In another experiment, Tobias "et al." (1971) exposed two people to a beam composed of neutrons ranging from 20 to 640 MeV after they were fully dark-adapted. One observer, who was given four exposures ranging in duration from one to 3.5 seconds, observed "pinpoint" flashes. The observer described them as being similar to "luminous balls seen in fireworks, with initial tails fuzzy and heads like tiny stars". The other observer who was given one exposure lasting three seconds long, reported seeing 25 to 50 "bright discrete light, he described as stars, blue-white in color, coming towards him".