Lithium be cut with a knife. When cut, it possesses a silvery-white color that quickly changes to gray as it oxidizes to lithium oxide. While it has one of the lowest melting points among all metals (180 °C), it has the highest melting and boiling points of the alkali metals. Lithium has a very low density (0.534 g/cm), comparable with pine wood. It is the least dense of all elements that are solids at room temperature; the next lightest solid element (potassium, at 0.862 g/cm) is more than 60% denser. Furthermore, apart from helium and hydrogen, it is less dense than
Finite element machine (NASA TM 84514). Based on the Finite Element Machine's success in demonstrating Parallel Computing viability, (alongside ILLIAC IV and Goodyear MPP), commercial parallel computers soon were sold. NASA Langley subsequently purchased a Flex/32 Multicomputer (and later Intel iPSC and Intel Paragon) to continue parallel finite element algorithm R&D. In 1989, the parallel equation solver code, first prototyped on FEM, and tested on FLEX was ported to NASA's first Cray YMP via Force (Fortran for Concurrent Execution) to reduce the structural analysis computation time for the space shuttle Challenger Solid Rocket Booster resdesign with 54,870 equations from 14 hours to 6