Knowing the precise forces required to move atoms “helps us to understand what is possible and what is not possible,” said Andreas J. Heinrich, a physicist at Almaden and an author of the new Science paper. “It’s a stepping stone for us, but it’s by no means the end goal.”

Image The tuning fork in the atomic force microscope, which measures the interaction between the tip and the atom. Credit... IBM

In the experiment, Dr. Heinrich and his collaborators at Almaden and the University of Regensburg in Germany used the sharp tip of an atomic force microscope to push a single atom. To measure the force, the tip was attached to a small tuning fork, the same kind that is found in a quartz wristwatch. In fact, in the first prototype, Franz J. Giessibl, a scientist at Regensburg who was a pioneer in the use of atomic force microscopes, bought an inexpensive watch and pulled out the quartz tuning fork for use in the experiment.

The tip vibrates 20,000 times a second until it comes into contact with an atom. As the tip pushes, the tuning fork bends, like a diving board, and the vibration frequency dips.

A single atom does not roll, and even a perfectly smooth surface is not perfectly smooth. Instead, the atom rests in small indentations in the lattice, in effect like an egg in an egg carton. The resistance  what becomes friction when multiplied by millions and billions of atoms  comes from the energy needed to rearrange the bonds between the cobalt atom and surface.

When the tip pushes hard enough, the atom hops, almost instantaneously to the next indentation. “It’s not smooth,” said Markus Ternes, another Almaden scientist working on the research. “It’s faster than we can detect.”