November 16, 2006: Scientists using NASA's Hubble Space
Telescope have discovered that dark energy is not a new
constituent of space, but rather has been present for most of
the universe's history. Dark energy is a mysterious repulsive
force that causes the universe to expand at an increasing rate.
Investigators used Hubble to find that dark energy was already
boosting the expansion rate of the universe as long as nine
billion years ago. This picture of dark energy is consistent
with Albert Einstein's prediction of nearly a century ago that a
repulsive form of gravity emanates from empty space. Data from
Hubble provides supporting evidence to help astrophysicists to
understand the nature of dark energy. This will allow them to
begin ruling out some competing explanations that predict that
the strength of dark energy changes over time. Researchers also
have found that the class of ancient exploding stars, or
supernovae, used to measure the expansion of space today look
remarkably similar to those that exploded