While researching dark matter and dark energy, I came across the following passage on NASA's website: "The first property that Einstein discovered is that it is possible for more space to come into existence. Then one version of Einstein's gravity theory, the version that contains a cosmological constant, makes a second prediction: "empty space" can possess its own energy. Because this energy is a property of space itself, it would not be diluted as space expands. As more space comes into existence, more of this energy-of-space would appear." LINK: http://science.nasa.gov/astrophysics/focus-areas/what-is-dark-energy/ In any high school physics class, we learn about the law of conservation of energy, yet this seems to violate it. Did I just misread the passage, or does this really violate the conservation of energy? If it does, how? If it does not, why? Also, how does empty space have energy? In order to have energy doesn't something have to be above absolute zero, and therefore be made up of matter (Or am I misinterpreting something)? If someone could explain this passage, it would be greatly appreciated!