The Shaw Prize in Astronomy 2025 is awarded in equal shares to John Richard Bond, Professor of the Canadian Institute for Theoretical Astrophysics and University Professor at the University of Toronto, Canada and George Efstathiou, Professor of Astrophysics at the University of Cambridge, UK for their pioneering research in cosmology, in particular for their studies of fluctuations in the cosmic microwave background. Their predictions have been verified by an armada of ground-, balloon- and space-based instruments, leading to precise determinations of the age, geometry, and mass-energy content of the universe.

Cosmology has undergone a revolution in the past two decades, driven mainly by increasingly precise measurements of the angular power spectrum of fluctuations in the temperature and polarization fields of the cosmic microwave background, a relic of the early universe, most notably by NASA’s Wilkinson Microwave Anisotropy Probe spacecraft (2001–2010) and the European Space Agency’s Planck spacecraft (2009–2013). These fluctuations are small — the strength of the background radiation is the same in all directions to better than 0.01% and it is only slightly polarized — but they offer a glimpse of the universe when it was very young, a test of many aspects of fundamental physics, insights into the nature of dark matter and dark energy, and measurements of many fundamental cosmological parameters with accuracies unimaginable to cosmologists a few decades ago.

Although many researchers contributed to the development of the theoretical framework that governs the behaviour of the cosmic microwave background, Bond and Efstathiou emphasised the importance of the background as a cosmological probe and took the crucial step of making precise predictions for what can be learned from specific models of the history and the composition of the mass and energy in the universe. Modern numerical codes used to interpret the experimental results are based almost entirely on the physics developed by Bond and Efstathiou. Their work exemplifies one of the rare cases in astrophysics where later experimental studies accurately confirmed unambiguous, powerful theoretical predictions. The interpretation of these experiments through Bond and Efstathiou’s theoretical models shows that the spatial geometry of the observable universe is nearly flat, and yields the age of the universe with a precision of 0.15%, the rate of expansion of the universe with a precision of 0.5%, the fraction of the critical density arising from dark energy to better than 1%, and so on. The measurements also strongly constrain theories of the early universe that might have provided the initial “seed” for all the cosmic structure we see today, and the nature of the dark matter and dark energy that dominate the mass-energy content of the universe.

Both Bond and Efstathiou have worked closely with experimentalists to bring their predictions to the test: they have been heavily involved in the analysis of cosmic microwave background data arising from a wide variety of experiments of growing sophistication and accuracy.

The Shaw Prize is also intended to recognise Bond and Efstathiou’s other contributions to cosmology. Bond and his collaborators introduced the concept of the “cosmic web”, the network of filaments and sheets that connects individual galaxies to larger structures such as groups and clusters of galaxies, developed the mathematical theory of the statistics of peaks of Gaussian random fields that underlies our understanding of clustering of galaxies in the universe, and made fundamental contributions to our understanding of primordial non-Gaussianity arising during the inflationary phase of the early universe. Efstathiou has been one of the leaders in the study of the clustering and evolution of galaxies as revealed by ever larger and deeper galaxy surveys, was an early advocate for a universe whose mass-energy was dominated by dark energy, and with his collaborators developed N-body simulations as a powerful tool for studying large-scale structure in the universe. He also played a leading role in the analysis of data from the Planck spacecraft. More generally, their research touches on almost every aspect of modern cosmology and has made fundamental contributions to the establishment of the standard cosmological model.

Astronomy Selection Committee
The Shaw Prize

27 May 2025, Hong Kong