Another problem of minimality also remains unsolved—to wit, what is the smallest number of digits a puzzle maker can place in a starting grid and still guarantee a unique solution?
While lots of creators were focused on entertainment, others were focused on criminal justice reform, on wrongful convictions, on bringing attention to long-cold, unsolved cases.
Your brain records everything you see and when you sleep, it builds logical chains for each of your unsolved problems, hence the phrase the night brings counsel.
Experimental measurements show Kolmogorov was remarkably close to the way turbulent flow works, although a complete description of turbulence remains one of the unsolved problems in physics.
Complex, unsolved questions include how climate warming affects forest health; how it affects the performance of forests as a carbon sink; and whether it alters the ecosystem services that forests provide.