Gilbert Collins and colleagues used the NOVA laser at the Lawrence Livermore National Laboratory in California to carry out the experiments (Science 281 1178). The deuterium was placed in a small copper cell with a plunger fitted at one end. When the laser hits the plunger, it sends a shock wave through the chamber. By shining a beam of X-rays through two windows in the cell, Collins and co-workers were able to measure the shock speed - and hence the pressure and density of the deuterium - in the few nanoseconds before the sample flew apart. Another laser measures the reflectivity of the deuterium, which increases when the molecular fluid changes into a metallic fluid.

Collins and colleagues discovered that deuterium compresses more easily than predicted by theory. "A lot of their data disagrees with every [theoretical] model available" writes David Ceperley, a theorist at the University of Illinois, in an accompanying article. The data might be able to explain why Saturn is so warm, and why Jupiter has such a strong magnetic field.