One of the strangest features of our universe may be entities that scientists call "virtual particles," fundamental particles that apparently come into existence from nothing for a brief period of time, then disappear. When I talk about virtual particles I usually get questions like: "Do these virtual particles really come into existence from nothing? How do you know they exist if they can never be seen? Do they do anything?" Because these virtual particles are a huge part of my scientific life, and because they invoke so many questions, I'm going to discuss what they are, their importance in our understanding of nature, and even some remarkable fine-tuning noticeable in their behavior.
