[periodontal]

While theoretically possible, it'll be very difficult to realize physically. If you allow fractal constructions, purely unrectifiable sets can fit the bill. For example, here's an example in 2-dimensional space that casts a solid shadow when the light source is along one axis but not from any other: https://books.google.com/books?id=usjNBQAAQBAJ&lpg=PP1&dq=&p...

[nightcracker]

With millisecond precision I think it's even theoretically impossible as the slits would become so small it destroys the shadow in an effect seen in the double slit experiment.

But that's just a gut feeling.

[Const-me]

You'll have to make 500 meters thick clock, but theoretically it's possible.

[meric]

And practically, too, perhaps not politically or economically possible.