2001 Einstein (prov. designation: ) is a bright Hungaria asteroid from the innermost region of the asteroid belt. It was discovered by Swiss astronomer Paul Wild at Zimmerwald Observatory near Bern, Switzerland, on 5 March 1973. The X-type asteroid (Xe) has a rotation period of 5.5 hours and measures approximately in diameter. It is named after physicist Albert Einstein (1879–1955). Orbit and classification Einstein is a member of the Hungaria family, which form the innermost dense concentration of asteroids in the Solar System. It orbits the Sun in the inner main-belt at a distance of 1.7–2.1 AU once every 2 years and 8 months (982 days). Its orbit has an eccentricity of 0.10 and an inclination of 23° with respect to the ecliptic. As no precoveries were taken, the asteroid's observation arc begins with its discovery in 1973. Naming This minor planet was named in honour of the German-born, Swiss–American physicist and Nobelist Albert Einstein (1879–1955). It is considered suitable, that the body discovered at Bern is named after the 1921 Nobel prize for physics laureate, since it was the place where he had his golden years while working as a clerk at the Swiss Patent Office in Bern. He is also honored by the lunar crater Einstein. The official was published by the Minor Planet Center on 15 October 1977 (). Arthur C. Clarke joked in the postscript of his novel 3001: The Final Odyssey that he was hoping asteroid 2001 would be named after him, but it was named for Einstein first. Asteroid 3001 was named 3001 Michelangelo. Clarke was later honoured with asteroid 4923 Clarke, named together with 5020 Asimov. Physical characteristics The Tholen classification, Einstein is an X-type asteroid, while in the SMASS classification, it is an Xe-subtype which transitions from the X-type to the very bright E-type asteroid. Rotation period Several rotational lightcurves for this asteroid were obtained from photometric observations. In December 2004, the first lightcurve by American astronomer Brian Warner at his Palmer Divide Observatory (PDS) in Colorado, gave a rotation period of hours with a brightness variation of in magnitude (). Between 2008 and 2012, three additional lightcurves at the PDS gave an almost identical period of 5.485 hours with an amplitude of 0.67, 0.74 and 1.02, respectively (). Other lightcurves were obtained by Hanuš at the French CNES and other institutions, which gave a period of hours (), and by Italian