Sunlight Questions

• How does a microwave oven heat up food even though it emits no thermal radiation?
• How does diffraction make a tree's shadow blurry?
• Light has no mass so it also has no energy according to Einstein, but how can sunlight warm the earth without energy?
• What is the color of the sun?
• Why doesn't the outside world appear blue even though so much light comes from the blue sky?
• Why is the sun cold in the winter?