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Comment by terminalbraid | Hacker News Reader

No. Consider two objects, two light sources, and an ant.

An ant outside any shadow can see both light sources.

An ant in a non-overlapping shadow cast from one object will have one light source blocked out but the other light source will be visible to the ant.

An ant in overlapping shadows from two objects will have both light sources blocked out. (Geometrically in this case it is necessary the overlapping shadows be cast from two separated points each from distinct light sources)

When one light source is visible to the ant that area must be lighter than when no sources are visible. This is the scenario presented by the OP.

edit: Since people seem to not believe this you can find a representation in part E in this diagram

https://i.imgur.com/r6x6QPQ.jpeg

and a photograph of this nicely done with colored lights here

https://i.imgur.com/NUlywpb.jpeg

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We aren’t questioning your logic, just your reading comprehension in this case :) OP was correctly describing the case where both lights are blocked from view.

Just to summarize, because someone is missing something:

otikik pointed out a case of multiple light sources where overlapping shadows will be darker (otikik is correct)

fregus says "that's not correct" and argues a true case (shadows from one light source will not be darker) which is a bad argument because it tries to overgeneralize. The case from fregus is for the same light source and they cannot use this to argue otikik is incorrect because otikik's argument explicitly requires multiple light sources.

I point out, responding to fregus, how otikik is correct and how you need to consider multiple sources as well as including examples and physical evidence.

You question my reading comprehension for some reason

> ... when any two shadows, one from each light, intersect. that's because if it is in shadow from light A and in shadow from light B ...

They actually reference two light sources TWICE in their comment: ("any two shadows, one from each light", "from light A and in shadow from light B"). Hence the question of reading comprehension.

Fregus point is that otikik seems to suggest that the darkest shadow will be the combination of all 6 shadows; thats obviously wrong, any shadow blocked from both lights will be as dark as any other shadow blocked from both lights, no matter the amount of "overlapping" shadows. You then respond to Fregus by unnecesarily just explaining shadows again, hence the reading comprehension comment.

Let’s all write long explanations of one another’s long explanations, then the people who couldn’t comprehend the simple point in the first place will definitely understand

I'm not talking to "people", I'm writing a specific response to a specific person. Do try to keep up

> when any two shadows, one from each light

@fregus explicitly described a scene with two light sources. Thus the question about your reading comprehension.

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