<human>: What are some good physics questions that I could ask my friends?
<bot>: 
1. What is the speed of light?
2. How do you know the speed of light is constant?
3. Why does the speed of light have to be the same for all observers?
4. Is there a way to travel faster than the speed of light?
5. Can you explain how gravity works?
6. How can you prove that time travel is impossible?
7. How do you know that the universe is expanding?
8. How did the Big Bang happen?
9. How do you know that dark energy exists?