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Whether this comes from the contacts slowly squashing and growing or from chemical bonds forming across them is disputed.","posed_since":"","precise":"The static friction coefficient grows as $\\mu_{s}(t) = \\mu_{0} + \\beta \\ln(1 + t / t_{c})$ with $\\beta$ of order 0.01 for rocks, polymers and metals, the basis of rate-and-state friction laws. Determine whether aging comes from creep growth of real contact area, from interfacial chemical bonding (reported in nanoscale silica contacts), or both, and predict $\\beta$ and $t_{c}$ from material properties.","problem_ref":null,"references":"","settled_by":"Simultaneous measurement of real contact area and interfacial bond density during aging for a well-characterized interface, accounting quantitatively for $\\beta$.","status_note":"","title":"Origin of the logarithmic aging of static 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