THE tale of Galileo dropping two cannonballs of unequal weights from the Leaning Tower of Pisa laid the cornerstone for a theory that explains the way matter behaves in a gravitational field. Now a test on a far grander scale, involving stars and galaxies, could determine how the unseen mass that makes up dark matter behaves under the influence of the unseen field known as dark energy.
Mike Kesden of the Canadian Institute for Theoretical Astrophysics in Toronto has a model for how the dark matter thought to make up 90 per cent of the mass of a galaxy interacts…
