Hi everybody How are you? I am a Vietnamese student. I hope to find this forum because I wanna development my lovely subject "physics." Here are some question: 1. Why the sky is blue, and why the ocean is blue, too. 2. Are there a double rainbow, and how can we see a full circle rainbow Why can't you ever find the end of the rainbow. 3. What is blue moon? 4. How can you distinguish left hand circularly polarized light and right hand circularly polarized light. thanks a lot !