  Who discovered the expanding universe? Was it Hubble, or Lema\^itre, or was
it just the end result of a long series of investigations? In this article we
summarise the main steps and contributions that led to one of the most exciting
discoveries ever made, of which Lema\^itre was the principal architect. In 1927
he combined his dynamical solutions of the Einstein equations with astronomical
observations to conclude that the universe is expanding. He derived the linear
velocity-distance relationship and calculated the first numerical value of what
later was called the "Hubble constant". His discovery paper of 1927 was written
in French and in 1931 it was translated into English and published in Monthly
Notices. However, the translation omits the section where Lema\^itre computed
the "Hubble constant". Why was that done, and who was responsible? We do not
speculate on this question, but present in a very condensed way the facts along
the path of discovery. The documented details from primary sources can be found
in our book "Discovering the Expanding Universe".
