When is it appropriate to challenge authority ? In what ways did einstein challenge authority?

Albert Einstein (1879-1955) was one of the most respected scientists who ever lived. A theoretical physicist and philosopher of science, Einstein developed the special and general theories of relativity, applying the latter to map out the large-scale structure of the universe. He is most well-known for developing what is perhaps the most famous equation of all time: the mass-energy equivalence formula E = mc^2. Einstein was awarded the Nobel Prize in Physics in 1921. Later in life, he was a staunch supporter of American civil rights and an activist against the dangers of nuclear weapons.

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the answer is:

carbon dioxide