  When two or more objects move relative to one another in vacuum, they
experience a drag force which, at zero temperature, usually goes under the name
of quantum friction. This contactless non-conservative interaction is mediated
by the fluctuations of the material-modified quantum electrodynamic vacuum and,
hence, is purely quantum in nature. Numerous investigations have revealed the
richness of the mechanisms at work, thereby stimulating novel theoretical and
experimental approaches and identifying challenges as well as opportunities. In
this article, we provide an overview of the physics surrounding quantum
friction and a perspective on recent developments.
