Planck, in 1909, compared the implications of the modern relativity principle — he particularly referred to the relativity of time – with the revolution by the Copernican system. Poincaré made a similar analogy in 1905. An important factor in the adoption of special relativity by physicists was its development by Poincaré and Minkowski into a spacetime theory. Consequently, by about 1911, most theoretical physicists accepted special relativity. In 1912 Wilhelm Wien recommended both Lorentz (for the mathematical framework) and Einstein (for reducing it to a simple principle) for the Nobel Prize in Physics – although it was decided by the Nobel committee not to award the prize for special relativity. Only a minority of theoretical physicists such as Abraham, Lorentz, Poincaré, or Langevin still believed in the existence of an aether. Einstein later (1918–1920) qualified his position by arguing that one can speak about a relativistic aether, but the "idea of motion" cannot be applied to it. Lorentz and Poincaré had always argued that motion through the aether was undetectable. Einstein used the expression "special theory of relativity" in 1915, to distinguish it from general relativity.