At The Frontier Of Our Understanding Of The Universe

"For nearly 20 years, physicists have known that the expansion of the universe has begun to speed up. This bizarre acceleration could arise because some form of mysterious dark energy is stretching space. Or, it could signal that physicists' understanding of gravity isn't quite right. But a new study puts the screws on a broad class of alternative theories of gravity, making it that much harder to explain away dark energy."

Attempt to explain away ‘dark energy’ takes a hit