The dogs have been at the window again.
It must be quite some operation — jump onto the chair at the desk (which certainly spins with them aboard), step onto the desk, clamber onto the flatbed scanner that sits near the window, and finally gaze out the window as they wait for the return of the mommy.
I know this happened from this evidence: the power button was glowing blue, and my tower of books was knocked askew. It is a fact that I never leave the blue button on. And I do not knock my books askew, least of all Foundations of Theoretical Mechanics, which was particularly misplaced.
From this evidence I know this to be true: the dogs have been at the window again.