The sun would not radiate if it were alone in space and no other bodies could absorb its radiation. … If for example I observed through my telescope yesterday evening that star … 100 light years away, then not only did I know that the light which it allowed to reach my eye was emitted 100 years ago, but also the star or individual atoms of it knew already 100 years ago that I, who then did not even exist, would view it yesterday evening at such and such a time.
– H. Tetrode quoted in Genius: Richard Feynman and Modern Physics, James Gleick, Abacus, London, 2006, p. 120
