Why is the expansion of our universe accelerating? Twenty-five years after its discovery, this phenomenon remains one of the greatest scientific mysteries. Solving it involves testing the fundamental laws of physics, including Albert Einstein’s theory of general relativity. Why is the expansion of our universe accelerating? Twenty-five years after its discovery, this phenomenon remains one of the greatest scientific mysteries. Solving it involves testing the fundamental laws of physics, including Albert Einstein’s theory of general relativity. Astronomy Phys.org – latest science and technology news stories