More information: There are 118 elements on the periodic table, Hydrogen being the first one listed.
More information: The Femur is not only the longest bone in the human body, it is also the strongest bone. The Femur bone is located in the thigh.
Answer: Paul Erdős, of course!
More information: As the Erdős number describes the "collaborative distance" in authorship of mathematical papers between mathematician Paul Erdős and another person it is only natural that Paul Erdős holds this position.
More information: The CO2 levels have risen about 40% since the industrial revolution. As of March 2011, the CO2 level was about 0.04%.
Answer: A perfect number.
More information: You might also think of a perfect number as a number that is half the sum of all of its positive divisors, including itself! This definition is at least 2300 years old as it appears in Euclid's "Elements".