"One type of observation used by the astronomers involves measuring a
pattern in how galaxies are distributed in space. This pattern is known
by the term "baryon acoustic oscillations".
The second type of observation involves measuring how quickly clusters
of galaxies have formed over time. Both of these techniques confirmed
the existence of dark energy and the acceleration in the expansion of
the Universe.
The concept of dark energy was first invoked in the late 1990s by
studying the brightness of distant supernovas - exploding stars.
Einstein was right
To explain why the expansion of the Universe was speeding up,
astronomers had to either rewrite Albert Einstein's theory of gravity or
accept that the cosmos was filled with a novel type of energy.
"The action of dark energy is as if you threw a ball up in the air, and
it kept speeding upward into the sky faster and faster," said co-author
Dr Chris Blake of the Swinburne University of Technology in Melbourne,
Australia.
"The results tell us that dark energy is a cosmological constant, as
Einstein proposed. If gravity were the culprit, then we wouldn't be
seeing these constant effects of dark energy throughout time."
[permaculture] Pattern observation in astronomy | BBC News - New method 'confirms dark energy',
Lawrence F. London, Jr., 05/22/2011