“Discover Science” is a new science entertainment series that makes science understandable by showing it in action. In this episode, the program asks the question: How fast does sound travel? 86 people make a straight line of 1.7 km in length. Each person is given a flag and raises it when they hear the sound from the 0km point. Different sounds and different level of sounds are used to compare the difference in the speed. The experiment also succeeds in visualizing the invisible, the speed of sound.