Explain the concept of gravitational waves and their detection. Your response should contain at least 2 placeholders represented by square brackets, such as [address]. Your answer must contain exactly 3 bullet points. Use the markdown bullet points such as: * This is point 1. In your response, the word "gravitational" should appear at least 3 times. Your entire response should be in English, and in all lowercase letters. no capital letters are allowed. highlight at least 2 sections in your answer with markdown, i.e. *highlighted section*.
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