Einstein wasn&#x27;t sure at first. It was Feynman who introduced the thought experiment that settled the debate in the physics community:<p><a href="https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Sticky_bead_argument" rel="nofollow">https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Sticky_bead_argument</a>