of human behaviour; and Jay Pasachoff, author of many fascinating papers and books on how eclipses and astronomy have inspired human culture.

The dog days of summer

The hottest days of summer are known as the dog days. There’s a fun bit of astronomy behind this expression: it’s the time of year when Sirius — also known as the dog star — rises just before the sun.

The August pre-dawn sky, with Sirius rising in the east just ahead of the sun. In 2020, Venus is also getting in on the act…
(Night Sky Map from

The dog star, which faithfully follows the hunter Orion across the sky, is easily our brightest star. It’s so bright, in fact, that the ancient Greeks believed it added to the heat of summer by rising at the same time as the sun. Hence, the dog days of summer.

The pump of curiosity

The summer 2020 issue of I-M Intelligent Magazine

I-M Summer 2020 cover

… includes “an exercise in fun speculation” by me on a potential link between solar eclipses and the Fermi paradox.

I-M VolXIII The pump of curiosity

According to the Copernican principle, there is nothing special about the earth’s place in the universe. Except for the awkward fact that — on current evidence — it’s the only place in the universe to have produced an intelligent and curious species capable of reaching beyond its home planet. In the words of the revered physicist Enrico Fermi: where is everybody?

One solution to the paradox is the rare earth hypothesis. This proposes that the development of complex life on our planet depended upon a labyrinthine set of circumstances that may be vanishingly rare within the universe. By chance, everything about the earth is perfectly balanced in terms of physics (eg, its stable orbit), chemistry (eg, its abundance of metals) and biology (eg, the development of photosynthesis).

In my article for I-M, I’ve taken the rare earth hypothesis one step further:

Does the earth have some unique ingredient that enabled not only the development of complex life, but also the development of intelligent and curious life? After all, it is not biological complexity per se that has led to humans reaching beyond our home planet, or pondering questions such as “where is everybody?”

We live in a world of routine processes: sunrises and sunsets, tides and seasons, predators and prey. (Even earthquakes and volcanoes are routine events in many parts of the world.) But, as the philosopher and cognitive scientist Daniel C Dennett points out, “too much regularity in the selective environment can be a trap.” In an environment where novelty remains below a certain threshold, brains may never receive the stimuli they require to develop human-like levels of curiosity.

A solar eclipse, on the other hand, is anything but routine. There is no warning or preamble; it comes — literally — out of a clear blue sky. Given that even modern-day observers can be overwhelmed by an eclipse, the sun’s sudden disappearance must have created an unparalleled cognitive crisis for our ancestors.

Could total and annular eclipses have acted as a pump of curiosity for early humans? Crucially, they occur at what might be an ideal frequency. If they occurred more frequently, they would have become routine events, and not provided sufficient novelty to stimulate the brain. If they occurred less frequently, they would not have provided enough stimuli to different communities, at different times, to kindle the first flames of human curiosity.

The frequency of solar eclipses — plus the scale of their impact on humans — depends upon two coincidences:

(1) The ratio of the moon’s and the sun’s diameters is the same as the ratio of their distances. This means that, although their actual sizes are two orders of magnitude different, the moon and the sun are the same size in our sky

(2) The moon’s orbit is tilted, which means the earth, moon and sun do not fall into alignment every month.

If such a combination of coincidences is rare within the cosmos, the pump of curiosity could be a solution to the Fermi paradox. Perhaps we are the only species in the universe to ask “where is everybody?”

Note: I’m grateful to Stephen Webb (the author of Where is everybody? Seventy-five solutions to the Fermi paradox and the problem of extraterrestrial life), John G Cramer (who proposed a Fermi paradox solution called the pump of evolution in the 1980s) and Daniel C Dennett (the above quote appeared in From bacteria to Bach and back: The evolution of minds) for their comments on a previous version of this article.