What is the most fascinating unsolved problem in physics?

Jeffrey K: What is the most fascinating unsolved problem in physics?
In your opinion, what is the most interesting unsolved problem in physics?
If you could ask one question about physics and be given the answer, what would you ask?

Answers and Views:

Answer by thehazmater
The string theory and the formation of blackholes.

Answer by Patrick B
string theory is the most complex, if i could ask one question it would be how to learn to fly! lol

Answer by Brian
Where does the gravitational force actually come from, is there a gravitron (partical of gravity), why is it such a weak force compared to the other 3 fundamental forces. String theory tries to explain some of this, but no one actually knows why yet.

Answer by Tristan S
Why did matter, not antimatter prevail since equal quantities were created by the big bang.

Answer by johnandeileen2000
From what did the big bang emerge?

Answer by Jay G
what happens when an irresistable force meets an immovable object