After decades of prominence as the "theory of everything," challengers say that String Theory is in trouble. Why? Because there haven't been much experiments to prove it and there don't seem to be any on the horizon. For decades, scientists have been looking for a "theory of everything" to unite the fundamental theories of physics: general relativity, electromagnetism, and quantum mechanics.

The problem is that general relativity remains distinctly divorced from the standard model of particle physics. The theory of the very very big, just can't seem to fit with the theory of the very very small.

Enter String theory. String theory in a broad sense envisions subatomic particles as strings and loops of vibrating energy rather than point-like particles of the standard model. The world is basically made up of "strings."

Detractors contend that aspects of string theory may turn out to be true, but most of the theory is built on elegant mathematics instead of empirical experiments. In particular, detractors charge that string theorists just fudged their models to explain away dark energy, a hypothetical energy that pulls galaxies away from one another at an accelerating rate.

John Schwartz of the California Institute of Technology, one of the fathers of modern string theory said that in the future, experiments will verify string theory. The issue is how much energy is needed for an experiment where you would have to pound into a collision of particles just to reveal strings.

Many physicists hope the Europe's Large Hadron Collider facility will offer some answers. Perhaps then, after they've pounded several particles into each other, they will find what they need.