The dub ( diastolic sound) occurs when part of the heart relaxes and the aortic and pulmonary valves close. A heart murmur is an extra sound, such as a whooshing, caused by irregular blood flow through the heart valves. Heart murmurs can be heard through a stethoscope and are often detected during routine physical examinations. If your heart murmur is related to more serious problems, your doctor may refer you to a cardiologist (heart specialist).
On July 20, 1969, Apollo 11 astronaut Neil Armstrong became the first man to walk on the moon. Armstrong is pictured here, shortly after collecting a sample of lunar dust and rocks. At his feet is the handle for the sample collection tool.
The Soviet Union is first to the Moon. Richard Cavendish explains how, on September 12th, 1959, the Soviet Union launched Luna 2, the first spacecraft to successfully reach the Moon. The space race between the United States and the Soviet Union brought an engaging touch of science fiction to the Cold War.