Academy symposium

Rhythms and a-rhythms in the Sky

16 April 2019 from 19:00 to 21:00 hrs
Pakhuis de Zwijger, IJzaal, Piet Heinkade 179, 1019 HC Amsterdam
020 551 0859
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This Academy symposium transports us to Io, Europa, Ganymedes and Callisto, the four moons that 'dance' around Jupiter. The form of our universe and stability of our solar system will also be addressed.


Henk Broer, Professor emeritus of Dynamical Systems, Bernoulli Institute, University of Groningen – A Galilean dance 

In 1610 Galileo Galileī reported on the four moons of Jupiter: Io, Europa, Ganymedes and Callisto. Around 1800 Pierre Simon de Laplace suggested these moons do so in a kind of dance: Europa’s orbital period is roughly twice that of Io, and Ganymedes has an orbital period that is approximately twice that of of Europa. We call this a 1:2:4 resonance. How can this be placed in a Newtonian context. We are following in the footsteps of Willem de Sitter who launched a debate about this subject around 1900. 

Gert Vegter, Professor of Mathematics, Bernoulli Institute, University of Groningen – Is the universe flat? 

For decades, cosmologists have wondered whether our universe is flat or curved, whether it is bounded, and how measurements can contribute to resolving these issues. Non-euclidean geometry, developed by Gauss, Bolyai and Lobachevsky at the beginning of the 19th century, and its further development by Riemann, Beltrami and Poincaré, provide mathematical tools to approach this problem. Data from satellite missions WMAP (2001-2010) and Planck (2009-2013) support the hypothesis that our universe is flat. Does this also provide conclusive evidence regarding the global shape of our universe? 

Jacques Laskar, Professor of Astronomy, CNRS, Observatoire de Paris, Académie des Sciences – Is the Solar system stable? 

Since Newton questioned the stability of the solar system, astronomers and mathematicians have sought to demonstrate that it is, in fact, stable. Thanks to the use of computers and the numerical simulations performed in recent decades, we now know that the orbital motion of the planets in the solar system is chaotic, which prohibits any accurate prediction of their movement beyond about 60 million years. Recent numerical simulations show that in the longer term, planetary collisions or ejections are even possible. 

Moderator of the symposium is Frank den Hollander, emeritus Professor of Mathematics, Leiden University.

The symposium will be conducted in English.