We all know the famous theory that an asteroid hits the earth and kill the dinosaurs by starting a chain reaction where the dust is all over the atmosphere preventing sunlight to reach plants causing them eventually to die thus causing herbivorous to die thus causing carnivorous to die. But when that happens did a complete darkness fell to the earth or a twilight ? I mean do plants need direct sunlight to make photosynthesis or can they do ok with dim lights too?? isn't visible lights' photons is enough for photosynthesis even scattered from clouds like in an overcast day? do they really "see" the sun directly? does that also mean they need UV too?