Researchers at Penn State use this apparatus to create an array of ultra-cold one-dimensional gases made up of atoms. These atoms are bosons, one of two classes into which all particles can be sorted. Generally, bosons and fermions, the other class of particle, behave quite differently. However, when the internal interactions among bosons in a one-dimensional gas are very strong, their spatial distribution is the same as non-interacting fermions. The researchers have now shown that when the gases are allowed to expand while still confined in one dimension, their velocity distribution also becomes the same as a gas of non-interacting fermions.