When Albert Einstein shook hands with Max Planck, what type of...

When two objects come into contact, the force exerted between them is a contact force, such as normal force or friction.

At the microscopic level, these contact forces arise due to the electromagnetic interactions between the electrons and protons of the atoms making up the interacting surfaces.

Gravitational force between the hands is negligible due to their small masses.

Strong nuclear and weak forces are short-range forces that operate only within the atomic nucleus and do not play a role in macroscopic contact.

Therefore, the force exerted during a handshake is fundamentally electromagnetic in nature.