Sunday, August 15, 2010
Dark Energy Is Taring The Universe Apart
dark energy is a repulsive force that opposes the gravitation of matter and accerates the expansion of the universe. Dark energy entered physics in 1998 after images from the Hubble Space Telescope of a distant supernova implied an accelerating, expanding universe. The discovery of this required a new cosmological model. Dark energy's presence is predicted in particle physics, however it has never been directly observed. It is generally accepted that dark energy makes up most of the universe which is 70% dark energy, 25% dark matter and 5% ordinary matter. In 2006, scientists found evidence of the effects of dark energy dating back to 9 billion years ago using a space telescope.
The name "dark energy" refers to the fact that "something" must be filling the vast reaches of mostly empty space in the Universe in order to explain the accelerating expansion of the universe. In this sense, it is a "field" just like an electric field or a magnetic field, both of which are produced by electromagnetic energy. This analogy can only be taken so far, because we can readily observe electromagnetic energy via the particle that carries it, the photon.
The nature of dark energy is speculative. It is known to be very homogeneous, not very dense and is not known to interact through any of the fundamental forces other than gravity. Since it is not very dense it is hard to create a testable laboratory expirament. Dark energy can only have such a profound impact on the universe, making up 70% of universal density, because it uniformly fills otherwise empty space. The two leading models are quintessence and the cosmological constant. Both models include the common characteristic that dark energy must have negative pressure.