Einstein's Blackboard

The lecture in which the blackboard was used was the second of three, delivered at Rhodes House in South Parks Road.

Einstein's visit to give the Rhodes Lectures, and also to receive an honorary Doctor of Science degree from Oxford University on 23 May 1931, was hosted by the physicist Frederick Lindemann.

[9] A summary of all three lectures can be found in the Archives of the Oxford Museum for the History of Science.

[10] The blackboard was rescued with another board by dons (including the chemist E. J. Bowen, zoologist Gavin de Beer, and historian of science Robert Gunther[11][12][3]) and formally donated by the Warden of Rhodes House, Sir Francis James Wylie.

[21][22] Einstein returned to Oxford again in 1932 and 1933 before he settled at Princeton University in the United States for the rest of his life.

In 2013, it was pointed out[16][17][24] that the equations on the Oxford blackboard had been taken directly from a key paper on relativistic cosmology written by Einstein in April 1931 and published in the Proceedings of the Royal Prussian Academy of Science on 9 May that year.

[15] The paper, known as the Friedmann–Einstein universe, is of historic significance because it constituted the first scientific publication in which Einstein embraced the possibility of a cosmos of time-varying radius.

In the paper,[15] Einstein adopts Alexander Friedmann's 1922 analysis[25] of relativistic models of a universe of time-varying radius and positive curvature, but sets the cosmological constant to zero, declaring it redundant, predicting a universe that expands and contracts over time.

With the use of Edwin Hubble's observations[26] of a linear redshift/distance relation for the spiral nebulae, Einstein extracts from his model estimates of ρ ~ 10−26 g/cm3, P ~ 108 light-years and t ~ 1010 years for the density of matter, the radius of the cosmos and the timespan of the cosmic expansion respectively.

It has also been noted[16][24] that the numerical estimates of cosmic parameters in Einstein's 1931 paper – and on the blackboard – contain a systematic error.

Analysis of the 1931 paper shows that, given the contemporaneous Hubble constant of 500 km s−1Mpc−1, Einstein's estimates of cosmic density, radius and timespan should have been ρ ~ 10−28 g/cm3, P ~ 108 light-years and t ~ 109 years respectively.

One line on the blackboard, not included in the published paper, makes the nature of Einstein's error clear.

[28] Einleintende Bemerkung Begriff des Körpers Räumliche Beziehungen der Körper Raumbegriff in der Mathematik (Deskartes) Newtons Raum Feldbegriff (Faraday Maxwells Lorentz) Spezielle Relativitätstheorie Allgemeine R.Th.