（初めに右欄で英語を１つ選び、続いて選択肢から１つを選んでください。やり直すときは、英語を選び直すことから始めてください。右の［単語帳］を参考にすることもできます。）The Soviets took the first step by creating Sputnik. This satellite was about the size of a basketball. It got its power from a rocket. It orbited Earth for three months. Within weeks, the Soviets launched another satellite into Earth orbit, Sputnik Two. It was much bigger and heavier than Sputnik one. It also carried a passenger: a dog named Laika. Laika orbited Earth for seven days.
The United States joined the space race about three months later. It launched a satellite from Cape Canaveral, in the southeastern state of Florida. This satellite was called Explorer One. It weighed about fourteen kilograms. Explorer One went into a higher orbit than either Sputnik. And its instruments made an important discovery. They found an area of radiation about nine hundred-sixty kilometers above Earth.
The next major space victory belonged to the Soviets. They sent the first man into space. In April, nineteen sixty-one, cosmonaut Yuri Gagarin was launched in the vehicle known as Vostok. He remained in space for less than two hours. He landed safely by parachute near a village in Russia. Less than a month later, the United States sent its first astronaut into space. He was Alan Shepard. Shepard remained in space only about fifteen minutes. He did not go into Earth orbit. That flight came in February, nineteen sixty-two, with John Glenn.
By nineteen sixty-five, the United States and the Soviet Union were experimenting to see if humans could survive outside a spacecraft. In March, Russian cosmonaut Alexei Leonov became the first person to do so. A special rope connected him to the spacecraft. It provided him with oxygen to breathe. And it permitted him to float freely at the other end.
After about ten minutes, Leonov had to return to the spacecraft. He said he regretted the decision. He was having such a good time!
A little more than two months later, an American would walk outside his spacecraft. Astronaut Edward White had a kind of rocket gun. This gave him some control of his movements in space. Like Leonov, White was sorry when he had to return to his spacecraft.