text: Tensor-vector-scalar' gravity is an extension to an alternative answer to the puzzles posed by this substance, known as MOND theory.
full_question: Tensor-vector-scalar' gravity is an extension to an alternative answer to the puzzles posed by this substance, known as MOND theory. String theory predicts a class of particles that do not interact via gauge boson forces, known as 'hidden sector' particles, another candidate for this substance. This substance derives its name from its apparent lack of interaction with light, and its existence is inferred from its gravitational effects, leading scientists to hypothesize the existence of a new class of particles known as WIMPs. For 10 points, identify this substance believed to greatly outnumber its baryonic counterpart in the universe, an as-yet-unobserved form of matter.
first_sentence: Tensor-vector-scalar' gravity is an extension to an alternative answer to the puzzles posed by this substance, known as MOND theory.