In the moments after the Big Bang, Augustin Louis Cauchy and Leonhard Euler are thrown out of causal contact. Light doesn’t have enough time since the beginning of the universe to travel from Cauchy to Euler. But, as time passes, light can travel further and, eventually, Cauchy and Euler can see each other. The red and blue lines represent Cauchy and Euler’s lines of sight respectively. The y axis is time and the x axis is space.