What kinds of things keep physicists up at night

Shaun Saunders send me this article from NewScientist. Here is the premise:
Recently:

• at the Perimeter Institute, in Waterloo, Canada, a panel of physicists was asked: "What keeps you awake at night?"

Those the responses were varied as one would suspect, a pattern of sorts showed up along several lines of interest.

• What is everything made of?

Ordinary matter, from atoms to galaxies are made of the same stuff. But that "stuff" only accounts for 4% of the total energy/mass of the universe. Physicists are very interested in "dark matter" - hypothetical matter that is undetectable by its emitted radiation, but whose presence can be inferred from gravitational effects on visible matter. And dark matter may account for upwards of 96% of the mass of the universe. Mix in the mind numbing concept of dark energy, which appears to be speeding up the expansion of the universe, and you start to understand what physicists may have stumbled onto, something that could explain the most inner workings of the universe.

• What is the singularity?

From the article:

• Conventional theory points back to an infinitely hot and dense state at the beginning of the universe, where the known laws of physics break down.

And that is exactly what is the most disturbing about the original singularity, that there is a point at which scientific theory can no longer explain or predict what the conditions were like in those first few fractions of a second before time and space began to expand at speeds approaching or surpassing that of light.

• What is reality really?

One of the weirdest occurrences in quantum mechanics is the effect an observer has on an experiment or for that matter the universe as a whole. The ability of an observer to collapse the wave effect has been well documented, But even stranger is this from the article:

• particles that are widely separated can somehow have quantum states that are linked, so that observing one affects the outcome of the other. No one has yet fathomed how the universe seems to know when it is being watched.

The NewScientist article is well worth the read, just the "something ain't quite right here" feeling you get when things aren't quite what you thought they were. There are several more really bent questions that are posited by the article that will certainly get you thinking.