52 min
What Is a Planet? The History of the Twentieth Century
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- History
Ever since the eighth planet, Neptune, was discovered in 1846, some astronomers searched for a hypothetical ninth planet. Clyde Tombaugh discovered the ninth planet in 1930. Or did he?
Ever since the eighth planet, Neptune, was discovered in 1846, some astronomers searched for a hypothetical ninth planet. Clyde Tombaugh discovered the ninth planet in 1930. Or did he?
52 min