Google Doodle today and YouTube is celebrating the 50th Anniversary of the first human space flight. In order to celebrate this they have changed both the logo of Google and YouTube specially to celebrate this day.
Yuri Gagarin or Yuri Alekseyevich Gagari is a soviet pilot and cosmonaut. The Soviet Union and the United States at that time were competing against each other for their space program. In this competition the Soviets won since Gagarin became the first human to journey into outer space when his Vostok spacecraft completed an orbit of the Earth on April 12, 1961.
Incidentally, it was the first and only spaceflight because later on his Soyuz 1 mission will end up in a fatal crash. His life was in fact ended by a crash of a Mig 15 training jet he was piloting, when it crashed in 1968.