Theory 10: The Dead Cosmonaut

During the 1960s, the Soviet Union and United States raced to become the world leader in space exploration. The winner would be able to claim technological superiority over the other. The Soviet Union had the early edge: In 1957, it launched Sputnik, the first man-made satellite. In 1961, the Soviet Union dealt the American space program another blow when cosmonaut Yuri Gagarin became the first human in space. But, according to the Judica-Cordiglia brothers from Italy, Gagarin wasn't the first.

The brothers set up a listening station in Italy to intercept communication transmissions between ground operations and spacecraft for both American and Soviet missions. Weeks before Gagarin's successful flight, the brothers claimed to have detected and recorded radio transmissions of a cosmonaut slowly dying while adrift in space. The Soviet Union denied the brothers' claim. Supporters of the theory believe the Soviet government hid the cosmonaut's death to preserve the country's reputation as a leader in space exploration. The truth remains a mystery, though the recordings are available online, if you're curious to hear for yourself.

What are some other space conspiracy theories? Keep reading.