astronomy: This planet's diameter is most equal to that of the earth's.?

Questions

Who was the violinist when Beethoven's Kreutzer Sonata for Violinand Piano had its first public performance?

What role did Michael Puchberg play in Mozart's life?

Who was Louis Moreau Gottschalk?

In what city was Tchaikovsky's Piano Concerto No. 1 in B-flat minorgiven its world premiere?

Who wrote the 1829 opera William Tell?