"The Universe is a strange place.  Apart from the normal matter that we see around us, there appears to be a far larger amount of matter that we cannot see—the infamous dark matter.  Even more puzzling, the Universe seems to be bathed in a similarly invisible dark energy, which drives the Universe to expand faster and faster.  This all points to something missing from our understanding.  At the moment, we tend to think that dark matter is something missing from quantum mechanics, a particle that provides dark matter.  Dark energy seems to be more gravity related."