question mark
The asking of a question or "query", such as English physicist Isaac Newton's famous 1718 Query 31, is precursor to arrival of the answer or solution.
In terminology, question, in contrast to answer, refers to the act or instance of asking, specifically in respect to a subject, aspect, seeming puzzle, or issue open for discussion or lacking in perceptual clarification or solution—the famous age three query “what's the go o' that?” by Scottish physicist James Maxwell being the epitome example.

Famous questions
English chemist-physicist Isaac Newton's famous 1718 "Query 31" the peak of which was the question:

Is it not for want of an attractive virtue between the parts of water () and oil, of quick-silver ()(Hg) and antimony ()(Sb), of lead ()(Pb) and iron ()(Fe), that these substances do not mix; and by a weak attraction, that quick-silver ()(Hg) and copper ()(Cu) mix difficultly; and from a strong one, that quicksilver ()(Hg) and tin ()(Sn), antimony ()(Sb) and iron ()(Fe), water () and salts, mix readily?

launched initially the science of affinity chemistry, eventually the chemical revolution, and resultantly the thermodynamic theory of affinity, and hence the modern chemical thermodynamic / quantum chemistry solution or answer to Newton's query.

German-born American Albert Einstein’s famous 1891 age 12 quest to solve the ‘riddle of the huge world’ and his followup question: ‘what happens when you run alongside a beam of light?’ resulted in the mass-energy equivalence principle and the theory of relativity.

American electrochemical engineer Libb Thims’ 1995 question: ‘what happens when one applies the "universal rule" (Gilbert Lewis, 1923) of thermodynamics to freely going reactions between people?’ has led to the initiation of the science of human chemistry (2007) and to the solution of the great problem of natural philosophy (2009) among other newly-emerging points of reality changing discernments.

Modern queries | Big three
See main: Modern queries
As to the most sought after or greatest "modern queries" pressing on the mind of the average person, according to 2005 polls, when asked the question: ‘what is humankind’s present-day greatest philosophical conundrum’, the following top three responses are found: [1]

1. What happens when you die? (27%)
2. What is love? (23%)
3. What is the meaning of life? (19%)

among other responses. These top three responses along with the "other responses", ten in total, were put into the form of an online poll, asking the same question, given the ten response options, the results of which, as of 2012, are shown below: [2]

1. What is the enigma of time (21%)
2. What is the meaning of life? (12%)
What is our purpose?
What is our function?
What is our design?
3. What happens when you die? (12%)
4. Does god exist? (11%)
5. What is love? (10%)
6. What is the paradox of existence? (38%)
Why are we here?
7. What is reality? (9%)
8. Is destiny ours to make or is it predetermined? (7%)
9. What is the perception of truth? (6%)
10. What is the nature of good and evil (4%)
Philosophical conundrums (poll)

Some type of votebot or multiple re-vote action, to note, may have skewed the top answer, to bias the results.

Best moral system
George Dvorsky’s 2012 philosophical question number 7 (of 8), namely: what is the best morality system, that he thinks will never be solved. [5]
Morality?
Question number seven from George Dvorsky’s 2012 superlist: “8 Great Philosophical Questions That We’ll Never Solve” is “what is the best moral system?”, the section of which is shown adjacent, which of course is really the "big" question underlying the above three big questions, being that one's belief system in regards to morality and one's understanding of the nature of "choice", underpins one's belief in life, love, meaning, and death. [5]

“All natural phenomena can be explained by the motion and organization of primary particles.”
Robert Boyle (1661), The Sceptical Chymist

In 1789, based British philosopher John Stewart introduced his "moral motion" theory, in which he did away with all of the mythological terms ‘life’, ‘death’, ‘god’, etc., and replaced these with modern physical sciences (astronomy, physics, and chemistry) based theory of ‘moral motion’, wherein man is viewed as an intelligent type of animate matter, made of particles (atoms), and that all that exists in the universe is matter and motion; an example quote of which is:

Body and identity of man or manhood, like fire and heat, may be changed or commuted, and in portions what was fire may become man, and what was man become fire; the connection with nature being the same in all its parts, animate or inanimate; but motion in the former has the power of procuring happy combinations or identities; and the volition that propels that motion is motived by happiness, which it procures to its present, and perpetuates to all future stages of its revolution into sensitive nature, by which self, or the moral system, is temporally and eternally benefited.”

