#:This is the dark energy/cosmological constant argument. The cosmological constant was added by Einstein after he discovered that his field equations (<math>\mathbf{G}=8\pi \mathbf{T}</math>) predicted that the universe was expanding, contradicting his firm philosophical belief in a static universe. So he inserted <math>\Lambda \mathbf{g}</math> to the LHS so that it would predict a static universe. A few years later, Hubble showed the universe to be expanding, and Einstein called the cosmological constant the worst mistake of his career. So, it sort of had a bad reputation, and people didn't want to seriously consider it, until recent observations have shown the universe's expansion to be accelerating forced them to do so. It could have had a very different history. Einstein could have had that term in the EFE's from the start, and pointed out that it would determine if the universe's expansion was accelerating (or not expanding at all!) and it would take further observation to determine its value. | #:This is the dark energy/cosmological constant argument. The cosmological constant was added by Einstein after he discovered that his field equations (<math>\mathbf{G}=8\pi \mathbf{T}</math>) predicted that the universe was expanding, contradicting his firm philosophical belief in a static universe. So he inserted <math>\Lambda \mathbf{g}</math> to the LHS so that it would predict a static universe. A few years later, Hubble showed the universe to be expanding, and Einstein called the cosmological constant the worst mistake of his career. So, it sort of had a bad reputation, and people didn't want to seriously consider it, until recent observations have shown the universe's expansion to be accelerating forced them to do so. It could have had a very different history. Einstein could have had that term in the EFE's from the start, and pointed out that it would determine if the universe's expansion was accelerating (or not expanding at all!) and it would take further observation to determine its value. |