Simulated near-weightless conditions reduced human sperm’s navigational abilities Male reproductive cells, sperm, might struggle to reach and fertilize female reproductive cells, eggs, in microgravity, according to a new study. Sperm and Embryo Biology Laboratory, Adelaide University Floating in near-weightless conditions can be disorienting for even the most experienced astronauts. Male reproductive cells—sperm—also seem to get confused in simulated microgravity, which has implications for human reproduction in space, according to a study published March 26 in the journal  Communications Biology . Near-weightlessness “causes [sperm] to flip around, to go upside down.… They don’t really know which way is up or down,”  Nicole McPherson , a study co-author and a biologist at Adelaide University in Australia, tells the  Guardian ’s Tory Shepherd.…