معنی عبارت widely held but false idea در جمله زیر

It's often been said that there are a similar number of neurons in the brain as there are stars in the Milky Way. But this is probably a ‘myth', a widely held but false idea, as scientists estimate that there are between 200 and 400 billion stars in the Milky Way.

ممنون میشم معنی این یک خط رو بگید

widely held but false idea