    Senterice‘1:'| ‘drédimt. that ‘an aligir civilization  from another galaxy shot. microbes ints space  billions oF years-ago; which started life on’ earth.  Isthis possiblé?, :    ‘Sentence 2: |. heard thata steam engine: was  invented in Ancient Greek, what wotild happen if  thig;had started‘a revolution.2,000 years ago?