Adding dark energy changes the equation that describes the speed at which the universe expands with time and the growth of density perturbations. |
The observed motion was small, and we could not duplicate it without the presence of dark energy. When we added the dark energy, we got a perfect match. |
We studied the properties of galaxies close to the Milky Way instead of looking billions of light years away. It's like traveling from Seattle to Portland, Ore., rather than from Seattle to New York, to measure the Earth's curvature. |