Stewart called this "natural religion." [1] Independently, less than seven years later, in 1796, German polyintellect Johann Goethe began to develop a more robust physical chemistry based moral system, the gist of which he explains as follows:

“The moral symbols in the natural sciences, that of the elective affinities invented and used by the great Bergman, are more meaningful and permit themselves to be connected better with poetry and society.”
Johann Goethe (1809), comment to Friedrich Riemer

Quotes
The following are related quotes:

“Let us now consider, for a little while, how wonderfully we stand upon this world. Here it is we are born, bred, and live, and yet we view these things with an almost entire absence of wonder to ourselves respecting the way in which all this happens. So small, indeed, is our wonder, that we are never taken by surprise; and I do think that, to a young person of ten, fifteen, or twenty years of age, perhaps the first sight of a cataract or a mountain would occasion him more surprise than he had ever felt concerning the means of his own existence; how he came here; how he lives; by what means he stands upright; and through what means he moves about from place to place. Hence, we come into this world, we live, and depart from it, without our thoughts being called specifically to consider how all this takes place; and were it not for the exertions of some few inquiring minds, who have looked into these things, and ascertained the very beautiful laws and conditions by which we do live and stand upon the earth, we should hardly be aware that there was any thing wonderful in it. These inquiries, which have occupied philosophers from the earliest days, when they first began to find out the laws by which we grow, and exist, and enjoy ourselves, up to the present time, have shown us that all this was effected in consequence of the existence of certain forces, or abilities to do things, or powers, that are so common that nothing can be more so; for nothing is commoner than the wonderful powers by which we are enabled to stand upright: they are essential to our existence every moment.”
Michael Faraday (1859), “On the Various Forces of Matter: Gravitation” [3]

“When I was first brought with this question of human chemistry, I was both completely mystified and very curious. Like most people, I’d never really stopped to think about it. But if chemistry in the social world is anything like chemistry is in the physical world, there has to be a logical, tangible definition.”
Chanel Wood (2007), “A Questions of Social Chemistry” (see: combination lock theory) [4]

See also
Homework problems
Modern queries
Love thought experiment
Problem

References
1. Thims, Libb. (2007). Human Chemistry (Volume One) (pgs. 301-02). Morrisville, NC: LuLu.
2. (a) Web Poll – HumanThermodynamics.com.
(b) Note: the conundrums (shown above) are real answers supplied by Chicagoans, in person street poll conducted by Libb Thims (2005).
3. (a) Faraday, Michael. (1859). “On the Various Forces of Matter: Lecture One: The Force of Gravitation”, in: A Course of Six Lectures on the Various Forces of Matter, and Their Relations to Each Other (pg. 15). Harper & Brothers, 1860.
(b) Thims, Libb. (2007). Human Chemistry (Volume One) (pgs. xviiii-xx). Morrisville, NC: LuLu.
4. Wood, Chanel. (2007). "A Question of Social Chemistry" (WayBack), June 06. Sociology, ChanelWood.com.
5. Dvorsky, George. (2012). “8 Great Philosophical Questions That We’ll Never Solve”, Sep 9, Io9.com.
6. (a) Stewart, John. (1789). Travels to Discover the Source of Moral Motion (volume one) (energy, 35+ pgs; heat, 8+ pgs; The Religion of Nature, pg. 75-). Ridgway.
(b) Stewart, John. (1790). The Apocalypse of Nature: wherein the Source of Moral Motion is Discovered (volume two). Ridgway.
(c) Griffiths, Ralph. (1791). The Monthly Review, Volume 5 (Art. VI, Review: Travels Over the Most Interesting Parts of the Globe and The Apocalypse of Nature, pgs. 144-46). G. Griffiths.

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