user: Question: What's the first aired date when Professor Hubert Whitehead was the role?
Columns: ['Year', 'Program', 'Role', 'Episode', 'First aired']
Types: ['real', 'text', 'text', 'text', 'text']
Sample row: [1957.0, 'Alfred Hitchcock Presents', 'Charles Courtney', 'Appeared in the episode "The Perfect Crime"', 'October 20, 1957']
SQL:

assistant: SELECT "First aired" FROM "Table" WHERE "Role" = 'Professor Hubert Whitehead';