robtillaart:
Sunlight does not need to be strong to get shadows, it should just not be diffused by clouds or fog or smog.
You can tell that from experience, but how do you actually measure if shadows will or will not be cast outdoors?
I have done quite a bit of searching but not found an answer.
Also some websites calculate that a 1m high stick can cast a shadow for about 95m and that a 100m hight column can cast a shadow for 9.5km. I can see that from trigonometry that might in theory be the case, but in reality the shadow is not going to be visible at that distance. So can you know if there will be a visible shadow next to an object and how far can the visible shadow extend?