Cosmology (1, 6)Many of the questions are interdisciplinary, so that my classification is rather arbitrary. Especially, the boundaries among biology, medical science and physiology are not clear, though some questions definitely belong to medical science and some others to physiology. Thus I made these three disciplines a single category of classification.
Physics (2, 14)
Chemistry (1, 4)
Energy-Source Science (1, 1)
Astronomy & Earth Science (2, 6)
Biology, Medical Science & Physiology (14, 50)
Ecology (1, 4)
Anthropology (1, 5)
Sociology (1, 4)
Mathematics (1, 6)
Total (25, 100)
However, the numbers of questions in the above three disciplines hold the unquestioned lead against any other combination of three. Therefore, we can guess that these three disciplines should be the busiest ones from present to the near future, only with the following caution: We should not accept the numbers at their face value, because the 125 questions were chosen by the editors and writers of the "Science" magazine, which is especially popular in the fields of biological science.
The introductory article  of the special section aptly cites James Clark Maxwell's witty words: "Thoroughly conscious ignorance is the prelude to every real advance in science." In other words, posing a good question is the start of good research.
- "25 Big Questions in Science", Femto-Essays (2005).
- "What don't we know?" Science Vol. 309, p. 75 (2005).
- T. Siegfried, "In praise of hard questions" Science Vol. 309, p. 75 (2005).