The sun IS the only light. Try to take a walk at night! You will see that in the forest the only light will be the moon. The moon is reflecting light from the sun. So the sun is the only light. If there is no moon you will see nothing. It will be pitch black.

If there is no sun then it will be extremely cold, dark and only death will surround us. There cannot be life without a star (sun) providing warmth and light.

So there cannot be plants without sun and there cannot be light without sun. This is indeed a bible contradiction right from the start. And there are much more if you try to simulate the development of the population of people, the heritage and much more. But this is not that bad for a fairy tale. But if you take it seriously then you should really realize these problems.