How dense is a cell?
More than 2,000 years after Archimedes found a way to determine the density of a king’s crown by measuring its mass in two different fluids, MIT scientists have used the same principle to solve an equally vexing puzzle — how to measure the density of a single cell. “Density is such a fundamental, basic property of everything,” says William Grover, a research associate in MIT’s Department of Biological Engineering. “Every cell in your body has a density, and if you can measure it accurately enough, it opens a whole new window on the biology of that cell.” The new method, described in the Proceedings of the National Academy of Sciences the week of June 20, involves measuring the buoyant mass of each cell in two fluids of different densities. Just as measuring the crown’s density helped Archimedes determine whether it was made of pure gold, measuring cell density could allow...