A Brief History of Time – Extended Version

“We go about our daily lives understanding almost
nothing of the world. We give little thought to the
machinery that generates the sunlight that makes life
possible, to the gravity that glues us to an Earth that
would otherwise send us spinning off into space, or to
the atoms of which we are made and on whose stability
we fundamentally depend. Except for children (who
don’t know enough not to ask the important questions),
few of us spend much time wondering why nature is the
way it is; where the cosmos came from, or whether it is
always here; if time will one day flow backward and
effects precede causes; or whether there are ultimate
limits to what humans can know.”

-Carl Sagan
From an introduction to A Brief History of Time
By Stephen Hawking