Tardigrade Tardigrades , also called water bears , space bears , moss - piglets , flec - mites , teeneylies , or weelocks , were microscopic creatures . ( PROSE : " The Short Briefing Sergeant ' s Tale " ) They lived in the air and in the water , capable of surviving the coldest temperatures and living almost forever . ( PROSE : " Normality " ) Each was half a millimetre long , had eight podgy legs , and fed on lichen and moss . A tardigrade was made of only 40 , 000 cells , which helped it survive in environments ranging from within one degree of the limits of normal entropy matter , to upwards of 1 . 5 times the boiling point of hydrogen oxide . They were also effective indestructible , surviving supernova e , gamma ray bursts , and large asteroid impacts . They could live without food for thirty years and still be able to reproduce in only fourteen days after rehydration . ( PROSE : " The Short Briefing Sergeant ' s Tale " ) According to the Sergeant - instructor , the tardigrades first appeared millions of years before the Great Houses , and during the anchoring of the thread they were embedded into the Web . ( PROSE : " The Short Briefing Sergeant ' s Tale " ) They lived not only on Earth ( PROSE : " Normality " ) but also on millions of other worlds , with a total population of a septillion septillion . Wherever life evolved , so would the tardigrade , as its form was directly implied in the Hausanthropic equation s . ( PROSE : " The Short Briefing Sergeant ' s Tale " ) The Eleventh Doctor compared the space - dwelling Tonnchenform to the tardigrades . ( PROSE : " Normality " ) The Sergeant - instructor explained that , despite their limited size , tardigrades ' brains had three lobes : one maintained bodily functions ; another linked each tardigrade ' s mind into a great collective psyche , with a debundled processing capacity large enough to run multiple nested simulations of the entire universe ; the third and final lobe performing transference calculus and solving incomprehensively complex logomantic equation s to edit reality , though the final purpose of their calculations was unclear . This made the tardigrades the Enemy or , at best , an Enemy tool . The Great Houses isolated worlds of tardigrades in timestop and built engines to replicate their brains neuron by neuron , but they could not find a way to communicate with the tardigrades . The Houses were unsure whether tardigrades were even conscious or if they even knew the forces they had set into motion , but the War - strategist s agreed that , when the tardigrades ' thoughts reached maximum observer criticality at some unpredictable time in the future , they would take control of the fixed point s and redefine history in their own image . This terrified the Conquistador , but they were uncertain if the Sergeant - instructor was telling the truth . ( PROSE : " The Short Briefing Sergeant ' s Tale " ) To explain tardigrades to Clara Oswald , the Eleventh Doctor got her to stare at the TARDIS column for ten seconds , then shut her eyes , count to five , and open them again . All she saw were those " tiny little things that float in front of your eye s when you look at a bright light " . She hypothesised that this was just fluid being reflected back , but the Doctor corrected her . In 2013 , Clara taught about tardigrades to her Coal Hill School English class , including Courtney Woods , Joshua Adams , Zehra Jalindra , Mackenzie Brooks , Liam Mannings , Chiana Holden , Tommy Breare , Kelly Squires and Sam Kaye - Jones . They went outdoors for this lesson . She gave her students much the same instructions as the Doctor did her , except to look at the sky . ( PROSE : " Normality " )