  In June 1930 Einstein visited Cambridge where he stayed with Eddington who
had just shown that Einstein's supposedly static universe of 1917 was not
stable. This forced Einstein to rethink his cosmology. He spent January and
February 1931 at Pasadena. There, he discussed cosmology intensely with Tolman,
conscious that he had to replace his original model of 1917. However, at the
end of February he still had not made up his mind about an alternative. The
Albert Einstein Archives of Jerusalem (AEA) hold an undated draft, handwritten
by Einstein, which I date to the beginning of January 1931. In this draft
Einstein hopes to have found a solution to the cosmological problem: a
stationary, dynamic universe in expansion. His model was stationary because
particles leaving a given volume were replaced by particles created out of the
vacuum, anticipating an idea of Bondi, Gold and Hoyle published in 1948. He saw
the cosmological term as energy reservoir. However, he realised that his
calculations contained a numerical error. When the error was corrected his
steady-state-model collapsed.
