February 20, 2004: The good news from NASA's Hubble Space Telescope is that Einstein was right — maybe. A strange form of energy called "dark energy" is looking a little more like the repulsive force that Einstein theorized in an attempt to balance the universe against its own gravity. Even if Einstein turns out to be wrong, the universe's dark energy probably won't destroy the universe any sooner than about 30 billion years from now, say Hubble researchers.See the rest:
Dark energy is an unknown form of energy that radiates from deep space. It behaves in the opposite manner from gravity. Rather than pulling galaxies together it pushes them apart.
Dark energy is a complete surprise. However, Albert Einstein theorized the existence of a repulsive form of gravity in space that would balance the universe against normal gravity and keep it from imploding. Einstein called it the cosmological constant.
Dark energy makes up the bulk of the universe's mass/energy budget. If dark energy is stable the universe will continue expanding and accelerating forever. If dark energy is unstable the universe could ultimately come unglued to the point where stars, planets and even atoms come apart, a doomsday scenario called the "big rip." Dark energy might also flip such that is becomes an attractive force and causes the universe to implode in a "big crunch."
Hubble can measure the faint glow of distant supernovae, stars that exploded billions of years ago. Supernovae trace the expansion history of the universe, hence, how dark energy "pushed" on space over the past epochs. Every second a star explodes somewhere in the universe, so it's a matter of Hubble looking in the right place at the right time.
These latest Hubble observations show that dark energy is not changing its behavior over time, and so may be the "constant" Einstein predicted. However, more observations are needed over the coming decade.
There will be a hiatus of at least several years in this type of research until some future space telescope with a wide field of view picks up where Hubble left off. This type of research cannot be done with even the largest ground-based telescopes, even those outfitted with adaptive optics for improving image quality.