A key component of a future gravitational wave observatory passed a series of tests with flying colors,while coming closer to experiencing true free fall than any other human-made thing ever has. At the heart of the experiment is a two-kilogram cube of a high-purity gold and platinum alloy that is currently sailing through space nearly completely free of any force other than gravity. The Laser Interferometer Space Antenna (LISA) Pathfinder mission is a European Space Agency (ESA) project that proves in principle that a formation of such cubes flown in space will be able to operate as a space-based gravitational wave observatory, which will be able to detect signals from supermassive black gap collisions and other violent events that would be impossible to see on soil.
Source: phys.org