A knock was heard in a Chinese spacecraft and no one could explain it.
Chinese taikonaut Yang Liwei was the first man China sent to space on the Shenzhou 5. During his 21-hour mission, he said he heard a strange knocking noise like someone was hitting the body of the spaceship. He tried to figure out what would cause it but found nothing. No solid explanation has been given, but some believe it could have been the spacecraft expanding and contracting in space.