Galileo's Dream by Kim Stanley Robinson

Science Fiction is not my thing but one of my book groups had this on the list.  I warned them off as a final choice but was compelled to finish nonetheless.  Galileo Galili - brilliant mathematician but annoying, selfish, egotistical man - devout Catholic and heretic.  So one day a mysterious man named Cartophilus arrives from one of the moons of Jupiter and provides the intellectual push that leads to the perfection of the telescope that leads Galileo to the absolute proof that the Earth revolves around the sun which Galileo denies to save himself from the Inquisition.  We mostly all know that - except the Jupiter part.  Through the use of the "entangler", Galileo makes many trips through time and space to the moons of Jupiter and meets a whole host of future humans.  Ganymede tries to convince Galileo that he must be martyred to save science from the power of the church.  Hera disagrees although she argues that all possibilities exist together so he will both burn and not burn, although now that he has asked to see those "times" he will bear the memory of both.  And so it goes back and forth with many interesting philosophical arguments and lots of 17th century history.  The last few pages offer an opportunity to think again about the power of scientific discovery and the weakness of humans to control it.  All the good parts would have taken up way less than 515 pages but if you like science fiction....