Horizon looks at dark energy - the mysterious force that is unexpectedly causing the universe's expansion to speed up. The effects of dark energy were discovered in 1998 bu Horizon looks at dark energy - the mysterious force that is unexpectedly causing the universe's expansion to speed up. The effects of dark energy were discovered in 1998 but physicists still don't know what it is. Worse, its very existence calls into question Albert Einstein's general theory of relativity - the cornerstone of modern physics. The hunt for the identity of dark en... 详情