I want to know the answer to the following question:
In what year did Lodygin demonstrate a lamp at the World's Fair?
All the background I'm provided with is that "He used as a burner two carbon rods of diminished section in a glass receiver, hermetically sealed, and filled with nitrogen, electrically arranged so that the current could be passed to the second carbon when the first had been consumed.". Is that enough to answer the question?
Answer: no