Achim Leistner

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Silicon sphere used in the Avogadro project being inspected by Achim Leistner.
Achim Leistner
Silicon sphere for Avogadro project.jpg
Achim Leistner at the Australian Centre for Precision Optics, holding a 1 kg, single-crystal silicon sphere for the Avogadro project.
Born20th century
Known forAvogadro project
Scientific career

Achim Leistner is an Australian optician of German origin.[1] During his retirement, he was asked to join the Avogadro project to craft a silicon sphere with high smoothness, as automated machining does not match his precision.[2]

In addition to precision instruments, Leistner uses his hands to feel for irregularities in the roundness of the sphere.[1] The research team has called his extraordinary sense of touch "atomic feeling".[3] As a result the sphere is the roundest man-made object ever manufactured in the world. If the sphere was scaled to the size of Earth, it would have a high point of only 2.4 metres above "sea level".[Note 1]

Leistner holds certificates in precision optics, geometrical optics, optical design drawing, and mathematics from Optic Carl Zeiss Jena Technical College. He has served as a member of the Australian Optical Society and on international conference working committees for SPIE and the Optical Society of America.[4]

See also[edit]


  1. ^ a b Keats, Jonathon (27 September 2011). "The Search for a More Perfect Kilogram". Wired. Retrieved 16 June 2015.
  2. ^ Powell, Devin (1 July 2008). "Roundest Objects in the World Created". New Scientist. Retrieved 16 June 2015.
  3. ^ Episode 2: Mass and Moles. Precision: The Measure of All Things. BBC Four. 4 July 2014. 48.4 minutes in.
  4. ^ Stanford Who’s Who: Achim Leistner. Accessed June 11, 2013.


  1. ^ The sphere shown in the photographs has an out-of-roundness value (peak to valley on the radius) of 50 nm. According to ACPO, they improved on that with an out-of-roundness of 35 nm. On the 93.6 mm diameter sphere, an out-of-roundness of 35 nm (deviation of ±17.5 nm from the average) is a fractional roundness (∆r/r) = 3.7×10−7. Scaled to the size of Earth, this is equivalent to a maximum deviation from sea level of only 2.4 m. The roundness of that ACPO sphere is exceeded only by two of the four fused-quartz gyroscope rotors flown on Gravity Probe B, which were manufactured in the late 1990s and given their final figure at the W.W. Hansen Experimental Physics Lab at Stanford University. Particularly, "Gyro 4" is recorded in the Guinness database of world records (their database, not in their book) as the world's roundest man-made object. According to a published report (221 kB PDF, here Archived 2008-02-27 at the Wayback Machine ) and the GP‑B public affairs coordinator at Stanford University, of the four gyroscopes onboard the probe, Gyro 4 has a maximum surface undulation from a perfect sphere of 3.4 ±0.4 nm on the 38.1 mm diameter sphere, which is a r/r = 1.8×10−7. Scaled to the size of Earth, this is equivalent to a deviation the size of North America rising slowly up out of the sea (in molecular-layer terraces 11.9 cm high), reaching a maximum elevation of 1.14 ±0.13 m in Nebraska, and then gradually sloping back down to sea level on the other side of the continent.