A comparison of beeps from Sputnik 2 (top) and Sputnik 1 (bottom), shown in oscilloscope readings. Pattern differences may be due to differences in coded data. Sputnik 1 was the first artificial Earth satellite. It was a shiny metal sphere, 23 inches in diameter, with four external radio antennae to broadcast radio pulses. The Soviet Union launched it into an elliptical low Earth orbit on 4 October 1957. Sputnik 2 was the second spacecraft launched into Earth orbit, on November 3, 1957, and the first to carry a living animal, a dog named Laika.